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）的恢复能力是一种认知功能优于基于实足年龄、遗传风险和/或晚期神经病理学的预测的现象，可能是因为存在尚未确定的保护因素。这些因素一旦确定，有望为阿尔茨海默病的治疗和预防提供关键靶点。然而，仅使用人类遗传方法发现恢复力的遗传机制存在重大障碍，包括：难以识别大量无症状阿尔茨海默病患者，难以从复杂的人类基因组中提取年龄和相互作用的遗传效应，难以控制环境因素，难以从无症状阿尔茨海默病患者中获取脑组织。此外，众所周知，转录物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反应是不同的。然而，由于无法对人类脑组织进行纵向分子分析，以及描述与阿尔茨海默病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，我们辨别蛋白质组在衰老和阿尔茨海默病进展过程中如何变化的能力受到限制。为了填补这些重大的技术和知识空白，我们将开发一个强大的管道，使用与人类大脑衰老和AD最相关的小鼠模型（即AD- bxds及其非转基因Ntg-BXDs对照）来获得特定细胞类型蛋白质组的纵向知识库，我们发现这些细胞类型表现出与高易感和高弹性表型相关的基因表达的强大变化。我们将重点关注海马体，因为它是小鼠和人类空间记忆形成和回忆所必需的，海马体依赖性记忆缺陷在阿尔茨海默病中很常见。事实上，我们的工作和初步数据表明，ad - bxd认知缺陷的发病和进展年龄（从极端易感到弹性）的小鼠品系差异是海马中基因表达的细胞类型特异性差异造成的。我们将这些小鼠数据与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Aim 1中，我们将使用生物正交非规范氨基酸标记（BONCAT）在AD- bxds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Aim 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Aim 3中，我们将利用杰克逊实验室无与伦比的基因工程资源，通过确定它们对CRISPRed ad - bxd的记忆、海马神经元兴奋性和突触可塑性的影响，从功能上验证“手头”弹性候选物。利用这一管道，我们将因此发现新的和翻译相关的蛋白质和复合物，供AMP-AD/TREAT-AD药物发现管道考虑，以延迟或预防易感AD小鼠的认知症状，并最终预防AD患者。

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.