Summary. (A) The three NPFs in C. elegans, WAVE, WASP, and WASH complexes, colocalize with Arp2/3 and control Arp2/3 localization at distinct subcellular locations. (B) Cell–cell signaling makes an essential contribution to apical constriction by basolaterally recruiting Arp2/3 via Rac and WAVE. (C) Rac signaling and myosin-activating kinase are active at opposing locations in migrating and apically constricting cells.