Genetic control of upper airway patterning (207.2)

In the trachea and bronchi of the mouse, airway smooth muscle (SM) and cartilage are localized to complementary domains surrounding the airway epithelium. Proper juxtaposition of these tissues produces a balance of elasticity and rigidity that is critical for effective air passage. It is unknown how this tissue complementation is established during development. Here we will present data where we dissected the developmental relationship of these tissues by genetically disrupting either SM formation (through Srf inactivation) or cartilage formation (through Sox9 inactivation), and assessed the impact on the remaining tissue. We found that in both the trachea and main bronchi, loss of one lineage led to an increase in cell number of the remaining lineage. However, only in the main bronchi, but not in the trachea, did the loss of one lineage led to a spatial expansion of the remaining lineage. In addition to SM defects, cartilage-deficient tracheas displayed epithelial phenotypes, including decreased basal ce...