The Role of LMO2 in the Pathogenesis of T-cell Leukemia

LMO2 在 T 细胞白血病发病机制中的作用

• 批准号: 9762024
• 负责人: Utpal P Dave
• 金额: $ 34.97万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2021-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9762024
• 关键词: Acute T Cell Leukemia; Address; Antigens; Attenuated; BHLH Protein; Binding; Binding Proteins; Cells; ChIP-seq; Complex; Data; Development; Disease; Distal; Distant; Elements; Enhancers; Epigenetic Process; Erythroid; Fibrinogen; GATA1 gene; Gene Expression Profile; Genes; Genetic; Genetic Transcription; Grant; Hematopoietic stem cells; Homodimerization; Human; Knock-out; LIM Domain; LYL1 gene; Leukemic Cell; Link; MYCN gene; Malignant Neoplasms; Mediating; Modeling; Molecular; Mus; Mutagenesis; Mutation; Nature; Oncogenes; Pathogenesis; Protein Binding Domain; Proteins; Regulatory Element; Resistance; Rhombotin 2; Role; Site; Stem cells; T-Cell Development; T-Cell Leukemia; T-Lymphocyte; TAL1 gene; Target Populations; Testing; Transcriptional Regulation; Transgenic Mice; Ubiquitin; Up-Regulation; clinically significant; design; experimental study; gene therapy; genetic approach; improved; leukemia; mutant; novel therapeutics; progenitor; promoter; protein complex; self-renewal; stem-like cell; thymocyte

PROJECT SUMMARY LIM domain only-2 (LMO2) is one of the most frequently deregulated oncogenes in sporadic and gene therapy- induced human acute T-cell lymphoblastic leukemia (T-ALL). Lmo2 encodes an 18 kDa protein that binds class II basic helix-loop-helix transcription factors (i.e. bHLH: TAL1 or LYL1) and GATA factors (GATA1-2) and LIM domain binding protein 1 (LDB1) in a large multi-subunit complex at promoters and enhancers of hematopoietic stem and progenitor cells (HSPCs). LDB1 binds to LMO2 via its LIM interaction domain (LID) and its homodimerization links near and distant E box-GATA sites in erythroid progenitors. The nature of the LMO2-associated protein complex in T-ALL and LMO2's transcriptional targets in T-ALL are not well characterized. We addressed these questions through a mouse genetic approach. We generated CD2-Lmo2 transgenic mice and defined two distinct subtypes of highly penetrant T-ALLs: one class of leukemias had familiar Notch1 mutation and Notch1-target gene upregulation and the second class closely modeled Early T- cell Precursor (ETP-) ALL, a highly treatment-resistant subtype. ETP-ALLs are derived from developing T-cell progenitors, express antigens of other lineages, have a transcriptional profile that resembles hematopoietic stem cells (HSCs), and express LMO2, HHEX, MYCN, MEF2C, and LYL1 oncogenes. All these features are recapitulated in CD2-Lmo2 transgenic mice including the ETP-ALL transcriptional signature, which is upregulated along with Lmo2-induced hematopoietic stem cell- (HSC) like features of differentiation arrest, relative quiescence, and enhanced self-renewal. In preliminary data, LDB1 was concordantly expressed and co-purified with LMO2 protein in ETP-ALL cells. Using conditional deletion in thymocytes, where Ldb1 is dispensable for T-cell development, we discovered that Ldb1 was required for Lmo2-induced T-ALL; through mutagenesis studies, we found specific residues within the LID of LDB1 that are required for LMO2 binding; most strikingly, LDB1 mutant proteins that could not bind LMO2 were unstable. In fact, LDB1 and LMO2 proteins stabilize each other. Additionally, to address the concordant upregulation of LMO2 with specific oncogenes in ETP-ALL, we performed LDB1 ChIP-seq analysis and discovered occupancy of LMO2 and LDB1 at many genes in the ETP-ALL HSC-like signature including LYL1 and HHEX. We also discovered that Hhex is a required transcriptional target for Lmo2-induced T-ALL. In summary, our preliminary data on Lmo2 and T- ALL establishes an essential protein partner, Ldb1, and an essential target, Hhex, in a highly treatment- resistant leukemia, ETP-ALL. In this proposal, we will test the hypothesis that Ldb1 deletion attenuates T-ALL development by reducing the pre-leukemic target population in CD2-Lmo2 transgenic mice. We will also investigate whether Ldb1 deletion causes destabilization of Lmo2 protein by ubiquitin-mediated proteasomal degradation and disrupts transcriptional regulation of key targets such as Hhex.

项目摘要 LIM域仅2（LMO2）是零星和基因治疗中最常见的失控癌基因之一 诱导人类急性T细胞淋巴细胞白血病（T-ALL）。 LMO2编码结合类别的18 kDa蛋白 II基本螺旋 - 环螺旋转录因子（即BHLH：TAL1或LYL1）和GATA因子（GATA1-2）和LIM 在启动子和增强子的大型多生成络合物中，结合蛋白1（LDB1）的结合蛋白1（LDB1） 造血干和祖细胞（HSPC）。 LDB1通过其LIM相互作用域（盖）与LMO2结合 及其同质二聚化链接在红斑祖细胞中附近和遥远的e盒子位点。的本质 T-ALL和LMO2的转录靶标在T-ALL中与LMO2相关的蛋白质复合物不好 特征。我们通过鼠标遗传方法解决了这些问题。我们生成了CD2-LMO2 转基因小鼠并定义了两个高度渗透t alls的两个不同的亚型：一类白血病具有 熟悉的Notch1突变和Notch1靶向基因上调，第二类是紧密建模的早期T- 细胞前体（ETP-）全部，一种高度治疗的亚型。 ETP-ALLS来自开发T细胞 祖细胞（其他谱系的表达抗原）具有类似于造血的转录特征 干细胞（HSC）和表达LMO2，HHEX，MYCN，MEF2C和LYL1致癌基因。所有这些功能是 在CD2-LMO2转基因小鼠中概括，包括ETP所有转录特征， 与LMO2诱导的造血干细胞（HSC）一起上调，如分化停滞的特征， 相对静止，并增强了自我更新。在初步数据中，LDB1一致表达，并且 与ETP-ALL细胞中的LMO2蛋白共纯化。在胸腺细胞中使用条件缺失，其中LDB1为 对于T细胞开发的可分配，我们发现LMO2诱导的T-all所需的LDB1是必需的。通过 诱变研究，我们发现了LMO2结合所需的LDB1盖中的特定残基。 最引人注目的是，无法结合LMO2的LDB1突变蛋白不稳定。实际上，LDB1和LMO2 蛋白质相互稳定。此外，要解决LMO2的一致上调 在ETP-ALL中，我们进行了LDB1芯片序列分析，并发现了LMO2和LDB1的占用率 在ETP-All HSC样特征中的许多基因中，包括LYL1和HHEX。我们还发现HHEX是 LMO2诱导的T-all所需的转录目标。总而言之，我们关于LMO2和T-的初步数据 所有人都在高度治疗中建立了必不可少的蛋白质伴侣LDB1和基本目标HHEX 抗性白血病，ETP-ALL。在此提案中，我们将检验以下假设：LDB1删除会减弱T-All 通过减少CD2-LMO2转基因小鼠中白细胞前靶群的发展。我们也会 研究LDB1缺失是否会导致泛素介导的蛋白酶体对LMO2蛋白的不稳定 降解和破坏关键目标（例如HHEX）的转录调节。