Interplay between bone morphogenetic proteins and cognate binding proteinsin bone and cartilage development: noggin, chordin and DAN

This commentary is a concise discussion of the interactions between bone mo rphogenetic proteins (BMPs) and their binding proteins in bone and cartilag e morphogenesis. BMPs are a family of growth and differentiation factors, a nd they act on mesenchymal cells to induce cartilage and bone differentiati on in concentration-dependent thresholds. The BMP-BMP receptor binding lead s to a cascade of signaling and transcription of BMP response genes. BMP bi nding proteins, noggin, chordin and DAN, act as antagonists and determine t he bioavailability of BMPs for binding to cognate receptors to elicit the b iological response. Noggin null mice with unrestricted action of BMPs exhib it defects in joint morphogenesis. BMPs and their binding proteins may reci procally regulate the dynamic topography of joints, muscle, tendons and lig aments during morphogenesis of the skeleton. In addition, BMP actions may b e potentiated by twisted gastrulation. BMPs and their binding proteins may play a critical role in regeneration of cartilage in osteoarthritis.