Dishevelled controls cell polarity during Xenopus gastrulation

Although cell movements are vital for establishing the normal architecture of embryos, it is unclear how these movements are regulated during developm ent in vertebrates. Inhibition of Xenopus Dishevelled (Xdsh) function disru pts convergent extension movements of cells during gastrulation, but the me chanism of this effect is unclear, as cell fates are not affected(1). In Dr osophila, Dishevelled controls both cell fate and cell polarity(2-4), but w hether Dishevelled is involved in controlling cell polarity in vertebrate e mbryos has not been investigated. Here we show, using time-lapse confocal m icroscopy, that the failure of cells lacking Xdsh function to undergo conve rgent extension results from defects in cell polarity. Furthermore, Xdsh mu tations that inhibit convergent extension correspond to mutations in Drosop hila Dishevelled that selectively perturb planar cell polarity. Finally, th e localization of Xdsh at the membrane of normal dorsal mesodermal cells is consistent with Xdsh controlling cell polarity. Our results show that pola rized cell behaviour is essential for convergent extension and is controlle d by vertebrate Dishevelled. Thus, a vertebrate equivalent of the Drosophil a planar cell polarity signalling cascade may be required for normal gastru lation.