Runx1 is necessary to downregulate key HSC and Meg genes during transition to GMP differentiation state. (A) Relative expression levels of TF genes in Runx1^Δ/Δ versus Runx1^+/+ GMPs. Expression levels (RPKM) in Runx1^+/+ GMPs were set as 1. Shown is the mean value of two independent experiments. Error bars, ±SD. Original P values for the comparison are indicated as *P < .05, **P < .01, ***P < .001, the latter of which have FDR P values ≤ .05. (B) GSEA plots showing top gene sets downregulated in Δ/ΔGMP compared with +/+GMP in four independently conducted microarray analyses. Signature sets for pre-GMP, MkP, HSC, and LSC were taken from published data.^24,84  (C) Bar graph depicting the fold-increase in expression levels for selected genes. Shown is the mean of four independent microarray analyses. Error bars, ±SD. (D) FACS analysis of LSK population, containing all HSC/MPP subtypes for expression of CD41⁺ cells. Bar graph depicts the results of 3 independent experiments. Horizontal line, median; error bars, ±SE. (E) Runx1^+/+ or Runx1^Δ/Δ whole BM cells were transplanted into lethally irradiated recipients. CD41 expression in donor-derived progenitors was analyzed by FACS analysis 14 weeks after transplantation (left). Bar graph depicts the percentage of CD41-expressing cells in Lin⁻Sca1⁻CD45.2⁺ compartment. Each dot represents one recipient mouse. Horizontal line, median; error bars, ±SE. P values were calculated by a unpaired Student t test; **P < .01. (F) Schematic representation of the activating / repressing function of Runx1 in myeloid cell lineages during differentiation. CLP, common lymphoid progenitor.