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Fig. 4. Positioning of placodal Six1 and Eya1 expression domains relative to neural plate and neural crest as revealed by whole mount double-staining procedures. (A–H) Dorsal views of neural plate stage Xenopus embryos (anterior is to the left). (I–R) Lateral (I–M, anterior to the left) and frontal (N–R) views of neural fold stage Xenopus embryos. Expression of Sox3, Six1, Slug, and FoxD3 is shown individually (A–D, I–K, and N–P) and after double in situ hybridization (E–G, L–M, and Q–R) or combination of in situ hybridization for FoxD3 with Sox3 immunostaining (H). The crescent of Six1 expression is shown to be closely apposed to the neural plate domain of Sox3 rostrally (E, L, and Q) and to the FoxD3-positive neural crest domain laterally (F, M, and R). Slug- and FoxD3-expressing neural crest cells are located in the lateral outer neural folds adjacent to the Sox3-positive neural plate (C, D, G, and H). Asterisks in E, L, and Q indicate a gap between Sox3 and Six1 expression, corresponding to this Slug- and FoxD3-positive neural crest domain. Arrowheads in L, M, Q, and R emphasize the position of rostral Six1 expression, which is shown to be located between the neural plate domain and the lateral domain of Sox3 expression. However, posteriorly, Six1 expression overlaps broadly with the lateral domain of Sox3 expression as indicated by the arrow in L. |
