Spinocerebellar ataxia 1 (SCA1) in the Japanese: Analysis of CAG trinucleitide repeat expansion and instability of the repeat for paternal transmission

Abstract

SCA1 is caused by expansion of an unstable CAG triplet repeat in a novel gene located on the short arm of chromosome 6. In 126 Japanese individuals from 12 pedigrees with SCA1, studies were done to determine if they carried this mutant gene. All the affected and presymptomatic individuals, determined by haplotype segregation analyses, carried an abnormally expanded allele with the range of 39-63 repeat units. This repeat size inversely correlated with the age at onset. However, contrary to reported results, size of the repeat did not correlate with gender of the transmitting parent. Therefore, the CAG triplet repeat instability on paternal transmission is not likely to be fundamental to SCA1. © 1995 The Japan Society of Human Genetics.