脊髓小脑性共济失调7型的分子遗传学诊断及临床分析

目的 研究分析脊髓小脑性共济失调7型(SCA7)的分子遗传学诊断、应用以及临床表现特征。方法 对临床诊断为SCA的36个家系43例病人、38例散发SCA患者、60名家系“健康个体”以及44名非家系正常对照人员,通过PCR及聚丙烯酰胺凝胶电泳等技术检测SCA7基因位点内CAG三核苷酸重复扩增次数,并利用ABI373测序仪对异常等位基因片段进行DNA测序。结果 我国南方正常人群SCA7等位基因CAG重复数为9~19。检出2个家族性、1个散发性共3例SCA7患者,测序证实其异常等位基因内CAG重复数目分别为65、65、63。结论 SCA7基因内部CAG三核苷酸重复异常扩增是该病致病原因,利用分子遗传学分析可进行基因诊断,为症状前诊断及遗传咨询提供依据。

Molecular genetic diagnosis and clinical analysis of spinocerebellar ataxia type 7

Objective To study the molecular genetic diagnosis and clinical cha ra cteristics of spinocerebellar ataxia type 7 (SCA7). Methods This study included 43 patients with autosomal dominant SCA from 36 families, 38 sporadic SCA patien ts, 60 healthy individuals from the SCA families and 44 normal controls without family SCA history. The SCA7 (CAG)n muta-tions were detected by PCR, denaturing polyacrylamide gel electrophoresis and silver staining technique. The abnormal a llele fragments were sequenced by ABI373 DNA sequencing machine. Results Normal alleles of SCA7 were found to have 9 to 19 CAG repeats. Two familial SCA and on e sporadic patients were identified by detecting the presence of abnormal CAG-re -peat expansion in the SCA7 alleles, which was confirmed by DNA sequencing. The repeats of CAG were 65, 65, and 63 re-spectively. Conclusions Abnormal CAG expan sion is the pathogenic cause of SCA7. Molecular genetic analysis is effective f or the diagnosis of SCA, prediction of presymptomatic patients and genetic couns eling.