Fig. 4

Fig. 4 Sox3 promotes neural fate in the early ectoderm. Lateral view of mid-gastrula embryos with dorsal to the right unless otherwise indicated. The prospective neural fate markers sox2 and sox31, and the prospective non-neural fate marker gata2 detected by in situ hybridisation are indicated at the top of panels. (A–C) Control wild-type embryos. (D–F) Injection of embryos with sox3 mRNA at the 1–2 cell stage causes expansion of the prospective neural ectoderm marked by sox2 (D, 42/77 embryos) and sox31 (E, 29/48) and loss of prospective non-neural ectoderm marked by gata2 (F, 13/29). (G–I) Injection of sox3 mRNA (with GFP mRNA lineage tracer) at the 16–32 cell stage causes ectopic expression of sox2 (G, 39/76) and sox31 (H, 13/24) and repression of gata2 (L, 41/76) in the injected region. (J–L) Immunostaining for GFP reveals the ectopic Sox3 expressing region (red colour). (M–P) Double in situ hybridisation for the expression of sox31 (blue) and ntl (red, appears brown when overlapping with blue stain). (M) Control wild-type embryo. (N–P) Lateral, animal pole and dorsal view of the same sox3 (16–32 cell) injected embryo. Ectopic sox31 is induced whilst the mesoderm marker ntl is unaffected (15/57). (Q–X) Views of wild-type embryos in which donor cells (dark brown) over-expressing HA-tagged Sox3 were transplanted to the animal pole at oblong stage. Transplanted, Sox3-expressing cells exhibit ectopic expression of the neural markers sox2 (Q–T, 5/5) and sox31 (U–X, 7/7) in a cell autonomous manner. Staining of embryos with anti-HA (dark brown) reveals the position of the transplanted cells (R, T, V, X) showing they are coincident with the ectopic marker expression.