The several uses for junctional actin assembly in epithelial migration. (a) A model of epithelial collective migration into open spaces (a.k.a. “wounds”). Migration is initiated by leader cells at the border with the wound but also involves follower cells behind the leader cells. Cells are linked by cadherin junctions and migrate with lamellipodia; both are sites for Arp2/3 and WAVE-mediated actin assembly. (b) A model for biogenesis of cryptic lamellipodia. Actin assembly is nucleated by Arp2/3-WAVE at cadherin junctions. Where cells retain close apposition, this remains the main site of branched actin nucleation. But when intercellular space is increased, Arp2/3 can flow into the free surface to form a cryptic lamellipodium.