Fig. 3. Wnt signalling regulates AP patterning in gastrula ectoderm. (A) Albino embryos were uninjected (co) or injected at the eight-cell stage into the four animal blastomeres with 0.05 ng/blastomere pCSKA-Xwnt8, 0.05 ng/blastomere (+) or 0.2 ng/blastomere (++) Xdkk1 mRNA. The embryos were cultured until late gastrula stage (stage 12) and analysed by in situ hybridization for the expression of HoxD1, Gbx2, Otx2 and Xanf1. Lateral views are shown, dorsal points to the right. 12-18 embryos were analysed per sample in three independent experiments. (B) Summary of the results shown in A. Colour code of gene expression domains is on the left. The approximate orientation of the prospective ectodermal AP axis is indicated on the left (PA). WT, wild-type embryo with normal Wnt levels.