"Location, Location, Location: Polarizing Contractile Forces in Cells to Sculpt Tissues"

Throughout the lifespan of an organism, epithelial tissues are remodeled to shape organs and organisms and to maintain tissue integrity and homeostasis. Apical constriction is a ubiquitous epithelial cell shape change that promotes epithelia folding and cell/tissue invagination in a variety of biological contexts. Drosophila gastrulation is one of the classic examples of apical constriction, where ventral cells constrict to fold the primitive epithelial sheet and internalize the mesoderm. We find that ventral cells constrict via repeated contractile pulses of actin and the molecular motor myosin II that are stabilized to promote incremental apical constriction, similar to a ratchet. Furthermore, we find that upstream signals that regulate apical constriction and myosin II activity exhibit a polarized spatial organization within the apical domain, which is critical for the ratchet-like cell shape change. We are investigating how biochemical and mechanical signals cooperate to establish cell polarity and how this polarity mediates the transmission of contractile forces across the tissue.