The forces and fates of extruding cells

Cell extrusion drives most epithelial cell death while maintaining a functional epithelial barrier. To extrude, a cell produces a lipid signal that triggers the neighboring cells to reorganize actin and myosin basally to squeeze the extruding cell out apically from the barrier. More studies continue to reveal other signals and mechanisms controlling apical extrusion. New developmental studies are uncovering mechanisms controlling basal extrusion, or ingression, which occurs when apical extrusion is defective or during de-differentiation in development. Here, we review recent advances in epithelial extrusion, focusing particularly on forces exerted upon extruding cells and their various later fates ranging from cell death, normal development, and cancer.