Integrative analysis reveals synergistic regulation of Sp7 by BRD9 and Wnt/ß-catenin signaling during osteogenic differentiation

Osteoporosis is a skeletal disorder involving low bone mineral density (BMD) and elevated fracture risk. While epigenetic mechanisms like DNA methylation are well-studied, the role of chromatin remodeling remains less clear. Using integrative genetics and functional studies, we identified BRD9—a non-canonical BAF subunit—as critical for osteoblast differentiation. BRD9 activates Wnt/ß-catenin signaling and directly upregulates the key osteogenic factor Sp7. Our findings reveal a novel osteogenic role for BRD9 and suggest its potential as a biomarker and therapeutic target for bone-related diseases. Overall design: HEK293T and MC3T3-E1 cells were cultured in Dulbecco's Modified Eagle Medium (DMEM, Gibco) and MEM Alpha Modification (Cytiva) respectively, with addition of 10% fetal bovine serum (FBS, Biological Industries) and 1% penicillin/streptomycin. For in vitro osteogenic differentiation, MC3T3-E1 cell line was maintained in basic medium supplemented with 10 mM M-glycerol phosphate, 0.25 mM ascorbic acid and 0.1 µM dexamethasone (all from Sigma-Aldrich, USA). For the BRD9 inhibition assays, cells were treated with either DMSO or I-BRD9 at the final concentrations of 10 µM.