Abstract P1107: Elmsan1 Regulates Differentiation And Maturation Of Cardiomyocytes Derived From Human Induced Pluripotent Stem Cells

Abstract

Introduction: ELMSAN1 is a scaffolding protein of the mitotic deacetylase complex (MiDAC) that is critical for early embryonic development. Studies on Elmsan1 knockout mice show that its absence results in heart malformation and embryo lethality. Despite this, the direct role of ELMSAN1 in heart development and formation remains unknown. To gain insights into this role, we differentiated human-induced pluripotent stem cell (hiPSC) into cardiomyocyte (hiPSC-CM) to mimic early cardiogenesis and assess the involvement of ELMSAN1 in CM maturation. Methods and Results: We utilized shRNA-mediated knockdown and CRISPR-Cas9-mediated knockout techniques to generate ELMSAN1-deficient hiPSC, which were differentiated into CM for characterization. We showed that ELMSAN1 depletion caused a delay in the deactivation of pluripotency genes during early differentiation, resulting in decreased expression of cardiac-specific markers (TNNT2, MHY6), and reduced differentiation efficiency of CM. We also observed the impaired expression of genes associated with contractile sarcomere structure, calcium handling, and ion channels in ELMSAN1-deficient CM. Moreover, through a series of structural and functional assessments, we found these cells exhibited incomplete sarcomere Z-line structure and length (1.3 μm in KD vs. 1.5 μm in control), decreased calcium amplitude, increased time to peak value, faster beat rate with a shorter beat period, decreased field potential duration (300 ± 10 ms in KD vs. 500 ± 10 ms in control), and prolonged propagation delay. Importantly, we confirmed similar immaturity and functional changes in ELMSAN1 knockout CM, excluding the potential off-target effect. Mechanistically, we discovered that ELMSAN1 depletion resulted in decreased levels of H3K27ac in both hiPSC and CM, indicating an unexpected role of ELMSAN1 in maintaining global H3K27ac and gene expression. Conclusion: Our findings offer compelling evidence for the direct involvement of ELMSAN1 in the differentiation and maturation of hiPSC-CM. Notably, we were the first to identify the impact of ELMSAN1 on various aspects of hiPSC-CM generation, including cardiac differentiation, sarcomere formation, calcium handling, and electrophysiological maturation.