Fig. 2. Differentiation of mouse ES cells. (A) Mouse ES cells differentiate into three cell types - primitive endoderm, trophectoderm (TE) and primitive ectoderm - mimicking the differentiation potential of pluripotent stem cells in preimplantation embryos. (B-E) Different culture conditions can induce ES cells to differentiate into certain lineages. (B) In the absence of Lif and in the presence of an excess of Oct3/4, ES cells differentiate into primitive endoderm-like cells, whereas (C) in the absence of Nanog and in the presence of Gata6, they differentiate into parietal endoderm-like cells. (D,E) Removing Oct3/4 from, and adding Cdx2 to, ES cell culture induces TE-like differentiation. MEFc, mouse embryonic fibroblast conditioned medium.