Increased proliferation of megakaryocyte progenitors in Dscr1 transgenic mice. (A) Increased BrdU uptake by CD41⁺ bone marrow (BM) megakaryocytes from Dscr1 Tg mice as compared with wild-type (WT) littermate controls. Quantification of BrdU-positive CD41⁺ cells (right); *P < .03 (n = 4). (B) Cellular DNA content was examined in CD41-positive BM-derived megakaryocytes from WT and Dscr1 Tg mice by flow cytometry. WT CD41⁺ 2N = 36.3% ± 3.4; Dscr1 Tg CD41⁺ 2N = 49.7% ± 4.7; *P < .03 (n = 7). (C) Increased numbers of megakaryocyte progenitors in the BM of Dscr1 transgenic mice as indicated by flow cytometry of CD9⁺CD41⁺ double-positive cells in the BM. Quantification of CD9⁺CD41⁺ cells (right); **P < .03 (n = 4). (D) Methylcellulose colony assays of BM cells from WT and Dscr1 Tg mice (n = 8). The numbers of CFU-megakaryocyte colonies are counted after staining with acetylcholinesterase. Results are shown as mean ± SD. *P = .001.