JAK2 and anemia (phenotype): The polycythemia induced by JAK2 V617F was maximal at 3 to 4 months post-transplantation, but tended to decrease with time in both strains, with hematocrit and reticulocyte counts returning to nearly normal ranges by 7 to 8 months after transplantation (Figure 5A), and some mice developing overt anemia.