Platelet and ploidy levels in the inducible double-transgenic mice (PF4-tTA-VP16/CMV–Aurora-B/β-gal no. 41/42). Double-transgenic mice and age- and sex-matched wild-type mice were killed after 4 weeks of treatment with and without doxycycline. Blood was withdrawn and subjected to platelet counts (A) as indicated in “Materials and methods.” Data are presented as platelet count averages ± SD for 10 mice in each group. To determine megakaryocyte ploidy status (B), primary bone marrow cells were isolated from the same population of mice, fixed, stained with anti-CD41 (FITC) antibody and propidium iodide, and subjected to flow cytometry analysis. A representative histogram is shown.