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

项目摘要/摘要 阿尔茨海默病(AD)是最常见的神经退行性疾病(NDD)，也是最常见的 导致成年后期痴呆的原因。病理上以淀粉样斑块、神经原纤维缠结、 和神经炎症(如小胶质细胞和星形胶质细胞激活)。迄今为止，AD领域的研究一直是人们关注的焦点 在阿尔茨海默病大脑中错误折叠和聚集的蛋白质(例如淀粉样β蛋白和Tau)。然而， 神经炎症在AD发病机制中的作用仍不清楚，也未被充分研究。 最近对AD风险基因的全基因组分析导致发现了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 先天免疫系统，已知在AD和相关的NDDS中介导神经炎症。在这些人中 新发现的AD危险基因--触发受体的R47H变异体在髓系细胞2上表达 (TREM2)是到目前为止最高的风险(即与对照相比风险高2-4倍)。TREM2是 仅在小胶质细胞和外周髓系细胞中表达。TREM2似乎调制了几个重要的 小胶质细胞/髓系细胞的功能，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，并支持小胶质细胞存活。然而，它仍然 尚不清楚TREM2功能或TREM2-R47H功能障碍如何调节完整动物模型的AD风险 广告。 在这个方案中，我们开发了表达野生型或野生型的新型人类基因组转基因模型 TREM2变异体(BAC-TREM2)或AD相关的R47H变异体(BAC-TREM2-R47H)。我们设计了一系列 通过将这些模型与现有的两个AD转基因小鼠模型杂交，进行体内遗传实验，以 测试我们的假设，即过度表达TREM2(因此增强TREM2信号)可能促进有益的 小胶质细胞功能与改善AD发病机制。此外，我们将能够测试是否 TREM2-R47H变异体表现出部分功能丧失或显性毒性来调节AD。此外，我们还将 应用综合基因组学方法将小鼠模型的转录组网络与 来自AD患者的那些。最后，我们将使用原代小胶质细胞进行体外信号分析。 从我们的模型中得出，以研究TREM2及其AD相关变体如何改变信号转导。我们的研究 可能有助于验证小胶质细胞TREM2过度表达在改善神经功能障碍中可能的神经保护作用 AD的发病机制，并阐明TREM2及其R47H变异体可能改变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.