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Figure 1. Morphogenesis Requires FGFR Signaling Independent of MAPK(A) Western blots against embryo lysates from various stages probed for active MAPK (dp-MAPK) and pan-MAPK. MAPK activity peaked at stage 11 and decreased by stage 14, and then returned at stage 19.(B) Blots for dp-MAPK and pan-MAPK against DMZ lysates at corresponding stages. Again, MAPK activity peaked at stage 11 and decreased sharply at stage 12, remaining low until stage 18.(C) DMZ extension (μm) plotted against the corresponding stage. The majority of extension occurred between stages 12–16. Error bars represent standard deviation.(D) dp-MAPK blots from animal cap lysates incubated for 15 min with and without FGF2 in the presence of increasing concentrations of FGFR1 inhibitor (SU5402) or MEK1 inhibitor (U0126). Both drugs abolished FGF-induced MAPK activation in a dosage-dependent manner.(E) Embryos injected with 10 nl of 2 mM SU5402, U0126, or DMSO into the blastocell and cultured with the same inhibitor at stage 8 or 12.5. Stage 8 treated embryos were fixed at stage 11.5 and 29–30 for in situ hybridization for Xbra and cardiac actin, respectively. Both inhibitors blocked mesoderm specification and gastrulation movements when treated at stage 8. Embryos treated at stage 12.5 with SU5402 exhibited morphogenetic defects, but U0126-treated were unaffected. |
