Figure 6. Selective reduction of the early endoderm markers Cerl and Gsc in Meteorin^{− /−} embryos.

At E7.0, the expression of various developmental markers and Nodal signaling downstream molecules was analyzed by in situ hybridization with each specific probe in Meteorin^+/+ and Meteorin^−/− embryos. (A and B) Brachyury (T) expression levels were comparable in Meteorin^−/− and Meteorin^+/+ embryos. (C–F) The expression levels of Lefty1 and Lefty2, downstream molecules of Nodal signaling, were analyzed. The expression levels of Lefty1 in the anterior visceral endoderm and Lefty2 in the posterior primitive streak in Meteorin^−/− embryos were similar to those of control embryos. (G and H) The expression level of FoxH1, a transcriptional coregulator of Nodal, was not changed in Meteorin^−/− embryos compared to controls. (I and J) Both the expression domain and the level of FoxA2, a marker of the anterior primitive streak, were maintained in Meteorin^−/− embryos. (K and L) Expression of Cerl, a marker of the anterior visceral endoderm and definitive endoderm, was downregulated specifically in the anterior primitive streak region of Meteorin^−/− embryos compared to that of control embryos. (M and N) Sox17 was expressed in extra-embryonic ectoderm and definitive endoderm, and its expression in definitive endoderm was markedly reduced in Meteorin^−/− embryos compared to controls. (O and P) Also, the expression of Gsc, another marker of definitive endoderm, was completely absent in Meteorin^−/− embryos. For all experiments, at least three samples for each genotype were analyzed. All scale bars: 200 µm.