JAK2 and polycythemia: Interestingly, recipients of Lyn−/−Hck−/−Fgr−/− BM transduced with JAK2 V617F developed polycythemia and reticulocytosis that tended to be greater than recipients of JAK2 V617F-transduced WT donor BM (Figure 6A–6C), although this did not reach statistical significance.