# SCA7 neurodegeneration: Molecular epigenetic basis and therapy

> **NIH NIH R01** · DUKE UNIVERSITY · 2020 · $279,844

## Abstract

Spinocerebellar ataxia type 7 (SCA7) is an inherited neurological disorder characterized by cerebellar and
retinal degeneration. SCA7 is caused by CAG/polyglutamine (polyQ) repeat expansions in the ataxin-7 gene.
We set out to determine the molecular basis of SCA7 neurodegeneration by focusing on polyQ-ataxin-7
transcriptional and epigenetic dysregulation, as ataxin-7 is a core component of the transcription co-activator
complex STAGA, which possesses histone acetyltransferase and histone deubiquitinase activity. By pursuing
unbiased transcriptome analysis, we discovered that SCA7 involves impaired regulation of Ca++ homeostasis.
Transcription factor binding site analysis of SCA7 down-regulated genes revealed putative binding sites for
peroxisome proliferator-activated receptors, which are known pathway targets of Sirtuin-1 (Sirt1), a NAD+-
dependent deacetylase implicated in lifespan extension and neuroprotection, whose function was impaired in
SCA7. Based upon these results, we crossed Sirt1 over-expressing mice with PrP-fxSCA7 92Q BAC mice,
and with SCA7 266Q knock-in mice. We observed amelioration of cerebellar and retinal degeneration, and
rescue of Purkinje cell synaptic dysfunction in Sirt1-SCA7 bigenic mice. We documented abnormalities in
bioenergetics and organelle quality control in SCA7 mice and neuronal progenitor cells (NPCs) from patient
stem cells. Using mass spectrometry, we detected significant reductions in NAD+ in SCA7 brain, accompanied
by activation of poly-ADP ribose polymerase 1 (PARP1), which led us to assay for DNA damage, and we noted
increased gH2AX levels in neurons from SCA7 mice. As USP22 deubiquitinase function promotes DNA repair,
and the ataxin-7 homologue ataxin-7-like 3 (Atxn7-L3) promotes deubiquitinase module function, we examined
Atxn7-L3, and found that Atxn7-L3 interacts with PARP1, and Atxn7-L3 over-expression can rescue impaired
histone H2B deubiquitination. These results, together with unbiased ChIP-Seq analysis of H3K9/14 acetylation
in SCA7 mice, support a model in which epigenetic dysregulation yields increases DNA damage, PARP1
hyperactivation, and excess NAD+ utilization to promote SCA7 disease pathogenesis. As genetic defects in
DNA repair cause inherited cerebellar ataxias, and recent studies implicate DNA damage and PARP1
activation, excessive NAD+ utilization may commonly occur in ataxias and retinal disease, offering an
opportunity for rationale therapy development. In this project, we will define the bioenergetics defects,
mitochondrial dysfunction, and Ca++ flux phenotypes in SCA7 to determine the basis of Sirt1 dysfunction and
contribution of NAD+ depletion to SCA7 pathogenesis. We will assess DNA damage and PARP activation in
SCA7, and consider the role of Atxn7-L3 and USP22 in epigenetic alterations linked to DNA damage in SCA7.
Finally, we will test if modulation of Atxn7-L3, USP22, or PARP1 can rescue DNA damage and molecular
pathology in SCA7 cell models, NPC patient cells, and mice, an...

## Key facts

- **NIH application ID:** 9961591
- **Project number:** 5R01EY014061-15
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** ALBERT R LA SPADA
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $279,844
- **Award type:** 5
- **Project period:** 2002-05-01 → 2020-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9961591

## Citation

> US National Institutes of Health, RePORTER application 9961591, SCA7 neurodegeneration: Molecular epigenetic basis and therapy (5R01EY014061-15). Retrieved via AI Analytics 2026-06-11 from https://api.ai-analytics.org/grant/nih/9961591. Licensed CC0.

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