Elucidating Molecular Mechanisms of Cardiomyocyte Maturation via Rbfox1 Activation

About This Grant

Project Summary: Mammalian infants exhibit immature circadian regulation: the establishment and maturation of cellular and systemic clocks occur postnatally, driven by maternal cues, feeding cycles, and light entrainment. In parallel, the neonatal heart undergoes profound structural and functional remodeling, characterized by decreased cardiomyocyte proliferation, metabolic shifts, altered expression of ion channels, enhanced electrical coupling, and changes in alternative splicing mediated by RNA-binding proteins (e.g., Rbfox1). Despite these parallel developmental processes, no molecular pathway has been determined to link the development of the circadian clock with cardiomyocyte maturation. Importantly, induced pluripotent stem cell-derived cardiomyocytes (iPSC- CMs) share a common deficiency in maturity, which is a significant limitation for their application in disease modeling, drug screening, or as cell therapy agents. Therefore, uncovering the intrinsic regulatory mechanisms of mammalian cardiomyocyte maturation has significant implications for both basic developmental biology and pre-clinical applications. We propose that a circadian clock checkpoint, comprising activators (ATF3/MEF2s) and a suppressor (NFIL3), serves as a temporal regulator of cardiac maturation during early life. The aims of this proposal are as follows: Aim 1. Determine the enhancer (Rb1en)-transcription factors circuitry (ATF3/MEF2/NFIL3) that initiates the temporal and tissue-specific expression of Rbfox1; and Aim 2. Determine the critical role for circadian clock regulatory mechanisms on cardiomyocyte maturation in vivo and hiPSC-CM maturation in vitro. These studies will establish a molecular bridge between developmental chronobiology and cardiac maturation, reveal new mechanisms of temporal regulation in postnatal heart growth, and may inform novel strategies for conditions associated with impaired cardiac maturation and enhance maturity and disease relevance of hiPSCs. Collectively these insights will reduce the burden of cardiovascular risk and advance pre- clinical applications of stem-cell-based modeling and therapeutics.