先天性耳聋是临床表型复杂多样的遗传性疾病，已报道全基因组数百种基因突变可导致感音神经性耳聋并伴有不同的外显性，某些遗传性耳聋确切发病机理不清楚。本研究对一个近亲婚配三个子女都有严重耳聋的家庭做69个已知耳聋致病基因的全外显子和邻近内含子测序，发现一个新的MITF错义基因突变，Arg341Leu，表现为II型Waardenburg综合症患者为纯合突变，单纯耳聋的儿子均为杂合突变，另有7例为无耳聋的杂合突变携带者。家谱和基因型分析提示耳聋患者为父源MITF基因突变，可能与遗传印迹相关。为阐明分子发病机制，本研究组将开展：1）MITF基因突变单倍体分析；2）MITF基因表达和基因型分析；3）MITF基因甲基化研究，4）MITF基因突变功能研究。本研究具有源头创新性，将为耳聋的分子发病机理提供信息，对耳聋的早期诊断和预防，防止耳聋出生缺陷，提高我国人口素质具有重大意义。

Hereditary deafness is complex genetic disease associated with various clinical presentations. Numerous genetic mutations in multiple genes across the genome have been reported to cause sensorineural hearing loss in a dominant manner with variable penetrance. Due to the complexity of genetic mutations in hereditary deafness, the exact mechanism is still under investigation. The lack of a comprehensive understanding of causal genetic mutations also significantly hinders the diagnosis, prognosis, and genetic consolation of the disease. To further understanding of hereditary deafness, we sequenced whole exons and partial boundary introns of 69 known deafness-causing genes in a multi-generation well-documented consanguineous Chinese family. The sequencing data revealed that a novel mutation in MITF (microphthalmia-associated transcription factor) gene, Arg341Leu, in this family. In addition to the missense mutation, the pedigree and fine-genotyping results suggest that the mutation is transmitted in a parent-of-origin specific manner. To elucidate the disease mechanism in this unique, we plan to 1) further genotype the patients and controls in this family to confirm the source of mutation, 2) compare MITF allele expressed in mRNA with the genotype of the individual, 3) elucidate the mechanism of imprinting via methylation assays, and 4) evaluate the functions of the mutated MITF protein in various cell types. The knowledge obtained in this study can potentially expand our understanding of the molecular mechanism of hereditary deafness, facilitate the early diagnosis, and establish an effective genetic analysis for disease prevention and genetic counseling for high-risk families.

先天性耳聋是临床表型复杂多样的遗传性疾病，已报道全基因组数百种基因突变可导致感音神经性耳聋并伴有不同的外显性，某些遗传性耳聋确切发病机理不清楚。本研究对一个近亲婚配三个子女都有严重耳聋的家庭做全外显子和邻近内含子测序，发现一个新的MITF错义基因突变，Arg341Leu，表现为II型Waardenburg综合症患者为纯合突变，单纯耳聋的儿子均为杂合突变，另有7例为无耳聋的杂合突变携带者。家谱和基因型分析提示可能耳聋患者为父源MITF基因突变表达，母源MITF基因遗传印迹相关。本研究对这个罕见多对近亲分配有3个先天性耳聋，其中大女表现为 Waardenburg 综合征的4代人大家系成员做MITF基因突变分析，不符合常染色体显性遗传规律，类似于遗传印记发病规律。通过对耳聋患儿和正常携带者全外显子测序和SNP 单倍体分析，第二到五代未发耳聋的MITF杂合突变携带者的突变均来自于母亲，既母源性MITF基因突变，三个耳聋患儿的MITF突变均来源父亲，且在突变两侧10Mb外均有重组，结果提示可能有母源性MITF基因表达的沉默，既母源性MITF基因遗传印记，而父源性MITF杂合患者多表达突变的MITF基因。但对外周血MITF基因表达分析未观察到父母源性MITF基因表达差异，通过研究发现外周血MITF表达量低，同时该基因有13个异构体，外周血MITF基因RT-PCR 仅扩增出有同一个第一外显子的MITF 异构体（isoform ）1、9、10、11、12、13。结果提示MITF致病的机理可能与其它组织器官和其它的异构体异常有关，为MITF基因的功能研究提供了新的依据和思路，为探索耳聋基因的发病机理提出了新的挑战。本研究的结果将为耳聋的分子发病机理提供信息，对耳聋的早期诊断和预防，防止耳聋出生缺陷，提高我国人口素质具有重大意义。