Figure 1—figure supplement 1.

Figure 1—figure supplement 1. This experiment summarizes control experiments that verify that our α-pSmad2 staining protocol detects Nodal signaling activity in wild-type embryos but not MZsmad2, MZoep, or Mvg1 mutants. Pixel intensities are directly comparable between all α-pSmad2 channel images. (A) Flat-mount image of wild-type 50% epiboly embryo stained with DAPI and α-pSmad2 antibody. Images are maximum intensity projections from a representative embryo. (B) Flat-mount image of MZsmad2 50% epiboly embryo stained with DAPI and α-pSmad2 antibody. Images are maximum intensity projections from a representative embryo. (C) Flat-mount image of MZoep 50% epiboly embryo stained with DAPI and α-pSmad2 antibody. Images are maximum intensity projections from a representative embryo. (D) Flat-mount image of Mvg1 50% epiboly embryo stained with DAPI and α-pSmad2 antibody. Images are maximum intensity projections from a representative embryo.