Xwnt11 and the regulation of gastrulation in Xenopus

The molecular basis of gastrulation is poorly understood. In this paper we address this problem by taking advantage of the observation that the transc ription activator Brachyury is essential of gastrulation movements in Xenop us and mouse embryos. We infer from this observation that amongst the targe t genes of Brachyury are some that are involved in the regulation of gastru lation. In the course of a screen for Brachyury targets we identified Xwnt1 1. Use of a dominant-negative Xwnt11 construct confirms that signalling by this class of Wnts is essential for normal gastrulation movements, and furt her investigation suggests that Xwnt11 signals not through the canonical Wn t signalling pathway involving GSK-3 and beta-catenin but through another r oute, which may require small GTPases such as Rho and Rac. Future work will concentrate on elucidating the Xwnt11 signal transduction pathway and on i nvestigating its influence on cell shape polarity during Xenopus gastrulati on.