Frequency of spinocerebellar ataxia types 1, 2, 3, 6, 7, 8, 10, 12, 17 and dentatorubral-pallidoluysian atrophy in Chinese Han population

Objective To assess the frequency of different subtype of spinocerebellar ataxias (SCAs) in Chinese Han population. Methods The nueleotide repeat mutations of SCA1, SCA2, SCA3/ MJD, SCA6, SCAT, SCA8, SCA10, SCA12, SCA17 and dentatorubral-pallidoluysian atrophy (DRPLA) were detected by the polymerase chain reaction (PCR), denaturing polyacrylamide gel electrophoresis (PAGE), Southern blot, recombinant DNA technology by T-vector cloning and direct sequencing technique in a cohort of 559 Mainland Chinese patients affected by spinocerebellar ataxia, including 363 families with autosomal dominant SCA (AD-SCA) and 196 sporadic cases. Results Among the 363 AD-SCA families, 15 families (4. 13%) were positive for SCA1, 26 (7. 16%) for SCA2, 187 (51.52%) for SCA3/MJD, 6 (1.65%) for SCA6, 7 (1.93%) for SCA7, 1 (0. 28%) for SCA12 and 1 (0. 28%) positive for SCA17; 120(33. 06%) were negative for all the tested SCAs. There were 2 (1.02%) SCAI, 3 (1.53%) SCA2, 15 (7. 65%) SCA3/MJD, 3 (1.53%) SCA6 and 173 (88.27%) not identified in the 196 sporadic SCA patients. None of the SCA8, SCA10 and DRPLA mutation was found. Conclusions SCA3/MJD is a substantially common subtype of AD-SCAs and sporadic SCA in Chinese Han patients with SCAs, subsequently followed by SCA2, SCA1, SCAT and SCA6; SCA12 and SCA17 are uncommon subtypes, while SCA8, SCA10, and DRPLA are rare, if not absent. SCA17 subtype was initially identified in mailand China. Some other genes might be causative in those unidentified AD-SCA pedigrees, and other etiological factors besides genetic cause might contribute for those sporadic cases. Key words: Spinocerebellar ataxias;  Trinueleotide repeat expansion;  Pedigree;  China;  Han nationality