一个非综合征型耳聋家系新致病基因变异分析

Novel pathogenic gene variants in a pedigree with nonsyndromic hearing loss

目的对一个非综合征型耳聋(NSHL)家系进行致病基因分析,明确其致病变异。方法采集先证者及其家系成员的外周血标本,应用全外显子测序(WES)技术对先证者及其父母、二姐共4名成员进行测序分析,并通过Sanger测序对所有家系成员进行一代验证,确定该家系的致病基因,利用细胞学实验检测基因的致病性。结果测序结果显示,该家系中3例患者同时携带PCDH15c.4765delC(p.Leu1589Serfs^(*)13)和CDH23c.9617G>A(p.Arg3206His)杂合变异,而家系中听力正常的成员携带PCDH15c.4765delC(p.Leu1589Serfs^(*)13)或CDH23c.9617G>A(p.Arg3206His)单杂合变异,其中PCDH15c.4765delC为未报道的新变异,PCDH15移码变异会导致终止密码子提前出现,产生截短蛋白,且蛋白表达量显著降低。免疫荧光结果显示,与野生型相比,变异型蛋白在细胞胞质内出现聚集现象,可能是由于基因变异引起的。结论PCDH15和CDH23双基因杂合变异可能是该家系的致病原因,新变异的检出丰富了耳聋致病基因的变异谱,为该家系遗传咨询和产前诊断提供依据。

Objective To explore the genetic basis of a pedigree with nonsyndromic hearing loss(NSHL).Methods Peripheral blood samples of all family members were collected and whole-exome sequencing(WES)technique was performed in four members.Then Sanger sequencing was performed in all members to identify the genetic cause of the disease and pathogenicity was detected with cytology.Results All patients in this pedigree carried PCDH15 c.4765 delC(p.Leu1589 Serfs^(*)13)and CDH23 c.9617 G>A(p.Arg3206 His)heterozygous variants,while other members carried PCDH15 c.4765 delC(p.Leu1589 Serfs^(*)13)or CDH23 c.9617 G>A(p.Arg3206 His)single heterozygous variant,of which PCDH15 c.4765 delC was an unreported new variant.The frame shift mutation of PCDH15 gene caused a truncated protein and its expression decreased significantly.Immunofluorescence showed that mutant proteins accumulated in cytoplasm,which might be caused by the gene variant.Conclusion The PCDH15 c.4765 delC(p.Leu1589 Serfs^(*)13)and CDH23 c.9617 G>A(p.Arg3206 His)digenic variants may cause the NSHL in the pedigree.The detection of new variant enriches the variants spectrum of deafness-causing genes and enables genetic counseling and prenatal diagnosis of the family.