Abstract 4365494: Mitochondrial Perinuclear Polarity Distribution Promotes Mammalian Heart Regeneration

Background: Irreversible myocardial injury and replacement fibrosis following myocardial infarction (MI) constitute key drivers of cardiac dysfunction. Consequently, promoting endogenous cardiomyocytes (CMs) regeneration represents a critical imperative. While mitochondria play pivotal roles in maintaining CMs functionality, the mechanisms governing mitochondrial regulation of CMs proliferative capacity remain incompletely elucidated. Aims: Our study aims to elucidate the role played by mitochondria in mammalian heart regeneration and the related regulatory mechanisms. Methods and Results: We first characterized the mitochondria of heart at different developmental stages, revealing that mitochondrial distribution dynamically correlate with CMs proliferative capacity. Notably, highly proliferative CMs exhibited pronounced mitochondrial perinuclear polarity distribution. Through optogenetic manipulation to alter mitochondrial distribution, we demonstrated that perinuclear mitochondrial clustering constitutes a key determinant of CMs proliferation. Further analysis identified that mitochondria and nucleus can form significant contact sites in highly proliferative CMs. Mechanistically, we identified that nuclear membrane-localized mitofusin 2 (MFN2) orchestrates mitochondrial perinuclear aggregation through spatial coupling, and efficiently promotes retrograde shuttling of the citrate to the nucleus. Additionlly, we found that intranuclear citrate cleavage is mediated by the nuclear enrichment of ATP citrate lyase (ACLY) , which could locally generate large amounts of acetyl-CoA, and in turn mediated histone acetylation modifications, particularly the acetylation of histone H3 lysine9 (H3K9ac) and histone H3 lysine27 (H3K27ac). By modulating citrate-derived acetyl coenzyme A in vivo and in vitro experiments, we confirmed that ACLY mediates the formation of the metabolism-epigenetic modification network, and enhances the transcriptional activity of cell cycle regulatory genes ( Ccna1, Ccne1 ) and pluripotency genes ( Erbb4, Mef2a ), exerting essential regulatory functions in mammalian CMs proliferation and myocardial injury repair. Conclusions: Our study demonstrated that mitochondrial perinuclear polarity distribution, essential for mammalian heart regeneration, promotes retrograde citrate transport into the nucleus. Nuclear ACLY then generates acetyl-CoA locally for histone acetylation, enhancing gene transcriptional activity and stimulating CMs proliferation.