The m6Am methyltransferase PCIF1 promotes osteogenic differentiation of mesenchymal stem cells through stabilization of Wnt-related transcripts

Osteogenesis depends on the self-renewal and differentiation of mesenchymal stem cells (MSCs). Emerging research underscores the regulatory functions of RNA methylation on bone homeostasis. Here, we show PCIF1, the N6,2'-O-dimethyladenosine (m6Am) methyltransferase, is essential for maintaining bone mass and promoting osteogenic differentiation of MSCs. Multiple complementary analyses-including GWAS, TWAS, and single-cell transcriptomics-collectively point to PCIF1 as a regulator of human bone mineral traits and early-stage mesenchymal differentiation. Global or MSC-specific Pcif1 deletion elicits osteoporotic pathology in mice, although myeloid cell-specific Pcif1 knockout does not induce femur bone alterations. Mechanistically, Pcif1 knockout decreases m6Am signals of Wnt-related genes (Wnt11, Fzd4, and Fgfr2) and accelerates mRNA degradation. This down-regulates active β-Catenin protein, and thus impairs osteogenic function of MSCs. Additionally, the WNT agonist attenuates the osteoporosis-like phenotype induced by Pcif1 deletion. These findings highlight the crucial role of PCIF1-mediated m6Am modification in regulating osteogenesis and suggest potential therapeutic implications for bone disorders.