MYBPC3 (c.194 C > T) mutation-mediated RyR2 dysfunction contributes to pathogenic phenotypes of DCM revealed by HiPSC modeling

Dilated cardiomyopathy (DCM) is a leading cause of heart failure and the primary indication for heart transplantation. The intricate and poorly elucidated pathogenesis of genetic DCM, coupled with the paucity of effective therapeutic options, imposes a substantial burden on both patients and their families. In this study, we identified a novel MYBPC3 mutation (c.194C > T) in a patient diagnosed with DCM and established a patient-specific human induced pluripotent stem cell (hiPSC) model. Cardiomyocytes derived from these patient-specific hiPSCs (hiPSC-CMs) exhibited hallmark features of DCM, including cell enlargement, aberrant distribution of sarcomeric α-actinin, and dysregulated calcium ion homeostasis, as compared to control hiPSC-CMs derived from a healthy individual. RNA sequencing analysis revealed a significant upregulation of CASQ2, which encodes calsequestrin, a protein that binds to Ryanodine receptor 2 (RyR2). Notably, treatment with the RyR2 inhibitor ryanodine effectively restored the abnormal calcium transients observed in DCM-hiPSC-CMs. In summary, our findings provide compelling evidence that the c.194 C > T mutation of MYBPC3 plays a definitive pathogenic role in DCM, and that modulation of the RyR2 receptor may alleviate calcium dysregulation in affected cardiomyocytes. These insights enhance our understanding of the molecular mechanisms underlying DCM and offer a promising therapeutic strategy for patients with calcium ion dysregulation associated with this condition. Cardiomyocytes differentiated from patient-specific induced pluripotent stem cells (hiPSCs) reproduce enlargement and sarcomeric disorganization. A novel c.194C>T mutation in MYBPC3 results in abnormal calcium transients in hiPSC-derived cardiomyocytes. c.194C>T mutation of MYBPC3 leads to a significant increase in the expression of calsequestrin that binds to the ryanodine receptor 2 (RyR2). Treatment with RyR2 inhibitor markedly improves the ability of calcium handling in DCM-hiPSC-cardiomyocytes.