A fraction of recipient mice that received transplants of total bone marrow cells expressing oncogenic Kras from its endogenous locus developed JMML-like phenotypes. Diseased and control mice were killed approximately 3 months after transplantation when diseased mice became moribund. (A) Diseased mice showed enlarged spleen and liver. Representative histologic H&E sections from spleen (×60) and liver (×60) showed an extensive infiltration of myelomonocytic cells in the splenic and hepatic parenchymas of the recipient mice that received transplants of bone marrow cells expressing oncogenic Kras G12D (original magnifications of camera lenses used to take the pictures listed in parentheses). (B) Flow cytometric analysis of peripheral blood samples from control mice or mice that received transplants of bone marrow cells expressing oncogenic Kras. These density plots were gated on donor-derived, live nucleated cells based on forward scatter, propidium iodide staining, and CD45.2 expression profiles. Representative data are shown. The percentages of cells in regions of interest are indicated. W1 cells were sorted, centrifuged on slides, and stained with May-Grunwald-Giemsa stains to confirm their monocyte identity (right). (C) A total of 105 bone marrow cells were plated in duplicate in semisolid medium with or without GM-CSF. The data were presented as percentages of the maximum number of colonies formed in culture with 0.2 ng/mL GM-CSF. The experiments were repeated independently using cells from at least 3 mice, and representative results obtained from one mouse are shown here. Photomicrographs (original magnification ×20) show wild-type and mutant Kras G12D myeloid progenitor colonies grown in different concentrations of GM-CSF. (D) Platelet counts in peripheral blood and bone marrow (BM) megakaryocyte analysis. CD41+ megakaryocytes from control BM and Kras G12D BM were analyzed for DNA content. Only mature megakaryocytes with 8N and greater ploidy are shown. The percentages of mature megakaryocytes are indicated. (A,D) Student t test was performed. The data are presented as averages plus SD.