TREM2-mediated microglial dynamic function in Alzheimer disease

项目总结 这项建议的主要目标是解决TREM2介导的小胶质细胞功能在脑内的动态作用 脑老化和阿尔茨海默病(AD)病理发展的不同阶段。TREM2是 一种小胶质细胞特异性基因，其几个罕见的变异与AD风险有关。尽管取得了一些进展，但 TREM2，尤其是TREM2-R47H风险变异的分子病理学仍不清楚。研究 研究小鼠模型中TREM2功能丧失的影响支持不一致的结论； TREM2缺乏可降低或增强淀粉样蛋白或tau病理及相关毒性，具体取决于 病理发展阶段或特定的小鼠模型。因此，TREM2介导的小胶质细胞 功能可能对淀粉样蛋白和tau蛋白的病理阶段有动态影响 在整个AD过程中。使研究TREM2-R47H变异的影响的挑战进一步复杂化， 最近的一项研究表明，将R47H突变引入小鼠TREM2基因座会导致异常 其mRNA的剪接和不稳定性。为了填补这些知识空白和缺乏适当的模型系统， 我们已经产生了表达人TREM2或TREM2的新型细胞类型特异性和可诱导的小鼠模型- R47H在小胶质细胞中表达。为了解决人类相关性和分子机制，我们还产生了人类 携带TREM2或TREM2-R47H的诱导多能干细胞(IPSC)系。因此，这一行动的主要目标是 建议研究人TREM2和TREM2-R47H对小胶质细胞和神经元的动态影响 在衰老和阿尔茨海默病中的作用；而在这个过程中，通过靶向和 无针对性的方法。我们假设TREM2介导的小胶质细胞功能对 AD病理的发展，但当这种病理与突触相关时，可能是有害的 丧失和神经退行性变。我们还假设TREM2-R47H代表特别是功能丧失 在小胶质细胞介导的对AD相关通路的保护中。我们将通过三个目标来检验我们的假设。 在目标1中，我们计划分析TREM2或TREM2-R47H在损伤模式和衰老过程中的作用。 缺乏AD病理。在目标2中，我们将研究TREM2或TREM2-R47H对 A-β和Tau在病理发展不同阶段的代谢、沉积和毒性。在目标3中，我们 计划使用IPSC-确定和验证与TREM2和TREM2-R47H相关的分子通路- 衍生的小胶质细胞样细胞，有或没有整合到脑器官中。这项创新的建议将需要 我们现有的条件小鼠模型和IPSC派生的细胞模型的优势，以及 最先进的技术包括活体微透析、双光子显微镜和单光子分子图谱 细胞RNA序列。这些努力应该有助于理解TREM2是如何调节小胶质细胞动力学的 在衰老和AD发病机制中的作用，以及我们如何针对这些途径治疗AD。

PROJECT SUMMARY The major goal of this proposal is to address the dynamic role of TREM2-mediated microglial function in brain aging and during different stages of the pathological development of Alzheimer’s disease (AD). TREM2 is a microglial specific gene with several of its rare variants associated with AD risk. Despite some progress, the molecular pathobiology of TREM2 in particular the TREM2-R47H risk variant is still not clear. Studies examining the effects of loss of TREM2 function in mouse models support inconsistent conclusions; with TREM2 deficiency either reduces or enhances amyloid or tau pathology and associated toxicity depending on the stage of the pathological development or the specific mouse models. As such, TREM2-mediated microglial function likely has dynamic effects on amyloid and tau pathologies depending on pathological stages throughout AD progression. Further complicating the challenge of studying the impact of TREM2-R47H variant, a recent study revealed that introducing the R47H mutation into the mouse Trem2 gene locus leads to aberrant splicing and instability of its mRNA. To fill these gaps in knowledge and the lack of appropriate model systems, we have generated novel cell type-specific and inducible mouse models expressing human TREM2 or TREM2- R47H in microglia. To address human relevance and molecular mechanisms, we have also generated human induced pluripotent stem cell (iPSC) lines carrying TREM2 or TREM2-R47H. Thus, the major goal of this proposal is to examine the dynamic effects of human TREM2 and TREM2-R47H on microglial and neuronal functions in aging and AD; while in the process defines the underlying molecular pathways by targeted and non-targeted approaches. We hypothesize that TREM2-mediated microglial function is protective against the development of AD pathologies but can be detrimental when such pathologies are associated with synaptic loss and neurodegeneration. We also hypothesize that TREM2-R47H represents a loss-of-function in particular in microglia-mediated protection against AD-related pathways. We will test our hypothesis through three aims. In Aim 1, we plan to analyze the effects of TREM2 or TREM2-R47H upon injury paradigms and during aging in the absence of AD pathology. In Aim 2, we will examine the effects of TREM2 or TREM2-R47H on the metabolism, deposition, and toxicity of Aβ and tau at different stages of pathological development. In Aim 3, we plan to identify and validate the molecular pathways associated with TREM2 and TREM2-R47H using iPSC- derived microglia-like cells with or without integration into cerebral organoids. This innovative proposal will take advantage of our existing conditional mouse models and iPSC-derived cellular models combined with state-of- the-art technologies including in vivo microdialysis, two-photon microscopy and molecular profiling by single cell RNA-Seq. These efforts should collectively help to understand how TREM2 modulates microglial dynamic roles in aging and AD pathogenesis and how we can target these pathways to treat AD.