Proviral integrations in cells isolated from spleen cells of diseased mice. DNA isolated from spleen cells of a control mouse (lane 1), FLT3-ITD mice (lanes 2-4), and FLT3 D835Y mice with T-phenotype (lane 5) and B-phenotype (lane 6) was digested with EcoRI, which cuts within the proviral sequence and in the flanking genomic sequence. After blotting onto a nylon membrane DNA was probed with a P³²-labeled probe corresponding to the EGFP cDNA to determine the clonality of the disease.