Role of polycomb group protein YAF2 in cardiac regeneration

Abstract Heart failure (HF) remains a major global health challenge, affecting over 23 million people worldwide, with high mortality despite advances in treatment. A key limitation is the adult mammalian heart’s inability to regenerate, leading to cardiomyocyte (CM) loss, fibrosis, and impaired function. In contrast, lower vertebrates such as zebrafish and newts retain lifelong cardiac regenerative capacity. Similarly, neonatal mice can regenerate hearts within the first week of life, suggesting the presence of latent regenerative mechanisms in mammals that become silenced postnatally. Identifying molecular regulators that reactivate these pathways could offer novel therapeutic strategies for HF. Using comparative bulk and single-cell transcriptome analyses of neonatal vs. adult mouse CMs, we identified a set of genes associated with cardiac regeneration, many of which are evolutionarily conserved in zebrafish. A pilot shRNA screen in neonatal mouse CMs validated their roles in CM proliferation, leading to the identification of YY1-associated factor 2 (YAF2) as a novel regulator of cardiac regeneration. YAF2, a polycomb group protein within the non-canonical polycomb repressive complex 1 (ncPRC1), is known for its roles in zebrafish embryogenesis and mouse embryonic stem cell pluripotency, but its function in cardiac regeneration remains unclear. Yaf2 is highly expressed in regenerative neonatal CMs and declines with age. Reanalysis of mouse cardiac snRNA sequencing data showed that Yaf2 is enriched in proliferating neonatal CMs post-injury. Functional studies confirmed that Yaf2 is necessary and sufficient to promote CM proliferation in vitro, and its expression is upregulated after cardiac injury in neonatal mice and zebrafish. Notably, a Ser166-to-Ala substitution in Yaf2, which is required for its interaction with the ncPRC1 complex, abolished its pro-regenerative effects, suggesting that Yaf2 drives CM self-renewal through ncPRC1-mediated epigenetic regulation. To elucidate its downstream mechanisms, we performed RNA and ATAC sequencing following Yaf2 depletion in neonatal CMs. Loss of Yaf2 led to upregulation of oxidative phosphorylation and TCA cycle genes, while genes involved in cell cycle regulation and extracellular matrix (ECM) organization were downregulated, suggesting that Yaf2 could regulate CM proliferation through metabolic reprogramming and ECM remodeling. Global deletion of Yaf2 in zebrafish reduced CM dedifferentiation and proliferation and delayed scar resolution, whereas forced Yaf2 expression in non-regenerative medaka fish hearts promoted cardiac regeneration and reduced post-injury scarring. Moreover, Yaf2 overexpression in adult mouse hearts enhanced CM proliferation and improved cardiac function following ischemic injury. Altogether, these findings reveal a critical yet previously unknown role of YAF2 as a key regulator of cardiac regeneration. Targeting YAF2, therefore, may be a powerful new therapeutic approach to treating HF.