遗传性脊髓小脑性共济失调7型的基因突变及临床特征分析

目的 研究遗传性脊髓小脑性共济失调7型（SCA7）的基因突变和临床特征。方法 对临床诊断为脊髓小脑性共济失调（SCA）的15个家系24例患者、20例散发SCA患者、41名家系“正常人”及30名非序列的突变，并利用ABI373例序仪对异常等位基因片段进行DNA测序。结果 24例SCA患者的SCA7等位基因CAG重复数目为9－18。正常人SCA7等位基因CAG重复数目为9－19。检出1例散发患者为SCA7，经基因测序证实，其异常等位基因的CAG重复数目为63。结论 CAG过度扩增是SCA7的致病原因，利用基因突变分析可进行基因诊断，提供症状前诊断及遗传咨询的依据，为基因分型奠定基础。

Analysis of the gene mutation and clinical characteristic of hereditary spinocerebellar ataxia type 7

Objective To study the gene mutation and clinical characteristic of hereditary spinocerebellar ataxia type 7 (SCA7).Methods The SCA7 (CAG) trinucleotide repeat mutations were detected by polymerase chain reaction(PCR) and polyacrylamide gel electrophoresis technique in 24 patients with autosomal dominant SCA from 15 families, 20 sporadic SCA patients and 41 normal persons from the same family and 30 healthy persons from different family,the abnormal allele fragments were sequenced by ABI 373 DNA sequencing machine.Results 24 patients with SCA had CAG repeat numbers of SCA 7 allele from 9~18.Normal alleles of SCA 7 had CAG repeat number from 9 to 19. One sporadic SCA patient had one abnormal SCA 7 allele with the CAG repeat expanded to 63 repeats, being confirmed by DNA sequencing.Conclusion CAG expansions were pathogenic cause of SCA 7. The technique of gene mutation detection could provide an effective way for the prediction of asymptomatic and genetic counseling,which was a basis for gene typing.