SETD2 Promotes Megakaryocyte Polyploidization and Platelet Generation through Methylation of α-tubulin

Background Megakaryocytes (MKs) are polyploid cells responsible for producing ∼1011 platelets daily in humans. Unraveling the mechanisms regulating megakaryopoiesis holds the promise for the production of clinical-grade platelets from stem cells, overcoming significant current limitations in platelet transfusion medicine. Previous work identified that loss of the epigenetic regulator SETD2 was associated with an increased platelet count in mice. However, the role of SETD2 in megakaryopoiesis remains unknown. Objective Here, we examined how SETD2 regulated MK development and platelet production using complementary murine and human systems. Methods We manipulated the expression of SETD2 in multiple in vitro and ex vivo models to assess the ploidy of MKs and the function of platelets. Results The genetic ablation of Setd2 increased the number of high-ploidy bone marrow MKs. Peripheral platelet counts in Setd2 knock-out mice were significantly increased ∼2-fold and platelets exhibited normal size, morphology, and function. By knocking down and overexpressing SETD2 in ex vivo human cell systems, we demonstrated that SETD2 negatively regulated MK polyploidization by controlling methylation of α-tubulin, microtubule polymerization, and MK nuclear division. Small molecule inactivation of SETD2 significantly increased the production of high ploidy MKs and platelets from human induced pluripotent stem cells and cord-blood CD34+ cells. Conclusion These findings identify a previously unrecognized role for SETD2 in regulating megakaryopoiesis and highlight the potential of targeting SETD2 to increase platelet production from human cells for transfusion practices.