USH2A基因大片段重复等突变导致中重度听力损失

Large Fragment Duplication and Other Mutations in USH2A Lead to Moderate to Severe Hearing Loss

目的寻找并确定2例中重度听力损失家系的临床表型和分子病因,为该家庭生育提供遗传指导。方法通过家系调查,临床检查和遗传学特征的分析和应用包含406个靶向耳聋基因高通量测序筛选出候选致病病因,再利用Sanger测序验证USH2A致病突变和荧光定量PCR检测USH2A中的大片段重复序列插入突变。结果先证者均中重度听力损失,发现USH2A c.8559-2A>G(p.(Try2854_Arg2894del))和USH2A c.dup(exon37-39)复合杂合突变是J193家系的致聋突变;USH2A c.9570+1G>A(splicing)和USH2A c.5581G>A(p.G1861S)复合杂合突变是J195家系的致聋突变。结论目标区域捕获结合二代测序技术为具有高度遗传异质性的耳聋个体及家庭提供了有力的检测手段。采用该方法成功为J195家系和J193家系明确了致聋突变,其中USH2A c.8559-2A>G、USH2A c.9570+1G>A、USH2A c.5581G>A是已报道的致聋突变,而USH2A c.dup(exon37-39)是目前USH2A首个被报道的大片段基因组重复插入致病突变,丰富了该基因的遗传突变类型和图谱。

Objective To identify causative mutations in autosomal recessive hearing loss in two small families and provide genetic guidance for their reproductive planning.Methods High-throughput sequencing was used to screen 406 targeted deafness genes for candidate pathogenic mutations.Pedigree investigation,clinical examination and analysis of genetic characteristics were completed in the two families(J193 and J195).USH2A gene mutations were verified by Sanger sequencing and repetitive sequence mutations of USH2A were detected by fluorescent quantitative PCR.Results The two probands had moderate to severe hearing loss.Compound heterozygous mutation of USH2A c.8559-2A>G(splicing)and USH2A c.dup(exon37-39)were determined to be the causative mutations in the J193 family;while compound heterozygous mutation of USH2A c.9570+1G>A(splicing)and USH2A c.5581G>A(p.G1861S)likely the causative mutations in the J195 family.Conclusion The target region capture technology combined with next generation sequencing provides a powerful tool for the detection for deaf individuals and families with a high degree of genetic heterogeneity.This method was successfully used to identify deafness gene mutations for the two families in the current study.While USH2A c.8559-2A>G,USH2A c.9570+1G>A,and USH2A c.5581G>A(p.G1861S)are known deafness mutations,USH2A c.dup(exon37-39)is the first reported large segment repeat insertion pathogenic mutation,an addition to the mutation types and patterns of hereditary deafness.