Lateral views (A, D, G, J), frontal views (B, E, H, K), and transverse sections (C, F, I, L-O) of representative embryos expressing Ende at the indicated stages. At the LS stage Ende was expressed in a small population of epiblast cells in the distal half of the embryo, and was absent from the surrounding extra-embryonic endoderm cells (A–C). At early head fold stages Ende was expressed in the anterior most definitive endoderm, and then spread along the proximal half of the embryo to the lateral and posterior definitive endoderm (G–N). Expression in the midline ectoderm in distal tip of embryo was maintained (arrowheads in I, K, O). Late streak (LS), early bud (EB), early head fold (EHF), epiblast (ep), extra-embryonic endoderm (ve), ectoderm (ect), mesoderm (mes)