BAC Transgenic Mouse Models of TREM2 to Study Neuroprotective Mechanisms in AD

项目概要/摘要 阿尔茨海默病（Alzheimer's disease，AD）是最常见的神经退行性疾病（neurodegenerative disorder，NDD）， 老年痴呆症的病因病理学上以淀粉样斑块、神经纤维缠结， 和神经炎症（例如小胶质细胞和星形胶质细胞活化）。迄今为止，AD领域的研究一直是 在AD脑中错误折叠和聚集的蛋白质（例如淀粉样β肽和Tau）上。然而，在这方面， 神经炎症在AD发病机制中的作用仍不清楚，研究不足。 最近对AD风险基因的全基因组分析发现了20多个基因， 调节AD风险。从这些研究中获得的一个令人兴奋的见解是，多个AD风险基因在阿尔茨海默氏症中起作用。 先天免疫系统，已知其介导AD和相关NDD中的神经炎症。中 新发现的AD风险基因，髓样细胞上表达的触发受体的R47 H变体2 （TREM 2）赋予了迄今为止最高的风险（即，与对照相比高2-4倍的风险）。trem 2是 仅在小胶质细胞和外周髓样细胞中表达。TREM 2似乎调节了几个重要的 小胶质细胞/骨髓细胞的功能，包括吞噬碎片，抑制促炎细胞因子 释放，增加神经营养因子的合成，并支持小胶质细胞的存活。但委员会仍 尚不清楚TREM 2功能或TREM 2-R47 H功能障碍如何在完整的动物模型中调节AD风险。 AD. 在这个建议中，我们开发了新的人类基因组转基因模型， TREM 2变体（BAC-TREM 2）或AD相关R47 H变体（BAC-TREM 2-R47 H）。我们设计了一系列 体内遗传实验，通过将这些模型与两种现有的AD转基因小鼠模型杂交， 测试我们的假设，即过表达TREM 2（因此增强TREM 2信号传导）可能促进有益的 改善AD的发病机制。此外，我们将能够测试 TREM 2-R47 H变体发挥部分功能丧失或显性毒性来调节AD。此外，我们将 应用整合的基因组方法来比较我们的小鼠模型的转录组网络， 来自AD患者。最后，我们将使用原代小胶质细胞进行体外信号传导试验 从我们的模型中获得，以研究TREM 2及其AD相关变体如何改变信号传导。我们的研究 可能有助于验证小胶质细胞TREM 2过表达在改善脑缺血中可能的神经保护作用。 AD发病机制，并阐明TREM 2及其R47 H变体可能改变AD风险的机制。

Project Summary/Abstract Alzheimer's disease (AD) is the most common neurodegenerative disorder (NDD), and the leading cause of dementia in late adult life. Pathologically it is characterized by amyloid plaques, neurofibrillary tangles, and neuroinflammation (e.g. microglia and astrocyte activation). Studies in AD field so far have been focused on proteins that are misfolded and aggregated in the AD brains (e.g. amyloid beta peptide and Tau). However, the role of neuroinflammation in AD pathogenesis remains unclear and underexplored. Recent genome-wide analyses of AD risk genes have lead to the discovery of over 20 genes that modulate AD risk. One exciting insight gained from these studies is that multiple AD risk genes function in the innate immune system, which are known to mediate neuroinflammation in AD and related NDDs. Among the newly discovered AD risk genes, the R47H variant of the Triggering Receptor Expressed on Myeloid cells 2 (TREM2) is conferring by far the highest risk (i.e. 2-4 fold higher risk compared to the controls). TREM2 is solely expressed in microglia and peripheral myeloid cells. TREM2 appears to modulate several important function of microglia/myeloid cells, including phagocytosis of debris, suppressing proinflammatory cytokine release, increasing neurotrophic factor synthesis, and supporting microglia survival. However, it remains unclear how TREM2 function or TREM2-R47H dysfunction may modulate AD risk in intact animal models of AD. In this proposal, we developed novel human genomic transgenic models expressing either the wildtype TREM2 variant (BAC-TREM2) or the AD-associated R47H variant (BAC-TREM2-R47H). We designed a series of in vivo genetic experiments, by crossing these models with two existing AD transgenic mouse models, to test our hypothesis that overexpressing TREM2 (hence boosting TREM2 signaling) may promote the beneficial function of microglia and ameliorate AD pathogenesis. Furthermore, we will be able to test whether the TREM2-R47H variant exerts partial loss-of-function or dominant toxicities to modulate AD. In addition, we will apply an integrative genomic approach to compare the transcriptome networks from our mouse models to those derived from AD patients. Finally, we will conduct in vitro signaling assays using primary microglia derived from our models to study how TREM2 and its AD-associated variant may alter signaling. Our study may help to validate the possible neuroprotective effects of microglial TREM2 overexpression in ameliorating AD pathogenesis, and elucidate mechanisms through which TREM2 and its R47H variant may modify AD risk.