Comparative Analysis of Genetic Variations in the Nav1.5 Sodium Channel Subunits that Underlie Brugada Syndrome Using Patient-Specific iPSC-CMs

Background: Brugada syndrome (BrS) is an autosomal dominant disorder that causes a high predisposition to sudden cardiac death. Several genes have been reported to be associated with BrS. Considering that the heterogeneity in clinical manifestations may result from genetic variations, the application of patient-specific induced pluripotent stem (iPS) cell-derived cardiomyocytes (CMs) may help to reveal cell phenotype characteristics resulting from different genetic backgrounds. The present study was to compare the structural and electrophysiological characteristics of sodium channel subunits with different genetic variations and evaluate the safety of quinidine for use with BrS patient-specific iPSC-derived cardiomyocytes. Methods: : Two BrS patient-specific iPS cell lines were constructed that carried missense mutations in SCN5A and SCN1B . One iPS cell line from a healthy volunteer was used as a control. The differentiated cardiomyocytes from the three groups were evaluated by flow cytometry, immunofluorescence staining, electron microscopy, as well as calcium transient and patch clamp analyses to assess different pathological phenotypes. Finally, we evaluated the drug responses to varying concentrations of quinidine by measuring the action potential. Results: : Compared to the control group, BrS-CMs showed a significant reduction in sodium current, prolonged action potential duration and varying degrees of decreased Vmax, but no structural difference was observed. After applying different concentrations of quinidine, the disease-specific groups and the control group had a downward trend in maximal upstroke velocity, resting membrane potential and action potential amplitude, and exhibited prolonged action potential duration without increasing incidence of arrhythmic events. Conclusion: Both patient-specific iPSC-CMs recapitulated the BrS phenotype at the cellular level. Although the SCN5A variation led to a markedly lower sodium current than what was observed with the SCN1B variation, their responses to quinidine were quite similar. The present study provides an advantageous platform for exploring disease mechanisms and evaluating drug safety in vitro .