Detection of expanded nucleotide repeat sequences of causative gene in patients with hereditary spinocerebellar ataxia

Abstract

Objective To determine a stable, exact and direct detection method for expanded nucleotide repeat sequences of the causative gene in patients with hereditary spinocerebellar ataxias (SCAs).Methods Quantitative fluorescent-polymerase chain reaction,8%denaturing polyacrylamide gel electrophoresis(PAGE),capillary electrophoresis(CE)and recombinant DNA technology by direct sequencing technique were employed to detect the CAG-repeat numbers of abnormal allele in 50 patients diagnosed as having SCA3/MJD.And then,the differences of CAG repeat numbers detected by CE and recombinant DNA technology were statistically analyzed.Results Of the 50 patients with SCA3/MJD detected by 8%denaturing PAGE,the expanded CAG repeat numbers measured by CE and recombinant DNA technology ranged from 63 to 74(69.56±2.12)and from 67 to 80(73.72±3.29),respectively.Significantly decreasedtendency was showed in the mean CAG repeat numbers of 69.56±2.12 using CE as compared with that in those of 73.72±3.29 using recombinant DNA technology,(t=-9.61,P=0.000). Conclusion Denaturing PAGE and CE can be used as preliminary screening for nucleotide repeat numbers,while the exact numbers depend on the recombinant DNA and direct sequencing technologies.Recombinant DNA technology combined with direct sequencing is a predominant,stable,exact and direct method to detect the repeat numbers of SCAs and analyze the polymorphism of nucleotide sequence. Key words: Denaturing polyacrylamide gel electrophoresis; Recombinant DNA technology; Nucleotide; Spinocerebellar ataxia