FGF inhibits ρ and enhances endothelial marker expression. (A) HH6-7 embryos are grafted with factor-soaked beads either within (black) or outside (yellow) the future ρ-expressing domain and cultured to HH10. (B-I) FGF4 beads inhibit ρ expression (C,E) and control beads have no effect (B,D). Boxed areas in panels B and C are magnified in panels D and E, respectively. Arrows point to grafted beads and arrowheads show the repression. F (section of E) shows presence of ρ^– cells around the bead. A similar effect is seen with FGF8 (G) but not BMP7 (H) or Noggin (I). (J-N) Expression of Vegfr2 at HH4 (J), 6 (K), and 10 (L). FGF4 beads enhance its expression (M-N). Arrows point to grafted beads. (O-Q) Normal expression of Ets1 at HH4 (O), 6 (P), and 10 (Q). FGF4 beads enhance its expression (R-S).