Histologic morphology, colony growth, and ploidy of CIP4-null MKs do not differ from WT MKs. (A) Histologic studies of MKs in CIP4 KO vs WT mice. Bone marrow sections were stained with hematoxylin and eosin. There were no consistent morphologic differences between MKs from either CIP-null mice or their WT littermates. Photographs were obtained by an Olympus model BX50 with Olympus model DP71 camera and bundled software (Olympus, Tokyo, Japan). Images shown are 1000×; numerical aperture of the objective 1.25. Bars represent 50. (B) CFU-MK assay. Harvested bone marrow cells were cultured for 6 days in collagen-MegaCult medium with TPO 50 ng/mL and IL3 10 ng/mL. At day 6, colonies were stained and counted. No effect of CIP4 deficiency on CFU-MK was seen. Data are shown as the average ± standard error of the mean from 3 to 8 independent experiments. (C) Distribution of ploidy in CD41+ megakaryocytes from WT and CIP4-null mice. Bone marrow cells harvested from femurs were stained with propidium iodine for DNA content and CD41 for megakaryocyte identity, and no difference was found. The cells were then analyzed using Becton-Dickinson flow cytometer LSRII and FlowJo 7.6 software (Tree Star Inc.). A minimum of 3 mice were analyzed per group.