Fig. 3. FGF signaling is required for neural crest induction by the DLMZ. (A) RT-PCR analysis after SU5402 treatment of the recombinants shows the lack of Slug induction, as well as defective paraxial mesoderm development (MA). Lane 3, DMSO treatment; lane 4, SU5402 treatment. (B) XFD injections (500 pg) in the ectoderm prevent normal induction of the most specific neural crest markers Slug and FoxD3 by the DLMZ. Zic5 and Sox9 are still induced. (C) Similar injections with dnFGFR4a (500 pg) do not prevent neural crest marker induction by the DLMZ. (D) Using situ hybridization, the recombinants show a strong downregulation of Slug expression after XFD injections (third panel) but not after dnFGFR4a injections (fourth panel). First panel, XFD-injected animal caps; second panel, control recombinants.