摘要
脆性 X 综合征是一最常见的 X 性连锁的遗传性智力低下病,是因 X 染色体上脆性部位的FMR—1基因内一段不稳定的 CGG 重复序列的异常扩增所致。本文建立了多聚酶链反应—变性梯度聚丙烯酰胺凝胶电泳(PCR—DGGE)方法,并成功地检测出83例正常人 X 染色体脆性位点FMR—1基因内 CGG 重复序列片段。在上述83例正常人中发现有16个不同大小的等位基因,说明该重复序列的长度在中国人中具有丰富的多态性,最常见的等位基因大小为308bP,有29个CGG 重复。文章对 PCR 方法扩增该 CGG 重复序列片段成功的关键如在反应体系中加入 dGTP 类似物7—deaza—dGTP,DMSO 以及它们在反应体系中理想的浓度等进行了详细的讨论。由于该方法能显示800bP 以内的 DNA 片段,并能准确确定 FMR—1基因内 CGG 重复序列的 CGG 重复数.在用于脆性 X 综合征的女性携带者检出时特别有意义,可根据 CGG 重复数估计其后代受累的风险率及受累程度。该方法稳定可靠,简便宜行,适合推广应用于脆性 X 综合征患者及携带者的临床诊断和遗传咨询及筛查。
In fragile X syndrome,the most common inherited cause of mental deficiency,the underlying mutation is a large increase in the number of CGG repeats in FMR-Ⅰ gene on chromo- some X.We have deveoped a polymerase chain reacton—denaturing gradient polyacrylamide gel elec- trophoresis (PCR—DGGE)method to amplify the P (CGG)n fragment.In this report,83 unrelated mormal Chinese were assayed by PCR—DGGE and 16 distinctly sized alleles were identified among the PCR products,ranging in size from 272bp to 332bp with CGG repeats of 17to 37.These suggested rich polymorphism in the allele in Chinese general population.The Keys to success in ampliflying the P(COG)n fragment by PCR,e.g.addng 7—deaza—dGTP in thise PCR reaction system,and the ad- vantages of PCR—DGGE in analysis of fragile X syndrome were also discussed in this paper.Clinical diagnosing of fragile X syndrome and genetic screening of population at risk for fragile X can now be achieved by PCR- DGGE rapidly,inexpensively and on small samples.
出处
《卒中与神经疾病》
1996年第2期65-69,共5页
Stroke and Nervous Diseases
