Epithelial morphogenesis during development and wound healing depends on coordinated changes in cell shape. Carl-Philipp Heisenberg and co-workers now describe a conserved mechanism that underlies the critical cell-shape changes that occur at the epithelial margin during both epiboly in zebrafish embryos and dorsal closure in Drosophila embryos (see ). They show that during epiboly (the movement of the outer epithelium over the yolk cell surface), the localized recruitment of actin and myosin 2 within the yolk syncytial layer drives cell-shape changes in the overlying, tightly attached marginal epithelial cells. This recruitment requires Msn1, a zebrafish orthologue of the Drosophila Ste20-like kinase Misshapen. Similarly, Drosophila Misshapen, which when mutated disrupts dorsal closure, is needed for the recruitment of actin and myosin 2, and for the subsequent constriction of epidermal marginal cells during dorsal closure; in this case,though, the marginal cells actively constrict rather than respond to changes in an underlying cell layer. Thus, a largely conserved mechanism underlies epithelial morphogenesis in both Drosophila and zebrafish.
