Deletion of Ldb1 reverses the abnormal phenotype of Lmo2-tg DN thymocytes. (A) Phenotype of Rag1-Cre;Ldb1^fl/fl;Lmo2-tg mice. Upper panels: flow cytometry (FACS) analysis of total thymocytes from the indicated mice stained with fluorochrome-conjugated anti-CD4 and anti-CD8. Lower panels: gated lin^neg DN thymocytes stained with fluorochrome-conjugated anti-c-kit and anti-CD25 to delineate DN (1-4) subsets. One representative of 10 independent experiments. Right panel, numbers of lin^neg (DN) thymocytes from the indicated preleukemic 2- to 3-month-old mice. (B) Lck-Cre-mediated deletion of Ldb1 fails to normalize the Lmo2-tg phenotype. Upper panels: flow cytometry (FACS) analysis of total thymocytes from the indicated mice stained with fluorochrome-conjugated anti-CD4 and anti-CD8. Lower panels: gated lin^neg thymocytes stained with fluorochrome-conjugated anti-c-kit and anti-CD25 to delineate DN (1-4) subsets. One representative of 10 independent experiments. Right panel, numbers of lin^neg (DN) thymocytes from the indicated preleukemic 2- to 3-month-old mice. (C) Histograms showing surface expression of c-kit (upper) or CD25 (lower) on DN2/3 thymocytes from the indicated mice. One representative of 10 independent experiments. (D) Ratio of DN3:DN4 thymocytes in the indicated preleukemic 2- to 3-month-old mice. P values and number of mice per group are shown.