Cell Type-Specific Proteins that Promote Resilience to Cognitive Aging and Alzheimer's Disease

对大脑衰老和阿尔茨海默病（AD）的复原力是一种认知功能比基于实际年龄、遗传风险和/或高级神经病理学预测的更好的现象，这可能是因为存在尚未确定的保护因素。这些因素，一旦确定，预计将提供治疗和预防AD的关键目标。然而，重大障碍限制了仅使用人类遗传学方法发现弹性的遗传机制，包括：难以识别大量无症状AD个体，从复杂的人类基因组中提取年龄和相互作用的遗传效应，控制环境因素，以及从无症状AD病例中获得脑组织。此外，众所周知，转录本丰度不足以推断蛋白质丰度，因为它们在空间上、时间上和对学习任务的响应上不同。然而，我们辨别蛋白质组如何在衰老和AD进展中变化的能力受到限制，因为不可能对人脑组织进行纵向分子分析，以及描述与AD易感性和恢复力相关的细胞类型特异性蛋白质组所需的技术。为了填补这些重大的技术和知识空白，在这里，我们将使用人类大脑老化和AD的最相关的小鼠模型（即，AD-BXD和它们的非转基因Ntg-BXD对照），以获得特定细胞类型中蛋白质组的纵向知识库，我们已经发现这些细胞类型在与高度易感和高度弹性表型相关的基因表达中表现出稳健的变化。我们将重点放在海马体，因为它是空间记忆形成和回忆所必需的小鼠和人类，和海马体依赖性记忆缺陷是常见的AD。事实上，我们的工作和初步数据表明，小鼠品系在发病年龄和AD-BXD中认知缺陷进展（从极敏感到有弹性）的差异是由海马中基因表达的细胞类型特异性差异引起的。我们将这些小鼠数据与来自NIA赞助的AMP-AD和Resilience-AD联盟的临床和组学数据相结合，以确定认知弹性的分子驱动因素。在目的1中，我们将使用生物正交非规范氨基酸标签（BONCAT）在AD-BXD中鉴定与AD恢复力相关的神经元和小胶质细胞蛋白表达的细胞类型特异性变化。在目标2中，我们将把认知弹性的驱动因素和分子网络转化为人类AD队列。在目标3中，我们将利用杰克逊实验室无与伦比的基因工程资源，通过确定CRISPRed AD-BXD对记忆、海马神经元兴奋性和突触可塑性的影响，在功能上验证“在手”恢复力候选物。使用这一管道，我们将发现新的和预防相关的蛋白质和复合物，以考虑在AMP-AD/AMPD-AD药物发现管道中延迟或预防易感AD小鼠和最终AD患者的认知症状。

Resilience to brain aging and Alzheimer’s disease (AD) is a phenomenon whereby cognitive functioning is better than predicted based on chronological age, genetic risk and/or advanced neuropathology, likely because of the presence of as yet unidentified protective factors. These factors, once identified, are expected to provide key targets for treatment and prevention of AD. However, significant barriers limit discovery of the genetic mechanisms of resilience using human genetic methods alone, including: difficulties in identifying large numbers of individuals with asymptomatic AD, extracting age and interacting genetic effects from complex human genomes, controlling environmental factors, and obtaining brain tissue from asymptomatic AD cases. Moreover, it is well known that transcript abundance is not sufficient to infer protein abundance, as they differ spatially, temporally, and in response to learning tasks. Yet, our ability to discern how proteomes change across aging and AD progression is limited by the impossibility of longitudinal molecular analyses on human brain tissues, as well as the technology needed to profile cell type-specific proteomes associated with susceptibility versus resilience to AD. To fill these significant technological and knowledge gaps, here we will develop a robust pipeline using the most translationally relevant mouse models of human brain aging and AD (i.e., the AD-BXDs and their non-transgenic Ntg-BXDs controls) to obtain a longitudinal knowledge base of proteomes in specific cell types that we have found to exhibit robust changes in gene expression associated with highly susceptible and highly resilient phenotypes. We will focus on the hippocampus as it is required for spatial memory formation and recall in mice and humans, and hippocampus-dependent memory deficits are common in AD. Indeed, our work and preliminary data suggest that mouse strain differences in the age at onset and progression of cognitive deficits in the AD-BXDs (from extremely susceptible to resilient) result from cell type-specific differences in gene expression in the hippocampus. We will integrate these mouse data with clinical and omics data from NIA-sponsored AMP-AD and Resilience-AD Consortia to identify molecular drivers of cognitive resilience. In Aim 1, we will identify cell type-specific changes in neuron and microglia protein expression associated with resilience to AD using bioorthogonal non-canonical amino acid tagging (BONCAT) in AD-BXDs. In Aim 2, we will translate drivers and molecular networks underlying cognitive resilience to human AD cohorts. In Aim 3, we will leverage the unmatched genetic engineering resources at The Jackson Laboratory to functionally validate ‘in-hand’ resilience candidates by determining their effects on memory, hippocampal neuronal excitability, and synaptic plasticity in CRISPRed AD-BXDs. Using this pipeline, we will thereby discover novel and translationally relevant proteins and complexes for consideration under AMP-AD/TREAT-AD drug discovery pipelines to delay or prevent cognitive symptoms in susceptible AD mice, and ultimately AD patients.