Unperturbed myelo-E progenitor hierarchies in steady-state BM of Rbpj-deficient mice. (A-D) Analysis of hematopoietic stem and myelo-E progenitor cells in 6- to 10-week-old Rbpj^fl/flVav^Cre/+ (N = 8) and Rbpj^fl/flVav^+/+ (N = 4) and Rbpj^fll+Vav^Cre/+ (N = 2) littermate controls. (A) Mean (standard deviation [SD]) BM cellularity per 2 femurs and 2 tibias. (B-D) Representative FACS profiles and mean (SD) frequencies of (B) lineage⁻Sca-1⁺c-Kit⁺CD150⁺Flt3⁻ HSCs and (C-D) myelo-E progenitor subsets. (E) Rbpj expression in HSCs and myelo-E progenitor subsets purified from 8-week-old Rbpj^fl/flVav^Cre/+ (N = 5) and Rbpj^fl/flVav^+/+ or Rbpj^fll+Vav^Cre/+ littermate controls (N = 1 and 2, respectively). Mean (standard error of the mean [SEM]) expression normalized to hypoxanthine phosphoribosyltransferase 1 (Hprt). Samples in which the mean value of replicates was ≤0.001 (relative to Hprt) were considered below cutoff value (#). (F-G) In vitro colony assays using total BM from Rbpj^fl/flMx1^Cre/+ (N = 5-6) and age-matched (10-14-week-old) Rbpj^fl/flMx1^+/+ (N = 2) or Rbpj^fl/+Mx1^Cre/+ (N = 6) control mice treated with Poly(I:C) 4 to 5 weeks before analysis. (F) Mean (SD) in vitro CFU-GM and burst-forming units-E (BFU-E) colonies. (G) Pure (CFU-Mk) and mixed-lineage (Mk-mix) Mk-containing colonies scored after staining with acetylthiocholiniodide. Mean (SD) values from 2 to 3 experiments. (H-I) Mean (SEM [H] or SD [I]) of circulating platelet and red blood cell (RBC) counts in 6- to 10-week-old Rbpj^fl/flVav^Cre/+ (N = 18-12) and age-matched controls (Rbpj^fl/flVav^+/+ [N = 8-11] or Rbpj^fl/+Vav^Cre/+ [N = 2-5]). For all data sets (A-I), statistical significance was investigated between homozygously Rbpj-deleted and control mice. *P < .05; **P < .01; ***P < .001. MegE, Mk-E progenitor; MkP, Mk progenitor; PreGM, pregranulocyte/macrophage progenitor; ProEry, pro-erythroblasts. See also supplemental Figure 1A-G.