Strikingly, mutation of Mpl-Y599 prevented Jak2V617F-induced thrombocytosis, with platelet, megakaryocyte and MkP numbers in MplY599F/Y599F;Jak2V617F/+ mice similar to that in parental MplY599F/Y599F animals (Fig. 6A–C, Supplementary Fig. 5A, Supplementary Fig. 6A). This evidence concerns the gene MPL and Thrombocytosis.