JAK2-V617F and interferon-α induce megakaryocyte-biased stem cells characterized by decreased long-term functionality

We studied a subset of hematopoietic stem cells (HSCs) that are defined by elevated expression of CD41 (CD41hi) and showed bias for differentiation toward megakaryocytes (Mks). Mouse models of myeloproliferative neoplasms (MPNs) expressing JAK2-V617F (VF) displayed increased frequencies and percentages of the CD41hivs CD41loHSCs compared with wild-type controls. An increase in CD41hiHSCs that correlated with JAK2-V617F mutant allele burden was also found in bone marrow from patients with MPN. CD41hiHSCs produced a higher number of Mk-colonies of HSCs in single-cell cultures in vitro, but showed reduced long-term reconstitution potential compared with CD41loHSCs in competitive transplantations in vivo. RNA expression profiling showed an upregulated cell cycle, Myc, and oxidative phosphorylation gene signatures in CD41hiHSCs, whereas CD41loHSCs showed higher gene expression of interferon and the JAK/STATand TNFα/NFκBsignaling pathways. Higher cell cycle activity and elevated levels of reactive oxygen species were confirmed in CD41hiHSCs by flow cytometry. Expression of Epcr, a marker for quiescent HSCs inversely correlated with expression of CD41 in mice, but did not show such reciprocal expression pattern in patients with MPN. Treatment with interferon-α further increased the frequency and percentage of CD41hiHSCs and reduced the number of JAK2-V617F+HSCs in mice and patients with MPN. The shift toward the CD41hisubset of HSCs by interferon-α provides a possible mechanism of how interferon-α preferentially targets the JAK2mutant clone.