Colony-forming capacity and actual Cebpa expression levels in Cebpa/EYFP⁺ and Cebpa/EYFP⁺ stem and progenitor populations. (A) Double- sorted EYFP⁺ and EYFP⁻ stem and progenitor cells were cultured in Methocult 3231 with a mixed cytokine cocktail (thrombopoietin, FLT3L, SCF, IL-3, IL-11, GM-CSF, and erythropoietin) and types of colonies were determined morphologically from day 7 to 14. The identity of single colonies was confirmed by staining cells of individual colonies with May-Grünwald-Giemsa. Results show the numbers of colony types of 1 representative of 3 experiments done in triplicates. (B) Indicated EYFP⁺ and EYFP⁻ cell populations were cultured in Methocult 3231 with GM-CSF, and the number of colonies was determined on day 8. Results show the mean ± SD of 3 independent experiments done in triplicate. **P < .01. ***P < .001. All colonies derived from EYFP⁻ progenitor cells eventually became EYFP⁺ after GM-CSF stimulation. (C) Cebpa mRNA levels relative to Gapdh expression in indicated EYFP⁺ and EYFP⁻ cell populations, as determined by quantitative PCR (mean ± SEM; n = 5). *P < .05.