TRINUCLEOTIDE REPEAT EXPANSION OF SPINOCEREBELLAR ATAXIA (SCA1) FOUNDIN A CHINESE FAMILY

Objective To investigate the gene mutation and the ratio of the spinoc erebellar ataxia type 1 (SCA1) in Chinese patients with autosomal domi nant spinocerebellar ataxia (ADSCA). Method The family material and DN A samples were collected from thirteen families with ADSCA. To determi ne the characteristics of the CAG trinucleotide repeats in SCA1 gene, the PCR products of the Rep1 and Rep 2 primers were analyzed, and the bands with CAG repeat expansion were cloned by PCR2.1 vector and seque nced. Results One family was found to have an expanded CAG repeat in t he 13 families with ADSCA. The clinically affected individual was hete rozygous with one disease allele being 55 CAG repeats, whereas the mea n size of the CAG repeats on 104 chromosomes generated from unrelated control Chinese individuals is 29.3 (ranging from 18 to 34). Conclusio ns The frequency of the SCA1 mutation is about 7% in the 13 Chinese fa milies with ADSCA, suggesting that this type of genetic defect is not the main cause involved in the pathogenesis of ADSCA in China. Since t he mutation has also been found in Caucasian, Japanese, Malaysian, and Bangladeshi kindreds, it is suggested that this genetic defect may we ll have multiple origins in different ethnic groups.