| CAG repeat expansion | Pathogenic mutation is an expanded CAG trinucleotide repeat in the ATXN2 gene on chromosome 12q24.1 |
| Normal alleles | 13-31 CAG repeats |
| Intermediate alleles | 32-33 repeats (may be unstable) |
| Full mutation alleles | 34-200+ repeats (disease-causing) |
| Anticipation | Larger repeats are associated with earlier onset, particularly through paternal transmission |
| Normal function | Ataxin-2 interacts with multiple RNA-binding proteins and is involved in translational control |
| Pathogenic mechanism | The expanded polyglutamine tract causes toxic gain-of-function, leading to RNA metabolism dysregulation and cellular stress |
| Expression pattern | Widely expressed in the central nervous system, with high levels in Purkinje cells and cerebellar nuclei |
| Cerebellar degeneration | Severe loss of Purkinje cells throughout the cerebellar cortex |
| Inferior olivary nucleus degeneration | Prominent neuronal loss in the inferior olive |
| Brainstem pathology | Degeneration of the pons and midbrain nuclei |
| Basal ganglia involvement | Variable involvement of the striatum and subthalamic nucleus |
| Databases | OMIMOrphanetClinicalTrialsPubMed |
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