gp96/grp94 deletion does not negatively affect megakaryopoiesis. (A) Number of megakaryocytes per field (200× magnification) in bone sections of pooled WT and WT → WT (□, n = 4) and KO and KO → WT (■, n = 4) mice 2-4 weeks PTD. No significant differences were observed in the number of megakaryocytes in nonchimeric and chimeric mice (P > .05). (B) Morphologic analysis of WT and KO bone marrow megakaryocytes by light microscopy after H&E staining and the ultrastructure of the demarcation membrane of megakaryocytes by transmission electron microscopy (magnification, 12 000×). (C) Propidium iodide (PI) ploidy analysis of bone marrow CD41⁺FSC^hiSSC^hi megakaryocytes from WT → WT (top) and KO → WT mice (bottom). Numbers represent percentage of PI⁺ cells indicated over the total population of megakaryocytes. Gray histograms represent control staining of lymphocyte gaiting. (D) Bar graph of megakaryocyte ploidy analysis of 5 WT → WT (□) and 5 KO → WT mice (■). No statistical difference was found between WT and KO mice. (E) BSA gradient–enriched megakaryocytes from WT (n = 3) and KO (n = 3) mice were analyzed for expression of the indicated genes relative to TPO-R expression. TPO-R expression was similar between WT and KO mice. (F) Number of granulocyte-erythroid-monocyte-megakaryocyte (GEMM), erythroid (E), and megakaryocyte (MEG) colonies per 10⁴ cells from WT → WT (n = 2) and KO → WT (n = 2) mice 2 months PTD.