This multi-phase study aims to validate the Synaptic Vesicle Trafficking Dysfunction Hypothesis in Parkinson's Disease by assessing vesicle dynamics in patient-derived neurons, correlating with genetic risk variants, and testing therapeutic interventions.
Impaired synaptic vesicle trafficking is an upstream driver of dopaminergic neurodegeneration in PD, not merely a downstream consequence.
flowchart TD
subgraph Phase_1
AiPSC-Derived["AiPSC-Derived<br/>Dopaminergic Neurons"] --> B["Vesicle Dynamics<br/>Assessment"]
end
subgraph Phase_2
B --> C["Genetic<br/>Correlation"]
end
subgraph Phase_3
C --> D["Therapeutic<br/>Testing"]
end
subgraph Phase_4
D --> E["Biomarker<br/>Validation"]
end
style A fill:#e1f5fe,stroke:#333
style B fill:#c8e6c9,stroke:#333
style C fill:#c8e6c9,stroke:#333
style D fill:#c8e6c9,stroke:#333
style E fill:#c8e6c9,stroke:#333
Characterize synaptic vesicle dynamics in dopaminergic neurons derived from PD patients with different genetic backgrounds vs. healthy controls.
| Parameter |
PD Cases |
Controls |
| Total subjects |
30 |
15 |
| LRRK2 G2019S carriers |
10 |
— |
| VPS35 D620N carriers |
5 |
— |
| Idiopathic PD |
10 |
— |
| Healthy controls |
— |
15 |
| Age range |
50-75 years |
50-75 years |
- Synaptic vesicle density in axonal terminals (electron microscopy)
- Vesicle cycling kinetics (FM 4-64 dye unloading assays)
- Dopamine release capacity (amperometry)
- VMAT2 binding (radioligand binding assay)
- SV2C, VAMP2, Synaptotagmin-1 expression levels (Western blot)
- Synaptic vesicle pool size (FM dye uptake)
- Endocytosis rate (fluorescent dextran uptake)
- Mitochondrial function in synaptic terminals (Seahorse)
Correlate synaptic vesicle function with known PD genetic risk variants.
| Gene |
Variant |
Expected Effect |
| SV2C |
rs1871678, rs6474359 |
Altered vesicle filling |
| VPS35 |
D620N |
Impaired endosomal sorting |
| SYNJ1 |
R258Q |
Impaired endocytosis |
| DNAJC13 |
R392H |
Endosomal dysfunction |
- Whole exome sequencing for all participants
- Polygenic risk score calculation
- Correlation with vesicle function parameters
Test whether enhancing synaptic vesicle trafficking improves dopaminergic neuron survival.
| Compound |
Target |
Dose |
Duration |
| R55 |
Retromer stabilizer |
10 mg/kg IP |
4 weeks |
| Tetrabenazine |
VMAT2 inhibitor |
25 mg/day PO |
4 weeks |
| DMSO (vehicle) |
— |
— |
4 weeks |
- C57BL/6 mice, 8-10 weeks old, male
- MPTP-induced parkinsonism model (30 mg/kg IP, 5 days)
- Behavioral testing: cylinder, grid, rotarod
- Primary midbrain cultures from E14.5 rat embryos
- Treatment with test compounds for 7 days
- Alpha-synuclein PFF addition (day 3)
- Dopaminergic neuron survival (TH+ count)
- Vesicle dynamics (FM dye assay)
- Dopamine release (HPLC)
- Behavioral recovery (mouse models)
Identify biomarkers for early detection of synaptic vesicle dysfunction in PD.
¶ Candidate Biomarkers
| Biomarker |
Source |
Method |
| SV2C |
CSF |
ELISA |
| VAMP2 |
Plasma exosomes |
Western blot |
| Synaptotagmin-1 |
CSF |
MSD |
| VMAT2 binding |
Brain PET |
[11C]DTBZ PET |
- 50 early-stage PD patients (Hoehn & Yahr 1-2)
- 50 healthy controls
- Longitudinal sampling at 0, 6, 12, 24 months
- 80% power to detect 30% difference in vesicle density
- Alpha = 0.05, two-sided
- Accounting for 20% dropout
- Mixed-effects model for repeated measures
- Covariates: age, sex, disease duration
- False discovery rate correction for multiple comparisons
- IRB approval required for iPSC studies
- Informed consent for genetic testing
- Animal studies under IACUC protocol
| Phase |
Duration |
Start |
End |
| Phase 1 |
18 months |
Month 1 |
Month 18 |
| Phase 2 |
12 months |
Month 12 |
Month 24 |
| Phase 3 |
12 months |
Month 18 |
Month 30 |
| Phase 4 |
24 months |
Month 24 |
Month 48 |
| Item |
Cost (USD) |
| Personnel |
$1,200,000 |
| iPSC generation |
$400,000 |
| Animal studies |
$300,000 |
| Biomarker assays |
$200,000 |
| PET imaging |
$250,000 |
| Misc |
$150,000 |
| Total |
$2,500,000 |
- Primary: Demonstrate reduced vesicle trafficking in PD patient-derived neurons
- Secondary: Identify genetic variants that modify vesicle function
- Tertiary: Show therapeutic benefit of vesicle trafficking enhancers
- Quaternary: Validate biomarker for early detection
| Risk |
Mitigation |
| iPSC reprogramming failure |
Use validated protocols, have backup lines |
| Insufficient biopsy material |
Use hair follicles or blood for reprogramming |
| Compound toxicity |
Dose-finding study in healthy mice first |
| Dropout |
Build in 20% cushion in enrollment |