Fig. 6. Representation of signaling events in early egg cylinder. Wild-type (A), Apc^Min/Min mutants (B) and chimeras with mutant extraembryonic lineages and wild-type epiblast (C). (A) (1) ExE induces proximodistal axis in epiblast and PrE/VE. (2) Through Nodal, epiblast induces the DVE that is restricted distally by Lefty1 and Cer1. (3) DVE distalizes the epiblast by restricting Nodal, cripto and later mesendoderm markers proximally. (4) DVE moves to the anterior side to become AVE. (5) Mesendoderm (T) is induced proximally and afterwards gastrulation movements begin on the posterior side. (B) In Apc^Min/Min mutants, the epiblast is unable to induce the DVE (2). T is not restricted proximally but is induced throughout the epiblast (5). The embryo is proximalized. (C) In chimeras, the extraembryonic tissues ExE and VE (or both) are unable to set up the proximodistal axis (1). Without distal pole, the DVE (Gsc, Hex) is induced throughout the PrE (2). DVE represses mesendoderm induction (3) in the whole epiblast. The embryo is distalized. D, distal; P, proximal.