Failure of Erg^+/Mld2 HSCs in stress-induced self-renewal. (A) Analysis of donor Lin⁻Sca⁺cKit⁺ HSC contribution to recipient bone marrow at 4 weeks and 6 months after transplantation of 1 × 10⁶GFP⁺Erg^+/+ or GFP⁺Erg^+/Mld2 unfractionated bone marrow cells into lethally irradiated recipients. The mean ± SD of percentage GFP⁺ donor contribution to the recipient LSK compartment (left panel) and the number of LSK cells per femur per 1000 transplanted LSK cells (right panel) are shown for 3 independent experiments with 4 recipients per donor. GFP⁺Erg^+/+ (open bars) and GFP⁺Erg^+/Mld2 (closed bars). *P < .005. **P < .02. (B) Recovery of the LSK (left panel) and Lin⁻cKit⁺Sca1⁻ committed myeloid progenitor cell fraction (right panel) after exposure of Erg^+/+ mice (○) and Erg^+/Mld2 (●) to 350 cGy sublethal irradiation. Data are mean ± SD of data from 3-6 mice per genotype per time point. *P ≤ .02. **P ≤ .0025. (C) Survival curve of lethally irradiated secondary transplant recipients receiving 5 × 10⁵ to 1 × 10⁶GFP⁺Erg^+/+ (solid line) or GFP⁺Erg^+/Mld2 (broken line) bone marrow cells from primary recipients 6 months after injection with 1 × 10⁶ unfractionated bone marrow cells from GFP⁺Erg^+/+ or GFP⁺Erg^+/Mld2 primary donors. Data shown are from 3 independent experiments with 4 recipients per transplant. (D) Donor-derived erythroid reconstitution at 6 months after transplantation in surviving secondary recipients (2°) of bone marrow from primary (1°) GFP⁺Erg^+/Mld2 recipients relative to GFP⁺Erg^+/+ bone marrow transplanted mice. Data are mean ± SD. *P < .05.