Study Of Cardiac Disease Associated Genetic Variants Of Sudden Manhood Death Syndrome And Y77C Variant Of IRX4 Gene In Regions With High Incidence Of Yunnan Sudden Unexplained Death

Objectives:1.To screen the variants within cardiac disease associated gene of sudden manhood death syndrome(SMDS),and search for sudden manhood death related susceptible genetic variants to identify potential causes of sudden manhood death.2.To detect the distribution of allele frequency of Y77C variant within IRX4 gene which is a susceptible pathogenic genetic variant of Yunnan sudden unexplained death(YNSUD)in regions with high incidence of YNSUD meanwhile provides theoretical evidence for the prevention and treatment of YNSUD.3.To investigate the association between sudden unexplained death including partial sudden manhood death and YNSUD and variants whthin cardiac disease including channelopathy and cardiomyopathy associated genes.Methods:1.Cardiac channelopathy and cardiomyopathy associated genetic variants of cases of SMDS identified by Judicial identification center of Kunming Medical University from 2017 to 2018 years were annotated and screened using whole exome sequencing after genomic DNA extraction from heart blood,then the bioinformatics software SIFT,MutationTaster and PolyPhen-2 were used to predict the pathogenicity of genetic variants screened.2.Taking four regions with high incidence of YNSUD as experimental group and Chinese Dai in Xishuangbanna and southern Han population in 1000 Genomes Project as control group.Sanger sequencing were used to screen the distribution of IRX4-Y77C,a susceptible pathogenic genetic variant detected in our previous study of four raletives of two YNSUD core family by whole exome sequencing,after extraction of Genomic DNA from peripheral blood samples and polymerase chain reaction.Electrocardiogram and color Doppler ultrasound examination were performed on all individuals of experimental group to check up whether there were abnormal changes of Electrocardiogram and abnormal heart structure.Results:1.Three cases of SMDS with blood samples can be genotyped were collected from SMDS identified by Judicial identification center of Kunming Medical University from 2017 to 2018 years.Missense variants of TTN,CACNB2,SCN5A and KCNH2 gene were identified through whole exome sequencing,prediction of pathogenicity and verified by Sanger sequencing,among them,the deceased of case one carried TTN-V23610 variant and the pathogenicity predicted by SIFT and MutationTaster were Deleterious and Disease causing.The deceased of case two carried TTN-P1698L、I24875T and CACNB2-S502L variant,the pathogenicity of these three variants predicted by SIFT and MutationTaster all were Deleterious and Disease causing.The deceased of case three carried TTN-R14571H、R24762H,SCN5A-R1193Q、KCNH2-K557T variants,and the pathogenicity of these four variants were R14571H:Deleterious and Disease causing,R24762H:Deleterious and Disease causing,R1193Q:Tolerated and Disease causing,furthermore PolyPhen-2 predicted R1193Q variant was benign,K557T:Tolerated and Polymorphism.2.The genetic sequencing in this study identified that 82 individuals carried YNSUD susceptible genetic variant IRX4-Y77C among 112 villagers from four regions with high incidence of YNSUD.The allele frequency of this variant in experimental group were higher than that in control group and the statistical significance was observed in distribution of allele frequency between two groups.As to the ECG examination of 112 villagers,abnormal ECG changes including clockwise(counterclockwise)rotation,left(right)axis deviation,nodal tachycardia or sinus bradycardia,heart-blocking,ST segment and T wave alteration and prolonged QT interval identified in 33 individuals IRX4-Y77C variant carrier indicated that a certain degree of abnormal cardiac electrophysiological function were existed in four regions with high incidence of YNSUD,furthermore atrial septal defect was identified in two individuals who have heart-blocking,while typical pathological changes of cardiomyopathy such as ventricular hypertrophy and atrial dilation were not detected by color Doppler ultrasound examination.Conclusions:1.This study performed a genetic screening in three cases of SMDS and finally eight missense variants were identified.The result of pathogenic predicted by SIFT and MutationTaster and functional study of genetic variants supports TTN-V23610I,TTN-P1698L,TTN-I24875T,TTN-R14571H,TTN-R24762H and SCN5A-R1193Q might be the genetic susceptible factors of variant carriers in this study who dead from SMDS.Variants within TTN gene,a pathogen ic gene of dialted cardiomyopathy,and slightly heavier heart was identified in three cases of SMDS,but lack of diagnosis basis for cardiomyopathy hints that genetic screening for pathogenic variants of cardiac diseases associated genes is necessary for SMDS cases in forensic practices.2.The allele frequency of IRX4-Y77C,a susceptible variant,in experimental group were higher than that in control and the difference have statistical significance,moreover the result of ECG and color Doppler ultrasound examination also indicated that IRX4-Y77C variant might be associated with high incidence of YNSUD in aggregative regions.3.Partial SMDS cases and YNSUD may be associated with variants within cardiac disease including channelopathy and cardiomyopathy associated genes.