Concept diagram of Sox9 function in lung development.Sox9 acts downstream of Tbx4/5. Sox9 feeds back negatively on Tbx4 and Tbx5 in the tracheal mesenchyme. Cartilage ring formation requires functional Sox9 expression in the tracheal mesenchyme. Lack of cartilage rings induce altered tracheal epithelium differentiation (increased Clara cells, and decreased basal and goblet cells) and defective development of tracheal vasculature structurest.
Turcatel et al. BMC Biology 2013 11:117 doi:10.1186/1741-7007-11-117