SLC26A4基因拷贝数变异致聋家系的遗传学分析

Genetic analysis of SLC26A4 gene copy number variants in families with hearing loss

目的探讨两个大前庭水管综合征(EVAS)耳聋家系患者的致病原因。方法应用靶向二代测序技术对两个家系先证者进行耳聋致病基因筛查,结合临床表型确定可能致病的候选基因。运用多重连接探针扩增技术(MLPA)和Sanger测序技术分别对先证者及其家系成员进行SLC26A4基因拷贝数变异和点突变验证。结果靶向二代测序检测结果发现家系1先证者存在SLC26A4基因EX13_EX15DEL/c.919-2A>G复合杂合突变,MLPA及Sanger测序结果提示该双等位基因突变分别遗传自先证者母亲和父亲。家系2先证者检出SLC26A4基因EX5_EX6DEL纯合突变,MLPA验证结果提示该纯合突变分别遗传自家系的父母亲。经检索人类突变数据库及相关文献,SLC26A4 EX13_EX15DEL和EX5_EX6DEL均为未报道过的新拷贝数变异。结论SLC26A4基因EX13_EX15DEL和EX5_EX6DEL是导致EVAS耳聋患者的新致病突变,SLC26A4基因拷贝数变异是SLC26A4基因突变单杂合或未检出突变EVAS耳聋患者的重要致病因素,应加强对该类患者的SLC26A4基因的拷贝数变异筛查。

Objective To reveal the genetic pathogenesis of the probands with enlarged vestibular aqueduct syndrome(EVAS)in two hearing loss pedigrees.Methods Target next generation sequencing(TNGS)technology was used to screen the cause of disease in two probands,and determine candidate genes that may cause disease in combination with clinical phenotypes.Multiplex ligation-dependent probe amplification(MLPA)and Sanger sequencing method were applied to verify the copy number variations and base variations of probands and their pedigree members.Results TNGS technology found compound heterozygous mutation of EX13_EX15DEL and c.919-2A>G in SLC26A4 gene in probands of pedigree 1.MLPA and Sanger sequencing verified these two variations and suggested that EX13_EX15DEL was inherited from his healthy mother and c.919-2A>G was inherited from his healthy father.Homozygous variation of SLC26A4 EX5_EX6DEL was identified in proband of pedigree 2.MLPA confirmed the deletion and showed that SLC26A4 EX5_EX6DEL homozygous variation was inherited from his prarents.After searching the human mutation databases and the related references,the two deletions are unreported copy number variations(CNVs).Conclusion The CNVs of SLC26A4 genes EX5_EX6DEL and EX13_EX15DEL are the causes of the disease in theses two pedigrees.SLC26A4 CNVs are important pathogenic factors in EVAS patients with heterozygous or no variation of SLC26A4 gene.It is necessary to strengthen the screening of CNVs of SLC26A4 gene in these patients.