FBXO11 Regulates Bone Development

FBXO11 is the substrate-recognition component of a ubiquitin ligase complex called SKP1-cullin-F-boxes. The role of FBXO11 in bone development is unexplored. In this study, we reported a novel mechanism of how bone development is regulated by FBXO11. FBXO11 gene knockdown by lentiviral transduction in mouse pre-osteoblast MC3T3-E1 cells leads to reduced osteogenic differentiation, while overexpressing FBXO11 acceler-ates their osteogenic differentiation in vitro. Furthermore, we generated two osteoblastic-specific FBXO11 conditional knockout mouse models, Col1a1-ERT2-FBXO11KO and Bglap2-FBXO11KO mice. In both conditional FBXO11KO mouse models, we found FBXO11 deficiency inhibits normal bone growth, in which the osteogenic activity in FBXO11cKO mice is reduced, while osteoclastic activity is not significantly changed. Mechanistically, we found FBXO11 deficiency leads to Snail1 protein accumulation in osteoblasts, leading to suppression of osteogenic activity and inhibition of bone matrix mineralization. FBXO11 knockdown in MC3T3-E1 cells reduced Snail1 protein ubiquitination and increased Snail1 protein accumulation in the cells, which eventually inhibited osteogenic differentiation. In conclusion, FBXO11 deficiency in osteoblasts inhibits bone formation through Snail1 accumulation, inhibiting osteogenic activity and bone mineralization.