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Fig. 6 In post-gastrula zebrafish and Xenopus embryos the neural crest domain overlaps with the dorsal-anterior domain of BMP activity.
(A) At early segmentation stages of zebrafish development the domains of expression of SNW1 and Sox10 partially overlap with the anterior “horseshoe” domain of BMP activity. Transgenic BRE-mRFP zebrafish embryos were stained for SNW1 (grey-purple) and Sox10 (dark blue), Sox10 (dark blue) and mRFP (grey-purple), mRFP (dark blue) and SNW1 (turquoise), mRFP (dark blue) and Hgg1 (maroon), or SNW1 (dark blue) and Hgg1 (maroon) at 11 hpf and 13 hpf. mRFP staining indicates regions of BMP activity. (B) A diagram representing the staining patterns of the four markers is shown. At 11 hpf, domains of expression of SNW1, Sox10, and mRFP partially overlap at the lateral edges of the dorsal-anterior horseshoe domain. However at 13 hpf, it is clear that although the neural crest marker Sox10 is still adjacent to the domain of SNW1 expression in the neural plate, the horseshoe mRFP expression domain (red arrowheads in [A]) is separated from the Sox10 and SNW1 expression domains. (C) Wild-type stage 13 Xenopus embryos were bisected transversely through the neural crest region. The anterior half was immunostained with an antibody against p-Smad1, and the posterior half was used for WISH against Slug. The embryos were then imaged along the plane of bisection and overlayed. The yellow lines outline the boundaries of detected p-Smad1 staining at the neural plate border, which overlaps with the Slug-positive neural crest cells.