Whole Exome Sequencing To Identify A Novel Mutation In SCN5A Associated With Inherited Cardiac Conduction Disease

Background:Whole exome sequencing (WES) is one of the next-generation sequencing developed in recent years. It makes use of exon trapping chip and sequencing by synthesis technology to get massive sequencing results in a short time. WES is more convenient and efficient than Sanger sequencing, which is able to complete sequencing of over ten thousands of genes at low cost. Since Ng has studied mendelian inherited disease by means of WES in2009, there are scores of causal genes for inherited diseases identified by this method. In cardiovascular field, the application of WES is focused on myocardiosis and many causal genes such as MRPL44, MTO1, AGK, MRPL3, AARS2for hypertrophic cardiomyopathy, BAG3, GATAD1for dilated cardiomyopathy and DES for arrhythmogenic right ventricular cardiomyopathy are identified in succession, whereas similar achievements are few in arhythmia. This article has studied causal genes in an inherited cardiac conduction disease pedigree, which could aid to the research of pathogenesis, prenatal diagnosis, genetic counseling and gene therapy in the future.Objective:To identify the causal gene in a pedigree with cardiac conduction disease.Method:(1) According to electrocardiogram results and medical history, patients with cardiac conduction disease were identified in a five-generation pedigree including37members.(2) The peripheral blood of11members was collected to extract DNA.(3) DNA of three patients and a normal member was analyzed by WES.(4) SNPs in sequencing data were excluded by the search of dbSNP database, TGP database, YH database and ESP database.(5) The variants carried by all three patients and not included in normal member were selected after SNPs exclusion.(6) The selected variants were predicted by three online softwares: MutationTaster, SIFT and PolyPhen-2to select deleterious variants.(7) The causal mutation was identified by Sanger sequencing of deleterious variants in other pedigree members and200normal persons.(8) The mutation identified in this article was searched in Pubmed, Google scholar and HGMD database.Result:The cardiac conduction disease was caused by autosomal dominant inheritance and there were10patients in this pedigree.12variants were left after WES and data analysis. Only one of12variants, C.4485C>A (p.Y1495X) in SCN5A, was shared by all patients and not in normal members. This heterozygous variant was not reported before.Conclusion:(1) A rare inherited cardiac conduction disease pedigree including10patients is described in this article.(2) The novel heterozygous variant c.4485>A (p.Y1495X) in SCN5A is the causal mutation for this disease.(3) The causal gene for inherited cardiac conduction disease can be identified by WES in a short time.