A Ca2+ wave generates a force during cell extrusion in zebrafish

When oncogenic transformed or damaged cells appear within an epithelial sheet, they are apically extruded by surrounding cells. Recently, using cultured mammalian epithelial cells and zebrafish embryonic epithelial cells, we found that a calcium (Ca 2+ ) wave propagates from RasV12-transformed cells and laser-irradiated damaged cells to surrounding cells and promotes apical extrusion by inducing polarized movements of the surrounding cells. In mammalian cell cultures, we reported that the inositol trisphosphate (IP 3 ) receptor, gap junctions, and the mechanosensitive Ca 2+ channel TRPC1 are involved in Ca 2+ wave-mediated polarized movements. However, which molecules regulate Ca 2+ wave-mediated polarized movements in zebrafish and whether the Ca 2+ wave can generate a force remain unknown. In this study, we aimed to answer these questions. By performing pharmacological and gene knockout experiments, we showed that a Ca 2+ wave induced by the IP 3 receptor and trpc1 led to formation of cryptic-lamellipodia and polarized movements of surrounding cells toward extruding cells in zebrafish. By using an in vivo force measurement method, we found that the Ca 2+ wave generated approximately 1 kPa of force toward extruding cells. Our results reveal a previously unidentified molecular mechanism underlying the Ca 2+ wave in zebrafish and demonstrate that the Ca 2+ wave generates a force during cell extrusion.