| |
Fig. 1. Xenopus laevis Ihh and Hh pathway components are expressed in the neural crest. (A, B, D–F and H) Dorsal views of Xenopus laevis embryos, anterior side is on the left. (C and G) Lateral views. (A) Ihh transcripts are first detected since the late gastrula stage (stage 12.5) in the lateral domains of the neural plate (arrowheads). (B) During neurulation Ihh is expressed in the neural plate and in the neural plate border (arrowheads). No expression is observed in the neural plate midline (small arrow). No staining was observed in the sense probe control (inset). The line (I) indicates the site of transverse section shown in I. (C) Stage 23 embryos show Ihh expression in the cranial neural crest migratory streams (arrowheads), mandibular (m), hyoid (h) and branchial (b), in the optic (Op) and otic (Ot) vesicles, and in the somites (s, arrow). (D) Ptc1 in situ hybridization in a stage14 embryo. Ptc1 expression is observed in the neural folds (arrowheads) and in the lateral neural plate, while expression is absent in the midline (arrow). No staining was observed using the Ptc1 sense probe (inset). The line (J) indicates the site of transverse section shown in J. (E) Smo transcripts are observed in the neural plate and neural plate border in stage 12.5 embryos. (F) Stage 14 embryos show Smo expression in the neural plate and neural folds (arrowheads). The line (K) indicates the site of transverse section shown in K. (G) In stage 22 embryos Smo is expressed in the neural crest migratory streams (arrowheads), optic vesicle and somites. (H) Gli3 transcription factor is expressed in stage 13 embryos at the lateral border of the neural plate and neural folds (arrowheads). The line (L) indicates the site of transverse section shown in L. (I–L) Transverse section of embryos displayed in B, D, F, and H showing Ihh (I), Ptc1 (J), Smo (K), and Gli3 (L) expression. Asterisks indicate neural crest tissue; np, neural plate; n, notochord. (M–O) Double in situ hybridizations for Ihh (purple) and FoxD3 (turquoise), Gli2 (purple) and FoxD3 (turquoise), and Gli3 (purple) and FoxD3 (turquoise). (M’–O’) Transverse sections of embryos displayed in M–O showing that Ihh, Gli2, and Gli3 expressions overlap with FoxD3 in the neural crest territory. (P) Schematic diagram summarizing the expression of Ihh, Gli2, Gli3 and neural crest markers FoxD3, Snail1/2 in the left half of a midneurula stage transversally sectioned embryo. Yellow (Ihh), red (Gli2) and green (Gli3) lines encircle the areas of expression for each gene. NP, neural plate; N notochord; NNE, non-neural ectoderm; M, mesoderm; E, ectoderm. |
