Whole-exome Sequencing To Identify Novel Mutations In PDYN Associated With Progressive Cardiac Conduction Disease

Background Progressive cardiac conduction disease(PCCD)is a rare cardiac disorder of genetic origin often with familial trade.Compared to other types of inherited cardiac disorders,the genetic cause of PCCD is uncovered rather limitedly.PCCD is associated with ion channel gene mutations,most commonly SCN5 A gene as well as SCN1 B,GJA5,and TRPM4.Additionally,mutations in several structural and regulatory genes such as LMNA,DES,and Nkx2–5 have been reported in conjuction with cardiac conduction abnormalities with or without dilated cardiomyopathy.A large number of genes have been linked to cardiac conduction disorders.It is now clear that cardiac conduction defects are not only associated with aging,but that many complex pathophysiological processes may lead to the occurrence of atrio-ventricular and intra-ventricular block.Many genes and gene networks are involved in the electrophysiological activity of the heart,and it is likely that only a small fraction of these genetic defects have been currently identified.In the future,it could be possible to determine most of the causative genetic alterations and in turn determine the actual proportion of conduction disorders due to genetic defects.Once this first step is achieved,genetic analysis would be part of the routine clinical assessment of patients affected by PCCD.Since the appearance of these conduction alterations is a slow process over time,genetic tests could help to better determine the risk of progression of a cardiac conduction defect and hence determine the best timing for pacemaker implantation.In the longer term,it may be possible,through early identification of patients at risk of developing cardiac conduction defects,notably by familial screening,to develop preventive strategies,using drugs able to slow the development of these potentially fatal disorders.Objective To explore the genetic mechanism for a family affected with progressive cardiac conduction disease.Methods We studied a 4-generation family including 34 members with autosomal dominant progressive cardiac conduction disease.Two patients and one healthy member from the family were further analyzed by Whole-Exome Sequencing followed by Sanger sequencing.The pathogenicity of suspected mutation was analyzed using bioinformatics software.The selected variants were predicted by three online softwares:SIFT 、 Poly Phen-2 and Mutationtaster to select deleterious variants.The causal mutations were identified by Sanger sequencing of deleterious variants in other pedigree members,HRM and SNa PShot sequencing in 410 normal persons.At the cellular level to detect whether the expression of causal gene has changed,whether the functional of gene changes,We Transfected causal gene and its mutants into cells.Result The cardiac conduction disease was caused by autosomal dominant inheritance.7variants were left after WES and data analysis.Only tow of 8 variants,(PDYN(c.581A>T,p.D194V)(c.580G>C,p.D194H)),was shared by all patients and not normal members.This gene and heterozygous variant was not reported before.After transfection of HEK293 T cells for 72 hours,the expression of mRNA of PDYN did not change.The expression of IL-6,IL-8,CRP and TNF-α was increased in the mutant groups,but there was no difference between the mutations.ROS were higher in the mutant groups,but there was no difference between the two mutations.Conclusion1.This study reported a PCCD family of 34 members with 8 patients.In addition to conduction block can be combined with sinus node disease and atrial arrhythmias.2.The novel heterozygous variants c.581A> T(p.D194V)and c.580G> C(p.D194H)in PDYN are the causal mutations for PCCD.3.PDYN mRNA level did not change,IL-6,IL-8,CRP and TNF-α expression increased,ROS levels increased.