RUNX1 activity promotes megakaryocytic fate in human MEPs. (A) Summary of human progenitor populations analyzed (left) and data predicting that RUNX1 regulates the differential gene expression between these populations (right). Shown are the number of DEGs that are increased (red) or decreased (blue) in expression between population pairs. Number of predicted RUNX1 target genes and adjusted P values from Enrichr. (B) Effects on colony formation of MEPs transduced with retrovirus encoding full-length RUNX1 or empty vector control. (C) Effects on colony formation of MEPs treated with DMSO (control) or 2 μM Ro5-3335 for 48 hours before plating for colony formation in the absence of drug. (D) Effects on colony formation of MEPs treated with 50 nM all-trans retinoic acid (ATRA) or 50 nM Rapamycin (Rapa), with or without 2 μM Ro5-3335 (Ro5) for 48 hours before plating for colony formation in the absence of drug. Colony types were determined based on CD41 and CD235 immunofluorescence. Mk/E, colonies contain both erythroid and megakaryocytic cells, Mk, megakaryocyte only colonies, E, erythroid only colonies. Each figure represents 3 individual experiments. Average ± standard deviation (SD) are graphed (∗P < .05, ∗∗P < .01). Data from individual experiments provided in supplemental Figure 2.