1552例重度感音神经性聋患者与SLC26A4基因IVS7—2A〉G突变相关的全序列分析

Sequencing analysis of whole SLC26A4 gene related to IVS7-2A 〉 G mutation in 1552 moderate to profound sensorineural hearing loss patients in China

目的在全国1552例聋哑学生中进行基于SLC26A4基因热点突变IVS7-2A〉G的全序列筛查，分析和探讨中国人SLC26A4基因相关大前庭水管综合征的分子流行病学状况。方法调查对象来自全国21个省市自治区的聋哑学校学生1552例，共涉及21个民族。听力正常的对照组人群150例。所有受检者均采集外周血并提取DNA，以序列分析方法检测SLC26A4基因外显子7＋8以筛查热点突变IVS7—2A〉G，对携带IVS7-2A〉G纯合突变的个体结束筛查，对携带IVS7-2A〉G单杂合突变的个体进行SLC26A4基因其他外显子测序，寻找可能存在的另外一个突变位点。结果1552例患者中197例携带IVS7-2A〉G突变，其中83例携带IVS7-2A〉G纯合突变，114例携带IVS7-2A〉G单杂合突变，IVS7-2A〉G突变总检出率达到12．69％（197／1552）。114例携带IVS7-2A〉G单杂合突变的患者中78例找到另外一个突变位点，其余36例未找到另外的突变。1552例耳聋患者中IVs7—2A〉G纯合突变及包含一个IVS7-2A〉G突变的复合杂合突变携带者共161例，占10．37％（161／1552）。78例携带SLC26A4基因复合杂合突变的患者中，除IVS7-2A〉G突变外的另一突变位点主要存在于外显子19、10、17、15、11＋12、14和3上，发现新突变类型21种。正常对照人群IVS7-2A〉G突变检出率为2％，均为单杂合突变，且均未找到另一个突变。结论中国耳聋群体中由SLC26A4基因突变引起的大前庭水管相关遗传性聋的比例超过10％，SLC26A4基因筛查和诊断在耳聋的病因学诊断中占有重要地位；通过在较大样本中进行与SLC26A4基因IVS7-2A〉G突变相关的全序列分析，可以明确相对热点突变分布密集的外显子区域，为制定高效的SLC26A4基因筛查策略提供依据；新发现的突变类型丰富了中国人群SLC26A4基因突变图谱。

Objective To investigate the whole sequence of SLC26A4 gene among 1552 deaf students from 21 regions of China with SLC26A4 hot spot mutation IVS7-2A 〉 G and analyze the epidemiological state of enlarged-vestibular-aqueduct-syndrome （EVAS） related hearing loss in China Methods DNA was extracted from peripheral blood of 1552 students from deaf and dumb school of 21 regions in China. The nationality of the 1552 cases covers Han （1290 cases）, Uigur （69 cases）, Hui （37 cases）, Mongolia （31 cases）, Yi, Zhuang, Bai, Miao and other 13 nationalities （125 cases）. Firstly, all subjects were analyzed for the hot spot mutation IVS7-2A 〉 G by direct sequencing. Those carrying a single heterozygous IVS7-2A 〉 G were given further analyzed for the probable second mutation in other exons except exon7 and exon8 of SLC26A4. One hundred and fifty cases with normal hearing were in the control group. Results The sequencing results revealed 197 cases carrying IVS7-2A 〉 G, of whom 83 carrying IVS7-2A 〉 G homozygous mutation, 114 carrying IVS7-2A 〉 G heterozygous mutation. Of the 114 cases with heterozygous IVS7-2A 〉 G, 78 cases were found to have another mutation and 36 cases were found no other mutation in SLC26A4. Of the 1552 cases, the percentage of cases carrying homozygous IVS7-2A 〉 G and compound heterozygous mutations was 10. 37% （ 161/1552）. Of the 78 cases with SLC26A4 compound heterozygous mutations, the mutations except IVS7-2A 〉 G were found mainly in exon 19,10,17,15, 11 ＋ 12,14 and 3. Twenty-one novel SLC26A4 mutations were found. In the control group, there were only 3 cases carrying heterozygous IVS7-2A 〉 G, and no other mutation in SLC26A4 was found. Conclusions SLC26A4 mutations account for at least 10% of EVAS related hereditary hearing loss in China. It＇s of great importance to screen SLC26Ad gene for making aetiological diagnosis for deafness. The discovery of novel variants of SLC26A4 gene makes the mutational and polymorphic spectrum more plentiful in Chinese population. We also provide preliminary evidence for the hot spot areas of SLC26A4.