Megakaryocyte numbers are increased in MYH9Δ bone marrow. (A) Sections of WT and MYH9Δ bone marrow samples were stained with hematoxylin-eosin. Arrows indicate megakaryocytes; bars: 30 μm. (B) In situ quantification of megakaryocytes in the bone marrow by TEM. Values are the mean plus or minus sem for 3 mice, with 3 transversal sections examined per mouse. **P < .01 using the Student unpaired t test. (C) Ploidy distribution of CD41⁺ bone marrow cells in MYH9Δ and WT mice. The histograms show the distribution of DNA labeling and are representative of 4 mice. (D) Proportion of megakaryocytes in each ploidy class. Results are the mean plus or minus sem for 4 mice.