Plant homeodomain finger protein 2 promotes bone formation by demethylating and activating Runx2 for osteoblast differentiation

Abstract

Plant homeodomain finger protein 2 (PHF2), which contains a plant homeodomain and a Jumonji-C domain, is an epigenetic regulator that demethylates lysine 9 in histone 3 (H3K9me2). On the other hand, runt-related transcription factor 2 (Runx2) plays essential roles in bone development and regeneration. Given previous reports that the PHF2 mutation can cause dwarfism in mice and that PHF2 expression is correlated with that of Runx2 in differentiating thymocytes, we investigated whether PHF2 regulates Runx2-mediated bone formation. Overexpression of PHF2 facilitated bone development in newborn mice, and viral shRNA-mediated knockdown of PHF2 delayed calvarial bone regeneration in adult rats. In primary osteoblasts and C2C12 precursor cells, PHF2 enhances osteoblast differentiation by demethylating Runx2, while suppressor of variegation 3-9 homolog 1 (SUV39H1) inhibits bone formation by methylating it. The PHF2-Runx2 interaction is mediated by the Jumonji-C and Runt domains of the two proteins, respectively. The interaction between Runx2 and osteocalcin promoter is regulated by the methylation status of Runx2, i.e., the interaction is augmented when Runx2 is demethylated. Our results suggest that SUV39H1 and PHF2 reciprocally regulate osteoblast differentiation by modulating Runx2-driven transcription at the post-translational level. This study may provide a theoretical basis for the development of new therapeutic modalities for patients with impaired bone development or delayed fracture healing.

Histone demethylase KDM7A reciprocally regulates adipogenic and osteogenic differentiation via regulation of C/EBPα and canonical Wnt signalling

“…Tri‐methylation of H3K4, H3K36 and H3K79 is a representative marker for euchromatin, which is loosely packed, so accessible for transcription factors. In contrast, mono‐methylation of H4K20, and di‐/tri‐methylation of H3K9 or H3K27 mark heterochromatin, which is too tightly packed to be accessed by transcription factors . Thus H3K4me2/3 and H3K79me3 usually correlate with transcriptional activation, whereas H3K9me2/3, H3K27me2/3 and H4K20me3 are preferentially associated with transcriptional repression .…”

“…While KDM7B plays an essential role in neuronal differentiation, craniofacial development and tumour growth, KDM7C is involved in various biological processes including osteogenesis and adipogenesis. In osteoblasts, KDM7C promotes DNA binding of Runx2 by directly demethylating mouse Runx2 at Lys245 or human Runx2 at Lys238, rather than by demethylating histones on Runx2 target genes . During adipogenesis, KDM7C physically interacts with C/EBPα and C/EBPδ and epigenetically boosts the C/EBP‐driven expression of adipogenic factors …”

“…In osteoblasts, KDM7C promotes DNA binding of Runx2 by directly demethylating mouse Runx2 at Lys245 or human Runx2 at Lys238, rather than by demethylating histones on Runx2 target genes. 24 During adipogenesis, KDM7C physically interacts with C/EBPα and C/EBPδ and epigenetically boosts the C/EBP-driven expression of adipogenic factors. 25 Histone lysine demethylase 7A (KDM7A), also known as JHDM1D, is a member of the plant homeodomain (PHD) finger protein (PHF) family of PHD-and JmjC domain-containing histone demethylases.…”

Lysine-Specific Histone Demethylases Contribute to Cellular Differentiation and Carcinogenesis

“…Interestingly, through its JmjC domain, KDM7C interacts with Runx2 and reduces its lysyl methylation level. The loss of Runx2's post-translational modifications enhances its DNA binding capability, thereby modifying the Runx2-mediated gene transcription [109].…”

“…FGF4 (fibroblast growth factor 4), in turn, phosphorylates the extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2, respectively), thereby allowing neural fate determination [108]. Additionally, KDM7C is required for osteoblast differentiation and bone development: its overexpression in mice enhances bone development, whereas its depletion in rats protracts calvarial bone regeneration [109]. Moreover, KDM7C modulates the function of Runx2 (Runt-related transcription factor 2), a key protein required for osteoblast differentiation during bone development.…”