New emerging roles for epithelial cell extrusion

Epithelia use a unique process called 'cell extrusion' to remove cells from a layer, while preserving their barrier function. Specifically, a cell destined to die triggers formation of an actin and myosin-ring in the live neighboring epithelial cells surrounding it, which squeeze the dying cell out. During extrusion, the surrounding cells expand toward one another and meet to fill the gap left by the extruded cell. Recent studies have revealed new roles of extrusion in controlling developmental morphogenesis, maintaining homeostatic cell numbers, and how this process is usurped during bacterial pathogenesis. Here, we review recent advances in new processes that require cell extrusion and the signaling pathways controlling it.