Effects of SU5402, the MEK inhibitor U0126, and the PI3K inhibitor LY294002 on gene expression in the primitive streak region. A-P': Whole mount images showing mRNA expression in control (DMSO), SU5402, U0126 and LY294002 treated embryos. Arrows in C'-D' point to Hensen's node. Brackets in k"-l" indicate the preingression epiblast. Q': Western blot analysis comparing total versus phosphorylated ERK1/2 (p-ERK) and AKT (p-AKT) in the preingression epiblast and primitive streak of DMSO versus SU5402, U0126 and LY294002 treated embryos.