The transcription factor Sox9 has essential roles in successive steps of the chondrocyte differentiation pathway and is required for expression of Sox5 and Sox6

To examine whether the transcription factor Sox9 has an essential role during the sequential steps of chondrocyte differentiation, we have used the Cre/loxP recombination system to generate mouse embryos in which either Sox9 is missing from undifferentiated mesenchymal cells of limb buds or the Sox9 gene is inactivated after chondrogenic mesenchymal condensations. Inactivation of Sox9 in limb buds before mesenchymal condensations resulted in a complete absence of both cartilage and bone, but markers for the different axes of limb development showed a normal pattern of expression. Apoptotic domains within the developing limbs were expanded, suggesting that Sox9 suppresses apoptosis. Expression of Sox5 and Sox6,…

• MO
  March of Dimes Foundation
• VF
  Volkswagen Foundation
• NI
  National Institutes of Health

  Awards: CA16672, AR42919
• NI
  National Institute of Dental and Craniofacial Research