JAK2 and acquired polycythemia vera: Eight weeks post-transplantation, the mice that received Jak2 p.V617F+Osm-/- BM developed no signs of polycythemia vera (PV), with red blood cell (RBC) count, hematocrit (HCT), and hemoglobin (HGB) values within the normal range, whereas the WT mice presented all the signs of disease (Fig. 6a–d).