Essential role of MESP1-RING1A complex in cardiac differentiation

Heart development is controlled by a complex transcriptional network composed of transcription factors and epigenetic regulators. Mutations in key developmental transcription factor MESP1, and chromatin factors such as PRC1 and cohesin components have been found in human congenital heart diseases (CHDs), although, their functional mechanism during heart development remains elusive. Here we find MESP1 interacts with RING1A/RING1, the core component of PRC1. RING1A depletion impairs human cardiomyocyte differentiation, and similar cardiac abnormalities were observed in Ring1A knockout mice as in patients with MESP1 mutations. Mechanistically, MESP1 associates with RING1A to activate cardiogenic genes through promoter-enhancer interactions mediated by cohesin and CTCF, and histone acetylation mediated by p300. Importantly, CHD mutations of MESP1 significantly affect such mechanisms and impair target gene activation. Together, our results demonstrate the importance of MESP1-RING1A complex in heart development and provide insights into pathogenic mechanisms of CHDs caused by mutations in MESP1, PRC1 and cohesin components. Overall design: We performed ChIP-seq of MESP1 in human cardiac progenitor stage cells (CPCs, day 4 post differentiation from hESCs) overexpressing Dox-induced FLAG-MESP1 using anti-FLAG tag antibody. We performed ChIP-seq of RING1/RING1A and RING2/RING1B in hESCs and CPCs, ChIP-seq of H3K4me3 and H3K27ac in CPCs, ChIP-seq of RING1/RING1A and H3K27ac in MESP1 KO CPCs, Input of ChIP-seq in hESCs and CPCs, Hi-C of WT and RING1A KO CPCs (day 4 post differentiation from hESCs), mRNA-seq of WT, MESP1 KO, and RING1A KO CPCs (day 4 and day 6 post differentiation from hESCs).