Decreased colony-forming ability of Notch1-IC– and Notch4-IC–transduced normal marrow (BM) and cord cells compared with MIG-transduced cord blood cells. Normal marrow cells (panel A) (Notch1-IC, n = 3; Notch4-IC, n = 4) and cord blood (panel B) (Notch1-IC, n = 4; Notch4-IC, n = 5) were retrovirally transduced with MIG, Notch1-IC, and Notch4-IC and sorted for GFP. Cultures were initiated with 1000 GFP⁺ normal marrow cells (panel A) or 500 cord blood cells (panel B) placed into methylcellulose in the presence of IL-3, IL-6, G-CSF, GM-CSF, and SF, and colonies were counted 10 days after initiation. A paired t test was performed to determine statistical differences between colony numbers in Notch1-IC or Notch4-IC and MIG. Error bars indicate the standard error of the mean. *P ≤ .05. Erythroid colonies are indicated by ▪; granulocyte and/or macrophage colonies, by ▦; and total colonies, by ▧.