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常染色体显性脊髓小脑型共济失调(Autosomal dominant spinocerebellar ataxias,ADCAs)是一种神经系统退行性疾病,具有高度的遗传异质性,其中脊髓小脑型共济失调3型(Spinocerebellar ataxias type 3,SCA3)是一种常见的类型。文章通过PCR扩增广西一个脊髓小脑共济失调家系SCA3/MJD基因片段,用毛细管电泳和测序方法检测了SCA3/MJD基因的CAG重复序列大小、传递特点以及SCA3/MJD基因的变异。结果显示:家系的所有4名患者和3名无症状携带者(Asymptomatic carrier)的SCA3/MJD基因第10外显子中存在异常扩增的CAG重复序列,重复次数为64~71次;CAG重复次数在具有cgg等位基因的正常个体间传递时保持不变,提示cgg等位基因不是正常个体两代间CAG重复序列稳定性的影响因素。SCA3/MJD基因中另有两个单碱基点突变,一个是内含子区的杂合性突变(IVS9-113 T>C),另一个是外显子区域的错义突变(220 G>A,220 Glu>Gly)。这两个点突变为首次报道,但尚不能明确这两个新的点突变对SCA3表型的影响。
Autosomal dominant spinocerebellar ataxias (ADCAs) is a kind of neurodegenerative disease with a high degree of genetic heterogeneity. Spinocerebellar ataxias type 3 SCA3) is a common type. In this study, a SCA3 / MJD gene fragment was amplified by PCR from a Spinocerebellar ataxia family in Guangxi. The size and transmission of CAG repeat of SCA3 / MJD gene and the variation of SCA3 / MJD gene were examined by capillary electrophoresis and sequencing. The results showed that all 4 patients in the pedigree and 3 asymptomatic carriers had abnormal amplified CAG repeats in exon 10 of SCA3 / MJD gene, with 64 to 71 repetitions; CAG repeat The number of cgg alleles in the normal transmission between individuals remained unchanged, suggesting that the cgg allele is not normal individuals CAG repeat between generations of two influencing factors. There are two single-base point mutations in the SCA3 / MJD gene, one is a heterozygous mutation in the intron region (IVS9-113 T> C) and the other is a missense mutation in the exon region (220 G> A, 220 Glu> Gly). The first two mutations were reported, but the effects of these two new point mutations on the SCA3 phenotype have not yet been elucidated.