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).