Fig. 2

U0126 blocks ERK activation, endomesoderm formation, and gastrulation. a–e Control embryos. f–j U0126-treated embryos. a, f Confocal z-sections using anti-phospho-ERK (cyan) to visualize activated ERK. The gray dotted lines indicate the outline of the embryo and yellow arrows the accumulation of phosphorylated ERK (pERK)-positive cells above background levels. b–e, g–j Confocal z-sections using phalloidin (green) to show f-actin filaments and propidium iodide (red) to visualize the nuclei. a, b, f, g Blastula stages [24 hours post fertilization (hpf)]. c, h Late gastrula stages (48 hpf). d, i Early planula (72 hpf). e, j Late planula (96 hpf). All images are lateral views with the animal/oral pole to the top. The insets in a and f correspond to animal pole views. Ratios in g–j indicate the number of embryos displaying the phenotype shown in the image to the total number of analyzed embryos