During neural tube closure, a crucial event in development of the brain and spinal cord, a flat sheet of epithelial cells is converted into a closed tube. As part of this process, a band of actin that encircles the tip of the columnar neuroectodermal cells contracts like a purse string, turning them into wedge-shaped cells. Jeffrey Hildebrand now reports that the actin-binding protein Shroom is a key regulator of this shape change (see ). Hildebrand shows that Shroom localizes to the apical tip of the adherens junctions of neuroectodermal cells in vivo and that expression of full-length Shroom or its C-terminal domain in polarized MDCK cells causes apical constriction by recruiting F-actin and myosin II to apical junctions. He goes on to show that myosin II accumulation is reduced at apical junctions in the neural tubes of Shroom-mutant mice. Thus, Shroom seems to act as a crucial determinant of epithelial cell shape during neural tube closure by influencing actomyosin distribution.
