Elucidating the Roles of Transposable Elements in Alzheimer's and related dementias

项目摘要 AD是一种与年龄相关的进行性神经退行性疾病，影响数百万美国人， 干预措施。异常蛋白质聚集形成的神经纤维缠结的逐渐积累，如 作为tau和淀粉样蛋白-β（A β）的蛋白，作为AD的神经病理学标志。近年来， TAR DNA结合蛋白43（TDP-43）是一种DNA和RNA结合蛋白，在临床上已被大量研究。 肌萎缩侧索硬化症（ALS）和额颞叶变性（FTLD-TDP），已经吸引了越来越多的 对AD发病机制的兴趣。TDP-43的病理作用可归因于其在AD中的神经毒性和其在AD中的神经毒性。 由于其在大脑各区域（如皮层）的病理性聚集增加而导致的大脑 中枢神经系统的正常功能。然而，TDP-43的详细机制作用 介导的AD进展仍然难以捉摸。TDP-43的一个既定生物学作用是调节细胞内的 转座子元件（TEs）是一种高度重复的DNA序列，占人类基因组的一半以上， 基因组TE的一个标志是它们具有三链DNA：RNA杂交结构，称为R-RNA。 环，这已被链接到各种各样的生物事件，如转录调控， 基因组稳定性维持。最近的出版物，沿着我们的初步数据，表明直接作用 TDP-43调节R环形成。我们的长期目标是阐明TDP-43的作用，通过R-loop 调节，用于控制年龄相关性神经退行性变中的TE表达，并将我们的发现转化为 改善AD治疗的临床相关策略。在本申请中，我们重点关注TDP-43损失- 功能缺失导致TE表达改变并导致AD发病。我们令人兴奋的初步数据表明： 1)在人类中观察到TE表达的整体改变和R环景观的相关变化 AD死后脑组织中，与AD小鼠模型不同; 2）进化上年轻的TE显示出更高的 表达水平和更强的R-Loop富集比更古老的TE，在一般情况下，他们也拥有更多的 AD脑中TE/R环的剧烈变化; 3）神经元细胞中TDP-43的稳定消耗导致异常的R-环， TE中的环改变，同时改变TE表达和5hmC谱; 4）TDP-43直接结合一个 与AD相关TE重叠的神经元细胞中TE的子集，和5）AD患者衍生的3D皮质 类器官证实了AD的细胞和分子表型，作为一个优秀的人类模型系统。 我们将检验TDP-43通过R环在调节TE表达中起重要作用的假设 由于TDP-43功能丧失导致的TE调节和TE失调对于AD发病机制至关重要。结果 从这些研究将提供独特的机械见解的基本规则TE表达 TDP-43的调节，这有可能发现新的分子靶点， 翻译和治疗的影响。

Project Summary AD is an age-related progressive neurodegenerative disorder affecting millions of Americans without effective interventions. The gradual accumulation of neurofibrillary tangles formed by abnormal protein aggregation, such as tau and amyloid-β (Aβ) protein, serves as the neuropathological hallmark of AD. In recent years, the role of TAR DNA-binding protein 43 (TDP-43), a DNA and RNA-binding protein that has been heavily studied in amyotrophic lateral sclerosis (ALS) and fronto-temporal lobar degeneration (FTLD-TDP), has drawn increasing interest for AD pathogenesis. The pathological role of TDP-43 can be attributed to both its neurotoxicity in AD brain caused by its increased pathological aggregation in various brain regions such as the cortex and its loss of normal function in the central nervous system. However, the detailed mechanistic role underlying TDP-43 mediated AD progression remains elusive. One established biological role of TDP-43 is to regulate the expression of transposon elements (TEs), highly repetitive DNA sequences that occupy more than half of human genome. A hallmark of TEs is that they harbor a three-stranded DNA:RNA hybrid structure referred to as R- loops, which have been linked to a wide variety of biological events, such as transcriptional regulation and genomic stability maintenance. Recent publications, along with our preliminary data, suggest a direct role of TDP-43 in regulating R-loop formation. Our long-term goals are to elucidate the role of TDP-43, via R-loop regulation, for controlling TE expression in age-related neurodegeneration, and to translate our findings into clinically relevant strategies for the improved treatment of AD. In this application, we focus on how TDP-43 loss- of-function results in altered TE expression and leads to AD pathogenesis. Our exciting preliminary data suggest: 1) Global alteration of TE expression and associated changes of the R-loop landscape are observed in human AD postmortem brains and are distinctive from AD mouse model; 2) Evolutionarily younger TEs show higher expression levels and stronger R-Loop enrichment than more ancient TEs, in general, and they also harbor more drastic TE/R-loops changes in AD brains; 3) Stable depletion of TDP-43 in neuronal cells leads to aberrant R- loop alterations in TEs, concurrent with altered TE expression and 5hmC profiling; 4) TDP-43 directly binds to a subset of TEs in neuronal cells which overlap with AD associated TEs, and 5) AD patient derived 3D cortical organoids corroborate cellular and molecular phenotypes of AD, serving as an excellent human model system. We will test the hypothesis that TDP-43 plays an important role in modulating TE expression via R-loop regulation, and TE dysregulation due to TDP-43 loss-of-function is critical for AD pathogenesis. Findings from these studies will provide unique mechanistic insights into the fundamental rules of TE expression regulation by TDP-43, which has the potential to discover new molecular targets with relevant clinical, translational, and therapeutic implications.