Fig. 4

Effects of dnsmad3b or smad3b overexpression on anteroposterior neuroectodermal patterning. Embryos were injected at the one-cell stage with dnsmad3b (dns3b) mRNA (A–D and A′–D′) or smad3b (s3b) mRNA (F–I and F′–I′) at indicated doses, and at around 90% epiboly stage simultaneously examined for the expression of the anterior neural marker otx2 and the posterior neural marker hoxb1b. Embryos were shown in dorsal view (A–H) with animal pole to the top or in lateral view (A′–H′) with animal pole to the top and dorsal to the right. Note that dnsmad3b injection caused both otx2 and hoxb1b domains to shrink from the ventral neuroectoderm but had little effect on the anteroposterior positioning of their boundary. By contrast, smad3b overexpression led to ventral expansion of both otx2 and hoxb1b domains and anterior expansion of the hoxb1b domain. (I, J) Statistical data for dnsmad3b (I) or smad3b (J) injection. The orange color in (J) indicated the proportion of embryos with ventral and anterior expansion of the hoxb1b domain accompanied by anterior reduction of the otx2 domain. The number of observed embryos was indicated in the parentheses.