ABSTRACT: Background ELMSAN1 is a newly identified scaffolding protein of the mitotic deacetylase complex (MiDAC), playing a pivotal role in early embryonic development. Studies on Elmsan1 knockout mice showed that its absence results in embryo lethality and heart malformation. However, the precise function of ELMSAN1 in heart development and formation has remained elusive. To gain insights into its potential role in cardiac lineage, we employed human-induced pluripotent stem cells (hiPSCs) to model early cardiogenesis and investigated the function of ELMSAN1. Methods and Results We generated ELMSAN1-deficient hiPSCs through both knockdown and knockout, revealing that ELMSAN1 appears to be unnecessary for hiPSC maintenance. During the process of cardiac differentiation, ELMSAN1 depletion led to a delay in pluripotency deactivation, decreased expression of cardiac-specific markers, and reduced differentiation efficiency. The impaired expression of genes associated with contractile sarcomere structure, calcium handling, and ion channels were also noted in ELMSAN1-deficient cardiomyocytes derived from hiPSCs (hiPSC-CMs). Additionally, through a series of structural and functional assessments, we found that these cells are immature, exhibiting incomplete sarcomere Z-line structure and length, decreased calcium amplitude, increased time to peak value, faster beat rate with a shorter beat period, decreased field potential duration, and prolonged propagation delay. Of note, we found that the cardiac specific role of ELMSAN1 is likely associated with histone H3K27 acetylation level. The transcriptome analysis provided additional insights, indicating maturation reduction with energy metabolism switch and restored cell proliferation in ELMSAN1 knockout cardiomyocytes. Conclusions In this study, we address the significance of the direct involvement of ELMSAN1 in the differentiation and maturation of hiPSC-CMs. We first report the impact of ELMSAN1 on multiple aspects of hiPSC-CM generation, including cardiac differentiation, sarcomere formation, calcium handling, electrophysiological maturation and proliferation.
