Canonical Notch signaling is dispensable for stem and myelo-E progenitor cell replenishment in competitive bone marrow chimeras. (A-C) One million BM cells were harvested from 10- to 14-week-old Rbpj^fl/flMx1^Cre/+ and control (Rbpj^fl/flMx1^+/+ and Rbpj^fl/+Mx1^Cre/+) mice (CD45.2) 4 to 5 weeks after poly(I:C) treatment and transplanted into lethally irradiated wild-type (WT; CD45.1 or CD45.1/2) recipients together with 1 million competitor WT (CD45.1 or CD45.1/2) adult BM cells. Reconstitution of HSC (N = 2 of Rbpj^fl/flMx1^Cre/+ and N = 1 and N = 3 of Rbpj^fl/flMx1^+/+ and Rbpj^fl/+Mx1^Cre/+, respectively) and myeloid progenitor subsets (N = 5 of Rbpj^fl/flMx1^Cre/+, N = 2 of Rbpj^fl/flMx1^+/+, N = 3 of Rbpj^fl/+Mx1^Cre/+) in the BM of engrafted mice was assessed 7 to 9 weeks after transplantation. Percentage donor (CD45.2)-derived reconstitution of (A) HSC (mean ± SD) and (B) myeloid progenitor subsets (mean ±SEM) relative to total BM cells. (C) Mean (SEM) CD45.2 contribution of Rbpj^fl/flMx1^Cre/+ (N = 6) and control (N = 2 and N = 6 of Rbpj^fl/flMx1^+/+ and Rbpj^fl/+Mx1^Cre/+, respectively) BM cells to total NK1.1⁻Mac1⁺ myeloid, NK1.1⁻Mac1⁻CD19⁺ B and NK1.1⁻Mac1⁻CD4/CD8⁺ T cells. (D) Reconstitution of CD45.2-derived blood platelets (CD41⁺CD150⁺eGFP⁻) of total platelets in Vwf-eGFP (CD45.1/2) recipients 4 to 5 weeks after transplantation with 1 million 10- to 11-week-old CD45.2 Rbpj^fl/flMx1^Cre/+ (N = 4) or control Rbpj^fl/+Mx1^Cre/+ (N = 6) BM cells and 1 million Vwf-eGFP (CD45.1/2) competitor BM cells. (Left) Representative FACS profiles of platelet reconstitution in engrafted mice. (Right) Mean (SEM) percentage of CD150⁺CD41⁺ platelets derived from transplanted CD45.2 BM cells. For all data sets (A-D), statistical significance was investigated between Rbpj-deleted and control mice. ***P < .001.