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. 2006 Jun 27;4(7):e225. doi: 10.1371/journal.pbio.0040225

Figure 4. The FGF and Nodal Pathways Control Dorsal Midline and CESN Formation.

Figure 4

(A) bFGF-treated embryos show ectopic expression of the midline marker msxb at the late neurula stage when the treatment starts at the 16-cell or early 32-cell stages. Embryos do not respond to bFGF at the 64-cell stage.

(B) Blocking Erk activity with the pharmacological inhibitor U0126 from the 16-cell stage abolishes dorsal KLF1/2/4 and ETR expression at tailbud stages, while treatment from the late 32-cell stage has no effect on these markers. FGF9/16/20 is sufficient to induce ectopic midline and ESNs formation (arrow), while Lefty prevents dorsal midline formation.

(C) FGF9/16/20 MO–injected embryos show a loss of dorsal KLF1/2/4 expression while embryos injected with a control MO are not affected. (Lateral view, anterior to the left, dorsal to the top in all panels).