Fig. 2. Genetic regulation of wntD expression. (A-F) The expression of wntD and sim in wild-type (WT) embryos. Both genes have lateral stripes of expression. Only wntD shows a lower level of expression in ventral cells, and only sim has a characteristic stripe in the posterior region (arrows in C and E). The embryo in E and F showed both characters, indicating that it contained both wntD and sim probes. Panels B, D and F are higher magnifications of the regions indicated by the brackets in A, C and E, respectively. The double in situ hybridization (E,F) shows that the wntD and sim patterns overlap in the mesectoderm. (G) In embryos laid by dorsal^–/– mothers, no wntD staining was observed at any stage of embryogenesis. (H) In embryos laid by Toll^10b mothers, an expansion of wntD expression into the dorsal side was observed. (I) Heterozygous snail embryos had increased expression in ventral cells but the mesectodermal expression was unchanged. (J) In the snail homozygous background, the mesectodermal expression of wntD disappeared, and the ventral staining became stronger. (K) In twist mutant embryos, the wntD pattern was narrower but overall was similar to that observed in wild-type embryos. (L) In twist snail double-mutant embryos, the mesectodermal staining disappeared, while a weaker ventral staining remained. (M) Sagittal view of a wild-type embryo during germ-band extension, showing wntD expression in the neuroectoderm. (N) In embryos that were zygotically mutant for Delta, the wntD expression in the neuroectoderm disappeared.