Molecular Pathophysiology of Brugada Syndrome Across Cellular Heterogeneity of the Fetal Heart

Recent data suggests that alterations in cardiac development participate to the pathogenesis of Brugada Syndrome (BrS), a rare inherited disorder responsible for sudden cardiac death. In vitro cardiac differentiation of human induced pluripotent stem cells (hiPSCs) can produce numerous cell types found in the fetal heart. This technique is well suited to decipher cell-type specific developmental mechanisms of BrS. This study aims at (1) describing the different cell types obtained after in vitro cardiac differentiation of hiPSCs and (2) identifying cell-type specific molecular alterations associated with BrS. Single-cell RNA-seq data were generated at day 30 of in vitro cardiac differentiation of hiPSCs from 1 control subject ( n = 2) and 1 BrS patient ( n = 2), producing individual transcriptomic expression profile for 29′915 cells. Among those 23′624 (79%) displayed a cardiac transcriptomic profile. Using public database annotations, 8′766 cells and 5′287 cells were assigned to ventricular and atrial cardiomyocytes phenotype, respectively. Focusing on ventricular cardiomyocytes we identified 213 and 153 genes up and down-regulated in BrS samples as compared to control. Interestingly, differentially expressed genes were enriched in genes involved in heart development (e.g. IRX4, NKX2-5, FZD2) and cardiac conduction (e.g. KCNJ5, CASQ2, CACNA1 C) functions. In vitro cardiac differentiation of hiPSCs can effectively generate numerous cardiac cell type with a majority (59%) of cardiomyocytes. Comparison of transcriptomic profiles of ventricular cardiomyocytes differentiated from BrS and control hiPSCs revealed alteration of heart development and cardiac conduction functions. Altogether, these data indicate that BrS may have developmental origins and that modeling BrS using cellular level data from in vitro cardiac differentiation of hiPSCs may be key to gain further insight into its molecular mechanisms.