连接片段在Duchenne型肌营养不良症携带者检测中的应用

摘要

目的：探讨连接片段在缺失型Duchenne型肌营养不良症（Duchenne muscular dystrophy, DMD）携带者检测中的应用价值。方法对1个DMD家系和1例DMD散发病例进行研究。DMD家系中以确诊的患者Ⅲ2和待查携带者Ⅱ3为研究对象；散发病例以患者Ⅱ1及其母亲Ⅰ2为研究对象。通过外显子检测确定家系中患者Ⅲ2第31~43外显子缺失，散发病例患者Ⅱ1第45~54外显子缺失。然后以PCR步移法在相应内含子设计引物定位断裂点的位点，最后在尽量靠近断裂连接点处设计1对引物直接对患者及其待查女性亲属进行连接片段的PCR扩增。结果对上述DMD家系中待查女性Ⅱ3的检测结果为PCR扩增出与患者Ⅲ2一致的阳性片段，诊断其为DMD携带者。对散发病例患者母亲Ⅰ2的检测结果为PCR反应阴性，而对照的患者Ⅱ1扩增出阳性结果，排除其母亲为DMD携带者。结论利用常规PCR技术直接检测缺失型DMD患者的女性亲属是否带有连接片段，可以同样达到进行携带者检测的目的。该方法有别于目前DMD携带者检测中所使用的各种定量分析方法。%Objective To investigate the value of the junction fragments between the breakpoints of introns in identifying deletional Duchenne muscular dystrophy (DMD) carriers. Methods A DMD family (including the index patient III2 and the suspected carrier II3) and a sporadic DMD case (including the patient II1 and his mother I2) were studied. The patient III2 of the DMD family was identified as having exons 31-43 deletion of the DMD gene, and the sporadic patient II1 had exons 45-54 deletion. A PCR-based genome-walking method was used to locate the breakpoints in the corresponding introns. The junction fragments of the patients and their female relatives waiting for a diagnosis were amplified by PCR with primers adjacent to the deletion junctions. Results PCR amplification yielded identical positive results for the female suspected carrier II3 of and the index patient of the DMD family, and the former was thus diagnosed as a carrier of DMD. PCR amplification of the sporadic patient’s mother I2 showed a negative result, but the patient II1 had a positive result, so that the patient's mother was excluded as being a carrier of DMD. Conclusion Routine PCR technique for detecting the junction fragments allows identification of carriers among female relatives of patients with deletional DMD.