Flow cytometric analysis of the differentiating ES cells.

Undifferentiated parental ES cells (top row) and ES cells transfected with GFP under the control of Flk-1 promoter/enhancer (bottom row) were cultured on type IV collagen–coated dishes in the absence of LIF and analyzed for the expression of Flk-1 and GFP for 4 days. The results shown are representative of 3 independent experiments.