The role of TGFbetas and Sox9 during limb chondrogenesis.

The majority of the skeletal elements, except the flat bones of the skull, are formed by endochondral ossification, in which cartilage is replaced by bone. The formation of cartilage is a multi-step process termed chondrogenesis, during which undifferentiated mesenchymal cells condense and undergo differentiation towards chondrocytes. Notwithstanding recent advances, our knowledge of the detailed mechanisms implicated in cartilage and bone formation is still scarce. Recent genetic, cellular and biochemical studies have highlighted the importance of TGFbeta signaling and the activity of the transcription factor Sox9 during the early stages of vertebrate limb chondrogenesis.