WO2024147114A1

WO2024147114A1 - Compositions and methods for treating parkinson's disease

Info

Publication number: WO2024147114A1
Application number: PCT/IB2024/050117
Authority: WO
Inventors: Ahad RAHIM; Simon Waddington; Manju Kurian
Original assignee: Bloomsbury Genetic Therapies Ltd
Current assignee: Bloomsbury Genetic Therapies Ltd
Priority date: 2023-01-06
Filing date: 2024-01-05
Publication date: 2024-07-11
Anticipated expiration: 2025-07-06

Abstract

Described herein are methods for treating a subject having or at risk of developing Parkinson's disease, by administering an adeno-associated viral (AAV) vector that contains a solute carrier family 6 member 3 (SLC6A3) transgene or an AAV vector that expresses a transgene encoding the Dopamine Transporter (DAT) protein. Also disclosed are compositions comprising an AAV vector, further comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein.

Description

PATENT ATTORNEY DOCKET: 51673-007WO3 COMPOSITIONS AND METHODS FOR TREATING PARKINSON’S DISEASE Sequence Listing The instant application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on January 4, 2024, is named “51673-007WO3_Sequence_Listing_1_4_24” and is 14,341 bytes in size. Field of the Invention The invention relates to compositions and methods for treating Parkinson’s disease. Background Parkinson’s disease (PD) is a progressive disorder of the nervous system that affects movement and produces symptoms such as resting tremor, rigidity, and bradykinesia. Patients suffering from PD may also experience non-motor symptoms, including depression, constipation, pain, sleep disorders, cognitive decline, and olfactory dysfunction. Post-mortem analyses of PD patient brains often reveal Lewy bodies containing ^-synuclein in affected brain regions and a loss of dopaminergic neurons in the substantia nigra pars compacta. There remains a need for improved therapeutic modalities for the treatment of PD. Summary of the Invention The present invention provides methods for treating a Parkinson’s disease (PD) patient using a viral vector, such as an adeno-associated viral (AAV) vector, expressing a solute carrier family 6 member 3 (SLC6A3) transgene. In some embodiments, the patient has idiopathic PD. Administration of an effective dose of the viral vector may be by any route of administration standard in the art, including, but not limited to, systemic (e.g., by intravenous administration), local (e.g., intracortical), and direct injection (e.g., stereotactic delivery to dopaminergic neurons of the substantia nigra pars compacta (SNc) or ventral tegmental area (VTA)). The viral vector may be administered to a patient having PD via one or more of a variety of routes, for example, intracerebroventricular (ICV), intracranial, intracortical, intracisternal, intracerebral, intra-cerebrospinal, intraparenchymal, intracisternal, intrahippocampal, intra- striatal (putamen and/or caudate), intravenous (IV), intrathecal, intraputaminal, intra-midbrain, intra- cisterna magna, intra-substantia nigra, intra-ventral tegmental area, and/or intrathalamic administration. In some cases, the vector is administered via intraparenchymal, intracerebral, ICV, intrathecal, intraputaminal, intrathalamic, intra-midbrain, intra-cisterna magna, intra-substantia nigra, and/or intra- ventral tegmental area routes. Administration may be performed by intrathecal injection with or without Trendelenberg tilting. In some cases, the viral vector may be administered, e.g., in a single administration. Exemplary compositions and methods of the disclosure are discussed in further detail below. In a first aspect, the disclosure provides a method of treating PD in a patient in need thereof by administering to the patient a viral vector that contains an SLC6A3 transgene. In another aspect, the disclosure provides a method of reducing bradykinesia in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene. 1 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 In another aspect, the disclosure provides a method of reducing tremors in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene. In another aspect, the disclosure provides a method of reducing rigidity and stiffness in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene. In another aspect, the disclosure provides a method of improving motor coordination in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene. In another aspect, the disclosure provides a method of reducing postural instability and improving balance in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene. In another aspect, the disclosure provides a method of prolonging the responsiveness to an antiparkinsonian therapy in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene, optionally wherein the antiparkinsonian therapy is levodopa. In a further aspect, the disclosure provides a method of reducing the dependency on an antiparkinsonian therapy in a patient diagnosed as having PD by administering to the patient a viral vector that contains an SLC6A3 transgene, optionally wherein the antiparkinsonian therapy is levodopa. In some embodiments of any of the foregoing aspects, the viral vector is an AAV vector. In some embodiments, the transgene is operably linked to a promoter. In some embodiments, the promoter is selected from a synapsin 1 promoter, a CAG promoter, a CMV promoter, a CAMKII promoter, a beta-actin promoter, and a human EF1-alpha promoter. In some embodiments, the promoter is a neuron-specific promoter. In some embodiments, the promoter is a synapsin 1 promoter. In some embodiments, the synapsin 1 promoter is selected from an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter, and a truncated hSYN1 promoter. In some embodiments, the synapsin 1 promoter has a nucleic acid sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the nucleic acid sequence of SEQ ID NO: 1. For example, in some embodiments, the synapsin 1 promoter has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 1, optionally wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 1. In some embodiments, the synapsin 1 promoter has the nucleic acid sequence of SEQ ID NO: 1. In some embodiments, the synapsin 1 promoter has a nucleic acid sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the nucleic acid sequence of SEQ ID NO: 6. For example, in some embodiments, the synapsin 1 promoter has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 6, optionally wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 6. In some embodiments, the synapsin 1 promoter has the nucleic acid sequence of SEQ ID NO: 6. In some embodiments, the SLC6A3 transgene has a nucleotide sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the nucleic acid sequence of SEQ ID NO: 2. For example, in some embodiments, the SLC6A3 transgene has a nucleotide sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 2, optionally wherein the SLC6A3 gene has a nucleotide sequence that is at least 95%, 96%, 2 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 2. In some embodiments, the SLC6A3 transgene has the nucleic acid sequence of SEQ ID NO: 2. In some embodiments, the transgene encodes a Dopamine Transporter (DAT) protein. In some embodiments, the DAT protein has an amino acid sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the amino acid sequence of SEQ ID NO: 3. For example, in some embodiments, the DAT protein has an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 3, optionally wherein the DAT has an amino acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the amino acid sequence of SEQ ID NO: 3. In some embodiments, the DAT protein has the amino acid sequence of SEQ ID NO: 3. In some embodiments, the transgene is operably linked to a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE). In some embodiments, the WPRE has a nucleic acid sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the nucleic acid sequence of SEQ ID NO: 4. For example, in some embodiments, the WPRE has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 4, optionally wherein the WPRE has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 4. In some embodiments, the WPRE has the nucleic acid sequence of SEQ ID NO: 4. In some embodiments, the AAV vector comprises capsid proteins from an AAV serotype selected from the group consisting of AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV9.47, AAV9(hu14), AAV10, AAV11, AAV12, AAVrh74, AAVrh.8, AAVrh.10, AAV-DJ and AAV-DJ8. In some embodiments, the AAV vector comprises a 5’ inverted terminal repeat (ITR) and/or a 3’ ITR from AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV9.47, AAV9(hu14), AAV10, AAV11, AAV12, AAVrh74, AAVrh.8, AAVrh.10, AAV-DJ or AAV-DJ8, optionally wherein the AAV vector comprises a 5’ ITR and a 3’ ITR from AAV2. In some embodiments, the AAV vector comprises a 5’ ITR and/or a 3’ ITR from one AAV serotype and one or more capsid proteins from a different AAV serotype. In some embodiments, the AAV vector is an AAV2 vector. In some embodiments, the AAV vector has a nucleic acid sequence that is at least 85% (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) identical to the nucleic acid sequence of SEQ ID NO: 5. For example, in some embodiments, the AAV vector has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 5. In some embodiments, the AAV vector has a nucleic acid sequence that is at least 95% identical to the nucleic acid sequence of SEQ ID NO: 5, optionally wherein the AAV has a nucleic acid sequence that is at least 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 5. In some embodiments, the AAV vector has a nucleic acid of SEQ ID NO: 5. In some embodiments, the AAV vector is an AAV2 vector that contains a synapsin 1 promoter and WPRE operably linked to the SLC6A3 transgene. In some embodiments, the patient has one or more symptoms of a condition selected from PD, juvenile PD, infantile dystonia-Parkinsonism, dystonia, unclassified movement disorders, unspecified 3 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 personality disorder with evasive and schizophrenic traits, hemiparkinsonism, adult early-onset Parkinsonism, and comorbid neuropsychiatric disease. In some embodiments, the patient has one or more symptoms selected from hand tremors, evasive and schizophrenic traits, self-injury, periodic depression, general bradykinesia, severe rigidity, resting and intention tremor of the upper extremities without consistent sidedness of symptoms, Parkinsonian gait with small shuffling steps, kyphosis, severe difficulties in turning around, postural instability, spontaneous falling, and severe hypomimia. In some embodiments, the patient has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. In some embodiments, the patient has one or more characterizations selected from dysfunctional dopaminergic neurotransmission, progressive loss of DAT availability, small (2-4 mm) white matter lesions compared to age-matched controls, reduced DAT binding in striatum (caudate nucleus and putamen), dopaminergic cell loss, reduced DAT expression, loss of DAT binding, accelerated loss of [123I]-FP-CIT binding compared to expected decline in age-matched controls, impaired dopamine (DA) uptake, dominant-negative impairments on DA uptake, impaired amphetamine-induced DA efflux, reduced surface expression of DAT, accelerated turnover of DAT leading to lower expression of active transporter, enhanced lysosomal degradation of DAT, and reduction in [3H]-CTF-binding capacity. In some embodiments, the patient has mild to moderate Unified Parkinson's Disease Rating Scale (UPDRS) III OFF score less than 5 years after clinical PD diagnosis, and/or moderate to severe UPDRS OFF score after 4 or more years since clinical PD diagnosis. In some embodiments, the patient has been diagnosed with PD and is in the modified Hoehn and Yahr stage I-III OFF medication or the patient has had the disease for a duration of more than 5 years and is in the Hoehn and Yahr Stage III or IV off medication. In some embodiments, the patient has PD with motor complications despite adequate oral antiparkinsonian therapy. In some embodiments, the patient with PD is undergoing treatment with an additional antiparkinsonian therapy. For example, in some embodiments, antiparkinsonian therapy is levodopa. In some embodiments of any of the foregoing aspects, the patient is responsive to the levodopa. In some embodiments, the patient is deficient in expression and/or activity of DAT protein. In some embodiments, the patient has a c.1857G>C single nucleotide substitution in exon 15 of SLC6A3. In some embodiments, the patient has one or more mutations in an endogenous DAT protein, optionally wherein the mutation is a monoallelic missense mutation. For example, in some embodiments, the one or more mutations are selected from I312F and K619N. In some embodiments, the patient has the K619N mutation. In some embodiments, the patient with the K619N mutation inherited the mutant allele from a parent, optionally wherein the mutant allele was paternally transmitted. In some embodiments, the patient has an A314V mutation in an endogenous DAT protein. In some embodiments, the patient has one or more mutations in endogenous DAT protein selected from R521W, R219S, Y343X, L224P, L368Q, P395L, Y470Sfs, p.I134SfsX5, p.G500EfsX13, p.G380_K384 delinse, and Q439X. 4 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 In some embodiments, the patient has mutations in the C-terminus of an endogenous DAT protein. In some embodiments, the patient has genotype GG and allele G of an rs2652510 single nucleotide polymorphism. In some embodiments, the patient has a plurality of repeat alleles of a variable number tandem repeat (VNTR) in the 3’-UTR of the SLC6A3 gene. In some embodiments, the patient has idiopathic PD. For example, in some embodiments, the patient with idiopathic PD has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. In some embodiments, the patient with idiopathic PD has levodopa-induced dyskinesia (LID). In some embodiments, the patient with idiopathic PD is at risk of developing LID. In some embodiments, the patient with LID is female. In some embodiments, the patient with LID is male. In some embodiments, either low or high levodopa doses can cause dyskinesia in late disease stages. In some embodiments, the age of PD onset for patients with dyskinesia risk at 5 years of levodopa treatment is 40 years or less. In some embodiments, the vector is administered to the patient via intraparenchymal, intracerebral, intracerebroventricular, intrathecal, intraputaminal, intrathalamic, intra-midbrain, intra- cisterna magna, intra-substantia nigra and/or intra-ventral tegmental area routes. In some embodiments, the vector is administered to the patient in an amount sufficient to achieve one or more of the following: reduce bradykinesia in the patient, reduce tremors in the patient, reduce rigidity and stiffness in the patient, improve motor coordination of the patient, reduce postural instability and improve balance in the patient, improve the cognitive performance of the patient, alter dopaminergic neurotransmission in the patient, improve DAT availability in the patient, reduce white matter lesions in the patient, improve DAT binding in striatum of the patient, improve DAT expression of the patient, improve DA uptake in the patient, improve [123I]-FP-CIT binding in the patient, improve [3H]-CTF-binding capacity of the patient, improve amphetamine-induced DA efflux in the patient, improve the motor function of the patient, reduce dopaminergic neuron loss in the patient, reduce neuroinflammation in the patient, reduce inflammatory cytokines in the blood and cerebrospinal fluid (CSF) of the patient, prevent, reduce, or reverse LID in the patient, and/or reduce ^-synuclein levels or aggregation thereof in the patient. In some embodiments, the vector is administered to the patient in an amount sufficient to change the baseline of motor symptoms as assessed by the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS). In some embodiments, the vector is administered to the patient in an amount sufficient to change the baseline of non-motor symptoms of PD as assessed by the Non-Motor Symptom Scale (NMSS), wherein the one or more non-motor symptoms are selected from being associated with cardiovascular health, sleep and fatigue, mood and cognition, perceptual problems and hallucinations, attention and memory, anxiety, depressive-like behaviors, gastrointestinal tract, urinary, and sexual function. In some embodiments, the vector is administered to the patient in an amount sufficient to change the brain dopaminergic cell integrity as measured by DaTscan SPECT imaging, wherein the percentage and absolute changes in Ioflupane retention as a marker for dopamine transporter protein expressed by dopamine producing cells within the brain are measured. 5 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 In some embodiments, the vector is administered to the patient in an amount sufficient to improve neurological symptoms of PD. In some embodiments, the vector is administered to the patient in an amount sufficient to improve brain metabolism as measured by PET scans. In some embodiments, the vector is administered to the patient in an amount sufficient to improve standard clinical rating scales. In some embodiments, the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient for the patient to exhibit a change in responsiveness to the antiparkinsonian therapy. In some embodiments, the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient to prolong responsiveness to the antiparkinsonian therapy. In some embodiments, the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient to reduce dependency on the antiparkinsonian therapy. For example, in some embodiments, the antiparkinsonian therapy is levodopa. In some embodiments, the vector is administered to the patient in an amount sufficient to increase the expression of DAT protein in target tissue. For example, in some embodiments, the target tissue is SNc or VTA. In some embodiments, the target tissue comprises non-dopaminergic neurons. In some embodiments, the non-dopaminergic neurons are striatal non-dopaminergic neurons. In another aspect, the disclosure provides a kit containing an AAV vector that contains an SLC6A3 transgene, wherein the kit further comprises a package insert instructing a user of the kit to perform the method of any of the foregoing aspects. Brief Description of the Drawings FIG.1 includes a series of images showing injection coordinates and the sectioning scheme in the rat brain. From each brain, up to 80 coronal sections were collected throughout the striatum and around the AAV injection sites, and from the substantia nigra. The experiments were performed as described in Example 1 below. FIG.1 abbreviations: SN, substantia nigra; CPU, caudate putamen; AP, anterior/posterior; ML, midline; DV, dorsoventral. FIG.2 is a graph showing measurement of body weight over time. Body weight of all animals was recorded weekly. Each time point shows the mean body weight ± standard error of the mean (SEM) determined for all animals per group. No statistically significant difference could be detected (2-way ANOVA, followed by Bonferroni’s multiple comparisons test). The experiments were performed as described in Example 1 below. FIG.2 abbreviations: PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.3 includes a set of graphs quantifying the rotational behavior of rats in the D-Amphetamine- induced rotation test. Displayed are total number of rotations (left panel) and percentage ipsilateral rotations (right panel) per individual animal. Dots indicate individual values per animal, and horizontal 6 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 lines indicate median. No statistical analysis was performed. The experiments were performed as described in Example 1 below. FIG.3 abbreviations: RT, Rotation Test. FIG.4 is a graph quantifying axial, limb, and orolingual abnormal involuntary movements (ALO AIMs) scores on week 7 (baseline). Displayed are sum of ALO AIMs scores over the entire observation period. Dots indicate individual values per animal, and horizontal lines indicate median of all tested animals. Animals which were allocated to treatment groups and used for efficacy testing are represented by filled dots; animals that were excluded are represented by empty dots. No statistical analysis was performed. The experiments were performed as described in Example 1 below. FIG.4 abbreviations: ALO AIMs, axial, limb, and orolingual abnormal involuntary movements. FIG.5 is a bar graph showing measurement of ALO AIMs assessment, total. Displayed are sum of ALO AIMs scores over the entire observation period. Dots represent values of individual animals, bars represent mean, error bars represent standard error of the mean (SEM). Animals initially showing low rotation, but dyskinesia are marked as filled dots. Statistical analysis: Mixed effects analysis, followed by Bonferroni’s multiple comparisons test, ** ^{/ ##}p<0.01; *** ^{/ ###}p<0.001. The experiments were performed as described in Example 1 below. FIG.5 abbreviations: ALO AIMs, axial, limb, and orolingual abnormal involuntary movements; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.6 is a bar graph showing measurement of ALO AIMs assessment, individual AIMS. Displayed are individual ALO AIMs scores for the indicated categories, for one timepoint (6 weeks post- AAV-DAT treatment). Dots represent values of individual animals, bars represent mean, and error bars represent standard error of the mean (SEM). Statistical analysis: 2-Way ANOVA, followed by Bonferroni’s multiple comparisons test, *** p<0.001. The experiments were performed as described in Example 1 below. FIG.6 abbreviations: ALO AIMs, axial, limb, and orolingual abnormal involuntary movements; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein; Oro, orolingual; Wk, week. FIG.7 includes a series of graphs showing measurement of ALO AIMs assessment, longitudinal. Displayed are sum of ALO AIMs scores over the entire observation period, per timepoint (top left panel – baseline, top right panel – week 2 post-AAV-DAT injection, bottom left panel – week 4 post-AAV-DAT injection, bottom right panel – week 6 post-AAV-DAT injection). Points represent mean ± standard error of the mean (SEM), for each group per timepoint. Statistical analysis: Mixed effects analysis, followed by Bonferroni’s multiple comparisons test, **p<0.01; ***p<0.001. The experiments were performed as described in Example 1 below. FIG.7 abbreviations: ALO AIMs, axial, limb, and orolingual abnormal involuntary movements; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a 7 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.8 includes a series of bar graphs showing performance of rats in the Elevated Plus Maze (EPM). Displayed are mean + standard error of the mean (SEM) for number of entries in closed arms (top left panel) or open arms (top right panel), as well as duration in closed arms (bottom left panel) and open arms (bottom right panel). Statistical analysis: unpaired student’s t-test (number of entries closed arms) or Mann-Whitney test (other panels). * p<0.05. The experiments were performed as described in Example 1 below. FIG.8 abbreviations: EPM, Elevated Plus Maze; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.9 includes a series of images showing immunofluorescent signals in the substantia nigra (SN) of rats. Images show examples of immunofluorescent labeling of tyrosine hydroxylase (TH) + human dopamine transporter (hDAT) + 5-hydroxytryptamine (serotonin) transporter (5-HTT) + Glial Fibrillary Acidic Protein (GFAP) on coronal sections; nuclei are labeled with 4^,6-diamidino-2-phenylindole (DAPI). The topmost panel shows a coronal section (including both hemispheres) from both groups (Group A: Control and Group B: AAV-DAT treatment) whereas all of the panels below show labeling at the position indicated by the boxes (either contralateral or ipsilateral) in the topmost panel images. Images in the top 2 panels for both groups are an overlay of all the channels (TH + hDAT + 5-HTT + GFAP + DAPI). Images in the bottom 5 panels for both groups show individual channels: TH, hDAT, 5-HTT, GFAP, and DAPI. Single channel magnifications show labeling at the position indicated by the boxes in the top panel images. The experiments were performed as described in Example 1 below. FIG.9 abbreviations: SN, substantia nigra; TH, tyrosine hydroxylase; hDAT, human dopamine transporter; 5-HTT, 5- hydroxytryptamine (serotonin) transporter; GFAP, Glial Fibrillary Acidic Protein; DAPI, 4^,6-diamidino-2- phenylindole; SNpc, substantia nigra pars compacta; SNpr, substantia nigra pars reticulata. FIG.10 includes a series of images showing immunofluorescent signals in the caudate putamen (CPU) of rats. Images show examples of immunofluorescent labeling of tyrosine hydroxylase (TH) + human dopamine transporter (hDAT) + 5-hydroxytryptamine (serotonin) transporter (5-HTT) + Glial Fibrillary Acidic Protein (GFAP) on coronal sections; nuclei are labeled with 4^,6-diamidino-2-phenylindole (DAPI). The topmost panel shows a coronal section (including both hemispheres) from both groups (Group A: Control and Group B: AAV-DAT treatment) whereas all of the panels below show labeling at the position indicated by the boxes (either contralateral or ipsilateral) in the topmost panel images. Images in the top 2 panels for both groups are an overlay of all the channels (TH + hDAT + 5-HTT + GFAP + DAPI). Images in the bottom 5 panels for both groups show individual channels: TH, hDAT, 5- HTT, GFAP, and DAPI. Single channel magnifications show labeling at the position indicated by the boxes in the top panel images. The experiments were performed as described in Example 1 below. FIG. 10 abbreviations: CPU, caudate putamen; TH, tyrosine hydroxylase; hDAT, human dopamine transporter; 5-HTT, 5-hydroxytryptamine (serotonin) transporter; GFAP, Glial Fibrillary Acidic Protein; DAPI, 4^,6- diamidino-2-phenylindole. 8 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 FIG.11 includes a set of images showing the definition of the areas of interest (ROIs). The images show the outline of the ROIs of the caudate putamen (CPU) (top panel) and the substantia nigra (SN) (bottom panel) in the left hemisphere. Equally shaped and sized ROIs were drawn to identify CPU and SN in the right hemisphere. The experiments were performed as described in Example 1 below. FIG. 11 abbreviations: SN, substantia nigra; CPU, caudate putamen. FIG.12 includes a set of bar graphs showing quantification of region size of the caudate putamen (CPU) (left graph) and substantia nigra (SN) (right graph). Quantification is shown for both left and right hemispheres. Graphs present the mean size of the target regions on 5 brain sections for each CPU and SN. Minor differences in region size differences were detected, which is expected in invasive models due to cell death and glial scarring. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: # p < 0.05, ## p < 0.01, ### p < 0.001. The experiments were performed as described in Example 1 below. FIG.12 abbreviations: SN, substantia nigra; CPU, caudate putamen; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.13 inlcudes a series of bar graphs showing quantification of human dopamine transporter (hDAT) immunofluorescence in the caudate putamen (CPU). Graphs present the means of immunofluorescent signals on 5 brain sections per rat (n = 8 per group). Lesioning with 6- hydroxydopamine (6-OHDA) significantly reduced hDAT signal in the right hemisphere. Striatal injection of AAV-DAT significantly increased hDAT in the right hemisphere compared to PBS. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: # p < 0.05, ## p < 0.01, ### p < 0.001. The experiments were performed as described in Example 1 below. FIG.13 abbreviations: hDAT, human dopamine transporter; CPU, caudate putamen; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.14 inlcudes a series of bar graphs showing quantification of hDAT immunofluorescence in the substantia nigra (SN). Graphs present the means of immunofluorescent signals on 5 brain sections per rat (n = 8 per group). Lesioning with 6-hydroxydopamine (6-OHDA) significantly reduced hDAT signal in the right hemisphere, while striatal injection of AAV-DAT significantly increased hDAT in the right hemisphere compared to PBS, resulting in severalfold difference between groups in the right hemisphere. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: # p < 0.05, ## p < 0.01, ### p < 0.001. The experiments were performed as described in Example 1 below. FIG.14 abbreviations: SN, substantia nigra; hDAT, human dopamine transporter; 9 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.15 inlcudes a series of bar graphs showing quantification of 5-HTT immunofluorescence in the CPU. Graphs present the means of immunofluorescent signals on 5 brain sections per rat (n = 8 per group). Neither lesioning with 6-hydroxydopamine (6-OHDA) nor intrastriatal injection of AAV-DAT or PBS did significantly affect 5-HTT. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: # p < 0.05, ## p < 0.01, ### p < 0.001. The experiments were performed as described in Example 1 below. FIG.15 abbreviations: 5-HTT, 5-hydroxytryptamine (serotonin) transporter; CPU, caudate putamen; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno- associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.16 inlcudes a series of bar graphs showing quantification of 5-HTT immunofluorescence in the SN. Graphs present the means of immunofluorescent signal on 5 brain sections per rat (n = 8 per group). Neither lesioning with 6-hydroxydopamine (6-OHDA) nor intrastriatal injection of AAV-DAT or PBS did significantly affect 5-HTT. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: # p < 0.05, ## p < 0.01, ### p < 0.001. The experiments were performed as described in Example 1 below. FIG.16 abbreviations: 5-HTT, 5-hydroxytryptamine (serotonin) transporter; SN, substantia nigra; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno- associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.17 inlcudes a series of bar graphs showing quantification of GFAP immunofluorescence in the CPU. Graphs present the means of immunofluorescent signals on 5 brain sections per rat (n = 8 per group). Lesioning with 6-hydroxydopamine (6-OHDA) and striatal injection of AAV-DAT or PBS significantly increased GFAP signal in the right hemisphere. No difference between AAV-DAT or PBS was detected in the right hemisphere, however. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001. Factor treatment: All n.s. The experiments were performed as described in Example 1 below. FIG.17 abbreviations: GFAP, Glial Fibrillary Acidic Protein; CPU, caudate putamen; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a 10 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.18 inlcudes a series of bar graphs showing quantification of GFAP immunofluorescence in the SN. Graphs present the means of immunofluorescent signal on 5 brain sections per rat (n = 8 per group). GFAP object density was significantly increased in the right hemisphere and a similar trend occurred for the readout immunoreactive area. No significant difference of intrastriatal injection with AAV- DAT or PBS was detected, however. Bar graphs represent group means + standard error of the mean (SEM). Data were analyzed by two-way ANOVA and Bonferroni’s post hoc test. Factor hemisphere: ^ p < 0.05. Factor treatment: All n.s. The experiments were performed as described in Example 1 below. FIG. 18 abbreviations: GFAP, Glial Fibrillary Acidic Protein; SN, substantia nigra; PBS, Phosphate-Buffered Saline; AAV-DAT, an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. FIG.19 inlcudes a series of images which are examples of hDAT colocalization with ChAT or CTIP2 in CPU of three rats from group B. The 3 panels: top, middle, and bottom represent 3 individual rats. Images show representative examples of labeling of the antibodies. The left panel for every rat shows the entire coronal section and has all the channels merged. The right panel for every rat has 4 images representing individual/merged channels: CTIP2 (top left), ChAT (top right), hDAT (bottom left), and merged (bottom right). Individual/merged channel images in the right panel indicate location of magnified views from the boxed region (left panel images) in the striatum. hDAT-positive somata were consistently negative for both ChAT and CTIP2. The experiments were performed as described in Example 1 below. FIG.19 abbreviations: ChAT, Choline acetyltransferase; hDAT, human dopamine transporter; CTIP2, COUP (chicken ovalbumin upstream promoter)-TF (transcription factor)-interacting protein 2. FIG.20 inlcudes a series of images which are examples of hDAT colocalization with VAChT or nNOS in CPU of three rats from group B. The 3 panels: top, middle, and bottom represent 3 individual rats. Images show representative examples of labeling of the antibodies. The left panel for every rat shows the entire coronal section and has all the channels merged. The right panel for every rat has 4 images representing individual/merged channels: VAChT (top left), nNOS (top right), hDAT (bottom left), and merged (bottom right). Individual/merged channel images in the right panel indicate location of magnified views from the boxed region (left panel images) in the striatum. hDAT-positive somata were consistently negative for VAChT, while coexpression with hDAT was detected in a subset of nNOS- positive interneurons (arrows). The experiments were performed as described in Example 1 below. FIG. 20 abbreviations: VAChT, vesicular acetylcholine transporter; hDAT, human dopamine transporter; nNOS, neuronal nitric oxide synthase. FIG.21 inlcudes a series of images which are examples of hDAT colocalization with calbindin, parvalbumin, or DARPP-32 in CPU of three rats from group B. Images show examples of the colocalization of hDAT and different neuronal markers on coronal sections. The 3 panels: top, middle, and bottom represent 3 individual rats. Images show representative examples of labeling of the antibodies. The left panel for every rat shows the entire coronal section and has all the channels merged. The right 11 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 panel for every rat has 4 images representing individual channels: DARPP-32 (bottom left), calbindin (top left), hDAT (bottom right), and parvalbumin (top right). Individual channel images in the right panel indicate location of magnified views from the boxed region (left panel images) in the striatum. hDAT- positive somata were consistently negative for calbindin, but very few weakly labeled DARPP-32 somata may be positive for hDAT (arrowheads). Coexpression with hDAT was evident in a subset of parvalbumin-positive interneurons (arrows). The experiments were performed as described in Example 1 below. FIG.21 abbreviations: DARPP-32, Dopamine- and cyclic AMP (adenosine monophosphate)- regulated phosphoprotein, Mr 32 kDa; hDAT, human dopamine transporter. Definitions As used herein, “administration” refers to providing or giving a subject a therapeutic agent (e.g., an adeno-associated viral (AAV) vector, comprising a solute carrier family 6 member 3 (SLC6A3) transgene or an AAV vector that expresses a transgene encoding the Dopamine Transporter (DAT) protein. Administration of an effective dose of the composition may be by exemplary routes of administration standard in the art, including, but not limited to, systemic (e.g., by intravenous administration), local (e.g., intracortical), and direct injection (e.g., stereotactic delivery to dopaminergic neurons of the substantia nigra pars compacta (SNc) or ventral tegmental area (VTA)). The AAV vector may be administered to a patient having PD via one or more of a variety of routes, for example, intracerebroventricular (ICV), intracranial, intracortical, intracisternal, intracerebral, intra-cerebrospinal, intraparenchymal, intracisternal, intrahippocampal, intra-striatal (putamen and/or caudate), intravenous (IV), intrathecal, intraputaminal, intra-midbrain, intra-cisterna magna, intra-substantia nigra, intra-ventral tegmental area, and/or intrathalamic administration. In some cases, the vector is administered via intraparenchymal, intracerebral, ICV, intrathecal, intraputaminal, intrathalamic, intra-midbrain, intra- cisterna magna, intra-substantia nigra, and/or intra-ventral tegmental area routes. Administration may be performed by intrathecal injection with or without Trendelenberg tilting. In some cases, the AAV vector may be administered, e.g., in a single administration. Direct delivery to the central nervous system (CNS) may involve targeting the intraventricular space, either unilaterally or bilaterally, specific neuronal regions or more general brain regions containing neuronal targets. Individual patient intraventricular space, brain region and/or neuronal target(s) selection and subsequent intraoperative delivery of AAV may be accomplished using several imaging techniques (magnetic resonance imaging (MRI), computerized tomography (CT), CT combined with MRI merging) and employing any number of software planning programs (e.g., Stealth System, Clearpoint Neuronavigation System, Brainlab, Neuroinspire etc). Intraventricular space or brain region targeting, and delivery may involve use of standard stereotactic frames (Leksell, CRW) or using frameless approaches with or without intraoperative MRI. Actual delivery of the vector may be by injection through needle or cannulae with or without inner lumen lined with material to prevent adsorption of the vector (e.g., Smartflow cannulae, MRI Interventions cannulae). Delivery device interfaces with syringes and automated infusion or microinfusion pumps with preprogrammed infusion rates and volumes. The syringe/needle combination or just the needle may be interfaced directly with the stereotactic frame. Infusion may include constant flow rate or varying rates with convection enhanced delivery. The vector may be administered at a single point in time. For example, a single injection may be given with no repeat 12 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 administrations. Combination therapies are also contemplated by the disclosure. Combinations of methods of the disclosure with standard medical treatments (e.g., corticosteroids or topical pressure reducing medications) are specifically contemplated, as are combinations with novel therapies. For example, the present disclosure also includes combination treatment with an antiparkinsonian therapy, e.g., leveodopa. In some cases, a subject may be treated with a steroid to prevent or to reduce an immune response to administration of the vector described herein. The term “codon” as used herein refers to any group of three consecutive nucleotide bases in a given messenger RNA molecule, or coding strand of DNA, that specifies a particular amino acid or a starting or stopping signal for translation. The term codon also refers to base triplets in a DNA strand. As used herein, “codon optimization” refers a process of modifying a nucleic acid sequence in accordance with the principle that the frequency of occurrence of synonymous codons (e.g., codons that code for the same amino acid) in coding DNA is biased in different species. Such codon degeneracy allows an identical polypeptide to be encoded by a variety of nucleotide sequences. Sequences modified in this way are referred to herein as “codon-optimized.” This process may be performed on any of the sequences described in this specification to enhance expression or stability. Codon optimization may be performed in a manner such as that described in, e.g., U.S. Patent Nos.7,561,972, 7,561,973, and 7,888,112, each of which is incorporated herein by reference in its entirety. The sequence surrounding the translational start site can be converted to a consensus Kozak sequence according to known methods. See, e.g., Kozak et al, Nucleic Acids Res.15 (20): 8125-8148, incorporated herein by reference in its entirety. Multiple stop codons can be incorporated. Throughout this specification and claims, the word “comprise,” or variations such as “comprises” or “comprising,” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. As used herein, the terms “conservative mutation,” “conservative substitution,” and “conservative amino acid substitution” refer to a substitution of one or more amino acids for one or more different amino acids that exhibit similar physicochemical properties, such as polarity, electrostatic charge, and steric volume. These properties are summarized for each of the twenty naturally-occurring amino acids in table 1 below. Table 1. Representative physicochemical properties of naturally-occurring amino acids Electrostatic Side- 3 Letter 1 Letter character at Steric Amino Acid chain Code Code physiological pH Volume^† Polarity (7.4) Alanine Ala A nonpolar neutral small Arginine Arg R polar cationic large Asparagine Asn N polar neutral intermediate Aspartic acid Asp D polar anionic intermediate Cysteine Cys C nonpolar neutral intermediate Glutamic acid Glu E polar anionic intermediate Glutamine Gln Q polar neutral intermediate 13 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Electrostatic Side- 3 Letter 1 Letter character at Steric Amino Acid chain Code Code physiological pH Volume^† Polarity (7.4) Glycine Gly G nonpolar neutral small Both neutral and Histidine His H polar cationic forms in large equilibrium at pH 7.4 Isoleucine Ile I nonpolar neutral large Leucine Leu L nonpolar neutral large Lysine Lys K polar cationic large Methionine Met M nonpolar neutral large Phenylalanine Phe F nonpolar neutral large non- Proline Pro P neutral intermediate polar Serine Ser S polar neutral small Threonine Thr T polar neutral intermediate Tryptophan Trp W nonpolar neutral bulky Tyrosine Tyr Y polar neutral large Valine Val V nonpolar neutral intermediate †based on volume in A³: 50-100 is small, 100-150 is intermediate, 150-200 is large, and >200 is bulky From this table it is appreciated that the conservative amino acid families include (i) G, A, V, L and I; (ii) D and E; (iii) C, S and T; (iv) H, K and R; (v) N and Q; and (vi) F, Y and W. A conservative mutation or substitution is therefore one that substitutes one amino acid for a member of the same amino acid family (e.g., a substitution of Ser for Thr or Lys for Arg). As used herein, the terms “effective amount,” “therapeutically effective amount,” and a “sufficient amount” of composition, vector construct, or viral vector described herein refer to a quantity sufficient to, when administered to the subject, including a mammal, for example a human, effect beneficial or desired results, including clinical results, and, as such, an “effective amount” or synonym thereto depends upon the context in which it is being applied. For example, in the context of treating Parkinson’s disease (PD), it is an amount of the composition, vector construct, or viral vector sufficient to achieve a treatment response as compared to the response obtained without administration of the composition, vector construct, or viral vector. The amount of a given composition described herein that will correspond to such an amount will vary depending upon various factors, such as the given agent, the pharmaceutical formulation, the route of administration, the type of disease or disorder, the identity of the subject (e.g., age, sex, weight) or host being treated, and the like, but can nevertheless be routinely determined by one skilled in the art. Also, as used herein, a “therapeutically effective amount” of a composition, vector construct, or viral vector of the present disclosure is an amount which results in a beneficial or desired result in a subject as compared to a control. As defined herein, a therapeutically effective amount of a 14 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 composition, vector construct, or viral vector of the present disclosure may be readily determined by one of ordinary skill by routine methods known in the art. Dosage regime may be adjusted to provide the optimum therapeutic response. As used herein, the term “endogenous” describes a molecule (e.g., a polypeptide, nucleic acid, or cofactor) that is found naturally in a particular organism (e.g., a human) or in a particular location within an organism (e.g., an organ, a tissue, or a cell, such as a human cell). As used herein, the terms “express” and “expression” refer to one or more of the following events: (1) production of an RNA template from a DNA sequence (e.g., by transcription); (2) processing of an RNA transcript (e.g., by splicing, editing, 5^ cap formation, and/or 3^ end processing); (3) translation of an RNA into a polypeptide or protein; and (4) post-translational modification of a polypeptide or protein. Expression of a gene of interest in a subject can manifest, for example, by detecting: an increase in the quantity or concentration of mRNA encoding a corresponding protein (as assessed, e.g., using RNA detection procedures described herein or known in the art, such as quantitative polymerase chain reaction (qPCR) and RNA seq techniques), an increase in the quantity or concentration of a corresponding protein (as assessed, e.g., using protein detection methods described herein or known in the art, such as enzyme-linked immunosorbent assays (ELISA), among others), and/or an increase in the activity of a corresponding protein (e.g., in the case of an enzyme, as assessed using an enzymatic activity assay described herein or known in the art) in a sample obtained from the subject. As used herein in the context of a protein of interest, the term “activity” refers to the biological functionality that is associated with a wild-type form of the protein. For example, in the context of the DAT protein, activity refers to its normal biological activity in regions of the brain like the substantia nigra pars compacta. As used herein, the term “deficient” refers to insufficient expression or the absence of normal levels of biological activity of a protein or gene. For example, in the context of the DAT protein, deficient means the protein is insufficiently expressed or not expressed or not functioning optimally in regions of the brain like the substantia nigra pars compacta. As used herein, the term “mutation” refers to a change in the nucleotide sequence of a gene (e.g., SLC6A3) or a change in the polypeptide sequence of a protein (e.g., DAT). Mutations in a gene or protein may occur naturally as a result of, for example, errors in DNA replication, DNA repair, irradiation, and exposure to carcinogens or mutations may be induced as a result of administration of a transgene expressing a mutant gene. Mutations may result from single or multiple nucleotide insertions, deletions, or substitutions. As used herein, the terms “neurodegenerative disorder” and “neurodegenerative disease” refer interchangeably to a disorder characterized by progressive loss of the number (e.g., by cell death), structure, and/or function of neurons. In some instances, a neurocognitive or a neuromuscular disorder (e.g., a neurodegenerative disease) may be associated with genetic defects (e.g., a mutation in the SLC6A3 gene, for example a “c.1857G>C” single nucleotide substitution in exon 15 of SLC6A3) protein misfolding, defects in protein degradation, programmed cell death, membrane damage, or other processes. Exemplary, non-limiting neurodegenerative disorders include frontotemporal disorders (FTD), Alzheimer’s disease (AD), PD, dementia with Lewy bodies, amyotrophic lateral sclerosis (ALS), Lou Gehrig's disease, motor neuron disease (MND), progressive bulbar palsy (PBP), progressive muscular 15 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 atrophy (PMA), primary lateral sclerosis (PLS), bulbar onset ALS, spinal onset ALS and ALS with multi- system involvement, and a related motor neuron disorder. As used herein, the term “neuromuscular disorder” refers to a disease impairing the ability of one or more neurons to control the activity of an associated muscle. Examples of neuromuscular disorders are PD, ALS, congenital myasthenic syndrome, congenital myopathy, cramp fasciculation syndrome, Duchenne muscular dystrophy, glycogen storage disease type II, hereditary spastic paraplegia, inclusion body myositis, Isaac's Syndrome, Kearns-Sayre syndrome, Lambert–Eaton myasthenic syndrome, mitochondrial myopathy, muscular dystrophy, myasthenia gravis, myotonic dystrophy, peripheral neuropathy, spinal and bulbar muscular atrophy, spinal muscular atrophy, Stiff person syndrome, Troyer syndrome, and Guillain–Barré syndrome, among others. It is to be understood that the above lists are not all-inclusive, and that a disorder or disease may fall within various categories. For example, AD can be considered a neurocognitive disorder, and a neurodegenerative disease. Likewise, PD can be considered a neuromuscular disorder and a neurodegenerative disease. As used herein, the terms “Parkinson's disease” and “PD” refer to a neurodegenerative disease characterized by motor and non-motor symptoms. Symptoms mainly include bradykinesia, tremors, resting tremors, rigidity, postural instability, dyskinesias, lack of motor coordination, balance impairment, hypotonia, stiffness and progression, where exercise dyskinesia includes exercise-induced relaxation and even anemia. Non-motor symptoms include pain, constipation, delayed gastric emptying, anxiety, depression, and sleep disorders. As used herein, patients suffering from PD are those patients that have been diagnosed as having PD, wherein optionally the patients have been diagnosed as having idiopathic PD. Mutations that patients with PD might have include I312F and K619N mutations in the DAT protein or mutations in the C- terminus of the DAT protein. Patients with PD might have monoallelic missense mutations such as the K619N mutation wherein the patient can inherit the mutant allele from a parent, wherein optionally, the mutant allele can be paternally transmitted. Mutations that patients with juvenile PD might have include a A314V mutation in the DAT protein. Mutations that patients with infantile dystonia-Parkinsonism might have include one or more mutations in the DAT protein selected from R521W, R219S, Y343X, L224P, L368Q, P395L, Y470Sfs, p.I134SfsX5, p.G500EfsX13, p.G380_K384 delinse, and Q439X. Patients with PD can have genotype GG and allele G of the promoter single nucleotide polymorphism rs2652510. Patients with PD can have 9 to 10 repeat alleles of a 40 bp variable number tandem repeat (VNTR) in the 3’-UTR of the SLC6A3 gene. As used herein, the terms “Dopamine Transporter” and “DAT” refer to the DAT protein encoded by the SLC6A3 gene responsible for the re-uptake of released dopamine (DA) from the synaptic cleft in pre-synaptic midbrain dopaminergic neurons where it is highly expressed. DAT is a key regulator of the amplitude and duration of dopaminergic transmission. The term SLC6A3 refers to variants of wild-type SLC6A3 (e.g., GenBank: D88570.2) and nucleic acids encoding the same, such as variant proteins having at least 85% sequence identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the amino acid sequence of a wild-type DAT protein (e.g., SEQ ID NO: 3) or polynucleotides having at least 85% sequence identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of a wild-type SLC6A3 gene (e.g., SEQ ID NO: 2), provided that 16 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 the DAT analog encoded retains the therapeutic function of wild-type DAT (e.g., NCBI Reference Sequence: NP_001035.1). The term SLC6A3 may also refer to codon-optimized polynucleotides encoding DAT, such as codon-optimized polynucleotides having at least 85% sequence identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 2. As used herein, the term “functional,” with respect to a gene, refers to a functional gene product, for example, a functional DAT protein. A gene product is functional if it fulfills its normal (wild-type) functions. Disruption of the gene prevents expression of a functional factor encoded by the gene and contains an insertion, deletion, or substitution of one or more bases in a sequence encoded by the gene and/or a promoter and/or an operator that is necessary for expression of the gene in the animal. As used herein, the term “plasmid” refers to an extrachromosomal circular double stranded DNA molecule into which additional DNA segments may be ligated. A plasmid is a type of vector, a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. Certain plasmids are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial plasmids having a bacterial origin of replication and episomal mammalian plasmids). Other vectors (e.g., non-episomal mammalian vectors) can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Certain plasmids are capable of directing the expression of genes to which they are operably linked. As used herein, the term "promoter" refers to a recognition site on DNA that is bound by an RNA polymerase. The polymerase drives transcription of the transgene. Exemplary promoters suitable for use with the compositions and methods described herein include a synapsin 1 promoter, a CAG promoter, a cytomegalovirus (CMV) promoter, a calcium/calmodulin-dependent protein kinase II (CAMKII) promoter, a beta-actin promoter, and a human eukaryotic translation elongation factor 1 ^ (EF1- ^) promoter. A synapsin 1 promoter includes any promoter comprising a functional portion of the synapsin 1 gene. For example, the promoter may be a human synapsin 1 (hSYN1) promoter, a human synapsin 1 with 5’ extension promoter, a human synapsin 1 with 3’ extension promoter, an enhanced synapsin (eSYN) promoter or a truncated human synapsin 1 promoter. As used herein, the term “synapsin 1 promoter” refers to the nucleic acid set forth in SEQ ID NO: 1, as well as nucleic acids having at least 85% identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 1 and that promote the expression of a transgene in a cell (e.g., a eukaryotic cell, such as a mammalian cell, human cell, or human muscle cell) when the transgene is operably linked to the enhancer. The promoter comprising a functional portion of the human synapsin 1 gene may additionally comprise an enhancer element, which may be any enhancer element. For example, the eSYN promoter is a hybrid promoter containing the human synapsin 1 promoter and a CMV enhancer. A beta-actin promoter includes any functional promoter comprising a functional portion of the beta-actin gene. The beta-actin promoter may be a human beta-actin promoter or a chicken beta-actin promoter. The promoter comprising a functional portion of the beta-actin gene may additionally comprise an enhancer element, which may be any enhancer element. For example, the promoter may be a CAG promoter, which comprises the CMV early enhancer element, the promoter, first exon and first intron of chicken beta-actin gene and the splice acceptor or the rabbit beta-globin gene. A CMV promoter may be a human CMV 17 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 major immediate early promoter or a super CMV promoter. A CAMKII promoter may be an ^-CAMKII promoter. Exemplary promoters suitable for use with the compositions and methods described herein include a neuron-specific promoter. For example, neuron-specific promoters include human synapsin 1 promoter and CAMKII promoter. The promoter can be a neuron-specific promoter selected from a human synapsin 1 promoter and a CAMKII promoter. The promoter can be a neuron-specific promoter selected from an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter, a truncated hSYN1 promoter and an ^-CAMKII promoter. The promoter can be a human synapsin 1 promoter. The promoter can be an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter or a truncated hSYN1 promoter. The promoter can be a dopaminergic neuron-specific promoter. As used herein, the term “operably linked” refers to a first molecule joined to a second molecule, wherein the molecules are so arranged that the first molecule affects the function of the second molecule. The two molecules may or may not be part of a single contiguous molecule and may or may not be adjacent. For example, a promoter is operably linked to a transcribable polynucleotide molecule if the promoter modulates transcription of the transcribable polynucleotide molecule of interest in a cell. Additionally, two portions of a transcription regulatory element are operably linked to one another if they are joined such that the transcription-activating functionality of one portion is not adversely affected by the presence of the other portion. Two transcription regulatory elements may be operably linked to one another by way of a linker nucleic acid (e.g., an intervening non-coding nucleic acid) or may be operably linked to one another with no intervening nucleotides present. As used herein, the term “transcription regulatory element” refers to a nucleic acid that controls, at least in part, the transcription of a gene of interest. Transcription regulatory elements may include promoters, enhancers, and other nucleic acids (e.g., polyadenylation signals) that control or help to control gene transcription. Examples of transcription regulatory elements are described, for example, in Goeddel, Gene Expression Technology: Methods in Enzymology 185 (Academic Press, San Diego, CA, 1990). As used herein, the term “woodchuck hepatitis virus (WHV) posttranscriptional regulatory element” or “WPRE” refers to a DNA sequence, which when transcribed, creates a tertiary structure enhancing expression. The AAV vector used in the methods and compositions described herein may include a WPRE. The WPRE acts at the transcriptional level, by promoting nuclear export of transcripts and/or by increasing the efficiency of polyadenylation of the nascent transcript, thus increasing the total amount of mRNA in the cells. The addition of the WPRE to the AAV vector results in a substantial improvement in the level of transgene expression from several different promoters, both in vitro and in vivo. As used herein, the term “WPRE” refers to the nucleic acid set forth in SEQ ID NO: 4, as well as nucleic acids having at least 85% identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 4 and that promote the expression of a transgene in a cell (e.g., a eukaryotic cell, such as a mammalian cell, human cell, or human muscle cell) when the transgene is operably linked to the enhancer. 18 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 “Percent (%) sequence identity,” with respect to a reference polynucleotide or polypeptide sequence, is defined as the percentage of nucleic acids or amino acids in a candidate sequence that are identical to the nucleic acids or amino acids in the reference polynucleotide or polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity. Alignment for purposes of determining percent nucleic acid or amino acid sequence identity can be achieved in various ways that are within the capabilities of one of skill in the art, for example, using publicly available computer software such as BLAST, BLAST-2, or Megalign software. Those skilled in the art can determine appropriate parameters for aligning sequences, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. For example, percent sequence identity values may be generated using the sequence comparison computer program BLAST. As an illustration, the percent sequence identity of a given nucleic acid or amino acid sequence, A, to, with, or against a given nucleic acid or amino acid sequence, B, (which can alternatively be phrased as a given nucleic acid or amino acid sequence, A that has a certain percent sequence identity to, with, or against a given nucleic acid or amino acid sequence, B) is calculated as follows: 100 multiplied by (the fraction X/Y) where X is the number of nucleotides or amino acids scored as identical matches by a sequence alignment program (e.g., BLAST) in that program’s alignment of A and B, and where Y is the total number of nucleic acids in B. It will be appreciated that where the length of nucleic acid or amino acid sequence A is not equal to the length of nucleic acid or amino acid sequence B, the percent sequence identity of A to B will not equal the percent sequence identity of B to A. As used herein, the term “pharmaceutically acceptable” refers to those compounds, materials, compositions and/or dosage forms, which are suitable for contact with the tissues of a subject, such as a mammal (e.g., a human) without excessive toxicity, irritation, allergic response, and other problem complications commensurate with a reasonable benefit/risk ratio. As used herein, the term “regulatory sequence” includes promoters, enhancers, and other expression control elements (e.g., polyadenylation signals) that control the transcription or translation of the antibody chain genes. Such regulatory sequences are described, for example, in Goeddel, Gene Expression Technology: Methods in Enzymology 185 (Academic Press, San Diego, CA, (1990)); incorporated herein by reference. As used herein, the term “sample” refers to a specimen (e.g., blood, blood component (e.g., serum or plasma), urine, saliva, amniotic fluid, cerebrospinal fluid, tissue (e.g., placental, or dermal), pancreatic fluid, chorionic villus sample, and cells) isolated from a subject. As used herein, the term “transfection” refers to any of a wide variety of techniques commonly used for the introduction of exogenous DNA into a prokaryotic or eukaryotic host cell, e.g., electroporation, lipofection, calcium- phosphate precipitation, DEAE- dextran transfection, Nucleofection, squeeze-poration, sonoporation, optical transfection, Magnetofection, impalefection, and the like. As used herein, the term “transgene” refers to a recombinant nucleic acid (e.g., DNA or cDNA such as the SLC6A3 transgene) encoding a gene product (e.g., DAT). The gene product may be an RNA, peptide, or protein. In addition to the coding region for the gene product, the transgene may include or be operably linked to one or more elements to facilitate or enhance expression, such as a promoter, 19 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 enhancer(s), destabilizing domain(s), response element(s), reporter element(s), insulator element(s), polyadenylation signal(s) and/or other functional elements. Embodiments of the disclosure may utilize any known suitable promoter, enhancer(s), destabilizing domain(s), response element(s), reporter element(s), insulator element(s), polyadenylation signal(s), and/or other functional elements. As used herein, the terms “subject” and “patient” refer to an animal (e.g., a mammal, such as a human). A subject to be treated according to the methods described herein may be one who has been diagnosed with PD or idiopathic PD, or one at risk of developing these conditions. Diagnosis may be performed by any method or technique known in the art. One skilled in the art will understand that a subject to be treated according to the present disclosure may have been subjected to standard tests or may have been identified, without examination, as one at risk due to the presence of one or more risk factors associated with the disease or condition. As used herein, the terms "transduction" and “transduce” refer to a method of introducing a vector construct or a part thereof into a cell. Wherein the vector construct is contained in a viral vector such as for example a lentiviral vector, transduction refers to viral infection of the cell, and subsequent transfer and integration of the vector construct or part thereof into the cell genome. As used herein, “treatment” and “treating” in reference to a disease or condition, refer to an approach for obtaining beneficial or desired results, e.g., clinical results. Beneficial or desired results can include, but are not limited to, alleviation or amelioration of one or more symptoms or conditions; diminishment of extent of disease or condition; stabilized (i.e., not worsening) state of disease, disorder, or condition; preventing spread of disease or condition; delay or slowing the progress of the disease or condition; amelioration or palliation of the disease or condition; and remission (whether partial or total), whether detectable or undetectable. “Ameliorating” or “palliating” a disease or condition means that the extent and/or undesirable clinical manifestations of the disease, disorder, or condition are lessened and/or time course of the progression is slowed or lengthened, as compared to the extent or time course in the absence of treatment. “Treatment” can also mean prolonging survival as compared to expected survival if not receiving treatment. Those in need of treatment include those already with the condition or disorder, as well as those prone to have the condition or disorder or those in which the condition or disorder is to be prevented. In some embodiments, treatment with the compositions and methods of the disclosure which includes an AAV vector, expressing an SLC6A3 transgene can be assessed by evaluating the change in the patient’s responsiveness to existing medication. One indication of successful treatment can be increased and/or prolonged responsiveness to levodopa. Another indication of successful treatment can be reduced dependency on levodopa. As used herein, the term “responsive” refers to the ability of a patient or subject to exhibit an improvement in disease symptoms following treatment. For example, a patient with PD maybe responsive to levodopa. As used herein, the term “vector” includes a nucleic acid vector, e.g., a DNA vector, such as a plasmid, a RNA vector, virus, or other suitable replicon (e.g., viral vector). A variety of vectors have been developed for the delivery of polynucleotides encoding exogenous proteins into a prokaryotic or eukaryotic cell. Examples of such expression vectors are disclosed in, e.g., WO 1994/011026; incorporated herein by reference as it pertains to vectors suitable for the expression of a gene of interest. Expression vectors suitable for use with the compositions and methods described herein contain a 20 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 polynucleotide sequence as well as, e.g., additional sequence elements used for the expression of proteins and/or the integration of these polynucleotide sequences into the genome of a mammalian cell. Certain vectors that can be used for the expression of an SLC6A3 transgene as described herein include plasmids that contain regulatory sequences, such as promoter and enhancer regions, which direct gene transcription. Other useful vectors for expression of an SLC6A3 transgene contain polynucleotide sequences that enhance the rate of translation of these genes or improve the stability or nuclear export of the mRNA that results from gene transcription. These sequence elements include, e.g., 5’ and 3’ untranslated regions, an internal ribosomal entry site (IRES), and polyadenylation signal site in order to direct efficient transcription of the gene carried on the expression vector. The expression vectors suitable for use with the compositions and methods described herein may also contain a polynucleotide encoding a marker for selection of cells that contain such a vector. Examples of a suitable marker are genes that encode resistance to antibiotics, such as ampicillin, chloramphenicol, kanamycin, nourseothricin, or zeocin. As used herein, the term “IRES” refers to an internal ribosomal entry site. In general, an IRES sequence is a feature that allows eukaryotic ribosomes to bind an mRNA transcript and begin translation without binding to a 5^ capped end. An mRNA containing an IRES sequence produces two translation products, one initiating form the 5’ end of the mRNA and the other from an internal translation mechanism mediated by the IRES. As used herein, the terms “adeno-associated virus” and “AAV” include, but are not limited to, AAV type 1, AAV type 2, AAV type 3 (including types 3A and 3B), AAV type 4, AAV type 5, AAV type 6, AAV type 7, AAV type 8, AAV type 9, AAV type 10, AAV type 11, AAV type 12, AAV type 13, snake AAV, avian AAV, bovine AAV, canine AAV, equine AAV, ovine AAV, goat AAV, shrimp AAV, and any other AAV now known or later discovered. See, e.g., Fields et al. Virology, 4^th ed. Lippincott-Raven Publishers, Philadelphia, 1996. Additional AAV serotypes and clades have been identified recently. (See, e.g., Gao et al. J. Virol.78:6381 (2004); Moris et al. Virol.33:375 (2004). The genomic sequences of various serotypes of AAV, as well as the sequences of the native inverted terminal repeats (ITRs), Rep proteins, and capsid subunits are known in the art. Such sequences may be found in the literature or in public databases such as GenBank. See, e.g., GenBank Accession Numbers NC—002077, NC—001401, NC—001729, NC—001863, NC—001829, NC—001862, NC—000883, NC—001701, NC—001510, NC—006152, NC—006261, AF063497, U89790, AF043303, AF028705, AF028704, J02275, J01901, J02275, X01457, AF288061, AH009962, AY028226, AY028223, AY631966, AX753250, EU285562, NC—001358, NC—001540, AF513851, AF513852 and AY530579; the disclosures of which are incorporated by reference herein for teaching AAV nucleic acid and amino acid sequences. See also, e.g., Bantel-Schaal et al. J. Virol.73:939 (1999); Chiorini et al. J. Virol.71:6823 (1997); Chiorini et al. J. Virol.73:1309 (1999); Gao et al. Proc. Nat. Acad. Sci. USA 99:11854 (2002); Moris et al. Virol.33:375 (2004); Muramatsu et al. Virol.221:208 (1996); Ruffing et al. J. Gen. Virol.75:3385 (1994); Rutledge et al. J. Virol.72:309 (1998); Schmidt et al. J. Virol.82:8911 (2008); Shade et al. J. Virol.58:921 (1986); Srivastava et al. J. Virol.45:555 (1983); Xiao et al. J. Virol.73:3994 (1999); WO 00/28061, WO 99/61601, WO 98/11244; and US 6,156,303; the disclosures of which are incorporated by reference herein for teaching AAV nucleic acid and amino acid sequences. As used herein, the term “AAV” encompasses an anterogradely-trafficked AAV and/or a retrogradely-trafficked AAV. 21 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 As used herein, the term “AAV” refers to the nucleic acid set forth in SEQ ID NO: 5, as well as nucleic acids having at least 85% identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 5 and that promote the expression of a transgene in a cell (e.g., a eukaryotic cell, such as a mammalian cell, human cell, or human muscle cell) when the transgene is operably linked to the enhancer. “Rep proteins” are proteins which fill capsids with a polynucleotide molecule (e.g., viral DNA) into a capsid. In addition, a Rep protein may enable nucleic acid molecule replication, transcriptional regulation of a nucleic acid molecule, and/or site-specific integration (e.g., chromosomal integration) of a nucleic acid molecule. The Rep protein may be from any parvovirus. As one of skill in the art will appreciate, in some parvovirus family virus species, a Rep protein is referred to as a “non-structural (NS) protein”. As used herein, a Rep protein may refer to a NS protein. As used herein, a Rep protein may refer to an AAV Rep protein, which have been found in all AAV serotypes examined to date, and a synthetic Rep protein. For example, in some embodiments, a AAV Rep protein (e.g., AAV Rep40, AAV Rep52, AAV Rep68, and AAV Rep78) is a capsid protein having an amino acid sequence derived from a particular AAV serotype, for example AAV type 1, AAV type 2, AAV type 3 (including types 3A and 3B), AAV type 4, AAV type 5, AAV type 6, AAV type 7, AAV type 8, AAV type 9, AAV type 10, AAV type 11, AAV type 12, AAV type 13, avian AAV, bovine AAV, canine AAV, goat AAV, snake AAV, equine AAV, and ovine AAV. Alternatively, for example, as used herein, a Rep protein may include a synthetic Rep protein. Any suitable Rep protein may be used. As used herein, the term “viral capsid protein” refers to a capsid protein composing a proteinaceous shell. Such a proteinaceous shell is generally composed of one or more viral capsid proteins and when assembled is capable of being loaded with one or more polynucleotide molecules. A viral capsid protein described herein may, for example, be a viral protein (VP) 1, VP2, and VP3. Further, a viral capsid protein described herein may refer to a synthetic protein or a viral capsid protein from Parvoviridae (e.g., an AAV). As used herein, the term “same capsid species” refers to a population of capsids having the same defined stoichiometry of viral capsid protein components, which may include one or more of VP1, VP2, and VP3. As used herein, the terms “viral protein 1” and “VP1” refer to any capsid protein that is a component of a capsid, for example, a parvovirus (e.g., AAV) capsid particle. As used herein, a VP1 may possess a surface binding site that interacts with one or more molecules on the surface of a cell to initiate the process of cell entry (e.g., endocytic entry and receptor-mediated fusion). As used herein, a VP1 may self-assemble into a structure consisting of VP1, VP2, and/or VP3 molecules. VP1 may exhibit self- binding properties and self-assemble around the exterior of a respective VP1-containing capsid. As used herein, a VP1 may be synthetic or a VP1 derived from Parvoviridae (e.g., an AAV). For example, a VP1 derived from an AAV may be a VP1 derived from AAV type 1, AAV type 2, AAV type 3, AAV type 4, AAV type 5, AAV type 6, AAV type 7, AAV type 8, AAV type 9, AAV type 10, AAV type 11, AAV type 12, AAV type 13, avian AAV, bovine AAV, canine AAV, goat AAV, snake AAV, equine AAV, ovine AAV, goat AAV, shrimp AAV, or any other AAV now known and later discovered. 22 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 As used herein, the terms “viral protein 2” and “VP2” refer to any capsid protein that is a component of a capsid, for example, a parvovirus (e.g., AAV) capsid particle. As used herein, a VP2 may facilitate capsid entry into a host cell, for example, by mediating associations with and exit from the endoplasmic reticulum of a host cell and by facilitating the entry of a nucleic acid molecule into a host cell nucleus. As used herein, a VP2 may self-assemble into a structure consisting of VP1, VP2, and/or VP3 molecules. VP2 may self-assemble within the interior of a respective VP2-containing capsid. As used herein, a VP2 may be synthetic or a VP2 derived from Parvoviridae (e.g., an AAV). For example, a VP2 derived from an AAV may be a VP2 derived from AAV type 1, AAV type 2, AAV type 3, AAV type 4, AAV type 5, AAV type 6, AAV type 7, AAV type 8, AAV type 9, AAV type 10, AAV type 11, AAV type 12, AAV type 13, avian AAV, bovine AAV, canine AAV, goat AAV, snake AAV, equine AAV, ovine AAV, goat AAV, shrimp AAV, or any other AAV now known and later discovered. As used herein, the terms “viral protein 3” and “VP3” refer to any capsid protein that is a component of a capsid, for example, a parvovirus (e.g., AAV) capsid particle. As used herein, a VP3 may facilitate capsid entry into a host cell, for example, by mediating associations with and exit from the endoplasmic reticulum of a host cell and by facilitating the entry of a nucleic acid molecule into a host cell nucleus. As used herein, a VP3 may self-assemble into a structure consisting of VP1, VP2, and/or VP3 molecules. VP3 may self-assemble within the interior of a respective VP3-containing capsid. As used herein, a VP3 may be synthetic or a VP3 derived from Parvoviridae (e.g., an AAV). For example, a VP3 derived from an AAV may be a VP3 derived from AAV type 1, AAV type 2, AAV type 3, AAV type 4, AAV type 5, AAV type 6, AAV type 7, AAV type 8, AAV type 9, AAV type 10, AAV type 11, AAV type 12, AAV type 13, avian AAV, bovine AAV, canine AAV, goat AAV, snake AAV, equine AAV, ovine AAV, goat AAV, shrimp AAV, or any other AAV now known and later discovered. As used herein, the terms “encapsidation,” “encapsulating,” “encapsidate,” and the like refer to non-enzymatically driven encasing of nucleic acid molecules in a capsid shell. Thus, when a suitable population of viral capsid proteins (e.g., VP1, VP2, and/or VP3) and conditions are combined with a nucleic acid molecule, the nucleic acid molecule can be encapsidated by the capsid to form an assembled capsid particle packaged with one or more nucleic acid molecules. The encapsidation process may occur simultaneously with capsid assembly or after capsid assembly is complete. An “ITR” is a palindromic nucleic acid, e.g., an inverted terminal repeat, that is about 120 nucleotides to about 250 nucleotides in length and capable of forming a hairpin. The term “ITR” includes the site of the viral genome replication that can be recognized and bound by a parvoviral protein (e.g., Rep78/68). An ITR may be from any AAV, with serotype 2 being preferred. An ITR includes a replication protein binding element (RBE) and a terminal resolution sequence (TRS). The term “ITR” does not require a wild-type parvoviral ITR (e.g., a wild-type nucleic acid sequence may be altered by insertion, deletion, truncation, or missense mutations), as long as the ITR functions to mediate virus packaging, replication, integration, and/or provirus rescue, and the like. The “5’ ITR” is intended to mean the parvoviral ITR located at the 5’ boundary of the nucleic acid molecule; and the term “3’ ITR” is intended to mean the parvoviral ITR located at the 3’ boundary of the nucleic acid molecule. 23 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Detailed Description Described herein are compositions and methods for the treatment of Parkinson’s disease (PD) in a subject (such as a mammalian subject, for example, a human). Using the compositions and methods described herein, one can treat PD (e.g., idiopathic PD) in a subject (e.g., a human subject) by administering an adeno-associated viral (AAV) vector, comprising a solute carrier family 6 member 3 (SLC6A3) transgene or an AAV vector that expresses a transgene encoding the Dopamine Transporter (DAT) protein. For example, described herein are compositions containing an AAV vector, comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein. The sections that follow describe the compositions and methods useful for the treatment of PD in further detail. Parkinson’s Disease PD is a progressive disorder that affects movement, and it is recognized as the second most common neurodegenerative disease after Alzheimer’s disease. Common symptoms of PD include resting tremor, tremor, postural instability, lack of motor coordination, balance impairment, rigidity, and bradykinesia, and non-motor symptoms, such as depression, anxiety, constipation, pain, sleep disorders, genitourinary problems, cognitive decline, and olfactory dysfunction, are also increasingly being associated with PD. A key feature of PD is the death of dopaminergic neurons in the substantia nigra pars compacta, and, for that reason, most current treatments for PD focus on increasing dopamine. Another well-known neuropathological hallmark of PD is the presence of Lewy bodies containing ^- synuclein in brain regions affected by PD, which are thought to contribute to the disease. Parkinsonian hypokinetic symptoms are generated because of the underactivity of the external segment of the globus pallidus in association with striatal dopaminergic dysfunction and overactivity of the subthalamus. There is also accumulating evidence that neuroinflammation is likely to play a critical role in PD with increased microgria activation and significant elevation of inflammatory cytokines such as such interleukin-1B (IL-1B), interleukin-6 (IL-6), and tumor necrosis factor (TNF) detected in the blood and cerebrospinal fluid (CSF) of PD patients. PD is thought to result from a combination of genetic and environmental risk factors. There is no single gene responsible for all PD cases, and the vast majority of PD cases seem to be sporadic and not directly inherited. Mutations in the genes encoding parkin, phosphatase and tensin homolog (PTEN)- induced putative kinase 1 (PINK1), leucine-rich repeat kinase 2 (LRRK2), and Parkinsonism-associated deglycase (DJ-1) have been found to be associated with PD, but they represent only a small subset of the total number of PD cases. Occupational exposure to some pesticides and herbicides has also been proposed as a risk factor for PD. The synthetic neurotoxin (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) MPTP can cause Parkinsonism, but its use is extremely rare. Treatments for PD have long focused on the replenishing of dopamine. Unlike these treatments, which have only treated a symptom of the disease, the compositions and methods described herein provide the benefit of treating a different biochemical phenomenon that can underlie the development of PD. As such, the compositions and methods described herein target the physiological cause of the disease, representing a potential curative therapy. The compositions and methods described herein can be used to treat PD by administering an AAV vector, comprising a solute carrier family 6 member 3 (SLC6A3) transgene or an AAV vector that expresses a transgene encoding the DAT protein. These compositions and methods can be used to treat 24 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 PD with any etiology, e.g., genetic mutation, environmental toxin, or sporadic. In some embodiments, a patient with PD has one or more symptoms of a condition selected from PD, juvenile PD, infantile dystonia-Parkinsonism, dystonia, unclassified movement disorders, unspecified personality disorder with evasive and schizophrenic traits, hemiparkinsonism, adult early-onset Parkinsonism, and comorbid neuropsychiatric disease. In some embodiments, a patient with PD has one or more symptoms selected from hand tremors, evasive and schizophrenic traits, self-injury, periodic depression, general bradykinesia, severe rigidity, resting and intention tremor of the upper extremities without consistent sidedness of symptoms, Parkinsonian gait with small shuffling steps, kyphosis, severe difficulties in turning around, postural instability, spontaneous falling, and severe hypomimia. In some embodiments, a patient with PD has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. In some embodiments, a patient with PD or a PD-linked mutation has one or more characterizations selected from dysfunctional dopaminergic neurotransmission, progressive loss of DAT availability, small (2-4 mm) white matter lesions compared to age-matched controls, reduced DAT binding in striatum (caudate nucleus and putamen), dopaminergic cell loss, reduced DAT expression, loss of DAT binding, accelerated loss of [¹²³I]-FP-CIT binding compared to expected decline in age-matched controls, impaired dopamine (DA) uptake, dominant-negative impairments on DA uptake, impaired amphetamine-induced DA efflux, reduced surface expression of DAT, accelerated turnover of DAT leading to lower expression of active transporter, enhanced lysosomal degradation of DAT, and reduction in [³H]-CTF-binding capacity. In some embodiments, a patient with PD has mild to moderate Unified Parkinson's Disease Rating Scale (UPDRS) III OFF score less than 5 years after clinical PD diagnosis, and/or moderate to severe UPDRS OFF score after 4 or more years since clinical PD diagnosis. In some embodiments, a patient has been diagnosed with PD and is in the modified Hoehn and Yahr stage I-III OFF medication or the patient has had the disease for a duration of more than 5 years and is in the Hoehn and Yahr Stage III or IV off medication. In some embodiments, a patient with PD has motor complications despite adequate oral antiparkinsonian therapy. In some embodiments, a patient with PD is undergoing treatment with an additional antiparkinsonian therapy such as levodopa. In some embodiments, a patient with PD is responsive to levodopa. In some embodiments, a patient might be deficient in expression and/or activity of DAT protein. In some embodiments, the patient with idiopathic PD has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. In some embodiments, the patient with idiopathic PD has levodopa-induced dyskinesia (LID). In some embodiments, the patient with idiopathic PD is at risk of developing LID. In some embodiments, a patient with PD might have mutations. In some embodiments, a patient with PD can have a mutation in the SLC6A3 gene, for example a “c.1857G>C” single nucleotide substitution in exon 15 of SLC6A3. Mutations that patients with PD might have include I312F and K619N mutations in the DAT protein or mutations in the C-terminus of the DAT protein. Patients with PD might have monoallelic missense mutations such as the K619N mutation wherein the patient can inherit the mutant allele from a parent, wherein optionally, the mutant allele can be paternally transmitted. Mutations that patients with juvenile PD might have include a A314V mutation in the DAT protein. Mutations that patients with infantile dystonia-Parkinsonism might have include one or more mutations in the DAT protein selected from R521W, R219S, Y343X, L224P, L368Q, P395L, Y470Sfs, p.I134SfsX5, p.G500EfsX13, 25 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 p.G380_K384 delinse, and Q439X. Patients with PD can have genotype GG and allele G of the promoter single nucleotide polymorphism rs2652510. Patients with PD can have 9 to 10 repeat alleles of a 40 bp variable number tandem repeat (VNTR) in the 3’-UTR of the SLC6A3 gene. Expression of DAT Protein The compositions and methods described herein target these dysfunctions by administering an AAV vector, comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein. A wide array of methods has been established for the stable expression of genes encoding such proteins in mammalian cells. Exemplary SLC6A3 transgenes include those having the nucleic acid sequence of SEQ ID NO: 2. SEQ ID NO: 2 is shown below: ATGAGTAAGAGCAAATGCTCCGTGGGACTCATGTCTTCCGTGGTGGCCCCGGCTAAGGAGCCCAAT GCCGTGGGCCCGAAGGAGGTGGAGCTCATCCTTGTCAAGGAGCAGAACGGAGTGCAGCTCACCAG CTCCACCCTCACCAACCCGCGGCAGAGCCCCGTGGAGGCCCAGGATCGGGAGACCTGGGGCAAGA AGATCGACTTTCTCCTGTCCGTCATTGGCTTTGCTGTGGACCTGGCCAACGTCTGGCGGTTCCCCTA CCTGTGCTACAAAAATGGTGGCGGTGCCTTCCTGGTCCCCTACCTGCTCTTCATGGTCATTGCTGGG ATGCCACTTTTCTACATGGAGCTGGCCCTCGGCCAGTTCAACAGGGAAGGGGCCGCTGGTGTCTGG AAGATCTGCCCCATACTGAAAGGTGTGGGCTTCACGGTCATCCTCATCTCACTGTATGTCGGCTTCT TCTACAACGTCATCATCGCCTGGGCGCTGCACTATCTCTTCTCCTCCTTCACCACGGAGCTCCCCTG GATCCACTGCAACAACTCCTGGAACAGCCCCAACTGCTCGGATGCCCATCCTGGTGACTCCAGTGG AGACAGCTCGGGCCTCAACGACACTTTTGGGACCACACCTGCTGCCGAGTACTTTGAACGTGGCGT GCTGCACCTCCACCAGAGCCATGGCATCGACGACCTGGGGCCTCCGCGGTGGCAGCTCACAGCCT GCCTGGTGCTGGTCATCGTGCTGCTCTACTTCAGCCTCTGGAAGGGCGTGAAGACCTCAGGGAAGG TGGTATGGATCACAGCCACCATGCCATACGTGGTCCTCACTGCCCTGCTCCTGCGTGGGGTCACCC TCCCTGGAGCCATAGACGGCATCAGAGCATACCTGAGCGTTGACTTCTACCGGCTCTGCGAGGCGT CTGTTTGGATTGACGCGGCCACCCAGGTGTGCTTCTCCCTGGGCGTGGGGTTCGGGGTGCTGATC GCCTTCTCCAGCTACAACAAGTTCACCAACAACTGCTACAGGGACGCGATTGTCACCACCTCCATCA ACTCCCTGACGAGCTTCTCCTCCGGCTTCGTCGTCTTCTCCTTCCTGGGGTACATGGCACAGAAGCA CAGTGTGCCCATCGGGGACGTGGCCAAGGACGGGCCAGGGCTGATCTTCATCATCTACCCGGAAG CCATCGCCACGCTCCCTCTGTCCTCAGCCTGGGCCGTGGTCTTCTTCATCATGCTGCTCACCCTGG GTATCGACAGCGCCATGGGTGGTATGGAGTCAGTGATCACCGGGCTCATCGATGAGTTCCAGCTGC TGCACAGACACCGTGAGCTCTTCACGCTCTTCATCGTCCTGGCGACCTTCCTCCTGTCCCTGTTCTG CGTCACCAACGGTGGCATCTACGTCTTCACGCTCCTGGACCATTTTGCAGCCGGCACGTCCATCCTC TTTGGAGTGCTCATCGAAGCCATCGGAGTGGCCTGGTTCTATGGTGTTGGGCAGTTCAGCGACGAC ATCCAGCAGATGACCGGGCAGCGGCCCAGCCTGTACTGGCGGCTGTGCTGGAAGCTGGTCAGCCC CTGCTTTCTCCTGTTCGTGGTCGTGGTCAGCATTGTGACCTTCAGACCCCCCCACTACGGAGCCTAC ATCTTCCCCGACTGGGCCAACGCGCTGGGCTGGGTCATCGCCACATCCTCCATGGCCATGGTGCCC ATCTATGCGGCCTACAAGTTCTGCAGCCTGCCTGGGTCCTTTCGAGAGAAACTGGCCTACGCCATTG CACCCGAGAAGGACCGTGAGCTGGTGGACAGAGGGGAGGTGCGCCAGTTCACGCTCCGCCACTGG CTCAAGGTGTAG 26 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Exemplary DAT proteins include those having the amino acid sequence of SEQ ID NO: 3. SEQ ID NO: 3 is shown below: MSKSKCSVGLMSSVVAPAKEPNAVGPKEVELILVKEQNGVQLTSSTLTNPRQSPVEAQDRETWGKKIDF LLSVIGFAVDLANVWRFPYLCYKNGGGAFLVPYLLFMVIAGMPLFYMELALGQFNREGAAGVWKICPILK GVGFTVILISLYVGFFYNVIIAWALHYLFSSFTTELPWIHCNNSWNSPNCSDAHPGDSSGDSSGLNDTFGT TPAAEYFERGVLHLHQSHGIDDLGPPRWQLTACLVLVIVLLYFSLWKGVKTSGKVVWITATMPYVVLTALL LRGVTLPGAIDGIRAYLSVDFYRLCEASVWIDAATQVCFSLGVGFGVLIAFSSYNKFTNNCYRDAIVTTSIN SLTSFSSGFVVFSFLGYMAQKHSVPIGDVAKDGPGLIFIIYPEAIATLPLSSAWAVVFFIMLLTLGIDSAMGG MESVITGLIDEFQLLHRHRELFTLFIVLATFLLSLFCVTNGGIYVFTLLDHFAAGTSILFGVLIEAIGVAWFYG VGQFSDDIQQMTGQRPSLYWRLCWKLVSPCFLLFVVVVSIVTFRPPHYGAYIFPDWANALGWVIATSSM AMVPIYAAYKFCSLPGSFREKLAYAIAPEKDRELVDRGEVRQFTLRHWLKV* Polynucleotides Encoding DAT Protein One platform that can be used to achieve therapeutically effective intracellular concentrations of DAT protein in mammalian cells is via the stable expression of genes encoding these agents (e.g., by integration into the nuclear or mitochondrial genome of a mammalian cell). These genes are polynucleotides that encode the primary amino acid sequence of the corresponding protein. In order to introduce such exogenous genes into a mammalian cell, these genes can be incorporated into a vector. Vectors can be introduced into a cell by a variety of methods, including transformation, transfection, direct uptake, projectile bombardment, and by encapsulation of the vector in liposomes. Examples of suitable methods of transfecting or transforming cells are calcium phosphate precipitation, electroporation, microinjection, infection, lipofection, and direct uptake. Such methods are described in more detail, for example, in Green et al., Molecular Cloning: A Laboratory Manual, Fourth Edition (Cold Spring Harbor University Press, New York (2014)); and Ausubel et al., Current Protocols in Molecular Biology (John Wiley & Sons, New York (2015)), the disclosures of each of which are incorporated herein by reference. DAT protein can also be introduced into a mammalian cell by targeting a vector containing a gene encoding such an agent to cell membrane phospholipids. For example, vectors can be targeted to the phospholipids on the extracellular surface of the cell membrane by linking the vector molecule to a vesicular stomatitis virus G (VSV-G) protein, a viral protein with affinity for all cell membrane phospholipids. Such a construct can be produced using methods well known to those of skill in the field. Recognition and binding of the polynucleotide encoding DAT protein by mammalian RNA polymerase is important for gene expression. As such, one may include sequence elements within the polynucleotide that exhibit a high affinity for transcription factors that recruit RNA polymerase and promote the assembly of the transcription complex at the transcription initiation site. Such sequence elements include, e.g., a mammalian promoter, the sequence of which can be recognized and bound by specific transcription initiation factors and ultimately RNA polymerase. Examples of mammalian promoters have been described in Smith et al., Mol. Sys. Biol., 3:73, online publication, the disclosure of which is incorporated herein by reference. 27 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Polynucleotides suitable for use with the compositions and methods described herein also include those that encode DAT protein downstream of a mammalian promoter. Promoters that are useful for the expression of DAT protein in mammalian cells include, e.g., include a synapsin 1 promoter, a CAG promoter, a cytomegalovirus (CMV) promoter, a calcium/calmodulin-dependent protein kinase II (CAMKII) promoter, a beta-actin promoter, and/or a human eukaryotic translation elongation factor 1 ^ (EF1- ^) promoter. A synapsin 1 promoter includes any promoter comprising a functional portion of the synapsin 1 gene. For example, the promoter may be a human synapsin 1 (hSYN1) promoter, a human synapsin 1 with 5’ extension promoter, a human synapsin 1 with 3’ extension promoter, an enhanced synapsin (eSYN) promoter or a truncated human synapsin 1 promoter. In some embodiments, the term “synapsin 1 promoter” refers to the nucleic acid set forth in SEQ ID NO: 1, as well as nucleic acids having at least 85% identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 1 and that promote the expression of a transgene in a cell (e.g., a eukaryotic cell, such as a mammalian cell, human cell, or human muscle cell) when the transgene is operably linked to the enhancer. SEQ ID NO: 1 is shown below: AGTGCAAGTGGGTTTTAGGACCAGGATGAGGCGGGGTGGGGGTGCCTACCTGACGACCGACCCCG ACCCACTGGACAAGCACCCAACCCCCATTCCCCAAATTGCGCATCCCCTATCAGAGAGGGGGAGGG GAAACAGGATGCGGCGAGGCGCGTGCGCACTGCCAGCTTCAGCACCGCGGACAGTGCCTTCGCCC CCGCCTGGCGGCGCGCGCCACCGCCGCCTCAGCACTGAAGGCGCGCTGACGTCACTCGCCGGTC CCCCGCAAACTCCCCTTCCCGGCCACCTTGGTCGCGTCCGCGCCGCCGCCGGCCCAGCCGGACCG CACCACGCGAGGCGCGAGATAGGGGGGCACGGGCGCGACCATCTGCGCTGCGGCGCCGGCGACT CAGCGCTGCCTCAGTCTGCGGTGGGCAGCGGAGGAGTCGTGTCGTGCCTGAGAGCGCAG Exemplary synapsin 1 promoters include those having the nucleic acid sequence of SEQ ID NO: 6. SEQ ID NO: 6 is shown below: ACTACAAACCGAGTATCTGCAGAGGGCCCTGCGTATGAGTGCAAGTGGGTTTTAGGACCAGGATGA GGCGGGGTGGGGGTGCCTACCTGACGACCGACCCCGACCCACTGGACAAGCACCCAACCCCCATT CCCCAAATTGCGCATCCCCTATCAGAGAGGGGGAGGGGAAACAGGATGCGGCGAGGCGCGTGCGC ACTGCCAGCTTCAGCACCGCGGACAGTGCCTTCGCCCCCGCCTGGCGGCGCGCGCCACCGCCGC CTCAGCACTGAAGGCGCGCTGACGTCACTCGCCGGTCCCCCGCAAACTCCCCTTCCCGGCCACCTT GGTCGCGTCCGCGCCGCCGCCGGCCCAGCCGGACCGCACCACGCGAGGCGCGAGATAGGGGGG CACGGGCGCGACCATCTGCGCTGCGGCGCCGGCGACTCAGCGCTGCCTCAGTCTGCGGTGGGCA GCGGAGGAGTCGTGTCGTGCCTGAGAGCGCAGCTGTGCTCCTGGGCACCGCGCAGTCCGCCCCC GCGGCTCCTGGCCAGACCACCCCTAGGACCCCCTGCCCCAAGTCGCAGCCTTCGA The promoter comprising a functional portion of the human synapsin 1 gene may additionally comprise an enhancer element, which may be any enhancer element. For example, the eSYN promoter is a hybrid promoter containing the human synapsin 1 promoter and a CMV enhancer. A beta-actin promoter includes any functional promoter comprising a functional portion of the beta-actin gene. The 28 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 beta-actin promoter may be a human beta-actin promoter or a chicken beta-actin promoter. The promoter comprising a functional portion of the beta-actin gene may additionally comprise an enhancer element, which may be any enhancer element. For example, the promoter may be a CAG promoter, which comprises the CMV early enhancer element, the promoter, first exon and first intron of chicken beta-actin gene and the splice acceptor or the rabbit beta-globin gene. A CMV promoter may be a human CMV major immediate early promoter or a super CMV promoter. A CAMKII promoter may be an ^-CAMKII promoter. Exemplary promoters suitable for use with the compositions and methods described herein include a neuron-specific promoter. For example, neuron-specific promoters include human synapsin 1 promoter and CAMKII promoter. The promoter can be a neuron-specific promoter selected from a human synapsin 1 promoter and a CAMKII promoter. The promoter can be a neuron-specific promoter selected from an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter, a truncated hSYN1 promoter and an ^-CAMKII promoter. The promoter can be a human synapsin 1 promoter. The promoter can be an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter or a truncated hSYN1 promoter. The promoter can be a dopaminergic neuron-specific promoter. Alternatively, promoters derived from viral genomes can also be used for the stable expression of these agents in mammalian cells. Examples of functional viral promoters that can be used to promote mammalian expression of these agents are adenovirus late promoter, vaccinia virus 7.5K promoter, simian virus 40 (SV40) promoter, cytomegalovirus promoter, tk promoter of herpes simplex virus (HSV), mouse mammary tumor virus (MMTV) promoter, long terminal repeat (LTR) promoter of human immunodeficiency virus (HIV), promoter of moloney virus, Epstein barr virus (EBV), Rous sarcoma virus (RSV), and the cytomegalovirus (CMV) promoter. Once a polynucleotide encoding the DAT protein has been incorporated into the nuclear DNA of a mammalian cell, the transcription of this polynucleotide can be induced by methods known in the art. For example, expression can be induced by exposing the mammalian cell to an external chemical reagent, such as an agent that modulates the binding of a transcription factor and/or RNA polymerase to the mammalian promoter and thus regulates gene expression. The chemical reagent can serve to facilitate the binding of RNA polymerase and/or transcription factors to the mammalian promoter, e.g., by removing a repressor protein that has bound the promoter. Alternatively, the chemical reagent can serve to enhance the affinity of the mammalian promoter for RNA polymerase and/or transcription factors such that the rate of transcription of the gene located downstream of the promoter is increased in the presence of the chemical reagent. Examples of chemical reagents that potentiate polynucleotide transcription by the above mechanisms are tetracycline and doxycycline. These reagents are commercially available (Life Technologies, Carlsbad, CA) and can be administered to a mammalian cell in order to promote gene expression according to established protocols. Other DNA sequence elements that may be included in polynucleotides for use in the compositions and methods described herein are enhancer sequences. Enhancers represent another class of regulatory elements that induce a conformational change in the polynucleotide containing the gene of interest such that the DNA adopts a three-dimensional orientation that is favorable for binding of transcription factors and RNA polymerase at the transcription initiation site. Thus, polynucleotides for use in the compositions and methods described herein include those that encode the DAT protein and 29 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 additionally include a mammalian enhancer sequence. Many enhancer sequences are now known from mammalian genes, and examples are enhancers from the genes that encode mammalian globin, elastase, albumin, ^-fetoprotein, and insulin. Enhancers for use in the compositions and methods described herein also include those that are derived from the genetic material of a virus capable of infecting a eukaryotic cell. Examples are the SV40 enhancer on the late side of the replication origin (bp 100-270), the cytomegalovirus early promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers. Additional enhancer sequences that induce activation of eukaryotic gene transcription are disclosed in Yaniv et al., Nature 297:17 (1982). An enhancer may be spliced into a vector containing a polynucleotide encoding a water-forming NADH oxidase, for example, at a position 5’ or 3’ to this gene. Polynucleotides encoding the DAT protein may include regulatory elements capable of turning gene expression on or off. The term “transcription regulatory element” refers to a nucleic acid that controls, at least in part, the transcription of a gene of interest. Transcription regulatory elements may include promoters, enhancers, and other nucleic acids (e.g., polyadenylation signals) that control or help to control gene transcription. Examples of transcription regulatory elements are described, for example, in Goeddel, Gene Expression Technology: Methods in Enzymology 185 (Academic Press, San Diego, CA, 1990). A “Woodchuck hepatitis virus (WHV) posttranscriptional regulatory element” or “WPRE” refers to a DNA sequence, which when transcribed, creates a tertiary structure enhancing expression. The AAV vector used in the methods and compositions described herein may include a WPRE. The WPRE acts at the transcriptional level, by promoting nuclear export of transcripts and/or by increasing the efficiency of polyadenylation of the nascent transcript, thus increasing the total amount of mRNA in the cells. The addition of the WPRE to the AAV vector results in a substantial improvement in the level of transgene expression from several different promoters, both in vitro and in vivo. In some embodiments, the term “WPRE” refers to the nucleic acid set forth in SEQ ID NO: 4, as well as nucleic acids having at least 85% identity (e.g., at least 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% identity, or more) to the nucleic acid sequence of SEQ ID NO: 4 and that promote the expression of a transgene in a cell (e.g., a eukaryotic cell, such as a mammalian cell, human cell, or human muscle cell) when the transgene is operably linked to the enhancer. SEQ ID NO: 4 is shown below: AATCAACCTCTGGATTACAAAATTTGTGAAAGATTGACTGGTATTCTTAACTATGTTGCTCCTTTTACG CTATGTGGATACGCTGCTTTAATGCCTTTGTATCATGCTATTGCTTCCCGTATGGCTTTCATTTTCTCC TCCTTGTATAAATCCTGGTTGCTGTCTCTTTATGAGGAGTTGTGGCCCGTTGTCAGGCAACGTGGCG TGGTGTGCACTGTGTTTGCTGACGCAACCCCCACTGGTTGGGGCATTGCCACCACCTGTCAGCTCC TTTCCGGGACTTTCGCTTTCCCCCTCCCTATTGCCACGGCGGAACTCATCGCCGCCTGCCTTGCCC GCTGCTGGACAGGGGCTCGGCTGTTGGGCACTGACAATTCCGTGGTGTTGTCGGGGAAATCATCGT CCTTTCCTTGGCTGCTCGCCTGTGTTGCCACCTGGATTCTGCGCGGGACGTCCTTCTGCTACGTCCC TTCGGCCCTCAATCCAGCGGACCTTCCTTCCCGCGGCCTGCTGCCGGCTCTGCGGCCTCTTCCGCG TCTTCGCCTTCGCCCTCAGACGAGTCGGATCTCCCTTTGGGCCGCCTCCCCGC 30 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Vectors for the Expression of DAT Protein In addition to achieving high rates of transcription and translation, stable expression of an exogenous gene in a mammalian cell can be achieved by integration of the polynucleotide containing the gene into the nuclear genome of the mammalian cell. A variety of vectors for the delivery and integration of polynucleotides encoding exogenous proteins into the nuclear DNA of a mammalian cell have been developed. Examples of expression vectors are disclosed in, e.g., WO 1994/011026 and are incorporated herein by reference. Expression vectors for use in the compositions and methods described herein contain a polynucleotide sequence that encodes DAT protein, as well as, e.g., additional sequence elements used for the expression of this protein and/or the integration of these polynucleotide sequences into the genome of a mammalian cell. Certain vectors that can be used for the expression of DAT protein include plasmids that contain regulatory sequences, such as promoter and enhancer regions, which direct gene transcription. Other useful vectors for expression of DAT protein contain polynucleotide sequences that enhance the rate of translation of these genes or improve the stability or nuclear export of the mRNA that results from gene transcription. These sequence elements include, e.g., 5’ and 3’ untranslated regions, an internal ribosomal entry site (IRES), and polyadenylation signal site in order to direct efficient transcription of the gene carried on the expression vector. The expression vectors suitable for use with the compositions and methods described herein may also contain a polynucleotide encoding a marker for selection of cells that contain such a vector. Examples of a suitable marker are genes that encode resistance to antibiotics, such as ampicillin, chloramphenicol, kanamycin, nourseothricin. Viral Vectors for the Expression of DAT Protein Viral genomes provide a rich source of vectors that can be used for the efficient delivery of exogenous genes into a mammalian cell. Viral genomes are particularly useful vectors for gene delivery as the polynucleotides contained within such genomes are typically incorporated into the nuclear genome of a mammalian cell by generalized or specialized transduction. These processes occur as part of the natural viral replication cycle, and do not require added proteins or reagents in order to induce gene integration. Examples of viral vectors are a retrovirus (e.g., Retroviridae family viral vector), adenovirus (e.g., Ad5, Ad26, Ad34, Ad35, and Ad48), parvovirus (e.g., AAVs), coronavirus, negative strand RNA viruses such as orthomyxovirus (e.g., influenza virus), rhabdovirus (e.g., rabies and vesicular stomatitis virus), paramyxovirus (e.g. measles and Sendai), positive strand RNA viruses, such as picornavirus and alphavirus, and double stranded DNA viruses including adenovirus, herpesvirus (e.g., Herpes Simplex virus types 1 and 2, Epstein-Barr virus, cytomegalovirus), and poxvirus (e.g., vaccinia, modified vaccinia Ankara (MVA), fowlpox and canarypox). Other viruses include Norwalk virus, togavirus, flavivirus, reoviruses, papovavirus, hepadnavirus, human papilloma virus, human foamy virus, and hepatitis virus, for example. Examples of retroviruses are: avian leukosis-sarcoma, avian C-type viruses, mammalian C- type, B-type viruses, D-type viruses, oncoretroviruses, human T-lymphotropic virus type I-bovine leukemia virus (HTLV-BLV) group, lentivirus, alpharetrovirus, gammaretrovirus, spumavirus (Coffin, J. M., Retroviridae: The viruses and their replication, Virology, Third Edition (Lippincott-Raven, Philadelphia, (1996))). Other examples are murine leukemia viruses, murine sarcoma viruses, mouse mammary tumor virus, bovine leukemia virus, feline leukemia virus, feline sarcoma virus, avian leukemia virus, human T- cell leukemia virus, baboon endogenous virus, Gibbon ape leukemia virus, Mason Pfizer monkey virus, 31 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 simian immunodeficiency virus, simian sarcoma virus, Rous sarcoma virus and lentiviruses. Other examples of vectors are described, for example, in McVey et al., (US 5,801,030), the teachings of which are incorporated herein by reference. AAV Vectors for Nucleic Acid Delivery Nucleic acids of the compositions and methods described herein may be incorporated into recombinant adeno-associated virus (rAAV) vectors and/or virions in order to facilitate their introduction into a cell. AAV vectors can be used in the central nervous system, and appropriate promoters and serotypes are discussed in Pignataro et al., J Neural Transm (2017), epub ahead of print, the disclosure of which is incorporated herein by reference as it pertains to promoters and AAV serotypes useful in central nervous system (CNS) gene therapy. The viral sequences may include those sequences of AAV that are required in cis for replication and packaging (e.g., functional inverted terminal repeats (ITRs) of the DNA into a virion. Such rAAV vectors may also contain marker or reporter genes. Useful rAAV vectors have one or more of the AAV WT genes deleted in whole or in part, but retain functional flanking ITR sequences. The AAV ITRs may be of any serotype suitable for a particular application. Methods for using rAAV vectors are described, for example, in Tal et al., J. Biomed. Sci. 7:279 (2000), and Monahan and Samulski, Gene Delivery 7:24 (2000), the disclosures of each of which are incorporated herein by reference as they pertain to AAV vectors for gene delivery. Exemplary AAV vectors of the disclosure include those having the nucleic acid sequence of SEQ ID NO: 5. SEQ ID NO: 5 is shown below: GCGCGCTCGCTCGCTCACTGAGGCCGCCCGGGCAAAGCCCGGGCGTCGGGCGACCTTTGGTCGC CCGGCCTCAGTGAGCGAGCGAGCGCGCAGAGAGGGAGTGGCCAACTCCATCACTAGGGGTTCCTT GTAGTTAATGATTAACCCGCCATGCTACTTATCTACGTAGCGGCAATTCAGTCGATAACTATAACGGT CCTAAGGTAGCGATTTAAATACGCGCTCTCTTAAGGTAGCCCCGGGACGCGTCAATTGACTACAAAC CGAGTATCTGCAGAGGGCCCTGCGTATGAGTGCAAGTGGGTTTTAGGACCAGGATGAGGCGGGGT GGGGGTGCCTACCTGACGACCGACCCCGACCCACTGGACAAGCACCCAACCCCCATTCCCCAAATT GCGCATCCCCTATCAGAGAGGGGGAGGGGAAACAGGATGCGGCGAGGCGCGTGCGCACTGCCAG CTTCAGCACCGCGGACAGTGCCTTCGCCCCCGCCTGGCGGCGCGCGCCACCGCCGCCTCAGCACT GAAGGCGCGCTGACGTCACTCGCCGGTCCCCCGCAAACTCCCCTTCCCGGCCACCTTGGTCGCGT CCGCGCCGCCGCCGGCCCAGCCGGACCGCACCACGCGAGGCGCGAGATAGGGGGGCACGGGCG CGACCATCTGCGCTGCGGCGCCGGCGACTCAGCGCTGCCTCAGTCTGCGGTGGGCAGCGGAGGA GTCGTGTCGTGCCTGAGAGCGCAGCTGTGCTCCTGGGCACCGCGCAGTCCGCCCCCGCGGCTCCT GGCCAGACCACCCCTAGGACCCCCTGCCCCAAGTCGCAGCCTTCGAGCTAGCGTTTAAACTTAAGC TTGGTACCGAGCTCGGATCCACTAGTCCAGTGTGGTGGAATTCCTCAACTCCCAGTGTGCCCATGAG TAAGAGCAAATGCTCCGTGGGACTCATGTCTTCCGTGGTGGCCCCGGCTAAGGAGCCCAATGCCGT GGGCCCGAAGGAGGTGGAGCTCATCCTTGTCAAGGAGCAGAACGGAGTGCAGCTCACCAGCTCCA CCCTCACCAACCCGCGGCAGAGCCCCGTGGAGGCCCAGGATCGGGAGACCTGGGGCAAGAAGATC GACTTTCTCCTGTCCGTCATTGGCTTTGCTGTGGACCTGGCCAACGTCTGGCGGTTCCCCTACCTGT GCTACAAAAATGGTGGCGGTGCCTTCCTGGTCCCCTACCTGCTCTTCATGGTCATTGCTGGGATGCC ACTTTTCTACATGGAGCTGGCCCTCGGCCAGTTCAACAGGGAAGGGGCCGCTGGTGTCTGGAAGAT 32 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 CTGCCCCATACTGAAAGGTGTGGGCTTCACGGTCATCCTCATCTCACTGTATGTCGGCTTCTTCTAC AACGTCATCATCGCCTGGGCGCTGCACTATCTCTTCTCCTCCTTCACCACGGAGCTCCCCTGGATCC ACTGCAACAACTCCTGGAACAGCCCCAACTGCTCGGATGCCCATCCTGGTGACTCCAGTGGAGACA GCTCGGGCCTCAACGACACTTTTGGGACCACACCTGCTGCCGAGTACTTTGAACGTGGCGTGCTGC ACCTCCACCAGAGCCATGGCATCGACGACCTGGGGCCTCCGCGGTGGCAGCTCACAGCCTGCCTG GTGCTGGTCATCGTGCTGCTCTACTTCAGCCTCTGGAAGGGCGTGAAGACCTCAGGGAAGGTGGTA TGGATCACAGCCACCATGCCATACGTGGTCCTCACTGCCCTGCTCCTGCGTGGGGTCACCCTCCCT GGAGCCATAGACGGCATCAGAGCATACCTGAGCGTTGACTTCTACCGGCTCTGCGAGGCGTCTGTT TGGATTGACGCGGCCACCCAGGTGTGCTTCTCCCTGGGCGTGGGGTTCGGGGTGCTGATCGCCTT CTCCAGCTACAACAAGTTCACCAACAACTGCTACAGGGACGCGATTGTCACCACCTCCATCAACTCC CTGACGAGCTTCTCCTCCGGCTTCGTCGTCTTCTCCTTCCTGGGGTACATGGCACAGAAGCACAGTG TGCCCATCGGGGACGTGGCCAAGGACGGGCCAGGGCTGATCTTCATCATCTACCCGGAAGCCATC GCCACGCTCCCTCTGTCCTCAGCCTGGGCCGTGGTCTTCTTCATCATGCTGCTCACCCTGGGTATC GACAGCGCCATGGGTGGTATGGAGTCAGTGATCACCGGGCTCATCGATGAGTTCCAGCTGCTGCAC AGACACCGTGAGCTCTTCACGCTCTTCATCGTCCTGGCGACCTTCCTCCTGTCCCTGTTCTGCGTCA CCAACGGTGGCATCTACGTCTTCACGCTCCTGGACCATTTTGCAGCCGGCACGTCCATCCTCTTTGG AGTGCTCATCGAAGCCATCGGAGTGGCCTGGTTCTATGGTGTTGGGCAGTTCAGCGACGACATCCA GCAGATGACCGGGCAGCGGCCCAGCCTGTACTGGCGGCTGTGCTGGAAGCTGGTCAGCCCCTGCT TTCTCCTGTTCGTGGTCGTGGTCAGCATTGTGACCTTCAGACCCCCCCACTACGGAGCCTACATCTT CCCCGACTGGGCCAACGCGCTGGGCTGGGTCATCGCCACATCCTCCATGGCCATGGTGCCCATCTA TGCGGCCTACAAGTTCTGCAGCCTGCCTGGGTCCTTTCGAGAGAAACTGGCCTACGCCATTGCACC CGAGAAGGACCGTGAGCTGGTGGACAGAGGGGAGGTGCGCCAGTTCACGCTCCGCCACTGGCTCA AGGTGTAGAGGGAGCAGAGACGAAGACCCCAGGAAGTCATCCTGCAATGGGAGAGACACGAACAA ACCAAGGAAATCTAAGTTTCGAGAGAAAGGAGGGCAACTTCTACTCTTCAACCTCTACTGAAAACACA AACAACAAAGCAGAAGACTCCTCTCTTCTGACTGTTTACACCTTTCCGTGCCGGGAGCGCACCTCGC CGTGTCTTGTGTTGCTGTAATAACGACGTAGATCTGTGCAGCGAGGTCCACCCCGTTGTTGTCCCAT CCAGCACAGTGGCGGCCGCTCGAGTCTAGAGGGCCCTTCGAACGTACCGGTTAATCGATAATCAAC CTCTGGATTACAAAATTTGTGAAAGATTGACTGGTATTCTTAACTATGTTGCTCCTTTTACGCTATGTG GATACGCTGCTTTAATGCCTTTGTATCATGCTATTGCTTCCCGTATGGCTTTCATTTTCTCCTCCTTGT ATAAATCCTGGTTGCTGTCTCTTTATGAGGAGTTGTGGCCCGTTGTCAGGCAACGTGGCGTGGTGTG CACTGTGTTTGCTGACGCAACCCCCACTGGTTGGGGCATTGCCACCACCTGTCAGCTCCTTTCCGG GACTTTCGCTTTCCCCCTCCCTATTGCCACGGCGGAACTCATCGCCGCCTGCCTTGCCCGCTGCTG GACAGGGGCTCGGCTGTTGGGCACTGACAATTCCGTGGTGTTGTCGGGGAAATCATCGTCCTTTCC TTGGCTGCTCGCCTGTGTTGCCACCTGGATTCTGCGCGGGACGTCCTTCTGCTACGTCCCTTCGGC CCTCAATCCAGCGGACCTTCCTTCCCGCGGCCTGCTGCCGGCTCTGCGGCCTCTTCCGCGTCTTCG CCTTCGCCCTCAGACGAGTCGGATCTCCCTTTGGGCCGCCTCCCCGCATCGAAACCCGCTGATCAG CCGGTTGAGTTTAAACCCGCTGATCAGCCTCGACTGCCCGGGTGGCATCCCTGTGACCCCTCCCCA GTGCCTCTCCTGGCCCTGGAAGTTGCCACTCCAGTGCCCACCAGCCTTGTCCTAATAAAATTAAGTT GCATCATTTTGTCTGACTAGGTGTCCTTCTATAATATTATGGGGTGGAGGGGGGTGGTATGGAGCAA GGGGCCCAAGTTGGGAAGAAACCTGTAGGGCCTGCCTTCTGAGGCGGAAAGAACCAGATCCTCTCT TAAGGTAGCATCGAGATTTAAATTAGGGATAACAGGGTAATGGCGCGGGCCGCTACGTAGATAAGTA 33 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 GCATGGCGGGTTAATCATTAACTACAAGGAACCCCTAGTGATGGAGTTGGCCACTCCCTCTCTGCGC GCTCGCTCGCTCACTGAGGCCGGGCGACCAAAGGTCGCCCGACGCCCGGGCTTTGCCCGGGCGG CCTCAGTGAGCGAGCGAGCGCGC The nucleic acids and vectors described herein can be incorporated into a rAAV virion in order to facilitate introduction of the nucleic acid or vector into a cell. The capsid proteins of AAV compose the exterior, non-nucleic acid portion of the virion and are encoded by the AAV cap gene. The cap gene encodes three viral coat proteins, viral protein (VP)1, VP2, and VP3, which are required for virion assembly. The construction of rAAV virions has been described, for example, in US 5,173,414; US 5,139,941; US 5,863,541; US 5,869,305; US 6,057,152; and US 6,376,237; as well as in Rabinowitz et al., J. Virol. 76:791 (2002) and Bowles et al., J. Virol.77:423 (2003), the disclosures of each of which are incorporated herein by reference as they pertain to AAV vectors for gene delivery. rAAV virions useful in conjunction with the compositions and methods described herein include those derived from a variety of AAV serotypes including AAV 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and rh74. For targeting cells located in or delivered to the central nervous system, AAV2, AAV9, and AAV10 may be particularly useful. Construction and use of AAV vectors and AAV proteins of different serotypes are described, for example, in Chao et al., Mol. Ther.2:619 (2000); Davidson et al., Proc. Natl. Acad. Sci. USA 97:3428 (2000); Xiao et al., J. Virol. 72:2224 (1998); Halbert et al., J. Virol.74:1524 (2000); Halbert et al., J. Virol.75:6615 (2001); and Auricchio et al., Hum. Molec. Genet.10:3075 (2001), the disclosures of each of which are incorporated herein by reference as they pertain to AAV vectors for gene delivery. Also useful in conjunction with the compositions and methods described herein are pseudotyped rAAV vectors. Pseudotyped vectors include AAV vectors of a given serotype pseudotyped with a capsid gene derived from a serotype other than the given serotype (e.g., AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV9.47, AAV9(hu14), AAV10, AAV11, AAV12, AAVrh74, AAVrh.8, AAVrh.10, AAV-DJ, AAV-DJ8 among others). In some embodiments, the AAV vector is an AAV2/8 or AAV2/9 vector. Techniques involving the construction and use of pseudotyped rAAV virions are known in the art and are described, for example, in Duan et al., J. Virol.75:7662 (2001); Halbert et al., J. Virol. 74:1524 (2000); Zolotukhin et al., Methods, 28:158 (2002); and Auricchio et al., Hum. Molec. Genet. 10:3075 (2001). AAV virions that have mutations within the virion capsid may be used to infect particular cell types more effectively than non-mutated capsid virions. For example, suitable AAV mutants may have ligand insertion mutations for the facilitation of targeting AAV to specific cell types. The construction and characterization of AAV capsid mutants including insertion mutants, alanine screening mutants, and epitope tag mutants is described in Wu et al., J. Virol.74:8635 (2000). Other rAAV virions that can be used in methods described herein include those capsid hybrids that are generated by molecular breeding of viruses as well as by exon shuffling. See, e.g., Soong et al., Nat. Genet., 25:436 (2000) and Kolman and Stemmer, Nat. Biotechnol.19:423 (2001). Viral Regulatory Elements The viral regulatory elements are components of delivery vehicles used to introduce nucleic acid molecules into a host cell. The viral regulatory elements are optionally retroviral regulatory elements. For 34 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 example, the viral regulatory elements may be the LTR and gag sequences from HSC1 or MSCV. The retroviral regulatory elements may be from lentiviruses or they may be heterologous sequences identified from other genomic regions. One skilled in the art would also appreciate that as other viral regulatory elements are identified, these may be used with the nucleic acid molecules described herein. Methods for the Delivery of Exogenous Nucleic Acids to Target Cells Techniques that can be used to introduce a polynucleotide, such as codon-optimized DNA or RNA (e.g., mRNA, tRNA, siRNA, miRNA, shRNA, chemically modified RNA) into a mammalian cell are well known in the art. For example, electroporation can be used to permeabilize mammalian cells (e.g., human target cells) by the application of an electrostatic potential to the cell of interest. Mammalian cells, such as human cells, subjected to an external electric field in this manner are subsequently predisposed to the uptake of exogenous nucleic acids. Electroporation of mammalian cells is described in detail, e.g., in Chu et al., Nucleic Acids Research 15:1311 (1987), the disclosure of which is incorporated herein by reference. A similar technique, Nucleofection^TM, utilizes an applied electric field in order to stimulate the uptake of exogenous polynucleotides into the nucleus of a eukaryotic cell. Nucleofection^TM and protocols useful for performing this technique are described in detail, e.g., in Distler et al., Experimental Dermatology 14:315 (2005), as well as in US 2010/0317114, the disclosures of each of which are incorporated herein by reference. Additional techniques useful for the transfection of target cells are the squeeze-poration methodology. This technique induces the rapid mechanical deformation of cells in order to stimulate the uptake of exogenous DNA through membranous pores that form in response to the applied stress. This technology is advantageous in that a vector is not required for delivery of nucleic acids into a cell, such as a human target cell. Squeeze-poration is described in detail, e.g., in Sharei et al., Journal of Visualized Experiments 81:e50980 (2013), the disclosure of which is incorporated herein by reference. Lipofection represents another technique useful for transfection of target cells. This method involves the loading of nucleic acids into a liposome, which often presents cationic functional groups, such as quaternary or protonated amines, towards the liposome exterior. This promotes electrostatic interactions between the liposome and a cell due to the anionic nature of the cell membrane, which ultimately leads to uptake of the exogenous nucleic acids, for example, by direct fusion of the liposome with the cell membrane or by endocytosis of the complex. Lipofection is described in detail, for example, in US 7,442,386, the disclosure of which is incorporated herein by reference. Similar techniques that exploit ionic interactions with the cell membrane to provoke the uptake of foreign nucleic acids are contacting a cell with a cationic polymer-nucleic acid complex. Exemplary cationic molecules that associate with polynucleotides so as to impart a positive charge favorable for interaction with the cell membrane are activated dendrimers (described, e.g., in Dennig, Topics in Current Chemistry 228:227 (2003), the disclosure of which is incorporated herein by reference) polyethylenimine, and diethylaminoethyl (DEAE)-dextran, the use of which as a transfection agent is described in detail, for example, in Gulick et al., Current Protocols in Molecular Biology 40:I:9.2:9.2.1 (1997), the disclosure of which is incorporated herein by reference. Magnetic beads are another tool that can be used to transfect target cells in a mild and efficient manner, as this methodology utilizes an applied magnetic field in order 35 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 to direct the uptake of nucleic acids. This technology is described in detail, for example, in US 2010/0227406, the disclosure of which is incorporated herein by reference. Another useful tool for inducing the uptake of exogenous nucleic acids by target cells is laserfection, also called optical transfection, a technique that involves exposing a cell to electromagnetic radiation of a particular wavelength in order to gently permeabilize the cells and allow polynucleotides to penetrate the cell membrane. The bioactivity of this technique is similar to, and in some cases found superior to, electroporation. Impalefection is another technique that can be used to deliver genetic material to target cells. It relies on the use of nanomaterials, such as carbon nanofibers, carbon nanotubes, and nanowires. Needle-like nanostructures are synthesized perpendicular to the surface of a substrate. DNA containing the gene, intended for intracellular delivery, is attached to the nanostructure surface. A chip with arrays of these needles is then pressed against cells or tissue. Cells that are impaled by nanostructures can express the delivered gene(s). An example of this technique is described in Shalek et al., PNAS 107: 1870 (2010), the disclosure of which is incorporated herein by reference. Magnetofection can also be used to deliver nucleic acids to target cells. The magnetofection principle is to associate nucleic acids with cationic magnetic nanoparticles. The magnetic nanoparticles are made of iron oxide, which is fully biodegradable, and coated with specific cationic proprietary molecules varying upon the applications. Their association with the gene vectors (DNA, siRNA, viral vector, etc.) is achieved by salt-induced colloidal aggregation and electrostatic interaction. The magnetic particles are then concentrated on the target cells by the influence of an external magnetic field generated by magnets. This technique is described in detail in Scherer et al., Gene Therapy 9:102 (2002), the disclosure of which is incorporated herein by reference. Another useful tool for inducing the uptake of exogenous nucleic acids by target cells is sonoporation, a technique that involves the use of sound (typically ultrasonic frequencies) for modifying the permeability of the cell plasma membrane permeabilize the cells and allow polynucleotides to penetrate the cell membrane. This technique is described in detail, e.g., in Rhodes et al., Methods in Cell Biology 82:309 (2007), the disclosure of which is incorporated herein by reference. Microvesicles represent another potential vehicle that can be used to modify the genome of a target cell according to the methods described herein. For example, microvesicles that have been induced by the co-overexpression of the glycoprotein VSV-G with, e.g., a genome-modifying protein, such as a nuclease, can be used to efficiently deliver proteins into a cell that subsequently catalyze the site- specific cleavage of an endogenous polynucleotide sequence so as to prepare the genome of the cell for the covalent incorporation of a polynucleotide of interest, such as a gene or regulatory sequence. The use of such vesicles, also referred to as Gesicles, for the genetic modification of eukaryotic cells is described in detail, e.g., in Quinn et al., Genetic Modification of Target Cells by Direct Delivery of Active Protein [abstract]. In: Methylation changes in early embryonic genes in cancer [abstract], in: Proceedings of the 18th Annual Meeting of the American Society of Gene and Cell Therapy; 2015 May 13, Abstract No. 122. 36 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Methods of Treatment Selection of Subjects Subjects that may be treated as described herein are subjects having or at risk of developing PD. The type of PD may be idiopathic PD, sporadic PD, PD caused by an environmental toxin, e.g., herbicides or pesticides, or PD associated with a mutation, e.g., a mutation in the DAT protein or the SLC6A3 gene. In some embodiments, the subject with idiopathic PD has levodopa-induced dyskinesia (LID) or is at risk of developing LID. One risk factor for LID development involves changes in striatal dopamine receptor levels induced by levodopa treatment. Another risk factor involves neural plasticity and differential adaptation to loss of dopaminergic neurons, for example, chronic levodopa intake can cause plastic alternations in postsynaptic regions, including significant rise in extracellular DA and defective monoamine oxidase-mediated dopamine breakdown. Several factors can contribute to impaired DAT activity in PD ultimately resulting in reduced DA reuptake and increased synaptic levels of DA, which can lead to motor response complications in later disease stages. Idiopathic PD includes loss of DA neurons loss and/or impaired function. Lower levels of DAT due to dopaminergic denervation disrupt presynaptic DA homeostasis and are associated with long-term motor response complications in PD. Idiopathic PD also includes compensatory mechanisms in early PD. DAT downregulation in premotor PD is a mechanism to compensate for reduced synaptic DA levels, but with potentially deleterious long-term effects due to increased DA turnover and reduced DAT. Genetically defined PD includes mutations in PD- linked genes regulating DAT. Impaired DAT activity, trafficking, and localization on plasma membrane are linked to PD-linked mutations, for e.g., ^-synuclein, LRRK2, Parkin. Genetically defined PD also includes some polymorphisms in the SLC6A3 gene, such as, mutations linked to neurological and neuropsychiatric disorders, for e.g., parkinsonism, attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorders (ASD), bipolar, and schizophrenia. Loss-of-function DAT mutation causes dopamine transporter deficiency syndrome (DTDS), a form of infantile parkinsonism dystonia. The compositions and methods described herein can be used to treat patients with reduced DAT activity, reduced DA re-uptake, and patients whose DAT or SLC6A3 mutational status and/or DAT activity level is unknown. The compositions and methods described herein may also be administered as a preventative treatment to patients at risk of developing PD, e.g., patients with a DAT mutation, patients with reduced DAT activity, patients with a mutation in the SLC6A3 gene. Patients at risk for PD may show early symptoms of PD or may not yet be symptomatic when treatment is administered. Routes of Administration The compositions described herein may be administered to a subject with PD by a variety of routes. Administration of an effective dose of the composition may be by exemplary routes of administration standard in the art, including, but not limited to, systemic (e.g., by intravenous administration), local (e.g., intracortical), and direct injection (e.g., stereotactic delivery to dopaminergic neurons of the substantia nigra pars compacta (SNc) or ventral tegmental area (VTA)). The AAV vector may be administered to a patient having PD via one or more of a variety of routes, for example, intracerebroventricular (ICV), intracranial, intracortical, intracisternal, intracerebral, intra-cerebrospinal, intraparenchymal, intracisternal, intrahippocampal, intra-striatal (putamen and/or caudate), intravenous (IV), intrathecal, intraputaminal, intra-midbrain, intra-cisterna magna, intra-substantia nigra, intra-ventral tegmental area, and/or intrathalamic administration. In some cases, the vector is administered via 37 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 intraparenchymal, intracerebral, ICV, intrathecal, intraputaminal, intrathalamic, intra-midbrain, intra- cisterna magna, intra-substantia nigra, and/or intra-ventral tegmental area routes. Administration may be performed by intrathecal injection with or without Trendelenberg tilting. In some cases, the AAV vector may be administered, e.g., in a single administration. Direct delivery to the CNS may involve targeting the intraventricular space, either unilaterally or bilaterally, specific neuronal regions or more general brain regions containing neuronal targets. Individual patient intraventricular space, brain region and/or neuronal target(s) selection and subsequent intraoperative delivery of AAV may be accomplished using several imaging techniques (magnetic resonance imaging (MRI), computerized tomography (CT), CT combined with MRI merging) and employing any number of software planning programs (e.g., Stealth System, Clearpoint Neuronavigation System, Brainlab, Neuroinspire etc). Intraventricular space or brain region targeting, and delivery may involve use of standard stereotactic frames (Leksell, CRW) or using frameless approaches with or without intraoperative MRI. Actual delivery of the vector may be by injection through needle or cannulae with or without inner lumen lined with material to prevent adsorption of the vector (e.g., Smartflow cannulae, MRI Interventions cannulae). Delivery device interfaces with syringes and automated infusion or microinfusion pumps with preprogrammed infusion rates and volumes. The syringe/needle combination or just the needle may be interfaced directly with the stereotactic frame. Infusion may include constant flow rate or varying rates with convection enhanced delivery. The vector may be administered at a single point in time. For example, a single injection may be given with no repeat administrations. Combination therapies are also contemplated by the disclosure. Combinations of methods of the disclosure with standard medical treatments (e.g., corticosteroids or topical pressure reducing medications) are specifically contemplated, as are combinations with novel therapies. For example, the present disclosure also includes combination treatment with an antiparkinsonian therapy, e.g., levodopa. In some cases, a subject may be treated with a steroid to prevent or to reduce an immune response to administration of the vector described herein. In some embodiments, the compositions described herein are administered to a subject by stereotactic injection into the substantia nigra, e.g., the dopaminergic neurons of the substantia nigra (a description of this method can be found in San Sebastian et al., Molecular Therapy, Methods and Clinical Development, 3, 14049 (2014) and Pearson et al., Nature Communications, 12:4251 (2021) incorporated herein by reference as it pertains to stereotactic injection of the compositions described herein into the substantia nigra of PD mouse models). In some embodiments, the compositions described herein are administered to a subject by stereotactic injection into the VTA, e.g., the dopaminergic neurons of the VTA (a description of this method can be found in San Sebastian et al., Molecular Therapy, Methods and Clinical Development, 3, 14049 (2014) and Pearson et al., Nature Communications, 12:4251 (2021) incorporated herein by reference as it pertains to stereotactic injection of the compositions described herein into the VTA of PD mouse models). The most suitable route for administration in any given case will depend on the particular composition administered, the patient, pharmaceutical formulation methods, administration methods (e.g., administration time and administration route), the patient's age, body weight, sex, severity of the diseases being treated, the patient’s diet, and the patient’s excretion rate. Multiple routes of administration may be used to treat a single subject, e.g., intracerebroventricular or stereotactic injection into the substantia nigra, e.g., the dopaminergic neurons of the substantia nigra. In another example, the composition is administered to the subject intravenously. 38 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Multiple routes of administration may be used to treat a single subject at one time, or the subject may receive treatment via one route of administration first and receive treatment via another route of administration during a second appointment, e.g., 1 week later, 2 weeks later, 1 month later, 6 months later, or 1 year later. The compositions of the disclosure may be administered to a subject once, or may be administered one or more times (e.g., 2-10 times) per week, month, or year to a subject treatment for PD. The AAV vector comprising the SLC6A3 transgene described herein can be administered in an amount sufficient to improve one or more pathological features in PD. Administration of compositions described herein may reduce bradykinesia in the subject, reduce tremors in the subject, reduce rigidity and stiffness in the subject, improve motor coordination of the subject, reduce postural instability and improve balance in the subject, improve the cognitive performance of the subject, alter dopaminergic neurotransmission in the subject, improve DAT availability in the subject, reduce white matter lesions in the subject, improve DAT binding in striatum of the subject, improve DAT expression of the subject, improve DA uptake in the subject, improve [123I]-FP-CIT binding in the subject, improve [3H]-CTF- binding capacity of the subject, improve amphetamine-induced DA efflux in the subject, improve the motor function of the subject, reduce dopaminergic neuron loss in the subject, reduce neuroinflammation in the subject, reduce inflammatory cytokines in the blood and cerebrospinal fluid (CSF) of the subject, prevent, reduce, or reverse LID in the patient, and/or reduce ^-synuclein levels or aggregation thereof in the subject. The change in the baseline of motor symptoms may be assessed by the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS). The change in the baseline of non- motor symptoms of PD may be assessed by the Non-Motor Symptom Scale (NMSS), wherein the one or more non-motor symptoms are selected from being associated with cardiovascular health, sleep and fatigue, mood and cognition, perceptual problems and hallucinations, attention and memory, anxiety, depressive-like behaviors, gastrointestinal tract, urinary, and sexual function. Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may cause the patient to exhibit a change in responsiveness to the antiparkinsonian therapy. Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may help prolong responsiveness to the antiparkinsonian therapy or reduce dependency on the antiparkinsonian therapy, for e.g., levodopa. Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may help reduce dependency on the antiparkinsonian therapy. Antiparkinsonian therapy can be levodopa or other existing medications in the field. Administration of compositions described herein may increase the expression of DAT protein in target tissue such as substantia nigra pars compacta. In some embodiments, the subject with PD or idiopathic PD has anxiety or displays anxiety-like behaviors. Severity of anxiety symptoms can be measured using different scales, such as, the Hamilton Anxiety Rating Scale (HAM-A), Hamilton M., Br. J. Med. Psychol.32:50-55 (1959). The total score range for this scale is from 0-56, with <17 indicating mild severity, 18-24 indicating mild to moderate severity, and 25-30 indicating moderate to severe severity. In some emodiments, administration of the compositions described herein to a subject suffering from PD or idiopathic PD can reduce anxiety or anxiety-like behaviors. In some embodiments, the subject with PD or idiopathic PD has depression or displays depressive-like behaviors. Depression can be measured using different scales, such as, the Hamilton 39 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Depression Rating Scale (HDRS), Hamilton M., J. Neurol. Neurosurg. Psychiatry.23:56-62 (1960). The scoring for this scale can vary based on version. In a version containing 17 items related to symptoms of depression during the previous week (HDRS17), a score of 0-7 is considered to be normal or in clinical remission and a score of 20 or above indicates atleast moderate severity and is required for clinical trial entry. In some emodiments, administration of the compositions described herein to a subject suffering from PD or idiopathic PD can reduce depression or depression-like behaviors. The change in brain dopaminergic cell integrity may be measured by dopamine transporter scan (DaTscan) single-photon emission computed tomography (SPECT) imaging (DaT-SPECT), wherein the percentage and absolute changes in Ioflupane retention as a marker for dopamine transporter protein expressed by dopamine producing cells within the brain are measured. The change in brain dopaminergic cell integrity may also be measured by DaT-SPECT imaging followed by estimation of the fractional volume occupied by the caudate, putamen, and globus pallidus within each voxel of a SPECT image using a tissue-fraction estimation-based segmentation method to reliably quantify DaT uptake. Degeneration of in vivo presynaptic dopaminergic neurons is found in PD patients and DaT-SPECT provides a mechanism to measure these neurons. There are various DaT-based ligands and Ioflupane I- 123 has been approved by the United States Food and Drug Administration (FDA) to assist with diagnosing Parkinsonian syndromes. One of the ways of estimating the severity of PD is through measuring the amount of DaT uptake in the globus pallidus (GP). The tissue-fraction estimation-based segmentation method for DaT-SPECT images can correctly segment the caudate, putamen, and GP, and quantify the DaT uptake within these brain regions in a reliable manner. The problem with conventional SPECT segmentation methods is that they often yield limited performance because they are unable to account for partial-volume effects (PVEs), and especially, tissue-fraction effects (TFEs). Most of the conventional methods perform segmentation via voxel-wise classification and are thus, unable to model the TFEs properly. The tissue-fraction estimation-based segmentation method can address this limitation because it can evaluate the fractional volume occupied by the caudate, putamen, and GP within each voxel of a SPECT image. Improvement in neurological symptoms of PD can be assessed using standard neurological tests before and after treatment. Dopaminergic neuron loss can be assessed using F18-dopa positron emission tomography (PET) scans or dopamine transporter imaging scans 123I-N-^-fluoropropyl-2^- carbomethoxy-3^-(4-iodophenyl) nortropane (123I-FP-CIT DaTSCANs). Improvement in brain metabolism can be measured by PET scans and overall improvement in symptoms can be measured by standard clinical rating scales. The patient may be evaluated 1 month, 2 months, 3 months, 4 months, 5 months, 6 months or more following administration of the compositions described herein depending on the route of administration used for treatment. Depending on the outcome of the evaluation, the patient may receive additional treatments. Kits The compositions described herein can be provided in a kit for use in treating PD. Compositions may include an AAV vector, comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein. The kit can include a package insert that instructs a user of the kit, 40 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 such as a physician, to perform the methods described herein. The kit may optionally include a syringe or other device for administering the composition. Examples The following examples are put forth so as to provide those of ordinary skill in the art with a description of how the compositions and methods described herein may be used, made, and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Example 1: Evaluation of the therapeutic effect of AAV-DAT on reducing or reversing levodopa- induced dyskinesia (LID) in a 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson’s Disease (PD) and assessment of the effect of AAV-DAT on anxiety-like behaviors Objective The primary aim of this study was to evaluate the therapeutic effect of AAV-DAT on reducing or reversing levodopa-induced dyskinesia (LID) in a 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson’s Disease (PD). In addition, the effect of AAV-DAT on anxiety-like behaviors was assessed. The test item used in this study was AAV-DAT, which is an adeno-associated viral (AAV2) vector with AAV2 inverted terminal repeats (ITRs), expressing a solute carrier family 6 member 3 (SLC6A3) transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE), and wherein the transgene encodes a human dopamine transporter (hDAT) protein. AAV-DAT is an adeno-associated virus (AAV) gene therapy expressing hDAT, a membrane protein critical for the physiological regulation of extrasynaptic dopamine levels and dopaminergic neurotransmission. In PD, the severe loss of DAT expressing dopaminergic terminals along with chronic treatment with oral levodopa (L-DOPA) have been associated with the development of LID. Materials and Methods Study Design An initial number of 60 male wild type rats were lesioned with 6-OHDA and the animals were then used in a 3-phase stepwise approach as follows. Phase 1: Habituation and 6-OHDA lesion 63 male wild-type rats (n = 60 study animals + 3 backup rats; Wistar Han, 6-8 weeks of age) were transferred from a commercial breeder and were habituated at standard housing conditions for at least 1 week. At an age of approximately 9 weeks, all animals were unilaterally lesioned by 6-OHDA injection into the medial forebrain bundle (MFB).3 weeks after 6-OHDA injection, the lesion efficacy was evaluated by the D-amphetamine induced rotational test. Phase 2: L-DOPA Priming and Dyskinesia Establishment After completing the D-amphetamine induced rotational test, all animals were treated with L-DOPA/Benserazide via intraperitoneal (i.p.) injection once daily for 21 consecutive days. Five minutes 41 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 (time critical ± 2 mins) after receiving the final L-DOPA/Benserazide priming dose on day 21, dyskinesia was determined by evaluating axial, limb, and orolingual abnormal involuntary movements (ALO AIMs). Based on the obtained results (FIG.4), 30 animals showing the weakest symptoms in ALO AIMs were eliminated at this stage (no tissues were collected). Phase 3: Gene Therapy Efficacy Assessment The remaining 30 animals were stratified based on the behavioral assays and accordingly assigned to 2 groups with n = 15 animals each. Specifically, a number of animals per group (4 animals in Group A and 5 animals in Group B) were included that showed high level of ALO AIMs, but no- or minor rotational behavior. Animals of group A received one injection of vehicle via unilateral injection into the ipsilateral striatum (see coordinates below), whereas rats of group B were injected with the test construct (AAV-DAT). Starting one day after striatal gene therapy injection, all animals were treated daily by single i.p. injections with L-DOPA/Benserazide for a total duration of 7 weeks. Dyskinesia (ALO AIMs) was evaluated every other week (total of 3 times), 5 minutes (time critical ± 2 mins) after each L- DOPA/Benserazide treatment as above. In the last week of the study, anxiety-like behaviors were evaluated by the Elevated Plus Maze (EPM) test. L-DOPA treatment on the testing days for EPM was performed after the behavioral tests. For a project schedule, see Table 2 below. Table 2. Project Schedule Study 1 2 end 4 5 6 7 8 9 10 11 12 13 duration of w3 (weeks) 6-OHDA x lesion n=60 Rotation x test n=60 L-DOPA x x x n=60 priming n=60 n=60 daily L-DOPA x n=30 x x x x x x n=30 L- treatment Start: n=30 n=30 n=30 n=30 n=30 DOPA daily day 1 treatment post- after EPM AAV inj. ALO/AIMS x n=60 x x x n=30 after n=30 n=30 after final L- completion DOPA of EPM priming 42 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Eliminate x n=30 30 animals that do not show dyskinesia AAV x n=30 injection Elevated x n=30 Plus Maze Tissue x sampling n= number of animals/group; EPM = Elevated Plus Maze; inj. = injection After completing the final evaluation of dyskinesia/ALO AIMs in week 13, daily i.p. treatment with L-DOPA/Benserazide was continued daily until the day of tissue collection.1 hour (time critical ± 5 mins) after the last L-DOPA/Benserazide treatment, all animals were euthanized by i.p. injection of pentobarbital. Following transcardial perfusion with saline, whole brains of n = 8 animals per group were collected for histological analysis. For histological analysis, the collected whole brains (total n = 16) were post-fixed by immersion in 4% paraformaldehyde (PFA) in phosphate buffer (PB; pH 7.4) overnight at 4 °C, followed by further processing for cryosectioning. From each brain, up to 80 coronal sections were collected around the AAV-DAT injection site.5 sections per animal were used for quantitative immunofluorescent labeling of 4 markers (tyrosine hydroxylase (TH), hDAT, Glial Fibrillary Acidic Protein (GFAP), and 5- hydroxytryptamine (serotonin) transporter (5-HTT)) in substantia nigra (SN) and striatum. Furthermore, qualitative histological assessments were performed on striatum sections for seven additional markers (Choline acetyltransferase (ChAT), Parvalbumin, COUP (chicken ovalbumin upstream promoter)-TF (transcription factor)-interacting protein 2 (CTIP2), vesicular acetylcholine transporter (VAChT), Calbindin, Dopamine- and cyclic AMP (adenosine monophosphate)-regulated phosphoprotein, Mr 32 kDa (DARPP-32), and neuronal nitric oxide synthase (nNOS)), together with hDAT. Whole slide images were acquired and overlay of hDAT and subtype-specific neuronal markers were evaluated qualitatively to identify neurons that were AAV-DAT-infected and express hDAT. Test System 6-OHDA – induced lesions in rodents in the nigrostriatal pathway induce unilateral motor deficits that model the motor deficits observed in PD patients. This is due to a loss of a high percentage of ipsilateral dopaminergic neurons in lesioned animals. Animals are sensitive to dopamine replacement therapy, and chronic L-DOPA treatment elicits abnormal involuntary movements (AIMs), similar to L- DOPA side effects seen in human patients, namely LID. It is a suitable model to study PD pathophysiology, as well as develop novel- and improve existing PD interventions. 43 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 The route of administration and dosage of AAV-DAT were selected based on the intended therapeutic target. Test and Reference Items Test Item The test item used in this study was AAV-DAT, which is an AAV2 vector, expressing an SLC6A3 transgene, wherein the transgene is operably linked to a synapsin 1 promoter and a WPRE, and wherein the transgene encodes an hDAT protein. The sequences of the promoter, transgene, and WPRE of the test item are shown below. SEQ ID NO: 1 (Synapsin 1 promoter) is shown below: AGTGCAAGTGGGTTTTAGGACCAGGATGAGGCGGGGTGGGGGTGCCTACCTGACGACCGACCCCG ACCCACTGGACAAGCACCCAACCCCCATTCCCCAAATTGCGCATCCCCTATCAGAGAGGGGGAGGG GAAACAGGATGCGGCGAGGCGCGTGCGCACTGCCAGCTTCAGCACCGCGGACAGTGCCTTCGCCC CCGCCTGGCGGCGCGCGCCACCGCCGCCTCAGCACTGAAGGCGCGCTGACGTCACTCGCCGGTC CCCCGCAAACTCCCCTTCCCGGCCACCTTGGTCGCGTCCGCGCCGCCGCCGGCCCAGCCGGACCG CACCACGCGAGGCGCGAGATAGGGGGGCACGGGCGCGACCATCTGCGCTGCGGCGCCGGCGACT CAGCGCTGCCTCAGTCTGCGGTGGGCAGCGGAGGAGTCGTGTCGTGCCTGAGAGCGCAG SEQ ID NO: 2 (SLC6A3 transgene) is shown below: ATGAGTAAGAGCAAATGCTCCGTGGGACTCATGTCTTCCGTGGTGGCCCCGGCTAAGGAGCCCAAT GCCGTGGGCCCGAAGGAGGTGGAGCTCATCCTTGTCAAGGAGCAGAACGGAGTGCAGCTCACCAG CTCCACCCTCACCAACCCGCGGCAGAGCCCCGTGGAGGCCCAGGATCGGGAGACCTGGGGCAAGA AGATCGACTTTCTCCTGTCCGTCATTGGCTTTGCTGTGGACCTGGCCAACGTCTGGCGGTTCCCCTA CCTGTGCTACAAAAATGGTGGCGGTGCCTTCCTGGTCCCCTACCTGCTCTTCATGGTCATTGCTGGG ATGCCACTTTTCTACATGGAGCTGGCCCTCGGCCAGTTCAACAGGGAAGGGGCCGCTGGTGTCTGG AAGATCTGCCCCATACTGAAAGGTGTGGGCTTCACGGTCATCCTCATCTCACTGTATGTCGGCTTCT TCTACAACGTCATCATCGCCTGGGCGCTGCACTATCTCTTCTCCTCCTTCACCACGGAGCTCCCCTG GATCCACTGCAACAACTCCTGGAACAGCCCCAACTGCTCGGATGCCCATCCTGGTGACTCCAGTGG AGACAGCTCGGGCCTCAACGACACTTTTGGGACCACACCTGCTGCCGAGTACTTTGAACGTGGCGT GCTGCACCTCCACCAGAGCCATGGCATCGACGACCTGGGGCCTCCGCGGTGGCAGCTCACAGCCT GCCTGGTGCTGGTCATCGTGCTGCTCTACTTCAGCCTCTGGAAGGGCGTGAAGACCTCAGGGAAGG TGGTATGGATCACAGCCACCATGCCATACGTGGTCCTCACTGCCCTGCTCCTGCGTGGGGTCACCC TCCCTGGAGCCATAGACGGCATCAGAGCATACCTGAGCGTTGACTTCTACCGGCTCTGCGAGGCGT CTGTTTGGATTGACGCGGCCACCCAGGTGTGCTTCTCCCTGGGCGTGGGGTTCGGGGTGCTGATC GCCTTCTCCAGCTACAACAAGTTCACCAACAACTGCTACAGGGACGCGATTGTCACCACCTCCATCA ACTCCCTGACGAGCTTCTCCTCCGGCTTCGTCGTCTTCTCCTTCCTGGGGTACATGGCACAGAAGCA CAGTGTGCCCATCGGGGACGTGGCCAAGGACGGGCCAGGGCTGATCTTCATCATCTACCCGGAAG CCATCGCCACGCTCCCTCTGTCCTCAGCCTGGGCCGTGGTCTTCTTCATCATGCTGCTCACCCTGG GTATCGACAGCGCCATGGGTGGTATGGAGTCAGTGATCACCGGGCTCATCGATGAGTTCCAGCTGC 44 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 TGCACAGACACCGTGAGCTCTTCACGCTCTTCATCGTCCTGGCGACCTTCCTCCTGTCCCTGTTCTG CGTCACCAACGGTGGCATCTACGTCTTCACGCTCCTGGACCATTTTGCAGCCGGCACGTCCATCCTC TTTGGAGTGCTCATCGAAGCCATCGGAGTGGCCTGGTTCTATGGTGTTGGGCAGTTCAGCGACGAC ATCCAGCAGATGACCGGGCAGCGGCCCAGCCTGTACTGGCGGCTGTGCTGGAAGCTGGTCAGCCC CTGCTTTCTCCTGTTCGTGGTCGTGGTCAGCATTGTGACCTTCAGACCCCCCCACTACGGAGCCTAC ATCTTCCCCGACTGGGCCAACGCGCTGGGCTGGGTCATCGCCACATCCTCCATGGCCATGGTGCCC ATCTATGCGGCCTACAAGTTCTGCAGCCTGCCTGGGTCCTTTCGAGAGAAACTGGCCTACGCCATTG CACCCGAGAAGGACCGTGAGCTGGTGGACAGAGGGGAGGTGCGCCAGTTCACGCTCCGCCACTGG CTCAAGGTGTAG SEQ ID NO: 4 (WPRE) is shown below: AATCAACCTCTGGATTACAAAATTTGTGAAAGATTGACTGGTATTCTTAACTATGTTGCTCCTTTTACG CTATGTGGATACGCTGCTTTAATGCCTTTGTATCATGCTATTGCTTCCCGTATGGCTTTCATTTTCTCC TCCTTGTATAAATCCTGGTTGCTGTCTCTTTATGAGGAGTTGTGGCCCGTTGTCAGGCAACGTGGCG TGGTGTGCACTGTGTTTGCTGACGCAACCCCCACTGGTTGGGGCATTGCCACCACCTGTCAGCTCC TTTCCGGGACTTTCGCTTTCCCCCTCCCTATTGCCACGGCGGAACTCATCGCCGCCTGCCTTGCCC GCTGCTGGACAGGGGCTCGGCTGTTGGGCACTGACAATTCCGTGGTGTTGTCGGGGAAATCATCGT CCTTTCCTTGGCTGCTCGCCTGTGTTGCCACCTGGATTCTGCGCGGGACGTCCTTCTGCTACGTCCC TTCGGCCCTCAATCCAGCGGACCTTCCTTCCCGCGGCCTGCTGCCGGCTCTGCGGCCTCTTCCGCG TCTTCGCCTTCGCCCTCAGACGAGTCGGATCTCCCTTTGGGCCGCCTCCCCGC Compound preparation: The test item was provided at a concentration of 1.7 x 10^13 vector genomes/ml (vg/ml) (as specified by ddPCR measurement). The formulation buffer contained: 8 mM Sodium Phosphate, 180 mM sodium chloride with 0.001% Poloxamer 188 at pH 7.3. The test item required further reformulation in phosphate-buffered saline (PBS) to obtain the final desired concentration. Briefly, all the following steps were performed under a tissue culture hood with verification of the volumes of stock vector and dilution buffer. Stock vial of the test item was thawed for approximately 20 mins on wet ice. To achieve the final titer required (i.e., 1.0 x10^10 vg in 5 ^l), a pre-established volume of stock vector was added to a vial containing a pre-established volume of dilution buffer (PBS – sterile tissue culture grade) and gently mixed with a pipette. The vial was then closed and manually shaken to allow the content of vial to reach the bottom (no vortexing). Vials used for dosing were maintained on wet ice throughout the procedure. Thawed stock vials were kept at 4 °C and used within 14 days. Lesion Items All parameters for lesion item 6-OHDA are included in Table 3 below. Table 3. Name of lesion item: 6-hydroxydopamine (6-OHDA) 45 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Storage condition: at room temperature, protected from light Vehicle: 0.02% ascorbic acid in physiological saline (0.9% NaCl) Treatment dosage: 1 x 8 µg unilateral Application volume: 1 x 2 µL unilateral Route of administration: unilateral intracranial injection (2 µl) into the MFB, once Formulation of 6-OHDA The concentration of 6-OHDA in treatment solution was 4

in saline with 0.02% added ascorbic acid.6-OHDA solution was freshly prepared on the day of treatment and stored at 4°C and protected from light until usage. All parameters for lesion item Desipramine hydrochloride are included in Table 4 below. Table 4. Name of lesion item: Desipramine hydrochloride Storage condition: 4 °C, protected from light Vehicle: physiological saline (0.9% NaCl) Treatment dosage: 25 mg/kg Application volume: 5 ml/ kg body weight Route of administration: i.p.30 min before surgery Formulation of Desipramine hydrochloride Formulation, application volume, route, and timing of administration of Desipramine hydrochloride were performed as follows: 25 mg/kg desipramine i.p. injection 30 mins before unilateral 6-OHDA injection). All parameters for lesion item Pargyline hydrochloride are included in Table 5 below. Table 5. Name of lesion item: Pargyline hydrochloride Storage condition: 4 °C Vehicle: physiological saline (0.9% NaCl) Treatment dosage: 5 mg/kg 46 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Application volume: 5 ml/kg body weight Route of administration: i.p., 30 min before surgery Formulation of a Mixture of Despiramine and Pargyline Solution As premedication, a mixture of despiramine and pargyline solution was freshly prepared on the day of treatment. Desipramine hydrochloride is a powder and was dissolved in vehicle (0.9% NaCl) at a double concentration of 10 mg/ml. Pargyline hydrochloride is a powder and was dissolved in physiological saline at a double concentration of 2 mg/ml. As premedication, a mixture of 1 part desipramine HCl and 1 part pargyline HCl solution was prepared for treatment. The solution resulted in a final concentration of 5 mg/ml desipramine HCl and 1 mg/ml pargyline HCl for the treatment dosage of 25 mg/kg desipramine HCl and 5 mg/kg pargyline HCl using an application volume of 5 ml/kg. All parameters for lesion item L-DOPA hydrochloride are included in Table 6 below. Table 6. Name of lesion item: L-DOPA hydrochloride Storage condition: room temperature Vehicle: physiological saline (0.9% NaCl) Treatment dosage: 10 mg/kg Application volume: 1 ml/kg body weight Route of administration: i.p. All parameters for lesion item Benserazide are included in Table 7 below. Table 7. Name of lesion item: Benserazide Storage condition: Room temperature Vehicle: physiological saline (0.9% NaCl) Treatment dosage: 15 mg/kg Application volume: 1 ml/kg body weight Route of administration: i.p. together with L-DOPA 47 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 L-DOPA/Benserazide Formulation The treatment solution containing L-DOPA/Benserazide was freshly prepared on the day of treatment. L-DOPA hydrochloride is a powder and was dissolved in physiological saline at double concentration (6 mg/ml). Benserazide is a powder and was dissolved in physiological saline at a double concentration of 30 mg/ml. A mixture of 1 part 2x L-DOPA HCl and 1 part 2x Benserazide HCl solution was prepared for treatment. The solution resulted in a final concentration of 3 mg/ml L-DOPA HCl and 15 mg/ml Benserazide HCl for the treatment dosage of 3 mg/kg L-DOPA HCl and 15 mg/kg Benserazide HCl using an application volume of 1 ml/kg. All parameters for lesion item D-amphetamine are included in Table 8 below. Table 8. Name of lesion item: D-amphetamine Storage condition: at room temperature, protected from light Vehicle: physiological saline (0.9% NaCl) Treatment dosage: 2.4 mg/kg Application volume: 1 ml/ kg body weight from a solution of 2.4 mg/ml Route of administration: i.p, immediately before amphetamine-induced rotation test Formulation of D-amphetamine D-amphetamine is a powder and was dissolved in vehicle at a concentration of 2.4 mg/ml. Animal Management Accommodation of Animals As soon as the animals arrived, they were brought to the assigned animal room, unpacked, and checked for their health status. Information on the transportation system and the data provided beforehand were crosschecked. An animal list was generated including individual registration numbers (IRN), date of birth, and sex. After delivery, animals were habituated for at least 1 week at standard housing conditions before start of the experiment. Housing Animals were single-housed before surgery in individual ventilated cages on standardized rodent bedding. The temperature in the keeping room was maintained between 20 to 24 °C and the relative humidity was maintained between 45 to 65 %. Animals were housed under a constant light-cycle (12 hours light/dark). Dried, pelleted standard rodent chow as well as normal tap water was available to the animals ad libitum. Identification Animals were numbered consecutively by classical earmarking. 48 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Each cage was identified by a colored card indicating the study number, sex, the IRN of the animals, date of birth, as well as the treatment group allocation. Group Allocation Only animals in apparently good health condition were included in the study. Randomization of group allocation was done per cage. If possible, animals were assigned to different starting groups (cohorts) comprising animals of all treatment groups. The number of animals in a starting group was limited to ensure same age and uniform handling. Health Status and Cage-Side Observations Before enclosure to the study, the health status of each individual animal was evaluated. During the study, any notable cage-side observations were recorded and immediately reported to the attending veterinarian, who decided on further actions (e.g., euthanasia). Body weights were recorded once a week. Vital functions were checked regularly during the surgery. After each surgery, animals were observed intensively for 14 days in order to check tolerability of the injections. All parameters for animals used in this study are included in Table 9 below. Table 9. Rat line: Wistar Han Age at arrival: ~ 6-8 weeks Sex: Male Number of animals: 63 (60 study animals + 3 backup) Overview of Treatment- and In-life Phase Phase 1: Habituation and 6-OHDA Lesion A number of 63 male wild-type Wistar Han rats (6-8 weeks of age) were habituated at standard housing conditions for at least 1 week prior to study start. At an age of approximately 9 weeks, all animals received a unilateral intracranial injection with 2 µl (4 µg/µl) 6-OHDA into the medial forebrain bundle (MFB).3 weeks after 6-OHDA injection, the lesion efficacy was evaluated by the D-amphetamine induced rotational test. For time schedule phase 1, see Table 10 below. Table 10. Time Schedule Phase 1 – Habituation and 6-OHDA Lesion Week: beginning of week 1 week 2 end of week 3 1 _e s 6-OHDA lesion (n=63) x a h _P Rotation test (n=60) x ^ 49 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Phase 2: L-DOPA Priming After completing the D-amphetamine induced rotational test, all animals were treated with L- DOPA/Benserazide (10 mg/kg and 15 mg/kg, respectively) via i.p. injection once daily for 21 consecutive days.5 minutes (time critical ± 2 mins) after receiving the final L-DOPA/Benserazide priming dose, dyskinesia was determined by evaluating axial, limb, and orolingual abnormal involuntary movements (ALO AIMs). Animals showing the weakest symptoms in ALO AIMS were eliminated without any test item treatment and tissue collection, after which 30 animals remained. For time schedule phase 2, see Table 11 below. Table 11. Time Schedule Phase 2 – L-DOPA Priming Week: week 4 week 5 week 6 early week 7* Daily L-DOPA priming for 21 x x x x consecutive days (n=60) 2 e s_a ALO/AIMS (n=60) x after final h _P L-DOPA priming Eliminate 30 animals that do x not show dyskinesia *performed on first day of week 7 Phase 3: Gene Therapy Efficacy Assessment The remaining 30 animals were stratified based on the behavioral assays and accordingly assigned to 2 groups with n = 15 animals each. The animals were equally distributed between groups based on the results of previous behavioral tests. Specifically, animals that displayed ALO AIMs but no- or only minor rotational behavior were also included (4 animals in Group A, 3 animals in Group B). Animals of group A received vehicle via one individual unilateral injection into the ipsilateral striatum, whereas those of group B were injected with the test item (AAV-DAT). For group allocation, see Table 11 below. Table 11. Group Allocation (T.I. = Test Item, R.I. = Reference Item) Sampled Group Genotype Sex n T.I. / R.I. T.I. / R.I. Dose for Histology A WT Male 15 PBS N/A n = 8 B WT Male 15 AAV-DAT 1e+10 vg (in 5 ^l) n = 8 50 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 total n = 16 Starting one day after striatal gene therapy injection, all animals were treated by daily i.p. injection with L-DOPA/Benserazide (10 mg/kg and 15 mg/kg, respectively) for a total duration of 7 weeks. Dyskinesia (ALO AIMs) was evaluated every other week (total of 3 times), 5 minutes (time critical ± 2 mins) after each L-DOPA/Benserazide treatment as above. In the last week of the study, anxiety-like behaviors were evaluated by the Elevated Plus Maze (EPM) test. L-DOPA treatment on the testing days for EPM was performed after the behavioral tests. For time schedule phase 3, see Table 12 below. Table 12. Time Schedule Phase 3 - Gene Therapy Efficacy Assessment Week 7 8 9 10 11 12 13 ALO/AIMS (n=60; Phase 2) x after final L- DOPA 2 _e priming s_a h _P x Eliminate 30 animals that do not show dyskinesia (phase 2) AAV injection (n=30) x x x x x x x x Daily L-DOPA treatment until Start: day 1 L-DOPA treatment tissue collection (n=30) post-AAV after EPM inj. 3 _e s_a x x x h _P ALO/AIMS (n=30) after completion of EPM Elevated Plus Maze (n=30) x Tissue sampling (n=30) x ^ 51 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 After completing the final evaluation of dyskinesia/ALO AIMs in week 13, daily i.p. treatment with L-DOPA/Benserazide was continued until the day of tissue collection. One hour (time critical ± 5 mins) after the last L-DOPA/Benserazide treatment, all animals were euthanized by i.p. injection of pentobarbital. Following transcardial perfusion with saline, whole brains of n = 8 animals per group were collected for histological analysis. Surgical Procedure (Phase 1, 6-OHDA Lesion) All 60 animals were treated by unilateral intracranial injection of 6-OHDA (containing 0.02% ascorbic acid). The 6-OHDA solution was prepared on the day of treatment and stored at 4 °C and protected from light until usage. 30 mins before intracranial injection, every animal received premedication consisting of an i.p. injection of a mixture of 25 mg/kg desipramine and 5 mg/kg pargyline. All surgical operations were performed under adequate inhalation anesthesia. For inhalation anesthesia, an isoflurane vaporizer was used. Anesthesia was induced with a concentration of 4.5-5% isoflurane and maintained during surgery with a concentration of 1.5-2% isoflurane. For pain management and sedation, buprenorphine 0.04 mg/kg was administered i.p. at least 10 minutes before surgery using an application volume of 1 µl per g bodyweight. The fur was shaved and the skin of the target area was disinfected. Eyes were covered with an eye ointment for protection. Rats were placed in a stereotaxic apparatus; a midline incision of the scalp was made, and the skull was carefully cleared from the skin and the muscles. Thereafter, a hole was drilled above the target region. Animals received one unilateral stereotaxic injection of 2 µL 6-OHDA (Sigma) into the MFB using a 2 ^l Hamilton microsyringe fitted with a 30-gauge steel cannula at the following coordinates from Bregma: ap (anterior/posterior): - 2.8 mm ml (midline): - 1.7 mm (right side) dv (dorsoventral): 8.2 mm (from the Dura) The injection rate was 0.5 ^l/min (for 4 mins) and the cannula was left in place for an additional 3 mins before slowly retracting it. To minimize variability due to degradation of the toxin, the 6-OHDA solutions were freshly made, kept on ice, and protected from exposure to light. After injection, wounds were closed with a surgical suture and if necessary, tissue adhesive was applied on the suture. Rodents were observed, and if needed, housed individually until they were fully ambulatory. Animals were observed intensively in order to check tolerability of the injection for at least 14 days after injection. Surgical Procedure (Phase 3, Gene Therapy Efficacy Assessment) After completion of the 3-week L-DOPA/Benserazide priming phase and the first ALO AIMs assessment (Phase 2), the remaining 30 animals of groups A and B received a unilateral injection with either vehicle (group A) or test construct (AAV-DAT, group B) into the ipsilateral (right side) striatum. For inhalation anesthesia, an isoflurane vaporizer was used. Anesthesia was induced with a concentration of 4.5-5% isoflurane and maintained during surgery with a concentration of 1.5-2% 52 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 isoflurane. For pain management, buprenoprhine 0.02 mg/kg + midazolam 0.75 mg/kg + ketamine 30 mg/kg was administered subcutaneously at least 30 minutes before surgery using an application volume of 10 µl per g bodyweight. The fur of the anesthetized animal was shaved on the head and the skin of the target area was disinfected. Eyes were covered with an eye ointment for protection. The animal was placed in a stereotaxic apparatus and on a heating pad to prevent hypothermia. The depth of anesthesia was verified by the toe pinch and eye blink reflex. A midline incision of the scalp was made and the skull was carefully cleaned to make skull suture lines visible. Thereafter, a hole was drilled above the target region, using Bregma as a reference point. The coordinates were measured from dura. The solutions (5 µl of vehicle or AAV-DAT) were injected unilaterally into the ipsilateral (right side) striatum with a Hamilton micro liter syringe. The following coordinates were used, corresponding to the caudate putamen (CPU) area in the striatum: ap (anterior/posterior): + 0.5 mm ml (midline): + 3.2 mm (right side) dv (dorsoventral): - 5.0 mm For the injection, Hamilton micro liter syringes were used. The injection was done by hand at an approximate speed of 0.5 ^l/min and 5 mins resting time. Afterwards, injection wounds were closed with a surgical suture and, if necessary, tissue adhesive was applied. Vital functions were checked regularly during the surgery. After the surgery, animals were observed intensively for 14 days in order to check tolerability of the injection. Behavioral Assessment The D-amphetamine induced rotational test and ALO AIMs assessments were performed in a time critical manner within a defined time period after the treatment. The Elevated Plus Maze test was not time critical. L-DOPA treatment on the testing days for EPM was performed after the behavioral tests. Amphetamine Induced Rotation in Rotometer Bowls (Phase 1) Three weeks after 6-OHDA injection, the lesion efficacy was assessed for all 60 animals by evaluation of locomotor asymmetry in the D-amphetamine induced rotational test. Amphetamine induced-rotational behavior was assessed with a video tracking software. The rotometer bowls were black hemispheres with 50 cm diameter. The process was videotaped and analysed using EthoVision XT ®, provided by Noldus, the Netherlands. The test took place under standard light illumination. On the test days, rats were placed in the rotometer bowls 30 minutes (time critical ± 2 mins) after injecting 2.4 mg/kg D-amphetamine i.p. The behavior during the test session was recorded for 60 minutes, and behavioral parameters were calculated, such as clockwise/counterclockwise rotation. ALO AIMs Assessment (Phase 2 and Phase 3) ALO AIMs were assessed at the following time points during the study. Phase 2 (Time Critical) 53 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 ALO AIMs were determined once for all 60 animals after receiving the final L-DOPA/Benserazide priming dose. On the testing day, ALO AIMs were scored starting 5 minutes (± 2 mins) after L-DOPA/Benserazide (10 mg/kg and 15 mg/kg, respectively) i.p. treatment and every 20 minutes thereafter for 3 hours. Based on the results of this test, 30 animals showing the weakest symptoms in ALO AIMS were eliminated without any test item treatment and tissue collection. Phase 3 (Time Critical) Each of the 30 animals of groups A and B underwent 3 individual testings (1 per day on 3 different days, see section on Overview of Treatment- and In-life Phase). On testing days, ALO AIMs were scored starting 5 minutes (± 2 mins) after L-DOPA/Benserazide (10 mg/kg and 15 mg/kg, respectively) i.p. treatment and every 20 minutes thereafter for 3 hours. On testing days, ALO AIMs were scored at start and every 20 mins thereafter for 3 hours, since within this timeframe after treatment, ALO AIMs almost always subside completely. All animals were placed in empty cages without bedding material. Axial, limbs, and oro-lingual (ALO) abnormal involuntary movements (AIMs) were rated by an observer blinded to treatment, which encompassed both time-based, i.e., “duration” and severity-based, i.e., “amplitude”, assessment of abnormal movements. ALO AIMs were scored for 1 min, every 20 mins for 180 mins. ALO AIMs duration was rated according to the following scale: 0 = no dyskinesia; 1 = occasional signs of dyskinesia, present for less than 50% of the observation period; 2 = frequent signs of dyskinesia, present for more than 50% of the observation period; 3 = dyskinesia present during the entire observation period, but suppressible by external stimuli (i.e., sudden, noisy opening of the cage lid) and 4 = continuous dyskinesia not suppressible by external stimuli. Axial AIMs amplitude was rated according to the following scale: 1 = sustained deviation of the head and neck at ^ 30° angle; 2 = sustained deviation of the head and neck at an angle between 30° and 60°; 3 = sustained twisting of the head, neck and upper trunk at an angle between 60° and 90°, and 4 = sustained twisting of the head, neck, and trunk at an angle ^ 90°, causing the rat to lose balance from a bipedal position. Limbs AIMs amplitude was rated according to the following scale: 1 = tiny movements of the paw around a fixed position; 2 = movements leading to a visible displacement of the whole limb; 3 = large displacement of the whole limb with visible contraction of shoulder muscles; and 4 = vigorous limb displacement of maximal amplitude, with concomitant contraction of shoulder and extensor muscles. Oro- lingual AIMs amplitude was rated according to the following scale: 1 = twitching of facial muscles accompanied by small masticatory movements without jaw opening; 2 = twitching of facial muscles accompanied by masticatory movements that result in jaw opening; 3 = movements with broad involvement of facial and masticatory muscles, with frequent jaw opening and occasional tongue protrusions; and 4 = involvement of all of the above muscles to the maximal possible degree. Integrated ALO AIMs were defined as the product of ALO AIMs amplitude × ALO AIMs duration, while cumulative ALO AIMs indicates the sum of ALO AIMs duration or of ALO AIMs amplitude over different consecutive measurement time points. Elevated Plus Maze (EPM) (Phase 3) 54 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 The EPM test was performed for each of the 30 animals of groups A and B in the last week of the study (week 13, not time critical). The EPM is one of the most widely used tests to study anxiety in small rodents. This test is based on the aversion of rodents to open spaces and height. The EPM-Apparatus is a four-arm maze with two opposing open arms and two opposing closed arms (sheltered arms, with walls), raised 50 cm above the surface. The test took place under red light illumination. On the testing day, animals were brought into the experimental room 45-60 mins prior to testing. The rat was placed in the center area facing an open arm. The behavior during the test session was recorded for five minutes, and behavioral parameters were calculated, such as time spent in the open and in the closed arms, number of visits in the open and closed arms as well as latency to enter the open arm. Data was generated by using Noldus, EthoVision XT 14 ®. Tissue Sampling (Time Critical) After completing the final evaluation of dyskinesia/ALO AIMs in week 13, daily i.p. treatment with L-DOPA/Benserazide was continued until the day of tissue collection. 1 hour (time critical ± 5 mins) after the last L-DOPA/Benserazide treatment, all animals were euthanized by i.p. injection of pentobarbital. Anesthesia Rats were terminally anesthetized by i.p. injection of Pentobarbital (600 mg/kg, dosing 10 ^l/g body weight). Perfusion and Brain Sampling Animals were transcardially perfused with 0.9% saline. To this end a 21-gauge needle connected to a bottle with 0.9% saline was inserted into the left ventricle. The thoracic aorta - between the lungs and the liver - was clamped with hemostatic forceps to block the blood flow from the heart to the abdomen but allowing the blood flow to the brain. The right atrium was opened with scissors. A constant pressure of 100 to 120 mm Hg was maintained on the perfusion solution by connecting the solution bottle to a manometer-controlled air compressor. Perfusion was continued until the skull surface had turned pale and only perfusion solution instead of blood was exiting the right atrium. After perfusion, the skull was opened and afterwards the brain was removed carefully. Brain Sampling for Histology Whole brains of n = 8 animals per group (total n = 16) were fixed by immersion in 4% paraformaldehyde (PFA) in phosphate buffer (PB; pH 7.4) overnight at 4 °C. Histological Analysis Following fixation by immersion in freshly prepared 4% paraformaldehyde in phosphate buffer (PB; pH 7.4) overnight at 4°C, whole brains of 8 animals per group (total n = 16 brains) were then transferred to 15% sucrose/PBS and stored at 4 °C until sample sunk to the bottom of the tube to ensure cryoprotection (usually overnight). Tissue blocks were then trimmed as needed, transferred to cryomolds, 55 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 embedded in optimal cutting temperature (OCT) medium, frozen in dry ice-cooled isopentane, and stored in an ultra-deep freezer (set at -80 °C). Sectioning From each brain, up to 80 coronal sections were collected throughout the striatum and around the AAV injection sites, and from the substantia nigra (for cutting scheme, see FIG.1). Immunofluorescence For each incubation, a uniform systematic random set of five sections per rat from both striatum and SN each were selected (80 sections per striatum and SN; total n = 160). Protocol: hDAT + TH + 5-HTT + GFAP + DAPI All steps were executed in Dulbecco’s phosphate buffered saline pH 7.2-7.8 (PBS) at room temperature unless noted otherwise. The steps are as follows: 1. Cryosections were air-dried for 45 mins and then washed in PBS for 10 mins. 2. Sections were postfixed with 4% paraformaldehyde in 0.1 M PBS for 10 mins. 3. Sections were washed 3 x 5 mins each in PBS. 4. Antigen demasking: sections were treated with 10% citrate buffer for 15 mins at 95 °C in a steamer, followed by cool down for 15 mins. 5. Sections were washed 2 x 5 mins each in PBS. 6. Reduction of autofluorescence by 4 mins in cold 1 mg/ml sodium borohydrate in PBS was performed. 7. Sections were washed 3 x 5 mins each in PBS. 8. Unspecific binding sites were blocked with 10% normal donkey serum in 0.1% Triton X-100 in PBS for 60 minutes in a damp chamber. 9. Sections were washed 3 x 5 mins each in PBS. 10. Sections were incubated with primary antibodies in 1% normal donkey serum over night at 4 ^°C in a damp chamber. rabbit polyclonal anti-human DAT (Merck Millipore, AB1766), 1:800 sheep polyclonal anti-TH (Novus Biologicals, NB300-110), 1:1000 guinea pig polyclonal anti-5-HTT (Synaptic Systems, 340004), 1:800 chicken polyclonal anti-GFAP (Synaptic Systems, 173006), 1:2000 11. Sections were washed 3 x 5 mins each in PBS. 12. Sections were incubated with secondary antibodies in 1% normal donkey serum for 60 mins in a damp chamber (light protected). donkey anti-rabbit IgG H+L Alexa 750-conjugated (Abcam, ab175728), 1:500 donkey anti-goat IgG H+L Alexa 488-conjugated (Abcam, ab150129), 1:500 donkey anti-guinea pig IgG H+L Cy3-conjugated (Jackson Immunoresearch, 706-165- 148), 1:500 donkey anti-chicken IgG H+L Alexa 647-conjugated, (Jackson Immunoresearch, 703-605- 155), 1:500 56 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 13. Sections were washed 3 x 5 mins each in PBS (light protected). 14. Sections were incubated with 4^,6-diamidino-2-phenylindole (DAPI) working solution for 15 mins (light protected). 15. Sections were washed 2 x 5 mins in PBS (light protected). 16. Sections were washed 5 mins in ddH2O (light protected). 17. Sections were automatically covered with Mowiol and coverslips (light protected) using a Leica CV5030 coverslipper. Protocol: hDAT + ChAT + Parvalbumin + CTIP2 1. Cryosections were air-dried for 45 mins and then washed in PBS for 10 mins. 2. Sections were postfixed with 4% paraformaldehyde in 0.1 M PBS for 10 mins. 3. Sections were washed 3 x 5 mins each in PBS. 4. Antigen demasking: sections were treated with 1x citrate buffer (Abcam, ab64236) for 15 mins at 95 °C in a steamer, followed by cooling down for 15 mins. 5. Sections were washed 2 x 5 mins each in PBS. 6. Reduction of autofluorescence by 4 mins in cold 1 mg/ml sodium borohydrate in PBS. 7. Sections were washed 3 x 5 mins each in PBS. 8. Unspecific binding sites were blocked with 10% normal donkey serum in 0.1% Triton X-100 in PBS for 60 mins in a damp chamber. 9. Sections were washed 3 x 5 mins each in PBS. 10. Sections were incubated with primary antibodies in 1% normal donkey serum in PBS over night at 4 °C in a damp chamber. rabbit polyclonal anti-human DAT (Merck Millipore, AB1766), 1:5000 goat polyclonal anti-ChAT (Merck Millipore, AB1766), 1:300 mouse monoclonal anti-parvalbumin (Swant, PV235), 1:1000 rat monoclonal anti-CTIP (Abcam, ab18465), 1:2000 11. Sections were washed 3 x 5 mins each in PBS. 12. Sections were incubated with secondary antibodies in 1% normal donkey serum for 60 mins in a damp chamber (light protected). donkey anti-rabbit IgG H+L Alexa 750-conjugated (Abcam, ab175728), 1:500 donkey anti-goat IgG H+L DyLight 650-conjugated (Abcam, ab96938), 1:500 donkey anti-mouse IgG H+L DyLight 550-conjugated (Thermo Fisher, SA5-10167), 1:500 donkey anti-rat IgG H+L Alexa Fluor 488-conjugated (Jackson Immunoresearch, 712- 545-153), 1:500 13. Sections were washed 3 x 5 mins each in PBS (light protected). 14. Sections were incubated with DAPI working solution for 15 mins (light protected). 15. Sections were washed 2 x 5 mins in PBS (light protected). 16. Sections were washed 5 mins in ddH2O (light protected). 17. Sections were automatically covered with Mowiol and coverslips (light protected) using a Leica CV5030 coverslipper. Protocol: hDAT + VAChT + Calbindin + nNOS 57 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 1. Cryosections were air-dried for 45 mins and then washed in PBS for 10 mins. 2. Sections were postfixed with 4% paraformaldehyde in 0.1 M PBS for 10 mins. 3. Sections were washed 3 x 5 mins each in PBS. 4. Antigen demasking: sections were treated with 1x citrate buffer (Abcam, ab64236) for 15 mins at 95 °C in a steamer, followed by cooling down for 15 mins. 5. Sections were washed 2 x 5 mins each in PBS. 6. Reduction of autofluorescence by 4 mins in cold 1 mg/ml sodium borohydrate in PBS. 7. Sections were washed 3 x 5 mins each in PBS. 8. Unspecific binding sites were blocked with 10% normal donkey serum in 0.1% Triton X-100 in PBS for 60 mins in a damp chamber. 9. Sections were washed 3 x 5 mins each in PBS. 10. Sections were incubated with primary antibodies in 1% normal donkey serum in PBS over night at 4°C in a damp chamber. rabbit polyclonal anti-human DAT (Merck Millipore, AB1766), 1:5000 guinea pig polyclonal anti-VAChT (Synaptic Systems, 139105), 1:1500 mouse monoclonal anti-calbindin D-28k (Swant, 300), 1:1000 goat polyclonal anti-nNOS (Abcam, ab1376), 1:100 11. Sections were washed 3 x 5 mins each in PBS. 12. Sections were incubated with secondary antibodies in 1% normal donkey serum for 60 mins in a damp chamber (light protected). donkey anti-rabbit IgG H+L Alexa 750-conjugated (Abcam, ab175728), 1:500 donkey anti-guinea pig IgG H+L Cy3-conjugated (Jackson ImmunoResearch, 706-165- 148), 1:500 donkey anti-mouse IgG H+L DyLight 488-conjugated (Thermo Fisher, A-21202), 1:500 donkey anti-goat IgG H+L DyLight 650-conjugated (Abcam, ab96938), 1:500 13. Sections were washed 3 x 5 mins each in PBS (light protected). 14. Sections were incubated with DAPI working solution for 15 mins (light protected). 15. Sections were washed 2 x 5 mins in PBS (light protected). 16. Sections were washed 5 mins in ddH2O (light protected). 17. Sections were automatically covered with Mowiol and coverslips (light protected) using a Leica CV5030 coverslipper. Protocol: hDAT + DARPP-32 + Parvalbumin + Calbindin 1. Cryosections were air-dried for 45 mins and then washed in PBS for 10 mins. 2. Sections were postfixed with 4% paraformaldehyde in 0.1 M PBS for 10 mins. 3. Sections were washed 3 x 5 mins each in PBS. 4. Antigen demasking: sections were treated with 1x citrate buffer (Abcam, ab64236) for 15 mins at 95 °C in a steamer, followed by cool down for 15 mins. 5. Sections were washed 2 x 5 mins each in PBS. 6. Reduction of autofluorescence by 4 mins in cold 1 mg/ml sodium borohydrate in PBS. 7. Sections were washed 3 x 5 mins each in PBS. 58 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 8. Unspecific binding sites were blocked with 10% normal donkey serum in 0.1% Triton X-100 in PBS for 60 mins in a damp chamber. 9. Sections were washed 3 x 5 mins each in PBS. 10. Sections were incubated with primary antibodies in 1% normal donkey serum in PBS over night at 4°C in a damp chamber. rabbit polyclonal anti-human DAT (Merck Millipore, AB1766), 1:5000 mouse monoclonal anti-DARPP-32 (Becton Dickinson, 611520), 1:1000 goat polyclonal anti-parvalbumin (Swant, PVG-213), 1:2000 chicken polyclonal anti-Calbindin D-28k (Synaptic Systems, 214006), 1:1000 11. Sections were washed 3 x 5 mins each in PBS. 12. Sections were incubated with secondary antibodies in 1% normal donkey serum for 60 mins in a damp chamber (light protected). donkey anti-rabbit IgG H+L Alexa Fluor 750-conjugated (Abcam, ab175728), 1:500 donkey anti-mouse IgG H+L DyLight 650-conjugated (Thermo Fisher, SA5-10169), 1:500 donkey anti-goat IgG H+L DyLight 550-conjugated (Abcam, ab96936), 1:500 donkey anti-chicken IgG H+L Alexa Fluor 488-conjugated (Jackson ImmunoResearch, 703-545-155), 1:500 13. Sections were washed 3 x 5 mins each in PBS (light protected). 14. Sections were incubated with DAPI working solution for 15 mins (light protected). 15. Sections were washed 2 x 5 mins in PBS (light protected). 16. Sections were washed 5 mins in ddH2O (light protected). 17. Sections were automatically covered with Mowiol and coverslips (light protected) using a Leica CV5030 coverslipper. Imaging Whole slide scans of the stained sections were recorded on a Zeiss ® automatic microscope AxioScan Z1 with high aperture lenses, equipped with a Zeiss ® Axiocam ® 506 mono and a Hitachi 3CCD HV-F202SCL camera, and Zeiss ® ZEN 3.7 software. Quantification of hDAT, TH, 5-HTT, and GFAP signal Image analysis was done with Image Pro 10 (Media Cybernetics). In the beginning, the target areas (contra – and ipsilateral SN and striatum) were identified by drawing regions of interest (ROI) on the images. Additional ROIs exclude wrinkles, air bubbles, or any other artifacts interfering with the measurement. Afterwards, signal of hDAT, TH, 5-HTT, and GFAP were quantitatively evaluated within the identified areas. For quantification, background correction was used and immunoreactive objects were detected by adequate thresholding and morphological filtering (size, shape). Different object features were then quantified, among them the percentage of cumulative object area based on ROI size (immunoreactive area; this is the most comprehensive parameter indicating whether there were differences in immunoreactivity), the number of objects normalized to ROI size (object density), the mean signal intensity of identified objects (mean intensity; this indicates if there are differences in the cellular 59 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 expression level of target proteins), and the size of above-threshold objects. Once the parameters of the targeted objects had been defined in a test run, the quantitative image analysis ran automatically so that the results are operator-independent and fully reproducible. Raw data were organized and sorted in Excel, and then transferred to GraphPad Prism™ for statistical analysis and preparation of graphs. Qualitative Evaluation of hDAT and Subtype-Specific Neuronal Markers The following qualitative histological assessments were also performed on striatum sections: Exp 1: Rb hDAT + gt ChAT + ms Parvalbumin + rt CTIP2 Exp 2: Rb hDAT + gp VAChT + ms Calbindin + gt nNOS Exp 3: Rb hDAT + ms DARPP-32 + gt Parvalbumin + ck Calbindin For Exps 1 and 2, sections from 3 animals of group B were used (6 sections in total). For Exp 3, sections from 3 animals of group B were used. Negative controls (omitted primary antibodies) were run on additional sections. Nuclei were labeled with DAPI. Whole slide images were acquired and overlay of hDAT and subtype-specific neuronal markers were evaluated qualitatively to identify neurons that were AAV-infected and express hDAT. Images were opened with Zeiss ® ZEN software and the labeling pattern was analyzed. Statistics All raw data were analyzed in GraphPad Prism™ 10 (GraphPad Software Inc., USA). For all experiments, normality distribution was performed first. Normality distribution of two groups was analyzed by Kolmogorov-Smirnov test. Depending on Gaussian distribution, unpaired Student’s T- test or the nonparametric Mann Whitney test was performed. If more than 2 groups were compared with each other, significance was calculated by one-way or two-way analysis of variance (ANOVA) followed by the Bonferroni post hoc test for normally distributed data. In case of missing values or non-normally distributed data, significance was calculated by mixed-effects analysis followed by Bonferroni’s multiple comparisons test or by Kruskal-Wallis test followed by Dunn’s multiple comparisons test, respectively. Unless described otherwise, graphs depict group means and standard error of the mean (SEM). Significance is defined as *p<0.05, **p<0.01, and ***p<0.001. Results General observations In general, the test compound (AAV-DAT) was tolerated well, with no unexpected negative side effects of the treatments observed over the entire duration of the study. Body Weight Body weight was measured weekly for the entire study duration (FIG.2). All animals gained weight as expected, especially, in the first three weeks after study start. Subsequently, body weight plateaued until approximately study week 8, when body weight started to increase again. No differences between PBS treated- or AAV-DAT-treated animals could be detected. Behavioral Analysis – Evaluation of Lesion Efficiency and Stratification Amphetamine Induced Rotation Test (Phase 1) 60 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Three weeks after 6-OHDA injection, all animals were tested for lesion efficacy using the D- amphetamine-induced rotation test. The majority of animals displayed robust rotational behavior as well as mainly ipsilateral rotations (which is to be expected with amphetamine induced rotation), which is indicative of a highly effective 6-OHDA lesion. The main purpose of this assay was to assess the individual performance of each animal; therefore, no group-wise statistical analysis was performed. Total number or rotations (left panel), and percentage of ipsilateral rotations (right panel) per individual animal are displayed in FIG.3. After this test, L-DOPA priming was continued on all animals for 21 consecutive days. ALO AIMs Assessment (Phase 2) 5 minutes after receiving the final L-DOPA/Benserazide priming dose, dyskinesia was determined by evaluating axial, limb, and orolingual abnormal involuntary movements (ALO AIMs). The majority of animals displayed robust ALO AIMs, again indicating high lesion efficiency, and effective L-DOPA induced dyskinesia (FIG.4). Based on these results, 30 animals generally showing the weakest symptoms in ALO AIMs were eliminated at this stage without tissue collection. The remaining 30 animals were stratified equally into two groups. To this end, animals were chosen in such a way, that as much as possible, two balanced groups were created. To maximize this balance, few animals with otherwise high ALO scores were disregarded and eliminated. A number of animals displayed robust ALO AIMs scores, however, had not previously displayed rotational behavior in the D-Amphetamine induced rotation test. A number of these animals were also specifically included for further testing (4 animals in Group A, 3 animals in Group B). Animals of group A received vehicle (PBS) via one individual unilateral injection into the ipsilateral striatum, whereas rats of group B were injected with the test construct (AAV-DAT). Behavioral Analysis – Efficacy Testing ALO AIMs Assessment In addition to baseline testing in study week 7, ALO AIMs were assessed a total of three times in all remaining animals (study week 9, 11, and 13, corresponding to 2-, 4- and 6- weeks post AAV-DAT treatment), each time 5 mins after L-DOPA/Benserazide treatment (FIG.5 and FIG.6). At baseline (week 7), before stereotactic application of test item or vehicle, no statistically significant differences in total ALO AIMs score between both groups were detected, confirming that animals were stratified equally based on dyskinesia (FIG.5, baseline). However, starting in week 9 (two weeks after test compound applications), rats treated with AAV-DAT showed markedly and statistically significantly reduced scores, compared to vehicle treated rats (FIG.5, Week 2). This effect was even more pronounced in week 11 (FIG.5, Week 4) and 13 (FIG.5, Week 6) (four- and six weeks after test compound applications, respectively). At both timepoints, vehicle treated animals still showed robust dyskinesia, while animals treated with AAV-DAT displayed hardly any dyskinesia at all. This suggests that a single application of AAV-DAT was able to effectively and lastingly suppress dyskinesia induced by continuous L-DOPA treatment. The statistical analyses from the results in FIG.5 are shown in Tables 14, 15, and 16 below. 61 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Table 14. Mixed effects analysis, followed by Bonferroni’s multiple comparisons test, Mean Diff., 95,00%, Cl of diff., Below Threshold? Summary Adjusted P Value A. PBS baseline vs Week 2 7 -5,08 to 19,1 No ns 0,48 baseline vs Week 4 17,5 5,45 to 29,6 Yes ** 0,002 baseline vs Week 6 15,4 3,32 to 27,5 Yes ** 0,008 Table 15. Mixed effects analysis, followed by Bonferroni’s multiple comparisons test, Mean Diff., 95,00%, Cl of diff., Below Threshold? Summary Adjusted P Value B. AAV-DAT baseline vs Week 2 48,6 36,5 to 60,7 Yes *** <0,001 baseline vs Week 4 61,3 49,2 to 73,4 Yes *** <0,001 baseline vs Week 6 63,7 51,6 to 75,8 Yes *** <0,001 Table 16. Mixed effects analysis, followed by Bonferroni’s multiple comparisons test, Mean Diff., 95,00%, Cl of diff., Below Threshold? Summary Adjusted P Value A. PBS – B. AAV-DAT baseline -3,93 -18,6 to 10,8 No ns >0,99 Week 2 37,7 23,0 to 52,4 Yes *** <0,001 Week 4 39,8 25,1 to 54,5 Yes *** <0,001 Week 6 44,3 29,6 to 59,0 Yes *** <0,001 Notably, in vehicle treated animals, a moderate but statistically significant reduction in ALO AIMs scores was observed between baseline and week 11 or 13, respectively. While the reason for this decline in dyskinesia severity is not clear, a similar pattern has been previously observed in striatum-lesioned mice after few weeks of L-DOPA treatment. It was hypothesized that the desensitization of postsynaptic D1 receptor, and the shortening of the motor response duration to L-DOPA similar to the “wearing-off” phenomenon observed in PD patients may account for this. Although motor response to L-DOPA was not monitored in this study and a different model was used, this could partly explain the decline in dyskinesia observed in vehicle control animals. However, AAV-DAT treatment was able to revert dyskinesia way beyond this intrinsic reduction at all tested timepoints. To further delineate these results, four individual categories of ALO AIMs (basic, limbs, axial, and orolingual) were analyzed separately for the 6-weeks post-test compound application time point (FIG.6). 62 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 In all four categories, AAV-DAT treatment significantly reduced ALO AIM scores in comparison to vehicle treated animals, indicating a generalized treatment effect rather than limited effects to specific AIMs. The statistical analyses from the results in FIG.6 are shown in Table 17 below. Table 17. Bonferroni’s multiple comparisons test A. PBS – B. AAV-DAT Below threshold? Summary Adjusted P Value Basic Yes *** <0,001 Limbs Yes *** <0,001 Axial Yes *** <0,001 Oro Yes *** <0,001 Longitudinal analysis of ALO AIMs scores showed a similar situation (FIG.7). At baseline, animals of both groups showed dyskinesia starting at 20 min after L-DOPA treatment,and peaking at around 60 min after L-DOPA treatment (FIG.7, top left panel, baseline). Subsequently, ALO AIMs scores started to subside, until no dyskinesia was detected anymore, around 160 min post-L-DOPA treatment. No group differences could be detected at any timepoint, again confirming that animals were equally stratified to both groups before stereotactic test compound application. In study week 9 (two weeks post gene therapy treatment), vehicle treated animals showed a similar dyskinesia profile, maintaining a sustained high level of LID severity. However, AAV-DAT treated animals showed a marked reduction in dyskinesia from 20 min post L-DOPA treatment, at all timepoints until the entirely subsided at 100 minutes post L-DOPA treatment (FIG.7, top right panel, Week 2). Again, this effect was even more pronounced at 4- (FIG.7, bottom left panel, Week 4) and 6- (FIG.7, bottom right panel, Week 6) weeks post vector administration, when hardly any dyskinesia was observed in AAV-DAT treated animals. This again suggests that AAV-DAT treatment was able to effectively counteract L-DOPA induced dyskinesia with an effect persisting for the entire duration of the study. The statistical analyses from the results in FIG.7 are shown in Tables 18, 19, and 20 below. Table 18. Bonferroni’s multiple comparisons test, Below Threshold? Summary Adjusted P Value (Week 2 post-AAV injection) Bonferroni’s multiple comparisons test Below threshold? Summary Adjusted P Value 20 Yes *** <0,001 40 Yes *** <0,001 60 Yes *** <0,001 63 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 80 Yes *** <0,001 100 Yes *** <0,001 120 Yes ** 0,006 Table 19. Bonferroni’s multiple comparisons test, Below Threshold? Summary Adjusted P Value (Week 4 post-AAV injection) Bonferroni’s multiple comparisons test Below threshold? Summary Adjusted P Value 20 Yes *** <0,001 40 Yes *** <0,001 60 Yes *** <0,001 80 Yes *** <0,001 100 Yes *** <0,001 Table 20. Bonferroni’s multiple comparisons test, Below Threshold? Summary Adjusted P Value (Week 6 post-AAV injection) Bonferroni’s multiple comparisons test Below threshold? Summary Adjusted P Value 20 Yes *** <0,001 40 Yes *** <0,001 60 Yes *** <0,001 80 Yes *** <0,001 100 Yes *** <0,001 Elevated Plus Maze (EPM) To test whether non-motor phenotypes of PD, specifically anxiety, are affected by AAV-DAT treatment, the EPM test was performed once at the end of the study (6 weeks post gene therapy treatment) (FIG.8). This test exploits the tendency of rodents to avoid open spaces. A higher proportion of time spent in the open arms of the maze, and a higher number of entries in the open arms can be interpreted as lower anxiety. 64 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 No statistically significant differences in number of entries in open- or closed arms between groups was observed. However, animals treated with AAV-DAT spent significantly lower time in the closed arms, compared to vehicle treated animals. Furthermore, AAV-DAT treated animals showed a slight tendency for more time spent in open arms compared to vehicle treated rats, even though this was not statistically significant. Together, these results suggest that treatment with AAV-DAT might positively influence anxiety levels in this model. It should be also noted that a L-DOPA naïve control group was not included in this study, however, it has been previously reported that chronic L-DOPA treatment may elicit a mild anxiogenic effect in hemiparkinsonian rats. The statistical analyses from the results in FIG.8 are shown in Table 21 below. Table 21. Mann Whitney Test Mann Whitney test P value P value summary Significantly different (P < 0.05)? 0,04 * Yes Histological Analysis Qualitative Assessment The brains were processed and no technical issues were encountered during histological analysis. Measurements in repeated sections led to comparable background throughout all sections from all animals of all groups. No differences in tissue quality were detected during histological procedures, and the tissue quality was generally good for all samples. Examples of immunofluorescence labeling are provided in FIG.9, showing immunofluorescence labeling in SN (containing both SN pars compacta (SNpc) and SN reticulata (SNr)), and in FIG.10, in CPU. The multichannel immunofluorescence clearly shows TH signal being largely to almost completely absent in the striatum of the 6-OHDA-injected hemisphere, indicating that the lesion was very effective. Intense immunofluorescence for hDAT was detected exclusively in the injected hemisphere, and the virus infected cells up to 1000 µm away from the injection site. However, the hDAT antibody showed some weaker but recognizable crossreactivity with rat DAT, resulting in faint immunofluorescence signal throughout the entire contralateral striatum. Antibody to serotonin-transporter (5-HTT) labeled axonal fibers in the striatum and in the substantia nigra. The morphology of 5-HTT-positive fibers looked very similar between hemispheres, indicating that they were not affected by the lesion and viral injection. A small number of neuronal somata was intensely positive for hDAT in the striatum, and the shape and size of these somata suggest these are either cholinergic interneurons or GABAergic parvalbumin-positive interneurons. It is likely that at least a large proportion of the dense hDAT-positive neuropil network at the injection site comes from these infected striatal interneurons. The identity of these cells was further checked by immunolabeling of striatal sections with antibodies to ChAT (cholinergic neurons), parvalbumin (subpopulation of GABAergic interneurons), somatostatin (GABAergic interneuronal subpopulation), VAChT (cholinergic neurons), calbindin (subpopulation of striatal 65 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 GABAergic neurons), DARPP-32 (medium spiny neurons), and nNOS (subpopulation of GABAergic interneurons). Definition of Target Regions Target regions were manually outlined by defining the region of interest (ROI) for the subsequent quantitative analyses of fluorescent labeling (FIG.11). Fluorescent objects were identified within the ROI using a sequence of background correction, thresholding, and morphological filtering of above-threshold objects. Different object features were then quantified, which are described below. Readouts of Quantitative Analysis Region size [mm²]: These data show the average area per brain section covered by the target region. This information is important to verify proper sampling. It is also helpful to identify brain atrophy which is part of the phenotype of some animal models. Immunoreactive area [%]: The percentage of the ROI that is covered by above-threshold immunoreactive objects (for example: cell somata, neurites, plaques); this is the most comprehensive parameter indicating whether there are overall differences in immunoreactivity. Object density [number of objects per mm²]: The number of above-threshold immunoreactive objects normalized to the size of the target area; this is especially useful to detect changes in neuronal density. Object intensity [a.u.]: The average brightness of pixels of above-threshold immunoreactive objects; this indicates if there are differences in the cellular expression level of target proteins. Object size [µm²]: The size of above-threshold immunoreactive objects; this is useful to detect differences in activation of microglia or growth of plaques. Region Size The size of the target regions was determined. The data presented in FIG.12 show the total average area per section of the CPU and the SN as measured from the ROI on five sagittal sections per region. Significant differences between hemispheres and between treatment groups were detected, which is a common finding in invasive models due to cell death and glial scarring. The difference in target area is accounted for by normalizing quantitative readouts “immunoreactive area” and “object density” to the size of target region. Human DAT Immunofluorescence of human DAT (hDAT) was detected with rabbit polyclonal antibody, and the signal was quantified in the caudate-putamen (CPU) (FIG.13), and substantia nigra (SN) (FIG.14). In the CPU, hDAT signal was detected in the non-lesioned hemisphere (left) of both AAV-DAT and control groups, indicating some degree of cross-reactivity of the human-specific antibody with endogenous DAT protein from dopaminergic fibers and/or background signal. On the 6-OHDA lesioned side (right), low levels of hDAT signal were also detected in control animals, either deriving from endogenous DAT expressed in fewer surviving dopaminergic fibers and/or background signal. Striatal injection of AAV-DAT significantly increased hDAT signal compared to PBS-injected rats, indicating efficient delivery and expression of the transgene protein in the target region. Notably, hDAT expression was also significantly 66 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 increased in the SN of gene therapy treated animals, and specifically localizing within the substantia nigra pars reticulata (SNpr), indicating potential anterograde transport of hDAT from the striatum to the SNpr by direct striatal GABA-ergic projections, in the absence of functional nigrostriatal fibres and SNpc due to 6- OHDA lesioning. 5-HTT Immunofluorescence of 5-HTT, which is a marker for the serotonin transporter, was detected with guinea pig polyclonal antibody, and the signal was quantified in CPU (FIG.15) and in SN (FIG.16). No difference in 5-HTT signal was detected between lesioned (right) and intact (left) hemispheres, indicating that 6-OHDA does not impact serotonergic projections in the striatum, as expected. No difference in signal was also detected between AAV-DAT treated and control groups, indicating that striatal injection of AAV-DAT does not affect survival of serotonergic neurons in the CPU or SN. GFAP Immunofluorescence of GFAP, which is a marker of astroglial activation, was detected with chicken polyclonal antibody, and the signal was quantified in CPU (FIG.17) and in SN (FIG.18). GFAP signal was increased in CPU and, to a lesser extent, also in SN, indicating inflammatory response to 6- OHDA lesion and intrastriatal injection. However, no difference between AAV-DAT and PBS was detected, indicating that gene therapy treatment did not exacerbate neuroinflammatory response. Colocalization of hDAT and Neuronal Markers Next, it was investigated whether hDAT-positive striatal somata may be identified by co-labeling with markers for several different types of neurons, including markers for all or subpopulations of medium spiny neurons (DARPP-32, CTIP2, and calbindin), markers for cholinergic interneurons (ChAT and VAChT), markers for different populations of GABAergic interneurons (nNOS, parvalbumin). These analyses were performed in three multichannel immunofluorescence experiments, each on one section per rat from three rats of group B. The results are presented in FIG.19, FIG.20, and FIG.21. Taken together, the coexpression analysis provided evidence for hDAT signal in subsets of either nNOS or parvalbumin-positive GABAergic interneurons, while medium spiny neurons and cholinergic interneurons seem to be negative for hDAT. Summary General Observations In general, the test compound (AAV-DAT) was received very well, with no obvious unexpected negative effects detected during the whole observational period of the study. All the animals receiving AAV-DAT or vehicle control survived the surgical procedure and reached planned study termination. Body Weight Animals gained weight as expected, over the entire post-treatment observational period. No group differences were detected. Behavioral Assessments 67 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Three weeks after unilateral 6-OHDA injection to the nigrostriatal fiber bundle, an amphetamine- induced rotation test was performed to assess dopaminergic lesion efficiency. The vast majority of animals showed strong ipsilateral rotational behavior, indicating a very high 6-OHDA lesion efficiency. After a L-DOPA priming period of three weeks, before AAV-DAT treatment, peak-dose dyskinesia was assessed by rating the severity of abnormal involuntary movements affecting the orofacial region, the limbs, and the trunk (ALO AIMs). The majority of animals displayed robust ALO AIMs at this point, confirming successful induction of dyskinesia. Based on these results, animals were equally distributed between two groups, which received the vehicle phosphate-buffered saline (PBS) or AAV-DAT, respectively, via stereotactic injection. A subset of animals, which hadn’t displayed rotational behavior (indicating potential suboptimal 6-OHDA lesion) but developed dyskinesia, were specifically included in both groups. At baseline, no difference in ALO AIMs between groups was detected, suggesting equal group stratification. Dyskinesia was then evaluated at two weeks following treatment with AAV-DAT, to enable peak expression of vector transgene, and at 4- and 6- weeks study endpoint. At all tested timepoints, all AAV- DAT treated animals displayed significantly reduced ALO AIMs scores, compared to the vehicle control group. The strongest anti-dyskinetic effect was observed at 4- and 6-weeks post gene therapy, where development of dyskinesia was completely blocked in all treated animals. At the end of the study, all animals were subjected to tests assessing non-motor phenotypes of PD. In an Elevated-Plus-Maze test, which evaluates anxiety-like behaviour, AAV-DAT treated animals showed significantly reduced time spent in the closed arms of the maze, compared to vehicle treated animals, and a tendency towards increased time spent in the open arms, indicating a potential improvement of anxiety due to gene therapy treatment. Taken together, these results suggests that treatment with AAV-DAT has a profound and sustained effect on counteracting the negative effects of prolonged L-DOPA treatment by completely suppressing the development of peak-dose dyskinesia in this induced PD model. Histological Analysis The immunofluorescence analysis clearly shows TH signal being largely to almost completely absent in the striatum of the 6-OHDA-injected hemisphere, confirming that the lesion of dopaminergic fibers was very effective. Intense immunofluorescence signal from hDAT-expressing cells was detected exclusively in the AAV-DAT injected hemisphere and covered an area up to 1000 µm away from the injection site, indicating that vector biodistribution was restricted to the striatum. A small number of neuronal somata was intensely positive for hDAT in the striatum, and the shape and size of these somata suggest these are either cholinergic interneurons or GABAergic parvalbumin-positive interneurons. It is likely that at least a large proportion of the dense hDAT-positive neuropil network at the injection site comes from these infected striatal interneurons. The identity of these cells was further evaluated by immunolabeling of striatal sections with antibodies to hDAT, ChAT, Parvalbumin, and other appropriate markers. 68 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Quantification analysis of hDAT signal revealed a significant increase in AAV-DAT treated animals compared to PBS-treated controls, both in the CPU (target site of injection) and in the SNr, suggesting vector anterograde transport to this region. hDAT signal was detected in the non-lesioned hemisphere of both AAV-DAT and control groups, indicating some degree of cross-reactivity of the human-specific antibody with endogenous DAT from dopaminergic fibers and/or background signal. On the 6-OHDA lesioned side, low hDAT signal was also detected in control animals, either deriving from fewer surviving dopaminergic fibers and/or background signal. All together, these results confirm that AAV-DAT delivery to the striatum resulted in efficient and sustained transgene expression in the striatum and ultimately this can be correlated with the therapeutic effect on dyskinesia observed in the gene therapy treated group. A strong 5-HTT signal in CPU or SN was observed in both treatment and control groups, which was comparable to that detected in the untreated hemisphere, indicating that neither 6-OHDA lesion or striatal injection of AAV-DAT affected the survival of serotonergic neurons. Colocalization of 5-HTT and hDAT was significantly reduced in the lesioned right hemisphere while striatal injection of AAV-DAT significantly increased the colocalized signal when compared to PBS- injected animals. However, qualitatively, it is apparent that the overlap is restricted to specific sections/spots of neurons, and not present (as one would expect) over entire neurons. Since the analysis of overlap was performed automatically, and doesn’t take this into account, the detected increase in overlap is likely an artifact from separate neurons crossing each other, expressing either of the markers. GFAP signal was increased in CPU and, to a lesser extent, also in SN, indicating an inflammatory response to 6-OHDA lesion and intrastriatal injection, as expected. However, no difference between AAV- DAT and PBS treated animals was detected, indicating that gene therapy treatment neither did ameliorate nor exacerbate neuroinflammation. To further confirm the identity of neuronal cell subtypes targeted by AAV-DAT and expressing hDAT, a qualitative assessment of striatal sections immunolabelled with antibodies to hDAT, ChAT (cholinergic neurons), parvalbumin (subpopulation of GABAergic interneurons), somatostatin (GABAergic interneuronal subpopulation), VAChT (cholinergic neurons), calbindin (subpopulation of striatal GABAergic neurons), nNOS (subpopulation of GABAergic interneurons) and DARPP-32 (medium spiny neurons) was performed. Colabeling of hDAT and cell markers occurred in subpopulations of nNOS somata and parvalbumin somata, which together may account for a large proportion of hDAT-positive striatal somata. Occasionally, hDAT signal was found in weakly DARPP-32-positive somata, suggesting hDAT may occur in a small number of medium spiny neurons. In contrast, we did not detect hDAT signal in cholinergic interneurons identified by antibodies against either VAChT or ChAT. Similarly, calbindin- positive striatal neurons were negative for hDAT. In conclusion, this analysis indicates that hDAT-positive somata represent mostly GABAergic interneurons of at least two different subtypes, nNOS-positive and parvalbumin-positive interneurons. Potentially, additional subpopulations of GABAergic interneurons may be hDAT positive; possible markers would be calretinin and somatostatin. Overall, neurons expressing hDAT presented a normal morphology, suggesting that the gene therapy treatment did not have any detrimental effects on these neuronal subtypes. 69 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Example 2. Administration of an adeno-associated viral vector comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the Dopamine Transporter (DAT) protein to a patient suffering from Parkinson’s disease Using conventional molecular biology techniques known in the art, a gene encoding a therapeutic protein, such as DAT, can be operably linked to a promoter and a posttranscriptional regulatory element such as the “woodchuck hepatitis virus (WHV) posttranscriptional regulatory element” or “WPRE”. The gene can subsequently be incorporated into a vector, such as a viral vector, and administered to a patient suffering from a disease. For instance, a patient suffering from Parkinson’s disease (PD), a neurodegenerative or neuromuscular disorder characterized by rigidity, tremors, bradykinesia, among others can be administered a viral vector containing a solute carrier family 6 member 3 (SLC6A3) gene under the control of promoter that promotes DAT expression, for example, in neurons. For instance, an adeno-associated viral vector (AAV) vector, such as an AAV2 vector, can be generated that incorporates the SLC6A3 gene between the 5’ and 3’ inverted terminal repeats of the vector, and the gene may be placed under control of a promoter. According to the methods disclosed herein, a physician of skill in the art can treat a patient, such as a human patient, so as to reduce or alleviate symptoms of PD. To this end, a physician of skill in the art can administer to the human patient an AAV vector, comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein. The AAV vector administered to the patient can be an AAV2 vector comprising a synapsin 1 promoter operably linked to the SLC6A3 transgene and a WPRE. Administration of an effective dose of the composition may be by exemplary routes of administration standard in the art, including, but not limited to, systemic (e.g., by intravenous administration), local (e.g., intracortical), and direct injection (e.g., stereotactic delivery to dopaminergic neurons of the substantia nigra pars compacta (SNc) or ventral tegmental area (VTA)). The AAV vector may be administered to a patient having PD via one or more of a variety of routes, for example, intracerebroventricular (ICV), intracranial, intracortical, intracisternal, intracerebral, intra-cerebrospinal, intraparenchymal, intracisternal, intrahippocampal, intra-striatal (putamen and/or caudate), intravenous (IV), intrathecal, intraputaminal, intra-midbrain, intra-cisterna magna, intra-substantia nigra, intra-ventral tegmental area, and/or intrathalamic administration. In some cases, the vector is administered via intraparenchymal, intracerebral, ICV, intrathecal, intraputaminal, intrathalamic, intra-midbrain, intra- cisterna magna, intra-substantia nigra, and/or intra-ventral tegmental area routes. Administration may be performed by intrathecal injection with or without Trendelenberg tilting. In some cases, the AAV vector may be administered, e.g., in a single administration. The AAV vector can also be administered to the patient by multiple routes of administration, for example, intrathalamic and intra-substantia nigra routes. The AAV vector is administered in a therapeutically effective amount. Direct delivery of the vector to the central nervous system (CNS) may involve targeting the intraventricular space, either unilaterally or bilaterally, specific neuronal regions or more general brain regions containing neuronal targets. Individual patient intraventricular space, brain region and/or neuronal target(s) selection and subsequent intraoperative delivery of AAV may be accomplished using several imaging techniques (magnetic resonance imaging (MRI), computerized tomography (CT), CT combined with MRI merging) and employing any number of software planning programs (e.g., Stealth System, 70 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Clearpoint Neuronavigation System, Brainlab, Neuroinspire etc). Intraventricular space or brain region targeting, and delivery may involve use of standard stereotactic frames (Leksell, CRW) or using frameless approaches with or without intraoperative MRI. Actual delivery of the vector may be by injection through needle or cannulae with or without inner lumen lined with material to prevent adsorption of the vector (e.g., Smartflow cannulae, MRI Interventions cannulae). Delivery device interfaces with syringes and automated infusion or microinfusion pumps with preprogrammed infusion rates and volumes. The syringe/needle combination or just the needle may be interfaced directly with the stereotactic frame. Infusion may include constant flow rate or varying rates with convection enhanced delivery. Typically, a physician will determine the actual dosage which will be most suitable for an individual subject, and it will vary with the disease, age, weight, and response of the patient. The appropriate dosage can be determined by one skilled in the art. The vector may be administered at a single point in time. For example, a single injection may be given with no repeat administrations. Combination therapies are also contemplated by the disclosure. Combinations of methods of the disclosure with standard medical treatments (e.g., corticosteroids or topical pressure reducing medications) are specifically contemplated, as are combinations with novel therapies. For example, the present disclosure also includes combination treatment with an antiparkinsonian therapy, e.g., leveodopa. In some cases, a subject may be treated with a steroid to prevent or to reduce an immune response to administration of the vector described herein. Example 3: Measurement of responsiveness after administration of an AAV vector comprising an SLC6A3 transgene or an AAV vector that expresses a transgene encoding the DAT protein to a patient suffering from PD The AAV vector comprising a solute carrier family 6 member 3 (SLC6A3) transgene or an AAV vector that expresses a transgene encoding the DAT protein can be administered to the patient in an amount sufficient to treat one or more of the pathological features of PD, following which, the responsiveness to treatment can be measured. Administration of the AAV vector described may, for example, reduce bradykinesia in the subject, reduce tremors in the subject, reduce rigidity and stiffness in the subject, improve motor coordination of the subject, reduce postural instability and improve balance in the subject, improve the cognitive performance of the subject, alter dopaminergic neurotransmission in the subject, improve DAT availability in the subject, reduce white matter lesions in the subject, improve DAT binding in striatum of the subject, improve DAT expression of the subject, improve DA uptake in the subject, improve [123I]-FP-CIT binding in the subject, improve [3H]-CTF-binding capacity of the subject, improve amphetamine-induced DA efflux in the subject, improve the motor function of the subject, reduce dopaminergic neuron loss in the subject, reduce neuroinflammation in the subject, reduce inflammatory cytokines in the blood and cerebrospinal fluid (CSF) of the subject, prevent, reduce, or reverse levodopa- induced dyskinesia (LID) in the subject, and/or reduce ^-synuclein levels or aggregation thereof in the subject. Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may cause the patient to exhibit a change in responsiveness to the antiparkinsonian therapy. Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may help prolong responsiveness to the antiparkinsonian therapy or reduce dependency on the antiparkinsonian therapy, for e.g., levodopa. 71 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 Administration of compositions described herein to a patient undergoing treatment with an existing antiparkinsonian therapy may help reduce dependency on the antiparkinsonian therapy. Antiparkinsonian therapy can be levodopa or other existing medications in the field. Administration of compositions described herein may increase the expression of DAT protein in target tissue such as substantia nigra pars compacta. The change in the baseline of motor symptoms may be assessed by the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS). The change in the baseline of non-motor symptoms of PD may be assessed by the Non-Motor Symptom Scale (NMSS), wherein the one or more non-motor symptoms are selected from being associated with cardiovascular health, sleep and fatigue, mood and cognition, perceptual problems and hallucinations, attention and memory, anxiety, depressive-like behaviors, gastrointestinal tract, urinary, and sexual function. The change in brain dopaminergic cell integrity may be measured by dopamine transporter scan (DaTscan) single-photon emission computed tomography (SPECT) imaging (DaT-SPECT), wherein the percentage and absolute changes in Ioflupane retention as a marker for dopamine transporter protein expressed by dopamine producing cells within the brain are measured. The change in brain dopaminergic cell integrity may also be measured by DaT-SPECT imaging followed by estimation of the fractional volume occupied by the caudate, putamen, and globus pallidus within each voxel of a SPECT image using a tissue-fraction estimation-based segmentation method to reliably quantify DaT uptake. Improvement in neurological symptoms of PD can be assessed using standard neurological tests before and after treatment. Dopaminergic neuron loss can be assessed using F18-dopa PET scans or dopamine transporter imaging scans (123I-FP-CIT DaTSCANs). Improvement in brain metabolism can be measured by PET scans and overall improvement in symptoms can be measured by standard clinical rating scales. The patient may be evaluated 1 month, 2 months, 3 months, 4 months, 5 months, 6 months or more following administration of the compositions described herein depending on the route of administration used for treatment. Depending on the outcome of the evaluation, the patient may receive additional treatments. Other Embodiments Various modifications and variations of the described invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that are obvious to those skilled in the art are intended to be within the scope of the invention. Other embodiments are in the claims. 72 ^

Claims

PATENT ATTORNEY DOCKET: 51673-007WO3 Claims 1. A method of treating Parkinson’s disease (PD) in a patient in need thereof, the method comprising administering to the patient an adeno-associated viral (AAV) vector comprising a solute carrier family 6 member 3 (SLC6A3) transgene. 2. A method of reducing bradykinesia in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene. 3. A method of reducing tremors in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene. 4. A method of reducing rigidity and stiffness in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene. 5. A method of improving motor coordination in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene. 6. A method of reducing postural instability and improving balance in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene. 7. A method of prolonging the responsiveness to an antiparkinsonian therapy in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene, optionally wherein the antiparkinsonian therapy is levodopa. 8. A method of reducing the dependency on an antiparkinsonian therapy in a patient diagnosed as having PD, the method comprising administering to the patient an AAV vector comprising an SLC6A3 transgene, optionally wherein the antiparkinsonian therapy is levodopa. 9. The method of any one of claims 1-8, wherein the transgene is operably linked to a promoter. 10. The method of claim 9, wherein the promoter is selected from a synapsin 1 promoter, a CAG promoter, a CMV promoter, a CAMKII promoter, a beta-actin promoter, and a human EF1-alpha promoter. 11. The method of claim 9, wherein the promoter is a neuron-specific promoter. 12. The method of any one of claims 9-11, wherein the promoter is a synapsin 1 promoter. 13. The method of claim 12, wherein the synapsin 1 promoter is selected from an hSYN1 promoter, an hSYN1 with 5’ extension promoter, an hSYN1 with 3’ extension promoter, an eSYN promoter, and a truncated hSYN1 promoter. 14. The method of claim 12, wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 85% identical to the nucleic acid sequence of SEQ ID NO: 1, optionally wherein the synapsin 1 73 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 promoter has a nucleic acid sequence that is at least 85% identical to the nucleic acid sequence of SEQ ID NO: 6. 15. The method of claim 14, wherein: the synapsin 1 promoter has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 1, optionally wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 1; optionally wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 6, optionally wherein the synapsin 1 promoter has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 6. 16. The method of claim 15, wherein the synapsin 1 promoter has the nucleic acid sequence of SEQ ID NO: 1, optionally wherein the synapsin 1 promoter has the nucleic acid sequence of SEQ ID NO: 6. 17. The method of any one of claims 1-16, wherein the SLC6A3 transgene has a nucleotide sequence that is at least 85% identical to the nucleic acid sequence of SEQ ID NO: 2. 18. The method of claim 17, wherein the SLC6A3 transgene has a nucleotide sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 2, optionally wherein the SLC6A3 gene has a nucleotide sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 2. 19. The method of claim 18, wherein the SLC6A3 transgene has the nucleic acid sequence of SEQ ID NO: 2. 20. The method of any one of claims 1-19, wherein the transgene encodes a Dopamine Transporter (DAT) protein. 21. The method of claim 20, wherein the DAT protein has an amino acid sequence that is at least 85% identical to the amino acid sequence of SEQ ID NO: 3. 22. The method of claim 21, wherein the DAT protein has an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 3, optionally wherein the DAT has an amino acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the amino acid sequence of SEQ ID NO: 3. 23. The method of claim 22, wherein the DAT protein has the amino acid sequence of SEQ ID NO: 3. 24. The method of any one of claims 1-23, wherein the transgene is operably linked to a Woodchuck Hepatitis Virus (WHV) Posttranscriptional Regulatory Element (WPRE). 74 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 25. The method of claim 24, wherein the WPRE has a nucleic acid sequence that is at least 85% identical to the nucleic acid sequence of SEQ ID NO: 4. 26. The method of claim 25, wherein the WPRE has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 4, optionally wherein the WPRE has a nucleic acid sequence that is at least 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 4. 27. The method of claim 26, wherein the WPRE has the nucleic acid sequence of SEQ ID NO: 4. 28. The method of any one of claims 1-27, wherein the AAV vector comprises capsid proteins from an AAV serotype selected from the group consisting of AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV9.47, AAV9(hu14), AAV10, AAV11, AAV12, AAVrh74, AAVrh.8, AAVrh.10, AAV-DJ, and AAV-DJ8. 29. The method of any one of claims 1-28, wherein the AAV vector comprises a 5’ inverted terminal repeat (ITR) and/or a 3’ ITR from AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV9.47, AAV9(hu14), AAV10, AAV11, AAV12, AAVrh74, AAVrh.8, AAVrh.10, AAV-DJ, or AAV-DJ8, optionally wherein the AAV vector comprises a 5’ ITR and a 3’ ITR from AAV2. 30. The method of any one of claims 1-29, wherein the AAV vector comprises a 5’ ITR and/or a 3’ ITR from one AAV serotype and one or more capsid proteins from a different AAV serotype. 31. The method of any one of claims 1-29, wherein the AAV vector is an AAV2 vector. 32. The method of any one of claims 1-31, wherein the AAV vector has a nucleic acid sequence that is at least 85% identical to the nucleic acid sequence of SEQ ID NO: 5. 33. The method of claim 32, wherein the AAV vector has a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 5. 34. The method of claim 33, wherein the AAV vector has a nucleic acid sequence that is at least 95% identical to the nucleic acid sequence of SEQ ID NO: 5, optionally wherein the AAV has a nucleic acid sequence that is at least 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of SEQ ID NO: 5. 35. The method of claim 34, wherein the AAV vector has a nucleic acid of SEQ ID NO: 5. 36. The method of any one of claims 1-35, wherein the AAV vector is an AAV2 vector comprising a synapsin 1 promoter and WPRE operably linked to the SLC6A3 transgene. 37. The method of any one of claims 1-36, wherein the patient has one or more symptoms of a condition selected from PD, juvenile PD, infantile dystonia-Parkinsonism, dystonia, unclassified movement disorders, unspecified personality disorder with evasive and schizophrenic traits, hemiparkinsonism, adult early-onset Parkinsonism, and comorbid neuropsychiatric disease. 75 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 38. The method of any one of claims 1-37, wherein the patient has one or more symptoms selected from hand tremors, evasive and schizophrenic traits, self-injury, periodic depression, general bradykinesia, severe rigidity, resting and intention tremor of the upper extremities without consistent sidedness of symptoms, Parkinsonian gait with small shuffling steps, kyphosis, severe difficulties in turning around, postural instability, spontaneous falling, and severe hypomimia. 39. The method of any one of claims 1-38, wherein the patient has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. 40. The method of any one of claims 1-39, wherein the patient has one or more characterizations selected from dysfunctional dopaminergic neurotransmission, progressive loss of DAT availability, small (2-4 mm) white matter lesions compared to age-matched controls, reduced DAT binding in striatum (caudate nucleus and putamen), dopaminergic cell loss, reduced DAT expression, loss of DAT binding, accelerated loss of [¹²³I]-FP-CIT binding compared to expected decline in age-matched controls, impaired dopamine (DA) uptake, dominant-negative impairments on DA uptake, impaired amphetamine-induced DA efflux, reduced surface expression of DAT, accelerated turnover of DAT leading to lower expression of active transporter, enhanced lysosomal degradation of DAT, and reduction in [³H]-CTF-binding capacity. 41. The method of any one of claims 1-40, wherein the patient has mild to moderate Unified Parkinson's Disease Rating Scale (UPDRS) III OFF score less than 5 years after clinical PD diagnosis, and/or moderate to severe UPDRS OFF score after 4 or more years since clinical PD diagnosis. 42. The method of any one of claims 1-41, wherein the patient has been diagnosed with PD and is in the modified Hoehn and Yahr stage I-III OFF medication or the patient has had the disease for a duration of more than 5 years and is in the Hoehn and Yahr Stage III or IV off medication. 43. The method of any one of claims 1-42, wherein the patient has PD with motor complications despite adequate oral antiparkinsonian therapy. 44. The method of any one of claims 1-43, wherein the patient with PD is undergoing treatment with an additional antiparkinsonian therapy. 45. The method of any one of claims 43 or 44, wherein the antiparkinsonian therapy is levodopa. 46. The method of claim 45, wherein the patient is responsive to the levodopa. 47. The method of any one of claims 1-46, wherein the patient is deficient in expression and/or activity of DAT protein. 48. The method of any one of claims 1-47, wherein the patient has a c.1857G>C single nucleotide substitution in exon 15 of SLC6A3. 76 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 49. The method of any one of claims 1-48, wherein the patient has one or more mutations in an endogenous DAT protein, optionally wherein the mutation is a monoallelic missense mutation. 50. The method of claim 49, wherein the one or more mutations are selected from I312F and K619N. 51. The method of claim 50, wherein the patient has the K619N mutation. 52. The method of claim 51, wherein the patient with the K619N mutation inherited the mutant allele from a parent, optionally wherein the mutant allele was paternally transmitted. 53. The method of any one of claims 1-52, wherein the patient has an A314V mutation in an endogenous DAT protein. 54. The method of any one of claims 1-53, wherein the patient has one or more mutations in endogenous DAT protein selected from R521W, R219S, Y343X, L224P, L368Q, P395L, Y470Sfs, p.I134SfsX5, p.G500EfsX13, p.G380_K384 delinse, and Q439X. 55. The method of any one of claims 1-54, wherein the patient has mutations in the C-terminus of an endogenous DAT protein. 56. The method of any one of claims 1-55, wherein the patient has genotype GG and allele G of an rs2652510 single nucleotide polymorphism. 57. The method of any one of claims 1-56, wherein the patient has a plurality of repeat alleles of a variable number tandem repeat (VNTR) in the 3’-UTR of the SLC6A3 gene. 58. The method of any one of claims 1-57, wherein the patient has idiopathic PD. 59. The method of claim 58, wherein the patient with idiopathic PD has one or more symptoms selected from tremor, resting tremor, rigidity, slowness of movement, cogwheel rigidity, motor fluctuations, and postural reflex impairment. 60. The method of claim 58, wherein the patient with idiopathic PD has levodopa-induced dyskinesia (LID). 61. The method of claim 58, wherein the patient with idiopathic PD is at risk of developing LID. 62. The method of any one of claims 1-61, wherein the vector is administered to the patient via intraparenchymal, intracerebral, intracerebroventricular, intrathecal, intraputaminal, intrathalamic, intra- midbrain, intra-cisterna magna, intra-substantia nigra, and/or intra-ventral tegmental area routes. 63. The method of any one of claims 1-62, wherein the vector is administered to the patient in an amount sufficient to achieve one or more of the following: a) reduce bradykinesia in the patient; 77 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 b) reduce tremors in the patient; c) reduce rigidity and stiffness in the patient; d) improve motor coordination of the patient; e) reduce postural instability and improve balance in the patient; f) improve the cognitive performance of the patient; g) alter dopaminergic neurotransmission in the patient; h) improve DAT availability in the patient; i) reduce white matter lesions in the patient; j) improve DAT binding in striatum of the patient; k) improve DAT expression of the patient; l) improve DA uptake in the patient; m) improve [¹²³I]-FP-CIT binding in the patient; n) improve [³H]-CTF-binding capacity of the patient; o) improve amphetamine-induced DA efflux in the patient; p) improve the motor function of the patient; q) reduce dopaminergic neuron loss in the patient; r) reduce neuroinflammation in the patient; s) reduce inflammatory cytokines in the blood and cerebrospinal fluid (CSF) of the patient; t) reduce ^-synuclein levels or aggregation thereof in the patient; and/or u) prevent, reduce, or reverse LID in the patient. 64. The method of any one of claims 1-63, wherein the vector is administered to the patient in an amount sufficient to change the baseline of motor symptoms as assessed by the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS). 65. The method of any one of claims 1-64, wherein the vector is administered to the patient in an amount sufficient to change the baseline of non-motor symptoms of PD as assessed by the Non-Motor Symptom Scale (NMSS), wherein the one or more non-motor symptoms are selected from being associated with cardiovascular health, sleep and fatigue, mood and cognition, perceptual problems and hallucinations, attention and memory, anxiety, depressive-like behaviors, gastrointestinal tract, urinary, and sexual function. 66. The method of any one of claims 1-65, wherein the vector is administered to the patient in an amount sufficient to change the brain dopaminergic cell integrity as measured by DaTscan SPECT imaging, wherein the percentage and absolute changes in Ioflupane retention as a marker for dopamine transporter protein expressed by dopamine producing cells within the brain are measured. 67. The method of any one of claims 1-66, wherein the vector is administered to the patient in an amount sufficient to improve neurological symptoms of PD. 68. The method of any one of claims 1-67, wherein the vector is administered to the patient in an amount sufficient to improve brain metabolism as measured by PET scans. 78 ^ PATENT ATTORNEY DOCKET: 51673-007WO3 69. The method of any one of claims 1-68, wherein the vector is administered to the patient in an amount sufficient to improve standard clinical rating scales. 70. The method of any one of claims 1-69, wherein the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient for the patient to exhibit a change in responsiveness to the antiparkinsonian therapy. 71. The method of any one of claims 1-70, wherein the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient to prolong responsiveness to the antiparkinsonian therapy. 72. The method of any one of claims 1-71, wherein the vector is administered to a patient undergoing treatment with an existing antiparkinsonian therapy in an amount sufficient to reduce dependency on the antiparkinsonian therapy. 73. The method of any one of claims 70-72, wherein the antiparkinsonian therapy is levodopa. 74. The method of any one of claims 1-73, wherein the vector is administered to the patient in an amount sufficient to increase the expression of DAT protein in target tissue. 75. The method of claim 74, wherein the target tissue is substantia nigra pars compacta or ventral tegmental area. 76. The method of claim 74, wherein the target tissue comprises non-dopaminergic neurons. 77. The method of claim 76, wherein the non-dopaminergic neurons are striatal non- dopaminergic neurons. 78. A kit comprising an AAV vector comprising an SLC6A3 transgene, wherein the kit further comprises a package insert instructing a user of the kit to perform the method of any one of claims 1-77. 79 ^