中国人群迟发性耳聋家系及散发病例凝血因子C同源物基因突变分析

目的分析中国常染色体显性遗传非综合征性耳聋（DFNA）群体凝血因子C同源物（COCH）基因突变发生率及突变谱。方法在我国汉族人群中收集26个DFNA家系、19个遗传方式不明的迟发性耳聋小家系、22例迟发性耳聋散发病例和100例正常对照者的临床资料及外周静脉血并提取DNA,采取PCR扩增后直接测序的方法进行COCH全序列突变分析。结果在1个巨大DFNA家系中发现COCH 1625G〉A杂合突变,使原来542位的半胱氨酸突变成酪氨酸（C542Y）;在1个遗传方式不明的迟发性耳聋小家系中发现COCH 1535 T〉C杂合突变,使512位蛋氨酸突变为苏氨酸（M512T）。进化保守性分析提示C542、M512在小鼠、牛、鸡和斑马鱼中高度保守。2个家系成员的表现型与基因型共分离。100例正常对照未见COCH突变。结论COCH M512T和C542Y突变是这2个迟发性耳聋家系患者致聋的分子病因。

Mutation screening of the COCH gene in familial and sporadic patients with late onset nonsyndromic sensorineural hearing loss among Chinese population

OBJECTIVE: To investigate the mutational of the coagulation factor C homology (COCH) gene related to autosomal dominant sensorineural nonsyndromic hearing loss (DFNA) with late onset in Chinese population. METHODS: Peripheral blood samples were collected from he members of 26 DFNA families, members of 19 small DFNA families with un recognized inheritance pattern, and 22 sporadic patients with sensorineural nonsyndromic late onset hearing loss, the hearing loss of all of which occurred during the age range 10 - 40, and 100 normal controls. From different parts of China, these subjects underwent questionnaire survey too. Genomic DNA was isolated, COCH mutation was screened by PCR and sequencing, and restriction endonuclease analysis was used to detect the mutation sites of the COCH gene. The conservation in evolution of the target amino acid sequences was analyzed using CluatalX1.82 software. RESULTS: DNA sequencing of coding regions and exon/intron boundaries of COCH 2 - 12 exons identified a heterozygous G-to-A substitution at position 1625 in exon 12 in a large DFNA family, leading to a C542Y substitution, and a heterozygous T-to-C substitution at position 1535 in exon 12 in a small family, leading to a M512T substitutions. Both the residues of Cys542 and M512 were conserved across human, mouse, chicken, and zebrafish. These mutations were not detected in the 100 control subjects. CONCLUSION: The C542Y and the M512T mutations cause hearing loss in Chinese DFNA families.