Convergent extension movements are the main driving force of Xenopus gastrulation. A fine-tuned regulation of cadherin-mediated cell–cell adhesion is thought to be required for this process. Members of the Wnt family of extracellular glycoproteins have been shown to modulate cadherin-mediated cell–cell adhesion, convergent extension movements, and cell differentiation. Here we show that endogenous Wnt/β-catenin signaling activity is essential for convergent extension movements due to its effect on gene expression rather than on cadherins. Our data also suggest that XLEF-1 rather than XTCF-3 is required for convergent extension movements and that XLEF-1 functions in this context in the Wnt/β-catenin pathway to regulate Xnr-3. In contrast, activation of the Wnt/Ca2+ pathway blocks convergent extension movements, with potential regulation of the Wnt/β-catenin pathway at two different levels. PKC, activated by the Wnt/Ca2+ pathway, blocks the Wnt/β-catenin pathway upstream of β-catenin and phosphorylates Dishevelled. CamKII, also activated by the Wnt/Ca2+ pathway, inhibits the Wnt/β-catenin signaling cascade downstream of β-catenin. Thus, an opposing cross-talk of two distinct Wnt signaling cascades regulates convergent extension movements in Xenopus.
