Lineage-specific conduction heterogeneity and CXCL12/CXCR4 signaling axis activation in human induced pluripotent stem cell models of MYBPC3 deficiency
V Jeyakumar, M Messner, C Puelacher, M Ungericht, G Poelzl, A Bauer, M M ZarubaAbstract
Introduction
Mutations in the myosin binding protein C (MYBPC3) gene are a primary cause of hypertrophic cardiomyopathy (HCM), leading to sarcomeric dysfunction and arrhythmias. The lineage-specific effects of these mutations on atrial versus ventricular electrophysiology remains poorly defined. This study utilizes induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) to compare the structural, molecular, and functional consequences of MYBPC3 deficiency in atrial and ventricular models.
Methods
Healthy (WTSli004-A) and MYBPC3-mutant (Ukki035-B) iPSCs were differentiated into atrial and ventricular cardiomyocytes. Pluripotency was confirmed via qPCR (DPPA5, NANOG) and immunofluorescence (TRA-1-60, SSEA-4). Gene expression profiling at day 21 assessed cardiac markers (MESP1, NKX2.5, TNNT2, MYBPC3, ACTC1, MYH6, MYH7, NPPB) and chemokine receptors CXCR4/CXCR7. RPL0 served as the reference gene due to its stability in this model compared to GAPDH. Structural organization was evaluated through ACTN4 immunostaining. Functional properties, including beat frequency, conduction velocity, and activation heterogeneity, were quantified using optical mapping.
Results
RPL0 provided a stable baseline for transcriptomic comparison, whereas GAPDH expression varied significantly. Transcriptional profiling showed significant CXCR4 upregulation in both atrial and ventricular MYBPC3-mutant lines, indicating the activation of inflammatory and survival signaling pathways. Ventricular mutants specifically showed MESP1 upregulation. ACTN4 staining revealed altered cytoskeletal architecture in mutant cells. Functional analysis demonstrated that MYBPC3-mutant ventricular cardiomyocytes displayed a bradycardia phenotype with significantly reduced beat frequency and high variance in conduction velocity compared to healthy controls. These data confirm an increased arrhythmogenic state in the mutant models.
Conclusion
The MYBPC3 mutation drives distinct transcriptional and electrophysiological remodeling in atrial and ventricular lineages. The observed conduction heterogeneity and CXCR4 upregulation suggest that non-sarcomeric mechanisms contribute to the HCM phenotype. This iPSC-CM model provides a platform for investigating lineage-specific pathophysiology and testing targeted therapies to stabilize cardiac conduction.