Fig. 5. Forward ephrin-Ad-Eph signals attenuate activation of ERK1/2. (A) Western blot analysis to detect activated ERK1/2 using anti-dpERK1/2 (top panel) in 44-cell-stage embryos following the treatment indicated. Lower panel shows the total amount of ERK1/2 protein, as a loading control. (B-D) Activation of ERK1/2 was detected by immunohistochemistry with the same antibodies in 44-cell-stage embryos following the treatments indicated above the panels. Orange arrows point to notochord precursors and yellow arrows to neural precursors. Histograms below each panel show the number of embryos obtained exhibiting the pattern schematised in the grid below. The grid represents the four neural (upper) and four notochord (lower) precursors. ERK activation is represented by a black dot, with very weak detection indicated by a grey dot.