Recent genetic data suggest that abnormal cardiac development participates to the pathogenesis of Brugada Syndrome (BrS), a rare inherited arrhythmia responsible for sudden cardiac death in young adults. In vitro cardiac differentiation of human induced pluripotent stem cells (hiPSCs) mimics cardiac development at the cellular level up to a prenatal stage.

This study aims at defining whether BrS impairs cardiac differentiation of hiPSCs.

Single-cell transcriptomic data were generated at day 30 of in vitro cardiac differentiation of hiPSCs from 2 control subjects (n=6139 cells) and 2 BrS patients (n=13756 cells). These transcriptomic data have been annotated using public data obtained from human heart samples at 7.5 post conception weeks (PCW). In addition, bulk 3′RNA-seq data were generated in triplicate for 3 control hiPSC lines and 3 BrS-patient hiPSC lines at each day of the 30-day cardiac-directed differentiation protocol.

Single-cell data revealed (1) differences in cell type distribution, with BrS-hiPSCs and control-hiPSCs cardiac-directed differentiation generating 9.8% and 32.85% cardiomyocytes and 16.6% and 2.75% smooth muscle cells, respectively, and (2) cardiomyocytes transcriptomic alterations associated with biological processes of cardiac development, morphogenesis and conduction in BrS. Based on the finding, showing that BrS is associated with alterations in cardiac differentiation, we used the bulk transcriptomic kinetic data to analyze temporal transcriptomic alterations during cardiac-directed differentiation. Differential gene expression analysis unveiled (1) gene expression signatures specific to each BrS patients and (2) expression alterations that were common to all 3 BrS-hiPSCs lines as compared with control lines. Interestingly, the misexpressed genes were associated to the cell differentiation process (GO: 0030154) and their expression kinetics were altered during the cardiac differentiation process.

By generating and analyzing single-cell and bulk transcriptomic data during cardiac-directed differentiation of hiPSCs, this study strongly suggests that transcriptomic remodeling occurs as early as the cardiac development for BrS patients.