In vivo BrdU incorporation by WT and Mx1-Cre, Kras^G12D bone marrow cells. (A) Gating strategy for enumerating progenitor populations in bone marrow and spleen, which are quantified in Table 1. (B) Bone marrow and spleen cells were harvested from Mx1-Cre, Kras^G12D (n = 3) and littermate control (n = 3) mice 2 hours after intraperitoneal injection with BrdU. Marrow samples from animals with like genotypes were pooled. CMPs, GMPs, and MEPs were isolated from the pooled samples by FACS and stained for BrdU incorporation (vertical axis) and DNA content (PI; horizontal axis). To assess variation among animals, splenic GMPs were isolated from each of the 3 individual Mx1-Cre, Kras^G12D mice and analyzed as described above (bottom panel).