Usher综合征2型一家系USH2A基因新突变

摘要

目的 定位1个Usher综合征2型(USH2)家系的致病基因突变.方法 1个USH2家系3代7名成员纳入研究.其中,患者2例、健康成员5名.2例患者均为男性.所有受试者均行最佳矫正视力、裂隙灯显微镜、间接检眼镜、全视野视网膜电图、光相干断层扫描、视野检查.采集所有受试者外周静脉血3 ml,提取基因组DNA.选择136个遗传性视网膜疾病致病基因作为目标基因;将提取的DNA采用高通量测序并与数据库对比,确定候选致病基因突变位点.聚合酶链反应和直接测序法在家系成员及100名正常对照者中进行验证,确定致病性突变位点.结果 DNA测序发现,2例患者均携带USH2A基因第27号外显子c.5459T＞C(p.M1820T)、第7号外显子c.1190T＞A(p.I397K)、第5号外显子c.802G＞A(p.G268R)3个杂合性错义突变,其中c.5459T＞C和c.1190T＞A为新发现突变.患者表型正常的父亲、母亲分别为c.1190T＞A(p.I397K)错义突变携带者和c.5459T＞C(p.M1820T)和c.802G＞A(p.G268R)复合杂合突变携带者.根据基因检测结果表明该家系的遗传方式为常染色体隐性遗传.其余表型正常的家系成员和正常对照者均未同时检测到这3个突变位点.突变在该家系中呈现共分离状态.结论 USH2A基因杂合性错义突变c.5459T＞C(p.M1820T)、c.1190T＞A(p.I397K)、c.802G＞A(p.G268R)是该家系的致病基因.%Objective To identify the pathogenic genes and mutations in a family with Usher syndrome type 2.Methods A three-generation family including 7 individuals was enrolled in this study.There were 2 male patients and 5 unaffected individuals.All participants was underwent related ophthalmologic examination,including best corrected visual acuity,slit-lamp,indirect ophthalmoscopy,electroretinogram (ERG),optical coherence tomography and visual field test.DNA was extracted from 3 ml peripheral venous blood of all participants.A total of 136 hereditary retinal disease target genes were screened and the DNA sequence was performed by Next-generation sequence analysis.Then the suspected mutations compared with databases to identify the suspected mutations,which should be verified with non-affected family members and 100 normal subjects by PCR and Sanger sequence.Results The sequence result showed that 2 patients,the proband and his brother,carried complex heterozygous mutations in the USH2A gene:c.5459T＞C (p.M1820T) in exon 27,c.802G ＞A (p.G268R) in exon 5 and c.1190T＞A (p.I397K) in exon 7.The c.5459T ＞ C and c.1190T ＞A mutations in USH2A have not been reported in the literature and database.Although their mother carried c.5459T＞C (p.M1820T) and c.802G＞A (p.G268R),and their father carried c.1190T＞A (p.I397K) heterozygous mutations,the parents did not present phenotype.These mutations were not detected in other normal family members.The result was supported by co-segregation analysis.Conclusion The heterozygous mutations c.5459T＞C (p.M1820T),c.1190T＞A (p.I397K) and c.802G＞A (p.G268R) in USH2A gene cause Usher syndrome in this family.