目的 应用基因诊断的方法调查内蒙古赤峰市特教学校耳聋患者的分子学病因,着重进行线粒体tRNA Ser(UCN)基因序列突变分析。方法 调查对象来自赤峰市特教学校耳聋患者134例,对照组为中国北方听力正常者75例。所有受检患者均采集外周血并提取DNA,进行线粒体tRNASer(UCN)基因测序,对发现携带线粒体tRNA Ser(UCN)基因突变的患者行详细的病史调查、家系分析及线粒体全序列测序。结果134例耳聋患者中检测到2例携带线粒体tRNASer(UCN)基因7444G〉A突变,该2例患者线粒体全序列测序均显示独特的多态性,但所有位点对应的氨基酸在进化上不保守。其中1例携带7444G〉A突变的患者同时携带SLC26A4基因IVS7-2A〉G纯合突变,颢骨CT显示为前庭水管扩大。对照组中未发现携带线粒体tRNASer(UCN)基因突变者。结论线粒体tRNASer(UCN)基因在内蒙古赤峰地区散发耳聋人群中突变比例不高,线粒体tRNASer(UCN)基因突变并非赤峰地区聋哑人群的主要致病病因。
Objective To investigate the genetic causes of students with severe--to--profound hearing loss from special educational school of Chifeng city, Inner Mongolia, Methods DNAs were extracted from peripheral blood of 13,1 severe--to--profound students of Chifeng special educational school and 75 normal hearing controls from Northern China. MtI)NA tRNASer (UCN) gene mutation was analyzed by direct sequencing. Individuals with mtDNA mutation were given further mtDNA whole sequence analysis as well as history and family examination. Resuits Two patients were found carrying 7 444G〉A mutation. No identical mutation was found in the control group. MtDNA of the 2 patients with 7 H4G〉A showed specific polymorphisms by whole sequence analysis. But none of the corresponding amino acids were conserved in evolution. One of the patients with 7 444G〉A also carried IVST--2A〉G mutation of SLC26A4 and was comfirmed to have enlarged vestibular aqueduct. Conclusion The mutation of MtDNA tRNASer (UCN) gene is not commomly associated with hearing impairment patients from northern China and it is not the main cause of hearing loss in Chileng city. This finding is helpful to establish appropriate gene screening of deafness in Chifeng area.