Project description:Interferon alpha (IFNa) is an effective treatment for patients with myeloproliferative neoplasms (MPN). In addition to inducing hematological responses in most MPN patients, IFNa reduces the JAK2V617F allelic burden and can render the JAK2V617F mutant clone undetectable in some patients. The precise mechanism underlying these responses is incompletely understood and whether the molecular responses that are seen occur due to the effects of IFNa on JAK2V617F mutant stem cells is debated. Using a murine model of Jak2V617F MPN, we investigated the effects of IFNa on Jak2V617F MPN-propagating stem cells in vivo. We report that IFNa treatment induces hematological responses in the model and causes depletion of Jak2V617F MPN-propagating cells over time, impairing disease transplantation. We demonstrate that IFNa treatment induces cell-cycle activation of Jak2V617F mutant long-term hematopoietic stem cells (LT-HSC) and promotes a predetermined erythroid-lineage differentiation program. These findings provide insights into the differential effects of IFNa on Jak2V617F mutant and normal hematopoiesis and suggest that IFNa achieves molecular remissions in MPN patients through its effects on MPN stem cells. Furthermore, these results support combinatorial therapeutic approaches in MPN, by concurrently depleting dormant JAK2V617F MPN-propagating stem cells with IFNa and targeting the proliferating downstream progeny with JAK2-inhibitors or cytotoxic chemotherapy. HSC-enriched population from WT (CD45.1) or Jak2VF knockin (CD45.2), after 4 weeks of interferon alpha or vehicle treatment. N=4 per condition
Project description:Inactivating EZH2 mutations have been associated with myelofibrosis (MF). Moreover, EZH2 mutations co-exist with the JAK2V617F mutation in a significant cases of MF. To determine the effects of concomitant loss of EZH2 and JAK2V617F mutation in hematopoiesis, we generated Ezh2-deficient Jak2V617F-expressing mice. To gain insights into the mechanisms by which Ezh2 deficiency promotes the development of MF in Jak2V617F knock-in mice, we performed microarray gene expression analysis on sorted LT-HSC from control, MxCre;Jak2VF/+ and MxCre;Jak2VF/+ EZH2-/- mice.
