Figure 5. VegT activity in the absence of FGF signaling.

VegT has dose-specific effects in the whole embryo. (C–L) Embryos were injected with different doses of VegT mRNA into one cell at the two-cell stage marked by the lineage tracer nuclear β-gal in red and analyzed at the mid-gastrula stage. All embryos are displayed in lateral views with the blastopore toward the bottom. At a very low dose, VegT mRNA has no detectable effect (C,D). At the 10 pg dose, VegT induces ectopic xbra expression but not sox17 while higher doses induce ectopic sox17 at the focal point of injection and xbra at the periphery (E–L). (M–X) FGF signaling is necessary for VegT-mediated expansion of xbra but not sox17. Embryos were either uninjected, or injected with VegT mRNA (250pg) or FGF8b mRNA (10 pg) and treated with either DMSO or SU5402 as indicated (M–X). At the early gastrula stage embryos were analyzed for xbra and sox17 expression. (Y) is an RTPCR experiment on whole embryos treated as indicated along the top and analyzed for a range of markers. EF1α and ODC were used as loading controls.