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目的在江苏淮阴一母系遗传非综合征型耳聋大家系中,寻找线粒体基因组上可能影响1555(A→G)突变表型的其他位点突变。方法采用聚合酶链反应限制性片段长度多态性分析(PCRrestrictionfragmentlengthpolymorphism,PCRRFLP)和测序技术,检测了核心分支家系中27名母系成员的线粒体DNA上1555位点和7445位点的碱基变化,进而对该家系2名母系成员的线粒体全基因组和其他25名母系成员线粒体12SrRNA基因MTRNR1和tRNASer(UCN)基因MTTS1进行了全长测序。结果再次证明了1555(A→G)突变是该家系成员致聋的分子生物学基础之一;并发现该家系27名母系成员的线粒体基因组中除1555(A→G)突变外,还同时存在有955960(insC)同质型突变,两突变共分离。另外,新发现一个线粒体DNA突变———7449(insG),但该突变仅在2名母系成员中存在。结论推测955960(insC)突变可能通过改变12SrRNA基因的高级结构,并与1555(A→G)突变协同作用,提高了突变携带者对氨基糖甙类药物的敏感性;同时该突变可能也会导致线粒体蛋白质的合成缺陷,从而提高1555(A→G)突变致聋的外显率。
Objective To search for other site mutations in the mitochondrial genome that may affect the 1555 (A → G) phenotype in a maternally inherited non-syndromic deafness pedigree in Huaiyin, Jiangsu. Methods PCR-restriction fragment length polymorphism (PCR) restriction fragment length polymorphism (PCR-RFLP) and sequencing were used to detect the base changes of mitochondrial DNA at positions 1555 and 7445 of 27 maternal members in the core pedigree. The whole mitochondrial genome of two maternal members of the pedigree and the other 25 maternal members of mitochondrial 12S rRNA gene MTRNR1 and tRNASer (UCN) gene MTTS1 were sequenced. The results again proved that the 1555 (A → G) mutation was one of the molecular biological basis for deafness of this pedigree. In addition, there were 1555 (A → G) mutations in mitochondrial genome of 27 maternal members of this pedigree. There are 955960 (insC) homozygous mutations, two mutations co-segregation. In addition, a new mitochondrial DNA mutation, 7449 (insG) was found, but the mutation was found in only two maternal members. Conclusion It is speculated that the 955960 (insC) mutation may increase the sensitivity of mutant carriers to aminoglycosides by changing the higher structure of 12S rRNA gene and cooperating with 1555 (A → G) mutation. At the same time, this mutation may also lead to Mitochondrial protein synthesis defects, thereby increasing the 1555 (A → G) mutation rate of deafness.