Ldb1 is required for induction of T-ALL in Lmo2-tg mice. (A) Kaplan-Meier survival plot of Ldb1^fl/fl, Ldb1^fl/fl;Lmo2-tg, and Rag1-Cre;Ldb1^fl/fl;Lmo2-tg mice. (B) Ldb1 gene deletion in thymocytes from the 4 Rag1-Cre;Ldb1^fl/fl;Lmo2-tg mice that developed T-ALL. (C) Ldb1 gene deletion in Rag1-Cre;Ldb1^fl/fl;Lmo2-tg thymocytes. Total thymocyte DNA from the indicated mice was used as a template for PCR with primers that amplify the Ldb1⁺ (wt), Ldb1^fl (floxed), or Ldb1^Δ (deleted) alleles. M, molecular weight standard. (D) Western blot of total thymocyte lysates from the indicated mice with anti-Ldb1, anti-Lmo2, or anti-actin (loading control). (E) Kaplan-Meier survival plot of Lmo2-tg and Lck-Cre;Ldb1^fl/fl;Lmo2-tg mice. (F) Ldb1 gene deletion in sorted DN2/3 or DN4 thymocytes from Lck-Cre;Ldb1^fl/fl or Lck-Cre;Ldb1^fl/fl;Lmo2-tg thymocytes. (G) Summary of Rosa26-EGFP^f Cre reporter expression in DN1-4 subsets from Rosa26-EGFP^f;Lck-Cre;Ldb1^fl/fl (n = 10), Rosa26-EGFP^f;Rag1-Cre;Ldb1^fl/fl, (n = 12), and Rosa26-EGFP^f;Il-7ra-Cre;Ldb1^fl/fl (n = 9) mice. Bar graphs show mean and standard deviation of EGFP expression. Panels B, C, and F are 1 representative of 3 experiments.