Discovery and validation of genetic variants affecting microglial activation in Alzheimer's disease

项目概要/摘要。虽然在神经炎淀粉样蛋白附近观察到活化的小胶质细胞， 阿尔茨海默病（AD）中的斑块，尚未对阿尔茨海默病（AD）中的小胶质细胞活化进行大规模评估。 衰老和神经退行性疾病。我们的长期目标是了解小胶质细胞的遗传基础， 反应-特别是小胶质细胞在形态学上定义的激活状态的比例-增加 因此，我们可以开发更有针对性的免疫疗法，以预防认知障碍。 衰退并发展为痴呆症。我们的目标是完善小胶质细胞激活的遗传结构， 确定影响活化小胶质细胞比例的新位点，并了解其功能 驱动AD小胶质细胞激活的变体的后果。我们的核心假设是， 变体影响小胶质细胞活化和对AD的易感性。我们将测试这个假设， 全基因组分析和识别基因变异和小胶质细胞激活之间的关联。小胶质 将在人尸体解剖组织（离体），使用PET成像的活体人脑（体内）， 和单核细胞衍生的小胶质样细胞（原位和体外）。我们的理论是， 驱动激活的小胶质细胞比例的结构将在开发第一代 多基因模型，并确定激活的小胶质细胞的比例是否捕获因果关系， 导致AD的级联的元素。我们的具体目标是：1）验证和发现影响基因组的基因座。 衰老和阿尔茨海默氏症中人类小胶质细胞活化（活化小胶质细胞的比例）的死后测量 2）GWAS的体内验证和使用TSPO PET成像的临床相关性评估， 测量小胶质细胞活化，和3）原位组织学和体外功能表征的验证 人类小胶质细胞样系统的变异。对于第一个目标，我们将执行GWAS并测量 从1,600人的尸检脑组织中提取激活的小胶质细胞，然后在一个 来自三个独立机构的独立、多样的样本集。在第二个目标中，我们将执行GWAS 和TSPO PET成像，使用最先进的放射性配体11 C-ER 176，在200名老年人的前瞻性队列中， 人类受试者（等比例的认知正常、轻度认知障碍和阿尔茨海默病）， 鉴定与AD相关的小胶质细胞活化相关的基因变异。在第三个目标中，我们将评估基因如何 目的1和2中鉴定的变异体影响单核细胞源性肿瘤中的细胞功能和蛋白质表达。 小胶质样细胞。我们的创新方法结合了尸检，PET和小胶质细胞的人类细胞测量 激活以创建对小胶质细胞反应的遗传结构的多模式调查。拟议 研究是重要的，因为绘制调节小胶质细胞激活的变体，并确定它们的 功能的后果，将提供关键的见解，优先考虑潜在的治疗靶点的药物 开发和创建新的结果指标，以指导临床试验设计。

Project Summary/Abstract. While activated microglia have been observed in the vicinity of neuritic amyloid plaques in Alzheimer's disease (AD), there have been no large-scale assessments of microglial activation in aging and neurodegenerative disease. Our long-term goal is to understand the genetic underpinning of microglial responses—particularly the proportion of microglia in a morphologically-defined state of activation—that increase susceptibility to AD, so we can develop more targeted forms of immune-based therapies to prevent cognitive decline and progression to dementia. Our objective is to refine the genetic architecture of microglial activation to identify novel loci that influence the proportion of activated microglia, and to understand the functional consequences of variants driving microglial activation in AD. Our central hypothesis is that identifiable gene variants influence microglial activation and susceptibility to AD. We will test this hypothesis by conducting genome-wide analysis and identifying associations between gene variants and microglial activation. Microglial activation will be measured in human autopsy tissue (ex vivo), living human brain using PET imaging (in vivo), and in monocyte-derived microglia-like cells (in situ and in vitro). Our rationale is that mapping the genetic architecture that drives the proportion of activated microglia will be important in developing a first generation of polygenic models for this trait and determine whether the proportion of activated microglia captures a causal element of the cascade leading to AD. Our specific aims are 1) Validation and discovery of loci influencing a postmortem measure of human microglial activation (proportion of activated microglia) in aging and Alzheimer's disease, 2) In vivo validation of GWAS and assessment of clinical relevance using TSPO PET imaging to measure microglial activation, and 3) In situ histological and in vitro functional characterization of validated variants in a human microglia-like system. For the first aim, we will perform GWAS and measure the proportion of activated microglia in autopsy brain tissue from 1,600 individuals, and then replicate our findings in an independent, diverse set of samples from three separate institutions. In the second aim, we will perform GWAS and TSPO PET imaging, using the state-of-the-art radioligand 11C-ER176, in a prospective cohort of 200 older human subjects (equal proportions of cognitively normal, mild cognitive impairment, and Alzheimer's disease) to identify gene variants associated with AD-related microglial activation. In the third aim, we will assess how gene variants identified in Aims 1 and 2 influence cellular function and protein expression in monocyte-derived microglia-like cells. Our innovative approach combines autopsy, PET, and human cell measures of microglial activation to create a multimodal investigation into the genetic architecture of microglial responses. The proposed research is significant, as mapping the variants that regulate microglial activation, and determining their functional consequences, will provide key insights in prioritizing potential therapeutic targets for drug development and in creating novel outcome measures with which to guide clinical trial design.