Hematopoietic progenitors are enriched in the MIXL1⁺PDGFRα⁺ fraction of differentiating HESCs. (A) Cell sorting and reculture experiment showing that day 4 GFP⁺ PDGFRα⁻ cells give rise to GFP⁺PDGFRα⁺ cells when cultured in SFM supplemented with BVS. Some GFP⁺ cells can still develop from the GFP⁻ PDGFRα⁻ fraction, but they remained PDGFRα⁻ at the time points examined. The fraction of MIXL1⁺ (red) cells is indicated, as is the proportion of cells in each quadrant (black text). (B) Low-power images of methylcellulose cultures showing that compared with the GFP⁺ PDGFRα⁺ fraction, approximately 5-fold fewer CFCs were present in cell populations expressing only GFP (G⁺P⁻) or PDGFRα (G⁻P⁺) (original magnification, ×12). (C) Results from 5 independent experiments (experiments 1–5) confirmed that the frequency of blast (Bl)-CFCs was highest in the GFP⁺(MIXL1⁺) PDGFRα⁺ fraction. The proportion of each subpopulation present at the time of sorting is shown across the top of the panel. (D) Summary of data in panel C showing that on average the GFP⁺ PDGFRα⁺ fraction contained approximately 300 Bl-CFCs/20 000 cells plated. (E) Summary of the blast colony distribution based on the data in panel C showing that approximately 90% of Bl-CFCs are present in the GFP⁺ PDGFRα⁺ fraction. (F) Graph showing that the frequency Bl-CFCs at day 4 correlates with proportion of cells that are GFP⁺ PDGFRα⁺. Error bars represent SEM. G⁻P⁻, GFP⁻ PDGFRα⁻; G⁺P⁻, GFP⁺PDGFRα⁻; G⁺P⁺, GFP⁺ PDGFRα⁺; G⁻P⁺, GFP⁻ PDGFRα⁺.