Fig. 9. Models of normal axis formation in wild-type embryos, compared to axes rescued in VegT^– and ß-catenin^– embryos by the injection of cm-BMP7 mRNA. (A) A diagrammatic view of normal axis formation at the gastrula (stage 10) and tailbud (stage 26) stages. For simplicity, the gastrulation movements that reverse the anterior-posterior axis are not drawn. (B) The lack of axis formation in a VegT^– embryo injected with cm-BMP7 mRNA at the 8-cell stage in the ventral equatorial region, showing the gene expression profile of these embryos, throughout the gastrula stage. These embryos have abnormal cement glands but no neural tube or notochord. (C) The rescue of the trunk in m ß-catenin^– injected embryos with cm-BMP7 mRNA as in B. The progeny of the cells injected with cm-BMP7 mRNA become the notochord and neural tube and induce somite formation. No cement gland or expanded brain forms because zygotic Wnt8 is expressed downstream of VegT and blocks anterior patterning. (D) The rescue of the trunk and partial rescue of the head in m/z ß-catenin^– embryos injected with cm-BMP7 mRNA as in B. They have notochords, abnormal brains, and enlarged cement glands. Zygotic Wnt 8 mRNA is expressed but its function is blocked because the ß-catenin morpholino oligo blocks translation of ß-catenin protein. In neither C nor D do normal anterior structures form.