Koob M D, Benzow K A, Bird T D, Day J W, Moseley M L, Ranum L P
Department of Neurology, University of Minnesota, Minneapolis 55455, USA.
Nat Genet. 1998 Jan;18(1):72-5. doi: 10.1038/ng0198-72.
Trinucleotide repeat expansions have been shown to cause a number of neurodegenerative diseases. A hallmark of most of these diseases is the presence of anticipation, a decrease in the age at onset in consecutive generations due to the tendency of the unstable trinucleotide repeat to lengthen when passed from one generation to the next. The involvement of trinucleotide repeat expansions in a number of other diseases--including familial spastic paraplegia, schizophrenia, bipolar affective disorder and spinocerebellar ataxia type 7 (SCA7; ref. 10)--is suggested both by the presence of anticipation and by repeat expansion detection (RED) analysis of genomic DNA samples. The involvement of trinucleotide expansions in these diseases, however, can be conclusively confirmed only by the isolation of the expansions present in these populations and detailed analysis to assess each expansion as a possible pathogenic mutation. We describe a novel procedure for quick isolation of expanded trinucleotide repeats and the corresponding flanking nucleotide sequence directly from small amounts of genomic DNA by a process of Repeat Analysis, Pooled Isolation and Detection of individual clones containing expanded trinucleotide repeats (RAPID cloning). We have used this technique to clone the pathogenic SCA7 CAG expansion from an archived DNA sample of an individual affected with ataxia and retinal degeneration.
三核苷酸重复扩增已被证明会引发多种神经退行性疾病。这些疾病大多的一个标志是存在遗传早现现象，即由于不稳定的三核苷酸重复序列在代代相传时倾向于延长，导致连续几代人的发病年龄降低。三核苷酸重复扩增与许多其他疾病有关，包括家族性痉挛性截瘫、精神分裂症、双相情感障碍和7型脊髓小脑共济失调（SCA7；参考文献10），这一点在遗传早现现象的存在以及对基因组DNA样本的重复序列扩增检测（RED）分析中均有提示。然而，三核苷酸扩增在这些疾病中的参与情况，只有通过分离这些人群中存在的扩增序列并进行详细分析，以评估每个扩增序列作为可能的致病突变，才能得到确凿证实。我们描述了一种新方法，通过重复序列分析、合并分离和检测含有扩增三核苷酸重复序列的单个克隆（RAPID克隆）过程，直接从小量基因组DNA中快速分离扩增的三核苷酸重复序列及其相应的侧翼核苷酸序列。我们已使用该技术从一名患有共济失调和视网膜变性的个体的存档DNA样本中克隆出致病性SCA7 CAG扩增序列。
