Dishevelled phosphorylation, subcellular localization and multimerization regulate its role in early embryogenesis

Dishevelled (Dsh) induces a secondary axis and can translocate to the membr ane when activated by Frizzleds; however, dominant-negative approaches have not supported a role for Dsh in primary asis formation. We demonstrate tha t the Dsh protein is post-translationally modified at the dorsal side of th e embryo: timing and position of this regulation suggests a role of Dsh in dorsal-ventral patterning in Xenopus. To create functional links between th ese properties of Dsh we analyzed the influence of endogenous Frizzleds and the Dsh domain dependency for these characteristics. Xenopus Frizzleds pho sphorylate and translocate Xdsh to the membrane irrespective of their diffe rential ectopic axes inducing abilities, showing that translocation is insu fficient for axis induction. Dsh deletion analysis revealed that axis induc ing abilities did not segregate with Xdsh membrane association. The DIX reg ion and a short stretch at the N-terminus of the DEP domain are necessary f or axis induction while the DEP region is required for Dsh membrane associa tion and its phosphorylation, In addition, Dsh forms homomeric complexes in embryos suggesting that multimerization is important for its proper functi on.