New roles of osteoblasts involved in osteoclast differentiation

Figure 3 Role of Wnt5a-receptor tyrosine kinase-like orphan receptor 2 signaling in osteoclast precursors. Receptor activator of nuclear factor-κB (RANK) expression in osteoclast precursors is much stronger than that in bone marrow and the spleen. Osteoblasts express Wnt5a, while osteoclast precursors express receptor tyrosine kinase-like orphan receptor 2 (Ror2), a co-receptor of Wnt5a. Wnt5a produced by osteoblasts enhances RANK expression in osteoclast precursors through Ror2. Wnt5a up-regulates RANK expression through the recruitment of c-Jun to Sp1 sites of the RANK promoter. The up-regulation of RANK expression in osteoclast precursors increases their sensitivity to RANK ligand. JNK: c-Jun N-terminal kinase.