Cardiomyocyte differentiation from human induced pluripotent stem cells is delayed following knockout of Bcl-2

Anti-apoptotic B-cell lymphoma 2 (Bcl-2) regulates a wide array of cellular functions involved in cell death, cell survival and autophagy. Less known is its involvement in the differentiation of cardiomyocytes. As a consequence, mechanisms by which Bcl-2 contributes to cardiac differentiation remain to be elucidated. To address this, we used CRISPR/Cas9 to knockout (KO) BCL2 in human induced pluripotent stem cells (hiPSCs) and investigated the consequence of this KO for differentiation towards cardiomyocytes. Our results indicate that differentiation of hiPSCs to cardiomyocytes was delayed following BCL2 KO. This was not related to the canonical anti-apoptotic function of Bcl-2. This delay led to reduced expression and activity of the cardiomyocyte Ca2+ toolkit. Finally, Bcl-2 KO reduced c-Myc expression and nuclear localization in the early phase of the cardiac differentiation process, which accounts at least in part for the observed delay in the cardiac differentiation. These results suggest that there is a central role for Bcl-2 in cardiomyocyte differentiation and maturation.