Abstract
We previously reported that a (CTG)n expansion causes spinocerebellar ataxia type 8 (SCA8), a slowly progressive ataxia with reduced penetrance. We now report a transgenic mouse model in which the full-length human SCA8 mutation is transcribed using its endogenous promoter. (CTG) 116 expansion, but not (CTG)11 control lines, develop a progressive neurological phenotype with in vivo imaging showing reduced cerebellar-cortical inhibition. 1C2-positive intranuclear inclusions in cerebellar Purkinje and brainstem neurons in SCA8 expansion mice and human SCA8 autopsy tissue result from translation of a polyglutamine protein, encoded on a previously unidentified antiparallel transcript (ataxin 8, ATXN8 ) spanning the repeat in the CAG direction. The neurological phenotype in SCA8 BAC expansion but not BAC control lines demonstrates the pathogenicity of the (CTG-CAG) n expansion. Moreover, the expression of noncoding (CUG)n expansion transcripts (ataxin 8 opposite strand, ATXN8OS) and the discovery of intranuclear polyglutamine inclusions suggests SCA8 pathogenesis involves toxic gain-of-function mechanisms at both the protein and RNA levels.
Original language | English (US) |
---|---|
Pages (from-to) | 758-769 |
Number of pages | 12 |
Journal | Nature Genetics |
Volume | 38 |
Issue number | 7 |
DOIs | |
State | Published - Jul 2006 |
Bibliographical note
Funding Information:We thank SCA8 family members for their participation; M.S. Swanson for critically reviewing our manuscript; H.T. Orr, M.T. Su, H.M. Hsieh-Li, G.W. Lee-Chen for helpful discussions and D. Norton, A. Rose and A. Koeppen for providing control autopsy tissues. Grant support from the National Ataxia Foundation and the US National Institutes of Health (RO1 NS40389) is gratefully acknowledged.