Cell shape changes brought about by, for example, apical constriction and apicobasal elongation, are a common feature of morphogenesis. But, although the basis of apical constriction is becoming clearer, the molecules that govern apicobasal elongation remain a mystery. Now, on , John Wallingford and colleagues report that Shroom3 - an actin-binding protein - is required for the apicobasal elongation of neuroepithelial cells during Xenopus neural tube closure. Surprisingly, Shroom3 redirects the apical distribution of the microtubule (MT) regulator γ-tubulin, causing apicobasal MT arrays to form, although how γ-tubulin interacts with MTs in this setting is unknown. Since Shroom3 is already known to act in apical constriction, it now appears to be required for both types of neuroepithelial cell shape change during neural tube closure. Shroom1 is also shown to directγ-tubulin redistribution, revealing a conserved function for Shroom proteins. By combining their data with those of earlier studies, the authors propose a model in which epithelial cell shape changes, but not polarity,depend on Shroom3.
