FLVCR-deleted bone marrow chimeras display subtle alterations in platelet numbers. (A) FLVCR^flox/flox;Mx-Cre mice were injected with polyinosinic:polycytidylic acid, and platelet counts were determined by Hemavet. (B) After red cell lysis, bone marrow mononuclear cells from conditionally deleted and normal mice were cultured in StemPro34 media with 100 ng/mL of recombinant human thrombopoietin (rh-TPO) for 5 days. DNA content was determined by staining for CD41 and propidium iodide. (C) Competitive repopulation assay using FLVCR-deleted or control bone marrow cells and GFP⁺ competitor cells. The contribution of each donor population to the platelet count was determined by flow cytometry of peripheral blood. (D) Total bone marrow was isolated from competitive repopulation studies, and the proportion of megakaryocytes derived from FLVCR-deleted or control bone marrow cells was determined by staining for CD41. (E-F) After red cell lysis, bone marrow mononuclear cells from mice competitively transplanted with FLVCR-deleted and wild-type Cre⁺ bone marrow and GFP⁺ competitor cells were cultured in StemPro34 media with 100 ng/mL of rh-TPO for 5 days. DNA content was determined by staining for CD41 and 4,6 diamidino-2-phenylindole (DAPI).