一母系遗传非综合征耳聋家系的线粒体DNA突变分析

在问卷调查及家系随访的基础上,在安徽省淮北市收集到一母系遗传非综合征耳聋家系,利用聚合酶链式反应-限制片段长度多态性分析(PCR-RFLP)和测序技术,检测了该家系成员线粒体DNA(mtDNA)上可导致非综合征耳聋的两个突变热点处(12S rRNA基因上的1 555位点和tRNASer(UCN)基因上的7 445位点)的碱基变化,发现该家系所有母系成员的mtDNA上都有A1555G同质型突变,但7 445位点无异常;进而对该家系两个表型明显不同母系成员(一例具有先天性耳聋表型,另一例听力正常)的mtDNA进行全长测序,结果未在mtDNA上发现除A1555G以外的其他位点突变,只发现了27处多态性序列变化,且两成员的mtDNA无序列差异.说明mtDNA上的A1555G同质型突变是该家系部分母系成员致聋的分子生物学基础之一;推测该家系A1555G突变携带者临床表型的差异可能与mtDNA多态性无关,而更可能是核修饰基因与A1555G突变协同作用的结果.

Mutation Analysis of the Mitochondrial DNA from a Pedigree with Maternally Inherited Nonsyndromic Hearing Loss

Based on the questionnaire and the follow-up study,a pedigree with maternally inherited nonsyn-dromic hearing loss in Huaibei,Anhui province was reported.PCR-RFLP and DNA sequencing were used to detect the nucleotide changes on the sites of nt1555 and nt7445,which are the hot spots for mutations associated with hearing loss in the mitochondrial 12S rRNA and tRNASer（UCN） genes respectively.Molecular analysis showed that all the matrilineal members in this pedigree carried the A1555G homozygous mutation,but no nucleotide changes were found on the site of nt7445.Subsequently,the complete mitochondrial genomes from two matrilineal members with different phenotypes were PCR amplified and sequenced.27 mitochondrial DNA polymorphisms were found to be common in these two matrilineal members.This indicated that the mitochondrial DNA A1555G mutation was one of the major factors leading to matrilineal nonsyndromic hearing loss in this pedgree,and the different phenotypes for the matrilineal members with the same A1555G mutation could mainly be the result of the nuclear modifier gene（s）.