Fig. 1.

Responses of target genes to either Shh or Fgf ligands. (A and B) Shh ligand dose and Gli1/Ptch1 expression titration curve. Naïve limb progenitors were dosed with varying concentrations of Shh for 24 h. Fgf was present at a fixed concentration of 120 ng/µL. (C) Fgf ligand dose and Sprouty1 expression titration curve. Limb progenitors were treated with increasing doses of Fgf8 for 12 h. (D and E) Fgf ligand dose and Ptch1/Gli1 expression titration curve. Limb progenitors were treated with increasing doses of Fgf8 for 12 h. (F) Shh ligand dose and Sprouty1 expression titration curve. Limb progenitors were treated with increasing doses of Shh for 24 h. (G) Ptch1 temporal titration curves with varying levels of Shh ligand. Limb progenitors were treated for either 10 or 24 h at one of four doses of Shh ligand (0, 0.03, 0.25, and 2 ng/µL). The expression level for each gene was normalized to Actb and depicted as fold change relative to the baseline (no ligand) in A, B, and G. Error bars indicate the SD of three biological replicates of each concentration dose or temporal course.