Pdgfra regulates multipotent cell differentiation towards chondrocytes via inhibiting Wnt9a/beta-catenin pathway during chondrocranial cartilage development.

The mammalian skull is composed of the calvarial bones and cartilages. Malformation of craniofacial cartilage has been identified in multiple human syndromes. However, the mechanisms of their development remain largely unknown. In the present study, we identified Pdgfra as a novel player of chondrocranial cartilage development. Our data show that Pdgfra is required for normal chondrocranial cartilage development. Using tissue-specific genetic tools, we demonstrated that Pdgfra is essential for chondrocyte progenitors formation, but not in mature chondrocytes. Further analysis revealed that Pdgfra regulates chondrocytes progenitors development at two stages: in embryonic mesenchymal stem cells (eMSCs), Pdgfra directs their differentiation toward chondrocyte progenitors; in chondrocytes progenitors, Pdgfra activation promotes cell proliferation. We also found that excessive Pdgfra activity causes ectopic cartilage formation. Our data show that Pdgfra directs eMSCs differentiation via inhibiting Wnt9a transcription and its downstream signaling, and activating Wnt signaling rescues ectopic cartilage phenotype caused by excessive Pdgfra activity. In summary, our study dissected the role of Pdgfra signaling in chondrocranial cartilage formation, and illustrated the underlying mechanisms at multiple stages.