Role of TET2 in normal hematopoiesis and pathogenesis of myeloid malignancies

TET2在正常造血和骨髓恶性肿瘤发病机制中的作用

• 批准号: 9025313
• 负责人: Mingjiang Xu
• 金额: $ 37.8万
• 依托单位: UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9025313
• 关键词: Acute Erythroblastic Leukemia; Acute Myelocytic Leukemia; Age; Age-Months; Alleles; Antibodies; Apoptosis; Behavior; Biological; Biological Assay; Catalytic Domain; Cell Differentiation process; Cells; Chronic Myelomonocytic Leukemia; Cytogenetics; Development; Dysmyelopoietic Syndromes; Erythroid; Exhibits; Family member; Flow Cytometry; Frequencies; Gene Expression; Genes; Genetic; Goals; Hematopoiesis; Hematopoietic; Hematopoietic Stem Cell Transplantation; In Vitro; Knock-in Mouse; Knockout Mice; Lead; MLL gene; Malignant - descriptor; Malignant Neoplasms; Mediating; Methylation; Modeling; Molecular; Molecular Target; Monocytosis; Mus; Mutate; Mutation; Myeloid Leukemia; Myelopoiesis; Myeloproliferative disease; Nature; Pathogenesis; Patients; Pharmaceutical Preparations; Phenotype; Physiological; Promoter Regions; Property; Proteins; Proto-Oncogene Protein c-kit; Regulation; Reporter; Role; Site; Splenomegaly; Stem cells; Testing; Transplantation; Tumor Suppressor Genes; Tumor Suppressor Proteins; White Blood Cell Count procedure; cancer risk; cohort; follow-up; improved; in vivo; leukemogenesis; loss of function; mouse model; novel; paralogous gene; protein complex; protein function; protein purification; reconstitution; self-renewal; small hairpin RNA; stem; tool; tumor

DESCRIPTION (provided by applicant): TET2 gene is mutated and/or deleted with high frequencies in multiple forms of myeloid malignancies including CMML, MDS, MPN and AML. The majority of the TET2 mutations lead to nonsense/frameshift, suggesting loss of function. Therefore, TET2 has been speculated to be a putative tumor suppressor gene that is strongly implicated in the pathogenesis of myeloid malignancies. Small hairpin RNA-mediated depletion of Tet2 in murine hematopoietic stem/progenitor cells (HSC/HPC) alters their cell differentiation and increase the proportion of HSC/HPC in culture, suggesting that Tet2 is important for regulating normal hematopoiesis. The objective of this project is to define the physiological function of Tet2 in vivo and in the pathogenesis of myeloid malignancies. We generated several Tet2-targeted murine models. Tet2- null mice displayed a phenotype resembling CMML at 3 months of age, and ~30% of these mice died by 10 months of age due to the progression to an erythroid/myeloid leukemia-like phenotype. Therefore, these Tet2-null mice allow us to model patients with myeloid malignancy. In a competitive reconstitution assay, Tet2-/- HSCs had an increased hematopoietic repopulating capacity. After transplantation of Tet2-/-, but not control BM cells, two of the seven recipients exhibited CMML phenotype similar to that of Tet2-/- mice. We, therefore, hypothesize that Tet2 acts as a tumor suppressor in myelopoiesis by regulating the behavior of HSC. Three specific aims are proposed: Aim 1: To prove Tet2 acts as a tumor suppressor gene in myelopoiesis by characterizing the phenotype of Tet2-/- and Tet2+/- mice. We will determine the hematological phenotype associated with the loss of Tet2 function in mice. The development of any type of myeloid malignancies at an elevated frequency in Tet2-null mice will add persuasive evidence to support Tet2 as a tumor suppressor gene in myelopoiesis. Aim 2: To define the cellular mechanisms by which loss of Tet2 function in mice leads to myeloid malignancies. We will examine if deletion of Tet2 induces a phenotype that is HSC autonomous by using serial transplantation of HSCs and mouse models with hematopoiesis-specific Tet2 inactivation. Aim 3: To define the molecular mechanisms by which Tet2 exerts its tumor suppressor function in myelopoiesis. We will identify potential genetic targets of Tet2 and Tet2-interacting proteins, which will allow us to unveil the regulatory network of Tet2 and pave a way for uncovering the mechanism by which Tet2 regulates hematopoiesis and exerts its tumor suppressor function. The completion of these studies will greatly improve our understanding of the role of Tet2 in normal hematopoiesis and pathogenesis of myeloid malignancies. This information could lead to the identification of novel molecular targets for the treatment of patients with myeloid malignancies. The Tet2 murine models also offer a biological context in which drugs and other therapies can be tested and developed.

描述（由申请人提供）：TET 2基因在多种形式的骨髓恶性肿瘤（包括CMML、MDS、MPN和AML）中突变和/或缺失频率较高。大多数TET 2突变导致无义/移码，表明功能丧失。因此，TET 2被推测是一个假定的肿瘤抑制基因，与髓系恶性肿瘤的发病机制密切相关。小发夹RNA介导的Tet 2在小鼠造血干/祖细胞（HSC/HPC）中的耗竭改变了它们的细胞分化并增加了培养物中HSC/HPC的比例，表明Tet 2对于调节正常造血是重要的。该项目的目的是确定Tet 2在体内的生理功能和骨髓恶性肿瘤的发病机制。我们产生了几种Tet 2靶向的鼠模型。Tet 2基因敲除小鼠在3月龄时表现出类似CMML的表型，约30%的这些小鼠在10月龄时由于进展为红细胞/髓细胞白血病样表型而死亡。因此，这些Tet 2-null小鼠使我们能够模拟骨髓恶性肿瘤患者。在竞争性重建试验中，Tet 2-/-HSC具有增加的造血重建能力。Tet 2-/-，但不是对照BM细胞移植后，两个7个受体表现出CMML表型类似的Tet 2-/-小鼠。因此，我们推测Tet 2通过调节HSC的行为在骨髓生成中起肿瘤抑制剂的作用。目的1：通过对Tet 2-/-和Tet 2 +/-小鼠骨髓细胞表型的分析，证明Tet 2在骨髓细胞中的抑癌基因作用。我们将确定与小鼠Tet 2功能丧失相关的血液学表型。Tet 2基因敲除小鼠中任何类型的骨髓恶性肿瘤的发生频率升高，这将为支持Tet 2作为骨髓生成中的肿瘤抑制基因提供有说服力的证据。目的2：确定Tet 2功能丧失导致小鼠骨髓恶性肿瘤的细胞机制。我们将通过使用造血干细胞和造血特异性Tet 2失活的小鼠模型的连续移植来检查Tet 2的缺失是否诱导HSC自主的表型。目的3：明确Tet 2在骨髓细胞增殖中发挥抑癌作用的分子机制。我们将确定Tet 2和Tet 2相互作用蛋白的潜在遗传靶点，这将使我们能够揭示Tet 2的调控网络，并为揭示Tet 2调节造血和发挥其肿瘤抑制功能的机制铺平道路。 这些研究的完成将大大提高我们对Tet 2在正常造血和骨髓恶性肿瘤发病机制中的作用的理解。这一信息可能导致识别新的分子靶点，用于治疗骨髓恶性肿瘤患者。Tet 2小鼠模型还提供了一个生物学背景，可以在其中测试和开发药物和其他疗法。