Project 1: Differential Roles of ApoE Isoforms in Neural Network Dysfunction of Alzheimer's Disease

项目1-摘要 阿尔茨海默病(AD)的复杂性和多因素特性对机械学提出了独特的挑战 研究和开发治疗方法。虽然AD-淀粉样β-多肽的三大致病因素， Tau和载脂蛋白E4(ApoE4)作为AD发病机制中的独立实体已被广泛研究。 针对单个AD相关途径的努力，如抗体的产生或清除，在人类中基本上失败了 审判。新出现的证据有力地表明，阿尔茨海默病是年龄依赖神经网络的结果 主要影响认知的大脑区域的功能障碍，可能是通过多个 致病因素。因此，迫切需要确定新的机制和治疗目标，在 神经网络层面和多种致病因素相互作用的背景下--这是本文的重点 求婚。 载脂蛋白E4编码人类载脂蛋白E的三种主要亚型之一，是罹患 并以基因剂量依赖的方式降低发病年龄。在大多数临床研究中，APOE4携带者 占AD病例的60%-75%，突显了APOE4在AD发病机制中的重要性。另一方面， 许多临床和人群研究表明，编码最罕见的载脂蛋白E亚型的APOE2具有很强的保护性 阿尔茨海默病的遗传因素。阿尔茨海默病的一个病理特征是形成神经原纤维缠结(NFT)，包括 一种过度磷酸化的不溶性tau，包含3R和4R两种tau异构体。在细胞培养和小鼠中 模型中，apoE亚型具有tau依赖的差异效应，tau具有apoE亚型依赖的差异效应， 提示交互作用在AD发病机制中的作用。然而，几乎所有这些关于载脂蛋白E亚型和tau的研究 得出的结论要么是基于老鼠tau，它几乎只存在于4R tau，要么是基于突变的人类 Tau，它与额颞部痴呆有关，但与阿尔茨海默病无关。在项目1中，我们建议确定单元格- 载脂蛋白E亚型在年龄依赖性神经网络功能障碍和行为障碍中的类型特异性和差异性作用 在野生型(WT)人tau(3R和4R tau亚型)背景下的缺陷，在AD的新小鼠模型中。 在目标1中，我们将确定载脂蛋白E亚型在神经网络功能障碍和行为学中的不同作用 缺陷，使用apoE-异构体-牙线敲入(APOEfE2/Fe2[Fe2]，APOEfE3/Fe3[Fe3]，和APOEfE4/FE4[FE4])小鼠 WT人tau(MAPT基因敲入或TAUWT)在不同年龄段的表达。在目标2中，我们将确定细胞类型- 载脂蛋白E亚型在神经网络功能障碍和行为缺陷中的特定、不同的作用 表达细胞类型特异性Cre重组酶(神经元特异性)的Fe2/TAUWT、Fe3/TAUWT和FE4/TAUWT小鼠 Cresyn1、星形胶质细胞特异的CreGFAP和小胶质细胞特异的CreCx3cr1)，以删除细胞中的APOE等位基因- 特定于类型的方式。本项目的研究，以及本项目的其他三个项目的研究 项目拨款，将对AD的多因素发病机制产生新的见解，并可能识别神经网络- 基于载脂蛋白E异构体依赖和细胞类型特异性治疗的靶点，以治疗或预防AD。

PROJECT 1 – SUMMARY The complexity and multifactorial nature of Alzheimer’s disease (AD) pose unique challenges for mechanistic studies and developing therapies. Although the three major pathogenic factors of AD—amyloid-beta peptides, tau, and apolipoprotein E4 (apoE4)—have been extensively studied as independent entities in AD pathogenesis, efforts to target individual AD-related pathways, such as Ab production or clearance, have largely failed in human trials. Emerging evidence strongly suggests that AD is a consequence of age-dependent neural network dysfunction in brain regions that mostly affect cognition, likely through the interactive effects of multiple pathogenic factors. Thus, there is a pressing need to identify novel mechanisms and therapeutic targets, at a neural network level and in the context of interactions between multiple pathogenic factors—the focus of this proposal. APOE4, which encodes one of the three major isoforms of apoE in humans, is the major genetic risk factor for AD and lowers the age of onset in a gene dose-dependent manner. In most clinical studies, APOE4 carriers account for 60–75% of AD cases, highlighting the importance of APOE4 in AD pathogenesis. On the other hand, many clinical and population studies show that APOE2, encoding the rarest apoE isoform, is a strongly protective genetic factor in AD. A pathological hallmark of AD is the formation of neurofibrillary tangles (NFTs) consisting of hyperphosphorylated, insoluble tau, containing both 3R and 4R tau isoforms. In cell cultures and mouse models, apoE isoforms have tau-dependent differential effects, and tau has apoE isoform-dependent effects, suggesting interactive roles in AD pathogenesis. However, almost all of these studies of apoE isoforms and tau drew conclusions based either on mouse tau, which is present almost exclusively as 4R tau, or on mutant human tau, which is associated with frontotemporal dementia but not AD. In Project 1, we propose to determine cell- type-specific, differential roles of apoE isoforms in age-dependent neural network dysfunction and behavioral deficits, in the context of wildtype (WT) human tau (both 3R and 4R tau isoforms), in novel mouse models of AD. In Aim 1, we will determine differential roles of apoE isoforms in neural network dysfunction and behavioral deficits, using apoE-isoform-floxed knock-in (APOEfE2/fE2 [fE2], APOEfE3/fE3 [fE3], and APOEfE4/fE4 [fE4]) mice expressing WT human tau (MAPT knock-in or TAUWT) at different ages. In Aim 2, we will determine cell-type- specific, differential roles of apoE isoforms in neural network dysfunction and behavioral deficits, using fE2/TAUWT, fE3/TAUWT, and fE4/TAUWT mice expressing cell-type-specific Cre recombinase (neuron-specific Cresyn1, astrocyte-specific CreGFAP, and microglia-specific CreCx3cr1) in order to delete the APOE allele in a cell- type-specific manner. The studies in this project, together with those of the three other projects of this program project grant, will yield new insights into the multifactorial pathogenesis of AD and may identify neural network- based targets for apoE isoform–dependent and cell type-specific therapies to treat or prevent AD.