27个省市聋校学生基于SLC26A4基因IVS7-2A＞G突变的全序列分析

摘要

目的 在全国27个省市聋校学生2352例中进行基于SLC26A4基因热点突变ⅣS7-2A＞G的该基因的全序列筛查,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27个省市自治区的聋哑学校学生2352例,共涉及21个民族.听力正常的对照人群150例.所有受检者均采集外周血并提取DNA,其中1552例以序列分析方法 检测SLC26A4基因外显子7+8以筛查热点突变IVS7-2A＞G,800例以试剂盒的方法 检测IVS7-2A＞G突变.对携带IVS7-2 A＞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 2352例来自全国多个地区的耳聋患者中271例携带SLC26A4基因IVS7-2A＞G突变,其中106例携带IVS7-2 A＞G纯合突变,165例携带IVS7-2A＞G单杂合突变,IVS7-2A＞G突变总检出率达到11.52％(271/2352),汉族患者中IVS7-2 A＞G突变检出率达到13.35％(254/1903);对165例携带IVS7-2A＞G单杂合突变的患者进行SLC26A4基因其他外显子序列分析显示其中105例找到另外一个突变位点,其余60例未找到另外的突变.2352例耳聋患者中基于IVS7-2A＞G突变的SLC26A4基因纯合及复合杂合突变携带者共211例,占总人数的8.97％(211/2352).其中1903例汉族耳聋患者中基于IVS7-2A＞G突变的SLC26A4基因纯合及复合杂合突变携带者共199例,占汉族人数的10.46％(199/1903).105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、11+12、3和15上.正常对照人群IVS7-2 A＞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 2352例聋哑学生通过基于SLC26A4基因热点突变IVS7-2A＞G的该基因的全序列筛查,将211例耳聋患者明确为SLC26A4基因突变致聋;发现在中国由SLC26A4基因热点突变引起的大前庭水管相关遗传性耳聋的比例较高,接近9％,汉族耳聋人群中该比例超过10％;揭示SLC26A4基因筛查和诊断在耳聋的病因学诊断中起重要作用,在大规模耳聋患者的病因学筛查方面具有优势.点突变区域提供了依据.%Objective To gather molecular epidemiological data on association between the SLC26A4 gene and enlarged-vestibular-aqueduct-syndrome related hearing loss in China with a focus on the hot spot mutation IVS 7-2 A>G. Methods DNA were extracted from peripheral blood of 2 3S2 students from deaf and dumb schools in 27 different regions across China. The ethnicity of the 2352 subjects covered Han(n = 1903), Tibetan (n = 119), Uygur (n = 69), Hui (n = 89), Mongolian (n = 33), Yi, Zhuang, Bai, Miao and 12 other minority groups (n = 139). Of these subjects, 1 552 were screened for the hot spot mutation IVS 7-2 A>G by- direct sequencing, and 800 were screened by the Genetic Testing Kit. Those carrying a single heterozygous IVS 7-2 A>G were further tested for a possible second mutation on the SLC26A4 gene in exons other than exons 7 and 8. One hundred and fifty normal hearing individuals served as the control group. Results There were 271 IVS 7-2 A >G carriers, of whom 106 were homozygous carriers and 165 were heterozygous carriers. Of the 165 heterozygous IVS 7-2 A>G carriers, 105 were found to have another mutation on the SLC26A4 gene. The rate of homozygous and compound heterozygous IVS 7-2 A>G mutations was 8.97% for the entire study population (211/2352), and 10.46% for the Hans (199/1903). In the 105 cases with SLC26A4 compound heterozygous mutations, the non-IVS 7-2 A>G mutations were found mainly in exons 19, 10, 17, 3, 11+12 and 15. Only 2 heterozygous IVS 7-2 A>G carriers were found in the control group, with no other SLC26A4 gene mutations. Conclusion Whole SLC26A4 gene analysis with focus on IVS7-2A>G mutation showed that 211 of the 2352 deaf students had SLC26A4 gene related mutations. SLC26A4 mutations account for about 9% of enlarged-vestibular-aqueduct-syndrome related hereditary hearing loss in China. It's of great importance to screen SLC26A4 gene for etiological diagnosis in deafness. This study also provides preliminary evidence of hot spot areas on the SLC26A4 gene.