CyclinD1 and the mechanisms of thymic involution

CyclinD1 和胸腺复旧机制

• 批准号: 8708368
• 负责人: Ellen R Richie
• 金额: $ 43.41万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-10 至 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8708368
• 关键词: Affect; Aging; Antigens; Binding; Bone Marrow Transplantation; Boxing; Cell Cycle; Cell Cycle Progression; ChIP-seq; Coupled; Cyclin D1; Cyclins; Data; Development; Differentiation and Growth; Emigrant; Endogenous Factors; Epithelial Cell Proliferation; Exons; Future; Genetic Screening; Genetic Transcription; Goals; Growth; Homeostasis; Hyperplasia; Immune; Immune response; Investigation; Maintenance; Modeling; Mus; Nuclear Receptors; Output; Pathway interactions; Peripheral; Phenotype; Preparation; Protein Isoforms; Proteomics; RNA Splicing; Recovery; Recruitment Activity; Reporting; Signal Transduction; Spleen; T-Cell Development; T-Lymphocyte; Testing; Therapeutic; Thymic epithelial cell; Thymus Gland; Thymus Hyperplasia; Time; Transcription Coactivator; Transcriptional Regulation; Transgenes; Transgenic Mice; Transgenic Organisms; Vaccines; base; chemotherapy; insight; keratin 5; overexpression; pathogen; prevent; progenitor; promoter; thymocyte; tool; transcription factor

DESCRIPTION (provided by applicant): The thymus is essential for T cell development. Thymic epithelial cells (TECs) supply essential growth, differentiation and survival signals as thymocytes differentiate mature to na¿ve T cells and emigrate to the periphery. Thymus involution reduces na¿ve T cell output, which restricts the TCR repertoire and impairs immune responses to newly encountered antigens. Depletion of TECs is a major factor contributing to thymus involution during aging or after cytoablative therapy. We find that enforcing Cyclin D1 expression in keratin 5 (K5) expressing TECs results in a hyperplastic, yet functional thymus that fails to undergo involution during aging. These data suggest that sustained high levels of Cyclin D1 enhances TEC proliferation and differentiation, which, in turn, regulates thymus homeostasis and involution. A major goal of this proposal is to determine the mechanism(s) by which the K5.Cyclin D1 transgene prevents thymus involution. Although Cyclin D1 is a well-known cell cycle regulator, it also functions as a transcriptional regulator. Cyclin D1b is an alternatively spliced isoform in which the cyclin box is retained, but exon 5 is deleted. Exon 5 contains an LxxLL motif, which is a nuclear receptor interaction domain that enhances transcription by recruiting transcriptional coactivators. We find that the thymus involutes within normal time frame in K5.CyclinD1b transgenic mice. The distinct involution phenotypes in K5.Cyclin D1 and K5.Cyclin D1b mice implicate transcriptional regulation as a key mechanism by which enforced expression of Cyclin D1 prevents involution. Consistent with this notion, we find that the K5.Cyclin D1 transgene enhances expression of Foxn1, a transcription factor required for TEC development and maintenance. We will use the K5.CyclinD1 and K5.CyclinD1b transgenic lines to identify endogenous factors and pathways that regulate thymus involution and naive T cell output. Aims 1 and 2 will test the hypothesis that K5.CyclinD1 influences thymus homeostasis both by control of cell cycle progression and by transcriptional regulation. Aim 3 explores the consequences of preventing thymus involution on the composition of the peripheral T cell pool. Since we find an increased number of recent thymic emigrants (RTEs) in spleens of young K5.Cyclin D1 mice, we will test the hypothesis that preventing thymus involution sustains RTE output, which in turn maintains a diverse pool of naive peripheral T cells during aging or after cytoablative therapy. This investigation will provid a rational basis for developing therapeutic strategies to prevent or reverse thymus involution.

描述（由申请人提供）：胸腺对于 T 细胞发育至关重要。当胸腺细胞分化为成熟 T 细胞并迁移到外周时，胸腺上皮细胞 (TEC) 提供必要的生长、分化和生存信号。胸腺退化会减少幼稚 T 细胞的输出，从而限制 TCR 库并损害对新遇到的抗原的免疫反应。 TEC 的耗竭是导致衰老期间或细胞清除治疗后胸腺退化的主要因素。我们发现，在表达角蛋白 5 (K5) 的 TEC 中强制表达 Cyclin D1 会导致胸腺增生但功能正常，且在衰老过程中无法退化。这些数据表明，持续高水平的 Cyclin D1 可增强 TEC 增殖和分化，进而调节胸腺稳态和退化。该提案的一个主要目标是确定 K5.Cyclin D1 转基因防止胸腺退化的机制。尽管 Cyclin D1 是众所周知的细胞周期调节因子，但它也具有转录调节因子的功能。细胞周期蛋白 D1b 是一种选择性剪接同工型，其中细胞周期蛋白框被保留，但外显子 5 被删除。外显子 5 包含一个 LxxLL 基序，它是一个核受体相互作用结构域，通过招募转录共激活因子来增强转录。我们发现 K5.CyclinD1b 转基因小鼠的胸腺在正常时间范围内退化。 K5.Cyclin D1 和 K5.Cyclin D1b 小鼠中不同的复旧表型表明转录调控是 Cyclin D1 强制表达防止复旧的关键机制。与这一观点一致，我们发现 K5.Cyclin D1 转基因增强了 Foxn1 的表达，Foxn1 是 TEC 发育和维持所需的转录因子。我们将使用 K5.CyclinD1 和 K5.CyclinD1b 转基因系来鉴定调节胸腺退化和初始 T 细胞输出的内源因子和途径。目标 1 和 2 将检验 K5.CyclinD1 通过控制细胞周期进程和转录调节影响胸腺稳态的假设。目标 3 探讨防止胸腺复旧对外周 T 细胞池组成的影响。由于我们发现年轻 K5.Cyclin D1 小鼠的脾脏中近期胸腺移出 (RTE) 数量有所增加，因此我们将检验以下假设：防止胸腺退化可维持 RTE 输出，从而在衰老期间或细胞清除治疗后维持初始外周 T 细胞的多样性。这项研究将为制定预防或逆转胸腺退化的治疗策略提供合理的基础。