Fig. 4.

Activin and Wnt can induce the development of PS cells in the absence of serum. ES cells were differentiated in serum-free media alone for 2 days. The EBs were dispersed and reaggregated in serum-free media with activin A (Act; in ng/ml), Wnt3a (Wnt; in ng/ml), SB-431542 (SB; in μM), and DKK1 (DKK; in ng/ml) as indicated. The percentages of CD4^hiGFP⁺ and CD4^lo/medGFP⁺ are indicated on the plots. (A) Kinetics of CD4 and GFP expression in cultures induced with activin or Wnt. (B) Expression of CD4 and GFP in day 4 EB cultures after the indicated treatments. (C) Cells were harvested at the indicated times, and gene-expression analysis was performed by RT-PCR.