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，影响着数百万美国人，但没有有效的 干预措施。由于蛋白质的异常聚集而形成的神经原纤维缠结逐渐积累，如 作为tau和A-β(A-β)的蛋白，是AD的神经病理标志。近几年来，中国的作用 TAR DNA结合蛋白43(TDP-43)，是一种DNA和RNA结合蛋白，在 肌萎缩侧索硬化症(ALS)和额颞叶变性(FTLD-TDP)的发病率越来越高 对阿尔茨海默病发病机制的兴趣。TDP-43的病理作用可归因于其在AD中的神经毒性 大脑皮质等不同脑区病理性聚集性增加引起的脑损伤 中枢神经系统功能正常的。然而，TDP-43背后的详细机制作用 介导的AD进展仍然难以捉摸。TDP-43的一个公认的生物学作用是调节 转座子元件(TES)的表达，这是一种占据人类一半以上的高度重复的DNA序列 基因组。TES的一个特点是它们含有一种三链DNA：RNA杂交结构，称为R- 与多种生物事件有关的环，如转录调控和 保持基因组的稳定性。最近的出版物以及我们的初步数据表明， TDP-43在调节R环形成中的作用。我们的长期目标是通过R-loop阐明TDP-43的作用 调控，以控制年龄相关神经退行性变中TE的表达，并将我们的发现转化为 改善AD治疗的临床相关策略。在本应用程序中，我们重点介绍TDP-43如何丢失- 功能障碍导致TE表达改变，从而导致AD的发病。我们令人振奋的初步数据表明： 1)在人类中观察到TE表达的整体变化以及与之相关的R环景观的变化 AD死后脑，与AD小鼠模型不同；2)进化较年轻的TES表现出更高的 一般来说，与更古老的TES相比，它们的表达水平和R-Loop丰度更高，而且它们也含有更多 AD脑内TE/R环的剧烈变化；3)神经细胞中TDP-43的稳定耗竭导致R-环的异常。 TES中的循环改变，同时改变TE表达和5hmC谱；4)TDP-43直接与 与AD相关的TES重叠的神经细胞中的TES亚群，以及5)AD患者的3D皮质 有机化合物证实了阿尔茨海默病的细胞和分子表型，是一个优秀的人体模型系统。 我们将验证TDP-43通过R环在调节TE表达中发挥重要作用的假设 TDP-43功能丧失所致的TE调节异常是AD发病的关键。发现 这些研究将为TE表达的基本规律提供独特的机械性见解 TDP-43的调控，有可能发现新的分子靶点与相关的临床， 翻译和治疗方面的影响。

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.