Functional validation of the Nav1.5/R1432G Brugada syndrome variant using a Nav1.5 knockout iPSC-derived cardiomyocyte model

Brugada syndrome is a rare inherited cardiac arrhythmia disorder primarily characterized by ventricular fibrillation, which can lead to sudden cardiac death. It follows an autosomal dominant pattern of inheritance and is most associated with dysfunction of the cardiac sodium channel Nav1.5. A novel and physiologically relevant approach to studying Nav1.5 variants involves the use of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes lacking endogenous Nav1.5 expression (Nav1.5 KO). This model allows for precise evaluation of variant-specific effects in a human cardiac cellular context. In this study, we investigated the Nav1.5/R1432G variant, which was previously identified in a patient diagnosed with Brugada syndrome. Sodium currents were recorded using the patch clamp technique in a whole-cell configuration. The Nav1.5/WT channel and the Nav1.5/R1432G variant were labeled by immunocytochemistry. Our results revealed a clear loss-of-function phenotype, consistent with Brugada syndrome. Furthermore, immunocytochemistry demonstrated a significant defect in membrane trafficking of the R1432G variant, supporting the hypothesis that impaired channel surface expression underlies its functional deficit. Action potential analysis revealed a marked reduction in the ventricular depolarization rate, consistent with impaired sodium channel function.