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Fig. 2. Nodal signalling controls gastrulation independently of mesendoderm induction. (A) Xenopus embryos were subjected to 200 μM SB-505124 as indicated and analysed by WISH at early neurula stage. Notochord elongation, visualised by Xbra and Xnot-2 staining (dashed lines), is reduced upon drug treatment prior to stage 11. The distance between the blastopore and the prechordal mesoderm expressing goosecoid (dashed line) is reduced in these embryos. (B) Late gastrula (stage 12) embryos were sectioned (50 μm) and stained for Xlim-1 to reveal the extending notochord, and for sox2 to mark the neural plate. The notochord was wider in drug-treated embryos, whereas the thickness of the neural tissue was unaffected. Note the absence of Brachet's cleft (arrows). (C) Immunostaining was used to reveal differentiated somitic muscles (12.101) and notochord (MZ15) at late tailbud stage. Horizontal sectioning, prior to staining, revealed the persistent reduction of convergent extension in notochordal tissue (insets). |
