Usher综合征Ⅰ型MYO7A基因的突变分析与产前诊断

Mutation analysis and prenatal diagnosis of MYO7A gene in a case of Usher syndrome type 1

目的对先天性耳聋一家系行遗传学分析,鉴定该病例的致聋基因突变。方法对陆军军医大学第一附属医院2016年6月就诊的一例4岁的先天性耳聋男性患儿进行详细病史询问,并进行临床检查,诊断为感音神经性耳聋。抽取患儿及其父母静脉血,提取基因组DNA,对先证者进行已知耳聋基因目标区域高通量测序,对于筛选出的候选突变进行Sanger测序验证,根据先证者耳聋基因诊断结果,补充眼科检查,对其父母再次怀孕的胎儿抽取羊水进行产前基因诊断。结果测序发现先证者MYO7A基因p.Trp1466Ter/p.Tyr2042Ter复合杂合突变,其中p.Trp1466Ter突变为已报道的致病性突变,而p.Tyr2042Ter未见报道。除先天性耳聋外,眼科检查发现先证者存在视网膜色素变性,确诊为Usher综合征Ⅰ型。对该家庭再次妊娠胎儿在孕18周进行羊水穿刺及胎儿DNA测序,发现仅携带MYO7A基因p.Tyr2042Ter杂合突变,另一个等位基因为野生型,预测胎儿不会出现先证者的Usher综合征Ⅰ型临床表现。胎儿出生后通过了新生儿听力筛查。结论本研究明确了一个Usher综合征Ⅰ型家系的遗传学病因,并丰富了该病的表型与基因型数据库,为遗传咨询提供了依据。

Objective To analyze the clinical characteristics and identify the causative gene of a case with congenital deafness.Methods Detailed medical history and clinical examination of a 4-year-old male child with congenital deafness were conducted in the First Affiliated Hospital of Army Military Medical University in June 2016.He was diagnosed with sensorineural deafness.The venous blood of the child and his parents was drawn,and genomic DNA was extracted.Proband's DNA was performed with targeted capture of high-throughput sequencing,then Sanger sequencing was used to verify the suspected mutation and segregation in this pedigree.According to the genetic diagnosis of the proband's deafness,ophthalmic examinations were performed.Genetic prenatal diagnosis was performed when the proband's mother was pregnant again.Results The patient was detected with p.Trp1466Ter/p.Tyr2042Ter compound heterozygous mutations of MYO7A gene with targeted high-throughput sequencing.The mutation of p.Trp1466Ter was a reported mutation,while p.Tyr2042Ter has not been reported.In addition to congenital deafness,retinitis pigmentosa was also found by ophthalmologic examination,and the patient was clinically diagnosed with Usher syndrome type 1.Amniocentesis and fetal DNA sequencing were performed on the repregnancy fetus of this family at 18 weeks of gestation.The heterozygous mutation of MYO7A gene p.Tyr2042Ter was found,and the other allele was the wild type,indicating that the child will not exhibit clinical manifestations of Usher syndrome type 1.Indeed,the second child passed neonatal hearing screening.Conclusions The clinical features and genetic variants were delineated in this family with Usher syndrome type 1.The results of the current study have enriched the phenotype and genotype data of the disease and provided a basis for genetic counseling.