Fig. 7. The differentiation processes from ES cells to mesendoderm cells. ES cells differentiate selectively into the Gsc⁺ECD⁺R⁺ intermediates in serum-free media containing activin. In vitro clonal analysis indicates that this population contains mesendoderm. Gsc⁺ECD⁺R⁺ intermediates diverge to Gsc⁺ECD⁺R^- and Gsc⁺ECD^-R⁺ cells, which further differentiate to endoderm and mesoderm cells, respectively. With this highly selective culture condition and surface markers, it is possible to obtain mesendoderm and their progenies without using Gsc as a marker.