Abstract 409: Regulation of Cardiomyocyte Maturation by an RNA Splicing Regulator Rbfox1

Abstract

The maturation of stem cell derived cardiomyocytes (iCMs) is incomplete relative to the fully matured adult myocytes. Lack of maturation represents a major limitation to the applications of iCMs as heart disease models or heart failure therapies. Current attempts to promote iCMs maturation, such as prolonged culture, mechanical stretching and electronic pacing, are often based on empirical methods with poor reproducibility or little mechanistic basis. In order to better understand the molecular mechanisms driving cardiomyocyte maturation, we performed extensive transcriptome analyses in neonatal vs. adult hearts. In addition to metabolic and cell cycle regulatory pathways, Gene Ontology analysis revealed RNA splicing regulation is significantly enriched in the transcriptome reprogramming during postnatal maturation in heart. Specifically, we find a cardiomyocyte enriched RNA splicing factor Rbfox1 is dramatically induced in the perinatal maturating mouse hearts. Ectopic expression of Rbfox1 in neonatal cardiomyocytes markedly promotes the cellular and molecular features of adult cardiomyocyte, including contractility, calcium handling, sarcomere organization, morphology, electrophysiology and gene expression. Most remarkably, expression of RBFox1 in human iPSC derived cardiomyocytes promotes similar maturation process as observed in the neonatal rat myocytes. At mechanistic level, RBFox1 expression in the iCMs enhances transcriptome maturation as indicated by targeted RNA splicing in genes involved in muscle contraction, gene expression, RNA processing and sarcomere organization. In summary, we have uncovered a novel molecular path towards neonatal myocyte maturation in perinatal murine hearts by targeted modulation of cardiomyocyte transcriptome via RNA-splicing. This approach has potential to be employed as a molecular approach to promote human iCMs maturation.