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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

基本信息

批准号：
9042413
负责人：
Mingjiang Xu
金额：
$ 38.38万
依托单位：
UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-03-01 至 2018-02-28
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9042413
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 Chips Gene Expression Genes Genetic Goals Hematopoiesis Hematopoietic Hematopoietic Stem Cell Transplantation In Vitro Knock-in Knock-in Mouse Knockout Mice Lead LoxP-flanked allele MLL gene Malignant - descriptor Malignant Neoplasms Mediating Methylation Modeling Molecular 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 molecular targeted therapies mouse model novel paralogous gene protein complex protein function protein purification reconstitution self-renewal small hairpin RNA stem tool tumor

项目摘要

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）：TET2基因在多种髓系恶性肿瘤（包括CMML、MDS、MPN和AML）中高频突变和/或缺失。大多数TET2突变导致无义/移码，表明功能丧失。因此，TET2被推测为一种推定的肿瘤抑制基因，与髓系恶性肿瘤的发病机制密切相关。小发卡rna介导的Tet2在小鼠造血干细胞/祖细胞（HSC/HPC）中的缺失改变了它们的细胞分化，增加了培养物中HSC/HPC的比例，提示Tet2在调节正常造血中起重要作用。该项目的目的是确定Tet2在体内和髓系恶性肿瘤发病机制中的生理功能。我们生成了几个tet2靶向小鼠模型。Tet2-缺失小鼠在3月龄时表现出类似于CMML的表型，约30%的小鼠在10月龄时因进展为红细胞/髓系白血病样表型而死亡。因此，这些tet2缺失的小鼠使我们能够模拟髓系恶性肿瘤患者。在竞争性重组实验中，Tet2-/-造血干细胞具有增加的造血再生能力。在移植Tet2-/-而非对照BM细胞后，7名受体中有2名表现出与Tet2-/-小鼠相似的CMML表型。因此，我们假设Tet2通过调节HSC的行为在骨髓形成中起肿瘤抑制作用。提出了三个具体目的：目的1：通过表征Tet2-/-和Tet2+/-小鼠的表型来证明Tet2在骨髓形成中作为肿瘤抑制基因。我们将在小鼠中确定与Tet2功能丧失相关的血液学表型。在Tet2缺失的小鼠中，任何类型的髓系恶性肿瘤的发生频率升高，将为支持Tet2在骨髓形成中作为肿瘤抑制基因提供有说服力的证据。目的2：明确小鼠Tet2功能缺失导致髓系恶性肿瘤的细胞机制。我们将通过造血特异性Tet2失活的小鼠模型和造血干细胞的连续移植来检验Tet2的缺失是否会诱导HSC自主表型。目的3：明确Tet2在骨髓形成中发挥肿瘤抑制功能的分子机制。我们将确定Tet2和Tet2相互作用蛋白的潜在遗传靶点，这将使我们能够揭示Tet2的调控网络，并为揭示Tet2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Tet2在正常造血和髓系恶性肿瘤发病机制中的作用的认识。这一信息可能导致髓系恶性肿瘤患者治疗的新分子靶点的鉴定。Tet2小鼠模型还为药物和其他疗法的测试和开发提供了生物学背景。