Epigenetic regulation of thrombopoiesis

项目摘要 血小板对于止血、血栓形成和炎症反应至关重要。数以亿计的血小板在体内循环 哺乳动物血液，以防止组织损伤时失血。血小板的寿命很短（5-9天）， 人类）;因此，每小时必须产生数百万个血小板以维持其 生理血细胞计数和避免出血的风险。血小板在骨髓中产生， 巨核细胞，其又从造血干细胞和祖细胞（HSPC）发育。虽然 重要的信号通路和转录因子已被证明在血小板中起重要作用， 生物发生（血小板生成），很少有人知道这一过程的表观遗传调控和关键 表观遗传调节因子的参与。因为表观遗传调控因子是调控网络的重要组成部分 在细胞分化过程中与转录因子协同作用， 显著阻碍了控制血小板生成和功能的分子网络的阐明。我们 发表了关于MLL 3/4（混合谱系白血病3&4; KMT 2C/KMT 2D）组蛋白的重要工作 甲基转移酶（KMT）复合物，包括揭示MLL 4在髓系白血病中的重要作用， 对于MLL 3/4复合体衔接子亚基PTIP（Pax与转录激活结构域蛋白-1的相互作用）， 淋巴细胞类别转换重组，最近，在维持正常和白血病造血干细胞 细胞壁龛对于后面的研究，我们已经产生了PTIP条件性失活的小鼠模型， HSPC和一致观察到PTIP缺乏导致血小板减少症。我们最近生成了一个MK- 特异性小鼠模型，并确定观察到的血小板减少是PTIP的内在效应 MK谱系中的缺失。对MLL 4缺陷小鼠进行的初步分析显示， 明显血小板减少根据我们的初步数据和已发表的工作，我们假设PTIP是 通过与MLL 3和MLL 4一起起作用以指导血小板生成所需的血小板生成特异性的血小板生成。 基因表达程序。本项目的目标是确定PTIP的作用及其相关的 KMT MLL 3/4在血小板生成中的作用。预计拟议研究的结果将从根本上 通过进一步定义调节血小板的表观遗传机制来推进血小板生物学领域 一代最后，我们的工作结果可能有助于开发新的体内治疗方法 目的在于增强血小板产生或血小板的离体扩增。我们的长期目标是利用 组蛋白翻译后修饰的可逆性，以促进人类健康。 !

PROJECT SUMMARY Platelets are critical for hemostasis, thrombosis and inflammatory responses. Billions of platelets circulate in mammalian blood to prevent blood loss in case of tissue injury. The lifespan of platelets is short (5-9 days in humans); as a consequence, several million platelets have to be produced every hour to maintain their physiological blood counts and to avoid the risk of bleeding. Platelets are generated in the bone marrow from megakaryocytes that, in turn, develop from hematopoietic stem and progenitor cells (HSPCs). Although important signaling pathways and transcription factors have been shown to play important roles in platelet biogenesis (thrombopoiesis), little is known about the epigenetic regulation of this process and the key epigenetic regulators involved. Because epigenetic regulators are essential components of regulatory networks that act collaboratively with transcription factors during cellular differentiation, lack of such knowledge significantly hinders the elucidation of the molecular networks controlling platelet generation and function. We have published significant work on the MLL3/4 (mixed lineage leukemia 3&4; KMT2C/KMT2D) histone methyltransferase (KMT) complex, including uncovering an important role for MLL4 in myeloid leukemia, a role for the MLL3/4 complex adaptor subunit PTIP (Pax interaction with transcription-activation domain protein-1) in lymphocyte class switch recombination and, recently, in maintaining normal and leukemic hematopoietic stem cell niches. For the latter studies, we have generated a mouse model of conditional inactivation of PTIP in HSPCs and consistently observed that PTIP deficiency led to thrombocytopenia. We recently generated a MK- specific mouse model and established that the observed reduction in platelets is an intrinsic effect of PTIP deletion in the MK lineage. Preliminary analysis performed on MLL4-deficient mice revealed mild, but significant, thrombocytopenia. Based on our preliminary data and published work, we hypothesize that PTIP is required for platelet generation by functioning together with MLL3 and MLL4 to direct a thrombopoiesis-specific gene expression program. The objective of this project is to determine the role of PTIP and its associated KMTs MLL3/4 in platelet generation. Results from the proposed studies are expected to fundamentally advance the fields of platelet biology by further defining the epigenetic mechanisms that regulate platelet generation. Finally, results from our work will likely contribute to the development of novel in vivo therapies aimed at enhancing platelet production or ex vivo expansion of platelets. Our long-term goal is to harness the reversibility of post-translation modifications of histones to promote human health. !