Ihh, parathyroid hormone related peptide, Wnts, Bone morphogenetic proteins and fibroblast growth factor etc., regulate progressive chondrocyte proliferation and hypertro-phy. PTHrP and Ihh are major regulators of chondrocyte hypertrophy by forming a negative feedback loop. Ihh activates PTHrP expression and PTHrP then signals to proliferating chondrocytes to inhibit Ihh expression and chondrocyte hypertro-phy by holding chondrocytes in a proliferating state. Wnt signaling pathways also regulate chondrocyte hypertrophy. Among known Wnt signaling pathways,Kinase Inhibitor Library the canonical Wnt signaling pathway mediated by b-catenin is the best understood and has been found to promote both chondrocyte hypertrophy and final maturation. Wnt/b-catenin signaling acts indepen-dently of Ihh signaling to promote chondrocyte hypertrophy, but it is unknown whether Wnt/b-catenin and PTHrP signaling pathways regulate each other to control chondrocyte hypertrophy and maturation. Here we have investigated the regulation of chondrocyte hypertrophy and final maturation and the genetic relationship between the canonical Wnt and PTHrP signaling pathways in sequential chondrocyte differentiation. We uncovered that chon-drocyte hypertrophy and final maturation are two distinct processes that are differentially regulated by Wnt/b-catenin and PTHrP signaling. Canonical Wnt signaling promotes chondrocyte hypertrophy by antagonizing PTHrP signaling activity. However,Lapatinib the final maturation of hypertrophy chondrocytes is controlled by Wnt/b-catenin signaling independently of PTHrP signaling. We report here that during mouse embryonic cartilage development, Wnt/b-catenin signaling controls chondrocyte hypertrophy and final maturation by two distinct mechanisms. Wnt/b-catenin signaling regulates initiation of chondrocyte hypertrophy by antagonizing PTHrP signaling, whereas it acts independently of PTHrP signaling in controlling the final maturation of hypertrophic chondrocytes. Our results indicate that chondrocyte hypertrophy and final maturation are two separate developmental events that are regulated by distinct signaling interactions.