Figure 3.

Restriction of trophectoderm-specific gene expression in the blastocyst. (A) Yap1 is found in the nuclei and weakly within the cytoplasm of all cells at the 8-cell stage. By the late morula stage, Yap1 is restricted to the nucleus of cells on the surface of the embryo and found in the cytoplasm of cells in the embryo interior. (B) In outer cells, Lats kinase is inactive and Yap1 is not phosphorylated. This permits Yap1 translocation into the nucleus, where it associates with Tead4 and promotes Cdx2 expression. Unknown cell contact-related factors promote activation of Lats kinase in inner cells, where it phosphorylates Yap1, preventing its entry into the nucleus.