Calcium wave propagation during cell extrusion.

Oncogenically transformed or apoptotic cells are removed from epithelial sheets by cell-cell communication between the transformed/apoptotic cells (extruding cells) and the nearest neighboring cells. Cell extrusion is driven by actomyosin contraction and lamellipodial crawling of the nearest neighboring cells. Recent studies have found that distal cell communication also plays a role in cell extrusion. Specifically, distal cells located 3-16 cells away from the extruding cell are coordinated by calcium waves and collectively migrate toward the extruding cell to initiate cell extrusion. Here, I describe how calcium waves are generated and contribute to the extrusion of cells in mammals and zebrafish.