m6Am methyltransferase PCIF1 regulates osteogenesis via WNT signaling

Skeletal development depends on the self-renewal and differentiation of 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 a marker of early mesenchymal stem cells. Global or MSC-specific Pcif1 deletion elicits osteoporotic pathology in mice, although myeloid cell-specific Pcif1 knockout does not induce femur bone alternation alterations. Mechanistically, Pcif1 knockout decreases m6Am signals of Wnt-related genes (Wnt11, Fzd4, 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.