Project 3: Roles of Tau Levels, Sequence and Interactors in Neural Network Dysfunction of Alzheimer's Disease

项目3 -概要 Tau有助于阿尔茨海默病（AD）和许多其他脑部疾病。然而，目前还不确定tau 导致神经元功能障碍和变性，部分原因是实验模型没有优化， 在疾病相关背景下比较不同tau种类的相对致病性。MAPT突变， 编码tau蛋白的基因引起额颞叶变性（FTLD）而不是AD。相比之下，罕见的A152 T tau蛋白的变异增加了这两种疾病的风险。这些关联值得进一步探讨，特别是 作为表达FTLD-突变体tau的模型，广泛用于研究AD中的tau和开发新的AD治疗。 临床AD发作之前是脑中淀粉样蛋白-b（Ab）肽的异常积累，并且许多AD 患者至少有一个载脂蛋白（apo）E4等位基因，这是AD最重要的遗传危险因素。因此，我们认为， 我们将产生新的小鼠模型，结合人类抗体和apoE 4表达，接近生理水平， 人tau蛋白是（1）野生型，如在大多数AD患者中，（2）携带A152 T置换，其增加AD 风险，或（3）携带P301 S突变，其导致FTLD并广泛用于过表达模型。 新模型的全面功能，病理学和转录组学分析，与 项目1、2和4以及核心B，应该对这些tau种类的差异效应及其生物学特性产生新的见解。 在痴呆症发病机制中的作用。我们假设增加AD风险或导致FTLD的tau蛋白种类 它们对神经元和神经网络的完整性和功能的影响不同，特别是当它们结合在一起时。 Aβ和apoE 4。在我们知道哪种形式的tau在不同情况下致病性最强之前， 我们认为，对tau蛋白的实用治疗方法是部分降低总体tau蛋白水平，这是耐受良好的 并且具有传统模型中的优点。因此，我们将使用靶向tau蛋白的反义寡核苷酸（ASO） （1）确定减少人tau是否可以减少神经网络功能障碍、神经变性和 在共表达人Ab和apoE 4的模型中认知能力下降，（2）确定这一点的最佳时机 干预，和（3）揭示最关键的共同致病机制的tau。我们假设阿索- 介导的tau蛋白减少不仅会减少一种或多种新模型中的tau蛋白病理， 缺陷，神经网络功能障碍和认知缺陷，即使它不太可能减少淀粉样蛋白沉积 或斑块相关的小胶质细胞增生。这个实验应该有助于确定何时必须开始tau减少 相对于认知缺陷的发作，它在AD相关背景下具有治疗益处。单- 核/单细胞转录组学分析将用于鉴定细胞类型特异性基因表达变化 以及可能介导tau的致病作用或tau的有益作用的新的分子和细胞机制。 tau减少。这些分析还将有助于项目1和项目2区分 apoE 4和Ab依赖或不依赖于tau蛋白，并可以鉴定新的分子和细胞机制， 在不存在或存在AD相关共病原体的情况下介导tau序列特异性作用。

PROJECT 3 – SUMMARY Tau contributes to Alzheimer’s disease (AD) and many other brain diseases. However, it is uncertain how tau causes neuronal dysfunction and degeneration, in part because experimental models are not optimized to compare the relative pathogenicity of different tau species in disease-relevant contexts. Mutations in MAPT, the gene encoding tau, cause frontotemporal lobar degeneration (FTLD) instead of AD. In contrast, the rare A152T variant of tau increases risk for both types of diseases. These associations merit further exploration, especially as models expressing FTLD-mutant tau are widely used to study tau in AD and to develop novel AD treatments. Clinical AD onset is preceded by abnormal accumulations of amyloid-b (Ab) peptides in brain, and many AD patients have at least one apolipoprotein (apo) E4 allele, the most important genetic risk factor for AD. Therefore, we will generate new mouse models combining human Ab and apoE4 expression with near-physiological levels of human tau that is (1) wildtype, as in most AD patients, (2) carries the A152T substitution, which increases AD risk, or (3) bears the P301S mutation, which causes FTLD and is widely used in overexpression models. Comprehensive functional, pathological, and transcriptomic analyses of the new models, in collaboration with Projects 1, 2, and 4 and Core B, should yield new insights into differential effects of these tau species and their roles in the pathogenesis of dementia. We hypothesize that tau species that increase AD risk or cause FTLD differ in their effects on the integrity and function of neurons and neural networks, especially when combined with Aβ and apoE4. Until we know which forms of tau are most pathogenic in different conditions, the most pragmatic therapeutic approach to tau in our view is partial reduction of overall tau levels, which is well tolerated and has benefits in conventional models. We will therefore use tau-targeting antisense oligonucleotides (ASOs) to (1) determine whether reducing human tau can diminish neural network dysfunction, neurodegeneration and cognitive decline in models co-expressing human Ab and apoE4, (2) define the optimal timing for this intervention, and (3) reveal the most critical co-pathogenic mechanisms of tau. We hypothesize that ASO- mediated tau reduction will diminish not only tau pathology in one or more of the new models, but also synaptic deficits, neural network dysfunction, and cognitive deficits, even though it is unlikely to reduce amyloid deposition or plaque-associated microgliosis. This experiment should help determine when tau reduction must be initiated relative to the onset of cognitive deficits for it to have therapeutic benefits in AD-relevant contexts. Single- nucleus/single-cell transcriptomic analyses will be used to identify cell-type-specific gene expression changes and novel molecular and cellular mechanisms that may mediate pathogenic effects of tau or beneficial effects of tau reduction. These analyses will also help Projects 1 and 2 distinguish between pathogenic mechanisms of apoE4 and Ab that do or do not depend on tau and could identify novel molecular and cellular mechanisms that mediate tau sequence-specific effects in the absence or presence of AD-relevant co-pathogens.