Mutation analysis of ion channel genes promoters in ventricular fibrillation survivors with coronary artery disease

IntroductionStrong evidence suggests that sudden cardiac death (SCD) is genetically determined. In our previous study we found that the prevalence of selected, rare coding variants in 5 long QT genes was significantly higher in ventricular fibrillation (VF) survivors with coronary artery disease (CAD) than in controls. In the present study we performed mutational analysis of the promoters of 5 LQTS-related myocardial ion channel genes in the same group of patients and in control populations.MethodsThe promoters of KCNQ1, KCNH2, SCN5A, KCNE1 and KCNE2 genes were analyzed in 45 CAD individuals – survivors of documented VF. The allelic frequencies were compared either to data from the 1000 Genomes Project or from a local DNA bank of patients with coronary artery disease and no malignant arrhythmia (141 individuals).ResultsIn 34 (75.5%) of 45 VF survivors 9 different promoter variants were found: 2 in KCNQ1 gene promoter, 1 in KCNE1 promoter, and 6 in SCN5A promoter. Statistically significant differences were found in the allelic frequencies of both KCNQ1 gene promoter variants: 1-182C>T (P=0.008), 1-119G>A (P=0.007). Nevertheless, these variants did not segregate with long QT phenotype in a previous study. While the allelic frequency of the SCN5A gene promoter variant 225-1072T>C significantly differed in VF survivors compared to the 1000 Genomes Project (P=0.001), this allelic frequency was not different when compared to the group of local CAD controls.ConclusionsOur findings demonstrated that variants of ion channel gene promoters are common, both in VF survivors and control groups. These results suggest that promoter variants are geographically-specific and are not a common cause of SCD.