Retroviral mutagenesis with MOL4070LTR in Mx1-Cre, 5A3fl/+ mice. (A) Survival of wt mice (+/+; n = 32), control 5A3fl/+ mice that did not inherit the Mx1-Cre transgene (fl/+; n = 15), and Mx1-Cre, 5A3fl/+ mice (fl/+, Cre, n = 30) treated with MOL4070LTR. In addition, we observed no difference in survival between Mx1-Cre, 5A3fl/+ mice with leukemia in which the latent 5A3 allele was recombined (n = 7) or not recombined (n = 23; data not shown). (B) Southern blot analysis of the bone marrow of 3 mice from the Mx1-Cre, 5A3fl/+ cohort that were diagnosed with acute myelomonocytic leukemia. The primary leukemia is designated P, and transplants are designated TP. The leukemia on the left (no. 40) demonstrated complete recombination, as indicated by the presence of a 20-kb band diagnostic of the del allele and the absence of the 15-kb band diagnostic of the fl allele. The leukemia in the center (no. 18) is partially recombined, as indicated by the presence of the del and fl bands at 20 kb and 15 kb, respectively. The leukemia on the right (no. 102) shows no evidence of the recombined 5A3 allele. (C) Quantitative RT-PCR analysis of the expression of 5 genes within the 5A3 interval in the unrecombined (+/fl Leuk; n = 4) and recombined (+/del Leuk; n = 7) leukemic cells from Mx1-Cre, 5A3fl/+ mice treated with MOL4070LTR. Total RNA was isolated from leukemic cells, and evaluated as described in Figure 2D. Armc10 is the only gene that showed significantly reduced expression in 5A3-excised leukemias (*).
