2型Usher综合征和视网膜色素变性家系USH2A基因突变及临床表型分析

目的观察2型Usher综合征(USH2)和视网膜色素变性(RP)患者的基因突变型及其临床表型。方法2018年8月至2019年1月于河南省立眼科医院就诊的USH2和RP 3个家系的4例患者和11名正常家系成员纳入研究。详细询问病史并行视力、眼底彩色照相、OCT、视野、全视野ERG检查。3个家系中,家系1为USH2;家系2、3为RP。采集患者及其家系成员外周静脉血,提取全基因组DNA,应用基于靶向捕获的二代测序技术进行基因测序,对可疑致病突变位点通过Sanger进行验证,并在家系成员中进行共分离。结果家系1先证者除眼底有RP表现外,同时合并神经性耳聋。基因检测结果显示,先证者USH2A基因第64、5号外显子分别存在c.13877-13880 del AGAC(p.Q4626P)(M1)、c.798 del T(p.F266L)(M2)2个杂合性移码突变。家系2、3先证者仅有眼底典型RP表现。基因检测结果显示,家系2先证者USH2A基因第70、37、29号外显子分别存在c.15178T>c(p.S5060P)(M3)、c.6986C>A(p.P2329H)(M4)2个杂合性错义突变和c.5836C>T(p.R1946X)(M5)终止突变。家系3先证者USH2A基因第67、57号外显子分别存在c.14951C>T(p.P4984L)(M6)、c.11156G>A(p.R3719H)(M7)2个杂合性错义突变。保守性分析结果显示,USH2A p.Q4626P、p.F266L、p.S5060P、p.P2329H、p.P4984L所对应的氨基酸位点在多个物种中均高度保守。检测出的7个致病突变中,M1~M4、M6为新发现突变位点。结论USH2A基因突变是导致USH2和非综合征性RP的主要原因;不同突变位点影响蛋白质翻译和合成,导致不同临床表型。

Analysis of USH2A gene mutation and clinical phenotype in families with Usher syndrome type 2 and retinitis pigmentosa

Objective To observe the gene mutations and clinical phenotypes in patients with Usher syndrome type 2(USH2)and retinitis pigmentosa(RP).Methods From August 2018 to January 2019,4 patients and 11 normal family members from 3 families of USH2 and RP who visited Henan Eye Hospital were enrolled in the study.Detailed medical history was obtained and visual acuity,fundus color photography,OCT,visual field,full field ERG examination were performed.Among the three families,pedigree 1 was diagnosed with USH2,pedigree 2 and pedigree 3 were diagnosed with RP.The peripheral venous blood of patients and their family members were collected,and the whole genomic DNA was extracted.Targeted capture next generation sequencing analysis was performed on these members,and Sanger sequencing and family cosegregation were verified.Results In the family F1,the proband had symptoms of RP and sensorineural deafness.Sequencing revealed two heterozygous frameshift variants:c.13877-13880 del AGAC(p.Q4626P)in exon 64 and c.798 del T(p.F266L)in exon 5 of USH2A.Both patients of family 2 and 3 showed RP signs without deafness.Two heterozygous variants c.15178T>C(p.S5060 P)in exon 70 and c.6986C>A(p.P2329H)in exon 37,and a pathogenic heterozygous variant c.5836C>T(p.R1946X)in exon 29 of USH2A were identified in family F2.A heterozygous missense variant c.14951C>T(p.P4984L)in exon 68 and a variant c.11156G>A(p.R3719H)in exon 57 of USH2A were found in family F3.The results of conservation analysis showed that the corresponding amino acid sites of USH2A p.Q4626P,p.F266L,p.S5060P,p.P2329H and p.P4984L were highly conserved in many species.Among these 7 pathogenic variants detected,M1-M4 and M6 were novel.Conclusions Mutation USH2A gene are the main cause of USH2 and non-syndromic RP.Different variants affect protein translation and synthesis,consequently causing different clinical phenotypes.