1. Eomes-deficient epiblast exhibits normal Fgf8/Snail expression but fails to downregulate E-cadherin.
Eomes-deficient epiblast exhibits normal Fgf8/Snail expression but fails to downregulate E-cadherin. (A) Scanning electron microscopy of transverse sections through E7.5 control and Eomes mutant embryos shows the mesenchymal morphology of cells accumulating at the primitive streak of mutant embryos. Eomes mutants are devoid of a mesodermal cell layer. (B) Immunofluorescence staining using an anti-E-cadherin antibody in E7.5 Eomes mutant embryos reveals failure of E-cadherin downregulation at the PS stage. Whereas mesoderm of wild-type embryos is devoid of E-cadherin (arrowhead), the distinctive tissue mass in mutants retains E-cadherin. (C,D) Fgf8 and Snail are expressed at appropriate sites and with normal intensity in EomesN/CA; Sox2.Cre embryos when analysed by whole-mount in situ hybridisation (C) or in situ hybridisation on sections (D). The mutant PS shows overlapping expression of E-cadherin and Snail, whereas in wild-type controls the expression domains are mutually exclusive. (C) The Fgf target Spry2 is widely expressed in Eomes mutants. (E) Wild-type and Eomes mutant primitive streak explant cultures show indistinguishable migration behaviour and efficiently downregulate E-cadherin in migrating cells. Broken lines indicate the border of E-cadherin-positive explants.
Sebastian J. Arnold et al. Development 2008;135:
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