Partial Loss of Ataxin-1 Function Contributes to Transcriptional Dysregulation in Spinocerebellar Ataxia Type 1 Pathogenesis

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disease caused by expansion of a CAG repeat that encodes a polyglutamine tract in ATAXIN1 (ATXN1). Molecular and genetic data indicate that SCA1 is mainly caused by a gain-of-function mechanism. However, deletion of wild-type ATXN1 enhances SCA1 pathogenesis, whereas increased levels of an evolutionarily conserved paralog of ATXN1, Ataxin 1-Like, ameliorate it. These data suggest that a partial loss of ATXN1 function contributes to SCA1. To address this possibility, we set out to determine if the SCA1 disease model (Atxn1154Q/+ mice) and the loss of Atxn1 function model (Atxn1−/− mice) share molecular changes that could potentially contribute to SCA1 pathogenesis. To identify transcriptional changes that might result from loss of function of ATXN1 in SCA1, we performed gene expression microarray studies on cerebellar RNA from Atxn1−/− and Atxn1154Q/+ cerebella and uncovered shared gene expression changes. We further show that mild overexpression of Ataxin-1-Like rescues several of the molecular and behavioral defects in Atxn1−/− mice. These results support a model in which Ataxin 1-Like overexpression represses SCA1 pathogenesis by compensating for a partial loss of function of Atxn1. Altogether, these data provide evidence that partial loss of Atxn1 function contributes to SCA1 pathogenesis and raise the possibility that loss-of-function mechanisms contribute to other dominantly inherited neurodegenerative diseases

Genetic and clinical analysis of spinocerebellar ataxia type 8 repeat expansion in Yugoslavia

Spinocerebellar ataxia type 8 (SCA8) is a slowly progressive ataxia causally associated with untranslated CTG repeat expansion on chromosome 13q21. However, the role of the CTG repeat in SCA8 pathology is not yet well understood. Therefore, we studied the length of the SCA8 CTA/CTG expansions (combined repeats, CRs) in 115 patients with ataxia, 64 unrelated individuals with non-triplet neuromuscular diseases, 70 unrelated patients with schizophrenia, and 125 healthy controls. Only one patient with apparently sporadic ataxia was identified with an expansion of 100 CRs. He had inherited the expansion from his asymptomatic father (140 CRs) and transmitted the mutation to his son (92CRs). Paternal transmission in this family produced contractions of 40 and 8 CRs, respectively. None of the subjects from other studied groups had an expansion at the SCA8 locus. In the control group the number of CRs at the SCA8 locus ranged from 14 to 34. Our findings support the notion that allelic variants of the expansion mutation at the SCA8 locus can predispose to ataxia

PP09.9 – 2907: Is it easy to recognize HINT1 neuropathy

Vol 19, Supp 1:S67M3