Can we develop effective disease-modifying therapies for Spinocerebellar Ataxias (SCAs) by targeting polyglutamine expansion toxicity and enhancing autophagic clearance of mutant protein aggregates?
Addresses the critical lack of disease-modifying treatments for SCAs, which are progressive neurodegenerative disorders causing cerebellar degeneration and severe motor impairment.
Spinocerebellar ataxias are a heterogeneous group of autosomal dominant disorders characterized by progressive cerebellar ataxia, often caused by CAG repeat expansions encoding polyglutamine (polyQ) tracts in various proteins:
- SCA1: ATXN1 gene (CAG repeat in encoded protein)
- SCA2: ATXN2 gene (CAG repeat)
- SCA3/MJD: ATXN3 gene (CAG repeat) — most common worldwide
- SCA6: CACNA1A gene (CAG repeat)
- SCA7: ATXN7 gene (CAG repeat)
Current treatments are only symptomatic (e.g., riluzole, amantadine) and do not modify disease progression.
Define the molecular mechanisms by which expanded polyQ proteins cause neuronal dysfunction.
- In vitro: Induced pluripotent stem cells (iPSCs) from SCA1, SCA2, SCA3, SCA6 patients, differentiated into cerebellar neurons
- In vivo: Mouse models for SCA1 (ATXN1[82Q] knock-in) and SCA3 (MJD1.92 transgenic)
- Cell lines: HEK293T for protein interaction studies
- Characterization: Verify mutant protein expression, aggregate formation, and cellular phenotypes
- Mechanism studies:
- Transcriptomic profiling (RNA-seq) to identify dysregulated pathways
- Proteomic analysis of aggregate composition
- Mitochondrial function assays
- Autophagy flux measurements
- Intervention testing: Test candidate compounds for aggregate reduction and function restoration
- Identify 2-3 key pathways driving polyQ toxicity in cerebellar neurons
- Establish scalable iPSC-based drug screening platform
- Identify compounds that reduce mutant protein levels by >50%
High-throughput screening for compounds that enhance autophagic clearance of mutant polyQ proteins.
| Parameter |
Specification |
| Primary screen |
5,000+ compounds (FDA-approved library) |
| Secondary validation |
Top 100 hits in iPSC-derived neurons |
| Tertiary in vivo |
Top 10 compounds in SCA mouse models |
| Readout |
Mutant protein level, aggregate burden, behavioral improvement |
- mTOR inhibitors (rapamycin, Torin1)
- Autophagy inducers (carbamazepine, tamoxifen)
- HSP90 inhibitors (geldanamycin analogs)
- Histone deacetylase (HDAC) inhibitors
- Novel autophagy-enhancing small molecules
| Measure |
Target |
| Pathway identification |
2-3 novel targets validated |
| Primary screen hits |
>50 compounds with >50% aggregate reduction |
| In vivo efficacy |
>30% mutant protein reduction in mouse brain |
| Behavioral rescue |
Significant improvement in rotarod/grid tests |
- Available: iPSC lines from multiple SCA subtypes exist; mouse models available
- Required: High-throughput screening facility, medicinal chemistry support
- Manageable: Cerebellar neuron differentiation protocols established
| Resource |
Estimated Cost |
| iPSC culture and differentiation |
$300,000 |
| High-throughput screening |
$200,000 |
| In vivo mouse studies |
$400,000 |
| Target validation |
$200,000 |
| Total |
$1,100,000 |
- Year 1: iPSC characterization and assay development
- Year 1-2: Primary and secondary screening
- Year 2-3: In vivo validation
- Year 3-4: IND-enabling studies for lead compound
Score: 8/10
- SCAs are monogenic, providing clean genetic model for polyQ toxicity
- Understanding common mechanisms may benefit all polyQ diseases (HD, SCA, SBMA)
- Cerebellar degeneration mechanism has broader implications
Score: 9/10
- SCAs affect 1 in 50,000 globally; no disease-modifying treatments exist
- Progressive disability leads to severe quality of life impairment
- Early intervention could prevent irreversible neuronal loss
Score: 9/10
- Therapeutic: Direct path to clinical trial for lead compounds
- Biomarker: Aggregate reduction as surrogate endpoint
- Platform: Expandable to other polyQ diseases
Score: 78/140 | SV:8 F:7 N:8 DI:9 R:8 CE:6 TE:6 EB:7 AU:8 TP:9