Project 1: Activation of Alternative L1 Lifecycles in the CNS with age and Alzheimer's Disease

项目 1：中枢神经系统中 L1 生命周期的激活随着年龄和阿尔茨海默病的增加

• 批准号: 10333661
• 负责人: John M Sedivy
• 金额: $ 57.97万
• 依托单位: BROWN UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10333661
• 关键词: Address; Age; Age related macular degeneration; Aging; Alzheimer' s Disease; Alzheimer' s disease brain; Alzheimer' s disease model; Alzheimer' s disease related dementia; Amyotrophic Lateral Sclerosis; Astrocytes; Biological Assay; Biological Models; Biology; Brain; Cell Aging; Cell Death; Cell Nucleus; Cells; Cessation of life; Chromatin; Clinical; Clinical Trials; Collaborations; Complementary DNA; Complex; DNA; DNA Damage; Disease; Down-Regulation; Elderly; Elements; Failure; Fibroblasts; Fluorescence Microscopy; Fluorescent Probes; Funding; Genome; Genomics; Heterochromatin; Host Defense Mechanism; Human; Human Genome; Inflammaging; Inflammation; Inflammatory; Innate Immune System; Interferon Type I; Interferons; Intervention; Invaded; Knowledge; L1 Elements; Lead; Link; Location; Long-Term Effects; Messenger RNA; Microglia; Microscopy; Modeling; Molecular; Monitor; Mus; Nerve Degeneration; Neuraxis; Neurodegenerative Disorders; Neuroglia; Neurons; Non-Insulin-Dependent Diabetes Mellitus; Nuclear; Nucleosides; Organism; Outcome; Paste substance; Pathologic; Pathology; Pathway interactions; Phenotype; Process; Proteins; RNA; RNA-Directed DNA Polymerase; Repetitive Sequence; Research Personnel; Resolution; Retrotransposition; Retrotransposon; Reverse Transcriptase Inhibitors; Ribonucleoproteins; Role; Site; Somatic Cell; Sterility; Stimulus; System; TREX1 gene; Tetanus Helper Peptide; Therapeutic; Time; Tissues; Transcript; Up-Regulation; Virus; Visualization; Work; age related; age related neurodegeneration; aged; bioinformatics pipeline; brain tissue; cell type; derepression; experimental study; gene therapy; induced pluripotent stem cell; inhibitor; inhibitor therapy; insight; interest; mitochondrial dysfunction; mouse model; neuroinflammation; novel; overexpression; particle; pseudotoxoplasmosis syndrome; response; senescence; sensor; single molecule; stem cell model; surveillance study; transcriptome sequencing; transposon/insertion element

PROJECT SUMMARY (PROJECT 1) Retrotransposable elements (RTEs) comprise ~45% of the human genome. Known as ‘mobile DNA’ they can insert into new genomic locations using a 'copy and paste' mechanism. This process, retrotransposition, can be deleterious at multiple levels and host organisms have evolved silencing mechanisms to protect their genomes. Until recently RTEs were thought to be largely silent in somatic cells. In the past 10 years evidence started emerging that somatic RTE activity is more frequent than anticipated, with our group contributing important early evidence. It is now apparent that with aging, multiple host defense mechanisms become compromised, and repetitive sequences in general, not just active RTEs, increase their expression. In the previous funding cycle we discovered that LINE-1 (L1) elements are upregulated in senescent cells and generate cytoplasmically local- ized cDNA reverse transcripts. These cDNAs are perceived as invading virus by the host and trigger a Type-I Interferon (IFN-I) response, which in turn stimulates the innate immune system. We believe this leads to a phe- nomenon known as 'sterile inflammation' or 'inflammaging', a known hallmark of aging that has been implicated in a variety of age-related diseases. The central nervous system (CNS) appears to be a 'privileged site' for RTE activity, with relatively high levels of expression and ease of further upregulation. Multiple lines of evidence indi- cate that RTE activation is associated with pathology, and has been linked with several neurodegenerative dis- eases, including Alzheimer’s disease (AD). We hypothesize that activation of RTEs contributes to age-related neurodegenerative diseases by promoting neuroinflammation. However, our knowledge of RTE biology in the CNS is very incomplete and presents a barrier to evaluating and exploiting this new framework. This project will explore the lifecycles of L1s in neuronal and non-neuronal cells of the CNS, the L1 surveillance mechanisms, how they fail, the consequences of that failure, and ultimately, how we can fix this. We will use human iPSC models to mechanistically explore pathways that lead to L1 activation in cells of the CNS, the sensors and down- stream pathways that communicate the presence of L1, and the cell inflammatory, senescence and death pro- cesses that are elicited. We will explore the subcellular lifecycles of L1 particles using high-resolution microscopy to understand where and how their cDNAs are synthesized. We will ablate endogenous L1s as well as overex- press L1s at will to further probe their interactions with host cells. We will extend these studies to normal aged mice, mouse AD models, and human AD brain tissue. We will inhibit the synthesis of L1 cDNAs with nucleoside reverse transcriptase inhibitors to evaluate beneficial effects. The outcome of the work proposed here will provide mechanistic insights into these complex processes and address the therapeutic potential of inhibiting RTEs for the treatment of Alzheimer’s disease, related dementias, and other age-related neurodegenerative diseases.

项目概要（项目1） 逆转录转座因子（RTEs）占人类基因组的45%。被称为“移动的DNA”， 使用“复制和粘贴”机制插入新的基因组位置。这个过程，反转录，可以是 在多个水平上有害，并且宿主生物已经进化出沉默机制来保护它们的基因组。 直到最近，RTEs被认为在体细胞中基本上是沉默的。在过去的10年里， 出现躯体RTE活动比预期的更频繁，我们的小组在早期做出了重要贡献， 证据现在很明显，随着年龄的增长，多种宿主防御机制受到损害， 通常，重复序列，而不仅仅是活性RTE，增加它们的表达。在上一个供资周期， 我们发现LINE-1（L1）元件在衰老细胞中上调，并产生胞质局部- 化cDNA反转录物。这些cDNA被宿主视为入侵病毒，并触发I型 干扰素（IFN-I）反应，进而刺激先天免疫系统。我们相信这会导致一场- 被称为“无菌炎症”或“炎症”的现象，这是一种已知的衰老标志， 与年龄有关的疾病中枢神经系统（CNS）似乎是RTE的“特权部位” 活性，具有相对高的表达水平和易于进一步上调。多条线索显示- 认为RTE激活与病理学有关，并与几种神经退行性疾病有关， 缓解，包括阿尔茨海默病（AD）。我们假设RTE的激活有助于年龄相关的 神经退行性疾病通过促进神经炎症。然而，我们对RTE生物学的了解 CNS是非常不完整的，并提出了一个障碍，以评估和利用这一新的框架。该项目将 探索L1在中枢神经系统神经元和非神经元细胞中的生命周期，L1的监测机制， 他们是如何失败的，失败的后果，以及最终，我们如何解决这个问题。我们将使用人类iPSC 模型，以机械地探索途径，导致L1激活的细胞的中枢神经系统，传感器和向下， 流通路，沟通L1的存在，细胞炎症，衰老和死亡的促 引发的事件。我们将使用高分辨率显微镜探索L1颗粒的亚细胞生命周期 以了解它们的cDNA是在哪里以及如何合成的。我们会切除内源性L1神经元同时过度刺激- 随意按压L1以进一步探测它们与宿主细胞的相互作用。我们将把这些研究扩展到正常年龄 小鼠、小鼠AD模型和人AD脑组织。我们将用核苷抑制L1 cDNA的合成， 逆转录酶抑制剂，以评估有益效果。本报告所建议的工作成果将提供 这些复杂的过程的机制的见解，并解决治疗潜力，抑制RTEs， 阿尔茨海默病、相关痴呆和其他年龄相关神经变性疾病的治疗。