Patient-specific iPSC-derived cardiomyocytes reveal aberrant activation of Wnt/[beta]-catenin signaling in SCN5A-related Brugada syndrome

Background Mutations in the cardiac sodium channel gene SCN5A cause Brugada syndrome (BrS), an arrhythmic disorder that is a leading cause of sudden death and lacks effective treatment. An association between SCN5A and Wnt/[beta]-catenin signaling has been recently established. However, the role of Wnt/[beta]-catenin signaling in BrS and underlying mechanisms remains unknown. Methods Three healthy control subjects and one BrS patient carrying a novel frameshift mutation (T1788fs) in the SCN5A gene were recruited in this study. Control and BrS patient-specific induced pluripotent stem cells (iPSCs) were generated from skin fibroblasts using nonintegrated Sendai virus. All iPSCs were differentiated into cardiomyocytes using monolayer-based differentiation protocol. Action potentials and sodium currents were recorded from control and BrS iPSC-derived cardiomyocytes (iPSC-CMs) by single-cell patch clamp. Results BrS iPSC-CMs exhibited increased burden of arrhythmias and abnormal action potential profile featured by slower depolarization, decreased action potential amplitude, and increased beating interval variation. Moreover, BrS iPSC-CMs showed cardiac sodium channel (Na.sub.v1.5) loss-of-function as compared to control iPSC-CMs. Interestingly, the electrophysiological abnormalities and Na.sub.v1.5 loss-of-function observed in BrS iPSC-CMs were accompanied by aberrant activation of Wnt/[beta]-catenin signaling. Notably, inhibition of Wnt/[beta]-catenin significantly rescued Na.sub.v1.5 defects and arrhythmic phenotype in BrS iPSC-CMs. Mechanistically, SCN5A-encoded Na.sub.v1.5 interacts with [beta]-catenin, and reduced expression of Na.sub.v1.5 leads to re-localization of [beta]-catenin in BrS iPSC-CMs, which aberrantly activates Wnt/[beta]-catenin signaling to suppress SCN5A transcription. Conclusions Our findings suggest that aberrant activation of Wnt/[beta]-catenin signaling contributes to the pathogenesis of SCN5A-related BrS and point to Wnt/[beta]-catenin as a potential therapeutic target. Keywords: iPSC-CMs, Brugada syndrome, SCN5A, Na.sub.v1.5, Wnt/[beta]-catenin signaling