Loss of Cxcl4 in hematopoietic cells ameliorates the MPN phenotype and restores MK and platelet abnormalities. (A) Hemoglobin (Hg) counts monitored over time, together with the frequency of GFP⁺ Ter119⁺ cells in peripheral blood and BM 9 weeks’ posttransplant (euthanasia). (B) WBC counts are monitored over time from peripheral blood. (C) Flow cytometric quantification of Gr1⁺ CD11b⁺ (granulocytes) and Gr1^– CD11b⁺ (monocytes) at euthanasia in peripheral blood. (D) Flow cytometric quantification of GFP⁺ Gr1⁺ CD11b⁺ (granulocytes) and GFP⁺ Gr1^– CD11b⁺ (monocytes) at euthanasia in BM. (E) Platelet counts are monitored at 5, 7, and 9 weeks’ posttransplant. Flow cytometric quantification of GFP⁺ CD41⁺ cells in peripheral blood. (F) May-Grünwald-Giemsa (MGG) staining and quantification of the number of platelets per high-powered field in murine blood smears. Original magnification ×100. Scale bar, 10 μm. (G) Flow cytometric quantification of GFP⁺ CD41⁺ (MKs) in BM. (H) Hematoxylin and eosin (HE) staining of 4-μm BM sections (femur) with particular focus on the size and morphology of MKs (blue arrows). Original magnification ×40. Scale bar, 50 μm. (I) Quantification of the mean area of MKs in BM. n = 5 mice/group, 3 males. Data are shown as mean ± standard error of the mean, 1-way analysis of variance followed by Tukey’s post hoc test. *P < .05, **P < .01, ***P < .001, ****P < .0001.