Defective T-cell development and myeloid hyperplasia are rescued by activated Notch1 (ICN1). Forty-eight hours after infection of 5-fluorouracil-treated Mx-Cre/P^F/F marrow cells with pMig-EGFP-vector or pMig-EGFP-ICN1, 2 to 5 × 10⁵ infected cells (Ly5.2) along with 2 × 10⁵ WT (Lt5.1) protective cells were transferred into lethally irradiated WT (Ly5.1) recipients. Peripheral granulocytes (Gr-1⁺) and T cells (CD4⁺/CD8⁺) were analyzed by FACS 3 to 4 weeks after transplantation in mice receiving Mx-Cre/P^F/F BM progenitors transduced with ICN1 or pMig vector (ICN1 > WT, Mig > WT). Peripheral T (CD4⁺ or CD8⁺; A) and granulocytes (Gr1⁺) (B) were enumerated in transduced GFP⁺ populations and nontransduced GFP⁻ populations (C-D). Data are the pool of 3 independent experiments with 1 or 2 mice of each donor-recipient pair per experiment.