BACKGROUND:During the neonatal stage, the cardiomyocyte undergoes a constellation of molecular, cytoarchitectural, and functional changes known collectively as cardiomyocyte maturation to increase myocardial contractility and cardiac output. Despite the importance of cardiomyocyte maturation, the molecular mechanisms governing this critical process remain largely unexplored.METHODS:We leveraged an in vivo mosaic knockout system to characterize the role of Carm1, the founding member of protein arginine methyltransferase, in cardiomyocyte maturation. Using a battery of assays, including immunohistochemistry, immuno-electron microscopy imaging, and action potential recording, we assessed the effect of loss of Carm1 function on cardiomyocyte cell growth, myofibril expansion, T-tubule formation, and electrophysiological maturation. Genome-wide transcriptome profiling, H3R17me2a chromatin immunoprecipitation followed by sequencing, and assay for transposase-accessible chromatin with high-throughput sequencing were used to investigate the mechanisms by which CARM1 (coactivator-associated arginine methyltransferase 1) regulates cardiomyocyte maturation. Finally, we interrogated the human syntenic region to the H3R17me2a chromatin immunoprecipitation followed by sequencing peaks for single-nucleotide polymorphisms associated with human heart diseases.RESULTS:We report that mosaic ablation of Carm1 disrupts multiple aspects of cardiomyocyte maturation cell autonomously, leading to reduced cardiomyocyte size and sarcomere thickness, severe loss and disorganization of T tubules, and compromised electrophysiological maturation. Genomics study demonstrates that CARM1 directly activates genes that underlie cardiomyocyte cytoarchitectural and electrophysiological maturation. Moreover, our study reveals significant enrichment of human heart disease–associated single-nucleotide polymorphisms in the human genomic region syntenic to the H3R17me2a chromatin immunoprecipitation followed by sequencing peaks.CONCLUSIONS:This study establishes a critical and multifaceted role for CARM1 in regulating cardiomyocyte maturation and demonstrates that deregulation of CARM1-dependent cardiomyocyte maturation gene expression may contribute to human heart diseases.

中文翻译：

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精氨酸甲基转移酶 CARM1 对心肌细胞成熟的表观遗传调控

背景：在新生儿阶段，心肌细胞经历一系列分子、细胞结构和功能变化，统称为心肌细胞成熟，以增加心肌收缩力和心输出量。尽管心肌细胞成熟很重要，但控制这一关键过程的分子机制在很大程度上仍未被探索。方法：我们利用体内嵌合敲除系统来表征Carm1（蛋白质精氨酸甲基转移酶的创始成员）在心肌细胞成熟中的作用。通过一系列检测，包括免疫组织化学、免疫电子显微镜成像和动作电位记录，我们评估了Carm1功能丧失对心肌细胞生长、肌原纤维扩张、T 管形成和电生理成熟的影响。采用全基因组转录组分析、H3R17me2a 染色质免疫沉淀和测序以及通过高通量测序检测转座酶可及染色质来研究 CARM1（共激活剂相关精氨酸甲基转移酶 1）调节心肌细胞成熟的机制。最后，我们对 H3R17me2a 染色质免疫沉淀检测人类同线区域，然后对与人类心脏病相关的单核苷酸多态性峰进行测序。 结果：我们报告Carm1的马赛克消融会自主破坏心肌细胞成熟细胞的多个方面，导致心肌细胞减少大小和肌节厚度、T 小管严重损失和混乱，以及电生理成熟受损。基因组学研究表明，CARM1 直接激活心肌细胞细胞结构和电生理成熟的基因。此外，我们的研究揭示了人类基因组区域中与 H3R17me2a 染色质免疫沉淀同线性的人类心脏病相关单核苷酸多态性的显着富集，随后是测序峰。结论：这项研究确立了 CARM1 在调节心肌细胞成熟和发育过程中的关键和多方面作用。表明 CARM1 依赖性心肌细胞成熟基因表达的失调可能导致人类心脏病。