EPO and acquired polycythemia vera: Spleens from Jak2V617F/+ mice exhibited large numbers of Epo-independent CFU-E colonies (Fig. 2N), a hallmark feature of PV [19], whereas spleens from Srsf2P95H/+Jak2V617F/+ mice had significantly reduced Epo-independent CFU-E colonies compared to Jak2V617F/+ mice (Fig. 2N).