Increased expression of DSCR1 attenuates calcineurin signaling and leads to an increase in megakaryocytes in vivo. (A) Bone marrow (BM) cytospins from wild-type (WT) and Dscr1 Tg mice were treated with and without ionophore and immunostained with anti-NFATc1 (red) and Hoechst (blue). Arrows indicate megakaryocytes. Bar represents 50 μM. (B) Quantification of CD41-positive BM and spleen megakaryocytes either from WT littermate controls or Dscr1 Tg mice by flow cytometry. (C) Hematoxylin and eosin images of BM and spleen sections from Dscr1 Tg mice demonstrate increased numbers of megakaryocytes. Arrows denote megakaryocytes. Bar represents 25 μM. (D) Quantification of megakaryocytes counted in 5 low power fields is shown on the right. Values are mean ± S.D. **P < .03; *P < .05. (E) Circulating platelet counts in Dscr1 Tg mice and WT littermate controls (n = 11).