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Fig. 2. Ventralized embryos do not express markers of differentiated neural tissue. X. laevis embryos were injected in both blastomeres at the two cell stage with β-catenin MO, then raised to the stages indicated, fixed in MEMFA and analyzed by in situ hybridization for expression of differentiated neural markers, the organizer markers chordin and gsc, or fgf8. Uninjected control sibling embryos are shown to the left. (A) ncam, nrp1 and n-tubulin are not expressed in β-catenin morphants. Among stage 14 β-catenin morphants, expression was observed in 0/10 embryos for ncam, 0/10 embryos for nrp, and 0/9 embryos for n-tubulin. At stage 16, expression was observed in 1/12 embryos for ncam, 0/10 embryos for nrp, and 0/10 embryos for n-tubulin. At stage 18, expression was observed in 0/32 embryos for ncam, 0/31 embryos for nrp, and 1/34 embryos for n-tubulin. The two embryos expressing detectable ncam or n-tubulin had morphologically normal neural plates, suggesting that they received a low dose of β-catenin MO. (B) fgf8 is expressed in a ring around the blastopore in β-catenin morphants at stage 14, in a pattern similar to that seen for sox2. This expression fades by stage 18. (C) Gastrula-stage β-catenin morphants do not express the organizer markers chordin or gsc (For chordin, 0/8 morphants showed expression, and 0/9 morphants expressed gsc) Embryos in A and B are shown in dorsal views with anterior to the top, while embryos in C are shown in vegetal views with dorsal to the top. |
