Fig. 4. Axial mesendoderm/definitive endoderm defects in Cripto^3loxP/null embryos. Wild-type and Cripto^3loxP/null embryos at the late head-fold stage (A-L) or early neural plate stage (M-P) are shown as whole mounts and corresponding transverse sections; B,D,F,H,J,L are counterstained with Methyl Green. (A-D) Expression of Shh in the prechordal plate is absent in the Cripto^3loxP/null embryo; instead, a small number of expressing cells (arrows) can be found displaced from the axial midline. (E-H) Expression of Foxa2 in the notochordal plate and prospective floor plate is absent in the Cripto^3loxP/null embryo. (I-L) Gsc expression in the prechordal plate, anterior diencephalic ventral midline neuroectoderm and foregut endoderm is completely abolished in the Cripto^3loxP/null mutant. (M-P) Expression of Cer1 marks the anterior definitive endoderm, but is mostly absent except for scattered staining cells (arrow) in the Cripto hypomorph. Scale bars: 100 µm. ade, anterior definitive endoderm; advm, anterior diencephalic ventral midline; fg, foregut endoderm; pfp, prospective floor plate; pp, prechordal plate.