遗传性非综合征型耳聋患者GJB2基因编码序列分析

Analysis of GJB2 gene coding sequence in patients with nonsyndromic hearing loss

目的对6个遗传性非综合征型耳聋家系成员的GJB2基因编码序列进行分析，寻找耳聋患者的致病基因突变，探讨GJB2基因突变致病的遗传模式。方法提取患者及家系成员的外周血基因组DNA，扩增GJB2基因的编码序列，然后对扩增产物进行DNA测序，对出现重叠峰形的扩增产物进行TA克隆后再测序，确定基因突变是否存在于同一拷贝。结果6个遗传性非综合征型耳聋家系中，4个家系是GJB2基因突变所致。患者的GJB2基因突变包括235delc、299—300delAT、79G→A＋341A→G和109G→A。非致聋突变79G→A与341A→G组合具有致聋效应，109G→A和235delC的杂合突变可能也有致聋效应。结论GJB2基因突变致聋具有明显异质性，非致聋突变并非完全不致聋，环境因素或其它基因可能参与GJB2基因突变所致耳聋。

Objective To analyze the coding sequence of GJB2 gene in six pedigrees with nonsyndromic hearing loss in order to find deafness-causing mutations in the GJB2 gene, and to explore the inherent pattern of deafness-causing mutations in the GJB2 gene. Methods Genomic DNA was extracted from peripheral blood for the probands and their family members. Coding sequence of the GJB2 gene was amplified by polymerase chain reaction, sequence variations were determined by DNA sequencing. Amplified fragments with overlapping peaks on sequencing chromatogram were sequenced by TA cloning in order to determine whether the mutations originated from the same allele. Results Mutations in the GJB2 gene were found in 4 out of the 6 pedigrees with nonsyndromic hearing loss. Four types of mutations were detected in the GJB2 gene, which were 235delC, 299-300delAT, 79G→A＋341A→G, and 109G→A. Compound heterozygous polymorphisms 79G→A and 341A→G, and mutations 109G→A and 235delC had deafnesscausing effects. Conclusion Heterogeneous mutations of the GJB2 gene are frequently seen in patients with nonsyndromic hearing loss. Sometimes, polymorphisms may cause deafness when they are combined. Environmental factors and other genes may contribute to hearing loss caused by the GJB2 gene mutations.