Loss-of-function of ACVR1 in osteoblasts increases bone mass and activates canonical Wnt signaling through suppression of Wnt inhibitors SOST and DKK1

► We investigate physiological roles of the BMP receptor ACVR1, a potent receptor for BMP7. ► Loss of ACVR1 in osteoblasts increases bone mass and activates Wnt signaling in mice. ► Wnt inhibitors SOST and DKK1 are both downregulated in the mutant bones. ► ACVR1 can repress osteogenesis and Wnt signaling via SOST/DKK1. ► This study proposes a new concept of the BMP7-ACVR1-SOST/DKK1 axis in osteoblasts.