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last update : 15-01-2021
Symbol SCA8
Location 13q21
Name spinocerebellar ataxia 8
Corresponding gene ATXN8OS , ATXN8
Main clinical features
  • adult onset, with dysarthria, nystagmus, tremor, gait instability, contradicting evidence on the frequency of the expansion in control patients as well as regard the paternal transmission, with reduced penetrance in patients born from affected fathers, maybe in relation with an "en masse" contraction of the repeat in sperm including typical cases of parkinson disease
  • Genetic determination autosomal dominant
    Function/system disorder neurology
    Type disease
    Gene product
    Name kelch-like 1 antisense (Drosophila)
    Gene mutationChromosome rearrangementEffectComments
    repeat expansion   abnormal protein/gain of function trinucleotide repeat(CUG)n expansion, unstable 13-34 (>110 repeats), non coding, and intranuclear polyglutamine inclusions
    Remark(s) bidirectional expression of CUG and CAG expansion transcripts and intranuclear polyglutamine inclusions, from both sense and antisense strands
  • relatively short CUGexp transcripts causing RNA gain-of-function effects and the growing number of antisense transcripts suggest unrecognized toxic RNAs contribute to the pathophysiology of polyglutamine CAG CTG disorders (Daughters 2009)
  • expression of ATXN8OS CUGexp transcripts dysregulate MBNL1-CUGBP1 pathways in the CNS and trigger downstream molecular changes in GABA-A transporter 4 (SLC6A11) regulation through an RNA gain-of-function mechanism (Daughters 2009)
  • caused by the expanded repeat CTA/CTG of two overlapping genes, ATXN8OS and ATXN8, expressed bidirectionally( PMID: 28229454))