The Role of p38 MAP Kinase in Branching Morphogenesis of the Embryonic Chicken Lung

Abstract

During lung branching morphogenesis, airway epithelium is remodeled into a highly stereotyped structure in order to promote efficient gas exchange in the mature organism by maximizing the ratio between the surface area and the volume. The process is conserved across many species and organ systems, but it has not been nearly as well characterized in the avian lung as in the mammalian lung. p38 MAP kinase has been implicated in branching morphogenesis of the mammalian lung as well as a breadth of other processes pertaining to the cell cycle and stress response. My first aim was to gain a better understanding of the regulatory role of p38 MAP kinase in branching morphogenesis of the chicken lung by quantifying the phenotype produced in samples cultured with SB202190, a specific inhibitor. The next set of experiments was focused on determining the mechanism by which p38 directs branching morphogenesis. I investigated the impact of p38 inhibition on apical constriction by checking for the characteristic wedge-shaped geometry of apically constricting cells, filamentous actin distribution within these cells, and phosphorylated myosin light chain (pMLC) at the apical surface of new branches using immunofluorescence. I then examined the distribution of E-cadherin under p38 inhibition since E-cadherin is vital to maintaining cell-cell contacts during remodeling of the epithelial tissue. Finally, I looked at the impact of p38 on cellular proliferation using EdU staining. An improved understanding of the role of p38 can teach us more about the mechanisms that drive embryonic chicken lung development and help treat diseases related to faulty lung development in humans.