Fig. 6. Wise interferes with Wnt signalling. (A-C) Wise blocks secondary axes induced by Wnt8. Injection of Wnt8 RNA into a ventral vegetal blastomere of four- to eight-cell stage embryos induces complete secondary axis formation (A). Co-injection of Wise blocks formation of Wnt8-induced secondary axes (B), as does co-injection of a dominant-negative dishevelled, Dsh (DIX) (C). (D) Wise functions extracellularly to block induction of siamois and Xnr3 by the Wnt pathway in ventral marginal zone (VMZ) explants. Wise blocks the ability of Wnt8 to induce siamois and Xnr3, but does not interfere with the ability of dishevelled (dsh) or ß-catenin (ß-cat) to induce these markers. DMZ, dorsal marginal zone explant. (E,F) Wise acts as a Wnt inhibitor and complements a truncated BMP receptor (tBR) to induce head structures. When BMP signalling is blocked in the ventral marginal zone by injection of tBR, an incomplete secondary axis is formed (E). Co-injection of tBR and Wise induces a complete secondary axis with eyes (arrows) and cement gland (F).

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