UBC Math Bio Seminar: Adam C. Martin (Online)

Throughout the lifespan of an organism, tissues are remodeled to shape organs and organisms and to maintain tissue integrity and homeostasis. Apical constriction is a ubiquitous cell shape change of epithelial tissues that promotes epithelia folding and cell/tissue invagination in a variety of contexts. Apical constriction promotes tissue bending by changing the shape of constituent cells from a columnar-shape to a wedge-shape. Drosophila gastrulation is one of the classic examples of apical constriction, where cells constrict to fold the primitive epithelial sheet and internalize cells that will give rise to internal organs. The actin cytoskeleton is organized in both time and space to facilitate apical constriction. We found that upstream signals that regulate apical constriction and myosin II activity exhibit a radially polarized spatial organization within the apical domain, which is critical for cell shape change. Furthermore, the cytoskeleton undergoes pulsatile dynamics, which are required for force transmission between cells. Finally, tissue wide forces orient cytoskeletal fibers to promote anisotropic force generation that promotes correct fold orientation.