Screening Of Pathogenic Gene Mutations In Families With Stargardt Disease, Cone-rod Dystrophy And Nance-Horan Syndrome

Background:Hereditary ophthalmopathy is caused by the change of genetic material.It has serious damage to the structure and function of the eyes,and some diseases are not easily detected in the early stage.It is currently a kind of important disease affecting the visual system.This type of disease has many characteristics including multiple disease types,high incidence,difficulty in treatment,poor prognosis,high blinding rate and high clinical and phenotypic heterogeneity.Whole-Exome Sequencing（WES）refers to a genome analysis method that uses sequence capture technology to capture and enrich DNA in whole genome exonic regions and perform high-throughput sequencing.Compared with traditional Sanger sequencing,this sequencing method has many advantages including high efficiency and convenience,low requirement on samples and high sensitivity,abundant information acquisition,and detection of new pathogenic genes.Objective:The purpose of this study was to identify the pathogenic mutations in three families with different hereditary ophthalmopathy including Stargardt disease（STGD）,Cone-rod dystrophy（CORD）and Nance-Horan syndrome（NHS）,and we expect to discover novel pathogenic mutations.At the same time,provideing effective genetic counseling for members in these families and further enriching the genetic research of related diseases.Methods:Firstly,the disease-causing genes reported in the literature were searched and obtained according to the initial diagnosis of the family.The blood sample and clinical examination results of the family members were collected,and WES was performed on the proband.Non-synonymous mutations of related pathogenic genes were screened in the sequencing results to as the initial candidate pathogenic mutations.Then a series of filtering steps including bioinformatics analysis,Sanger sequencing validation,and co-segregation analysis were performed to screen the candidate mutations and obtain pathogenic mutation in the family.Finally,the pathogenic mutation in family were classified using the ACMG Standards and Guidelines.If the disease-causing mutation of the family are not screened in known pathogenic genes,it is necessary to expand the range of candidate genes or to study new genes.Results:Compound heterozygous mutations NM₀00350.2:c.5646G>A:p.M1882I,c.3523-2A>G in ABCA4 were screened in the STGD family;a frameshift mutation NM₀00554.4:c.538dupG:p.Vall 80fs in the CRXgene was screened in the CORD family;and a frameshift mutation NM₀01291867.1:c.302dupA:p.A1a102fs in NHS gene was screened in the NHS family.The results of the co-segregation analysis showed that these mutations were co-segregated with the disease phenotype in the family,and they were pathogenic mutations in the family.Among them,splice site mutations in ABCA4 and frameshift mutations in CRX and NHS were reported for the first time.Conclusion:Three new pathogenic mutations were screened in three families with different hereditary ophthalmopathy by WES.Novel disease-causing mutations broaden the pathogenic mutations spectrum and contribute to provide effective genetic counseling for family members.This study showed that WES is an effective tool for the genetic diagnosis in family with hereditary disease.For some patients with atypical manifestations,the diagnosis of the disease requires a combination of clinical manifestations and genetic diagnosis.