The axial mesendoderm is subdivided into different territories with complementary snail1 and E-cadherin (Cdh1) expression. (A-H) Expression of snail1 genes and that of E-cadherin protein. (A,B) At 70% epiboly, snail1a-expressing cells surround the anterior limit of the hgg1- expressing domain and snail1b transcripts are absent from the hgg1-expressing prechordal plate region. (C,D) These expression domains are better observed in sections. (E) The domain of strong snail1a expression surrounding the hgg1-expressing cells is already present at 60% epiboly. (F) Diagram depicting the domains of snail1a, 1b and hgg1 expression in the anterior half of the embryo. (G,H) snail1b and E-cadherin (Cdh1) expression in the posterior half of an embryo at 90% epiboly. Note the complementary domains of snail1b and cadherin expression (compare E with F). (I) Diagram showing the relationship between the expression of snail1 genes and those of hgg1 and ntl. Also note the inverse correlation between snail1 and Cdh1 expression.