HDAC7 promotes cardiomyocyte proliferation by suppressing Myocyte Enhancer Factor 2.

Postnatal mammalian cardiomyocytes (CMs) rapidly lose proliferative capacity and exit the cell cycle and undergo further differentiation and maturation. Cell cycle activation has been a major strategy to stimulate postnatal CM proliferation, albeit achieving modest effects. One impediment is that postnatal CMs may need to undergo dedifferentiation before proliferation, if not simultaneously. Here, we report that overexpression of Hdac7 in neonatal mouse CMs results in significant CM dedifferentiation and proliferation. Mechanistically, we show that HDAC7-mediated CM proliferation is contingent on dedifferentiation, which is accomplished through suppressing MEF2. Hdac7 overexpression in CM shifts the chromatin state from binding MEF2, which favors the differentiation transcriptional program to AP-1, which favors the proliferative transcriptional program. Further, we found that HDAC7 interacts with minichromosome maintenance complex (MCM) components to initiate cell cycle progression. Our findings reveal that HDAC7 promotes CM proliferation by its dual action on CM dedifferentiation and proliferation, uncovering a potential new strategy for heart regeneration/repair.