ATXN1 (Ataxin-1), located on chromosome 6p22.3, encodes a nuclear protein involved in transcriptional regulation and RNA processing. Expansion of a CAG trinucleotide repeat in the ATXN1 gene causes Spinocerebellar Ataxia Type 1 (SCA1), a progressive neurodegenerative disorder characterized by cerebellar ataxia, dysarthria, and cognitive impairment. Normal ATXN1 function is essential for proper neuronal development and synaptic plasticity.
The ATXN1 gene encodes Ataxin-1, an 816-amino acid protein with multiple cellular functions:
- Transcriptional regulation: Binds to transcription factors including RORα, Capicua (CIC), and histone deacetylases
- RNA processing: Associates with RNA splicing machinery; regulates alternative splicing
- Nuclear localization: Localizes to nuclear bodies; mutant ATXN1 forms aggregates
- Synaptic plasticity: Regulates synaptic function in Purkinje cells
- Neuronal survival: Modulates apoptosis and autophagy pathways
- Development: Essential for normal cerebellar development
Ataxin-1 contains an AXH (axin homeodomain) domain that mediates protein-protein interactions. The polyglutamine (polyQ) tract is normally 6-44 glutamines; expansion beyond 41 causes SCA1.
| Feature |
Details |
| Molecular weight |
~87 kDa (full-length) |
| Structure |
AXH domain (residues 571-689); polyQ tract (N-terminus) |
| Domains |
Nuclear localization signal; serine/proline-rich regions |
| Post-translation |
Phosphorylation, sumoylation, acetylation |
| Crystal structure |
PDB: 1M4E (AXH domain) |
- Inheritance: Autosomal dominant; CAG repeat expansion
- Normal repeat: 6-41 glutamines
- Pathogenic repeat: 41-130 glutamines
- Anticipation: Earlier onset in subsequent generations (repeat expansion)
- PolyQ expansion: Causes toxic gain-of-function
- Protein aggregation: Mutant ATXN1 forms nuclear inclusions
- Transcriptional dysregulation: Alters gene expression in Purkinje cells
- Purkinje cell degeneration: Primary pathology; progressive loss
- Cognitive impairment: Prefrontal cortex dysfunction in advanced disease
- Progressive cerebellar ataxia (gait, limb, truncal)
- Dysarthria (slurred speech)
- Dysphagia (difficulty swallowing)
- Oculomotor abnormalities (nystagmus, slow saccades)
- Cognitive impairment (executive dysfunction)
- Peripheral neuropathy
- SCA1-like disorders: Overlap with other polyQ ataxias
- Alzheimer's disease: ATXN1 variants may modify risk
- ALS: Some association with ATXN1 repeat expansions
- Brain: High in cerebellum (Purkinje cells), hippocampus, cerebral cortex
- Cell types: Neurons (particularly Purkinje cells), astrocytes
- Subcellular: Nuclear localization
- Regulation: Tissue-specific expression; developmentally regulated
- Allen Brain Atlas: Very high expression in cerebellar cortex
- Orr et al., Expansion of CAG repeat in SCA1 (1993)
- Zoghbi and Orr, Molecular pathogenesis of SCA1 (2009)
- Lam et al., ATXN1 transcriptional dysregulation in SCA1 (2006)
- Servadio et al., ATXN1 expression and toxicity (1995)
- Cvetanovic et al., Vascular endothelial growth factor in SCA1 (2011)
- Friedman et al., Cerebellar circuitry dysfunction in SCA1 (2012)
- Mizutani et al., ATXN1 in Alzheimer's disease (2015)
- Liu et al., Gene therapy for SCA1 (2019)
- Histone deacetylase inhibitors: May normalize transcription
- Antisense oligonucleotides: ASO-mediated knock-down in clinical trials
- Chemical chaperones: For protein folding
- ASO therapy (validated in mouse models)
- AAV-delivered RNAi approaches
- Transcriptional correction
- Protein aggregation prevention
- Purkinje cell protection
- Cerebellar circuit restoration