The mechanics of epithelial folding*

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. Drosophilagastrulation 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. We find that the apical constriction of these cells constrict via repeated contractile pulses of the cytoskeleton, specifically actin filaments and the molecular motor myosin II. Contractility of the cells results in anisotropic tension, which is essential for the proper orientation of the fold. We are investigating mechanisms that pattern contractility across the tissue to ensure robust folding.