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遗传性脊髓小脑型共济失调的CAG三核苷酸突变检测 |
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68 to 83 repeats. Analysis of the mutation in these families showed a strong negative correlation between the size of the expanded CAG repeat and the age of disease onset. None of the SCA patients were positive for SCA6,SCA7,or DRPLA. Nor was any of the sporadic SCA patients positive for the CAG repeat expansion in the SCA1,SCA2, SCA3/MJD, SCA6,SCA7,or DRPLA gene.Conclusion The frequency of SCA3/MJD is substantially higher than that of SCA1 and SCA2 in the autosomal dominant SCA from Chinese families. Chinese SCA3/MJD patients are non-Portuguese. Clinical expressions of the various SCAs overlap one another and hence can make the phenotype-based diagnostic classification inaccurate in many instances. It is important for SCA clinical studies to make an SCA gene diagnosis and genotype analysis.
【Key words】 Hereditary spinocerebellar ataxia Trinucleotide repeat Gene diagnosis
遗传性脊髓小脑型共济失调(spinocerebellar ataxia,SCA)是一类包括Machado-Joseph disease (MJD)等多种亚型共济失调在内的进行性神经系统变性疾病，多为常染色体显性遗传。有作者将齿状核红核苍白球丘脑下部核萎缩(dentatorubral-pallidoluy-sian atrophy,DRPLA)也归为这类疾病。近年来，国外学者先后克隆了SCA1、SCA2、SCA3/MJD、SCA6、SCA7和DRPLA的致病基因［1-6］，发现与CAG三核苷酸异常扩增突变［(CAG)n］相关。为评价中国人SCA患者各SCA基因型的分布频率，我们对中国人85个SCA家系的167例SCA患者及37例散发SCA患者进行了SCA1、SCA2、SCA3/MJD、SCA6、SCA7和DRPLA(CAG)n检测分析，现将结果报告如下。
1 材料与方法
1.1 一般资料 共收集85个SCA家系167例SCA患者，37例散发SCA患者，来自湖南、浙江、江苏、山东和湖北等地，均为汉族。SCA患者临床诊断按Harding标准［7］，部分病例有“遗传早现”现象，遗传方式为常染色体显性遗传。按Hirayama标准［8］，稍作改良，将疾病严重程度分为三级，一级：能独立或偶尔需要帮助行走；二级：完全需要帮助才能行走；三级：只能坐轮椅或卧床。167例SCA患者，男93例，女74例，平均年龄(42.71±18.81)岁，平均发病年龄(34.23±15.72)岁，平均病程(8.37±6.31)年。64名无血缘关系的正常人作对照组。
1.2 实验方法
1.2.1 DNA提取 抽取家系中各位SCA患者及成员外周静脉血10ml，按常规方法提取基因组DNA作为PCR模板。
1.2.2 PCR引物 根据文献［1-6］，分别合成SCA1引物Rep1/Rep2,SCA2引物SCA2-A/SCA2-B，SCA3/MJD引物MJD25/MJD52，SCA6引物S-5-F1/S-5-R1，SCA7引物4U1024/4U716，DRPLA引物DRPLA-1/DRPLA-2。
1.2.3 PCR检测技术 PCR反应体系及反应条件，根据文献［1-6］，稍作适当改变。为准确可靠计算CAG重复数，避免非特异性条带的出现，采用了含42%甲酰胺的高变性聚丙烯酰胺凝胶电泳技术［9］。(CAG)n重复数测定：取4μl P上一页 [1] [2] [3] 下一页
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