Elucidating roles of microglial lipid droplets in neurodegeneration

项目总结/摘要 阿尔茨海默病（AD）影响美国约600万人，目前没有 明确有效的疾病改善疗法。AD的病理定义是β淀粉样蛋白的积累 （Aβ）斑块和tau神经元缠结，并且已知， 小胶质细胞和其它非神经元细胞类型在形成疾病过程中起重要作用。大部分 AD的多基因风险来自于小胶质细胞表达的基因变异，特别是那些参与 内溶酶体和脂质加工途径，以及含有丰富脂滴的小胶质细胞（LD-MG）， 在AD病人死后的大脑中观察到由于以前针对Aβ的干预措施尚未得到 在临床试验中取得成功，调节小胶质细胞脂质代谢的概念是一个新的和令人兴奋的途径 然而，我们需要更多地了解脂质代谢如何控制 小胶质细胞功能状态。在淀粉样变性的小鼠模型中，小胶质细胞从稳态转变为稳态。 疾病相关（DAM）转录状态，代表保护性、吞噬性和斑块- 紧凑表型虽然小胶质细胞活性可能在AD的早期淀粉样阶段是有益的， 小胶质细胞的药理学或遗传学抑制已经显示在小鼠模型中具有保护性， tau蛋白病LD-MG在tau蛋白病小鼠模型中的活跃变性脑区域中观察到，但LD-MG在tau蛋白病小鼠模型中的活跃变性脑区域中观察到。 这些细胞在疾病过程中的功能目前尚不清楚。为了开始解决这个问题，我们 将使用与scRNAseq偶联的FACS来表征LD高与LD低之间的任何转录差异 分离自9.5月龄Tau病小鼠的小神经胶质细胞。鉴于最近的证据表明LD-MG 在老年小鼠中观察到的LD-MG具有促炎、低吞噬细胞表型，我们假设LD-MG 在我们的tau蛋白病模型中，将具有类似的途径改变，因此可能部分负责 小胶质细胞对神经变性的贡献。为了评估这些发现与人类的相关性，我们将 对死后人AD脑样品进行染色，以寻找任何有希望的小鼠LD-MG标记物。阐明本 为了研究LD-MG在tau蛋白病进展中的功能作用，我们将利用一种新的小鼠模型， 可诱导的小胶质细胞特异性敲除二酰基甘油酰基转移酶（DGAT）酶，这些酶已被 在多种生物学背景下被证明是LD生物发生所需的。大量的文献 支持脂滴在隔离潜在有毒脂质中的作用，我们假设， MG通过DGAT KO形成LD的能力将加速tau蛋白病的进展，我们将使用 免疫组织化学、scRNAseq和脂质组学分析的组合。我们的研究将描述一个 研究不足的小胶质细胞亚群，增加我们对骨髓功能状态多样性的了解， 评估调节小胶质细胞脂质代谢治疗阿尔茨海默病的潜力。

PROJECT SUMMARY/ABSTRACT Alzheimer disease (AD) affects approximately 6 million people in the United States and currently has no clearly-effective disease modifying therapies. AD is pathologically defined by the accumulation of amyloid β (Aβ) plaques and tau neurofibrillary tangles in the brain and it is known that alterations in the activities of microglia and other non-neuronal cell types play important roles in shaping the disease course. Much of the polygenic risk for AD is derived from variants in genes expressed by microglia, specifically those involved in endolysosomal and lipid processing pathways, and microglia containing abundant lipid droplets (LD-MG) have been observed in post-mortem human AD brains. As previous interventions targeting Aβ have not yet been successful in clinical trials, the concept of modulating microglial lipid metabolism is a novel and exciting avenue being explored in preclinical studies, however we need to know more about how lipid metabolism governs microglial functional states. In mouse models of amyloidosis, microglia transition from a homeostatic to a disease-associated (DAM) transcriptional state that represents a protective, phagocytic, and plaque- compacting phenotype. While microglial activity may be beneficial in the early amyloid phase of AD, pharmacological or genetic inhibition of microglia has been shown to be protective in mouse models of tauopathy. LD-MG are observed in actively degenerating brain regions in a tauopathy mouse model, but the functions of these cells in the disease process are not currently known. To begin addressing this question, we will use FACS coupled with scRNAseq to characterize any transcriptional differences between LDhigh vs LDlow microglia isolated from 9.5 month old tauopathy mice. Given recent evidence suggesting that the LD-MG observed in aged mice have pro-inflammatory, hypo-phagocytic phenotypes, we hypothesize that the LD-MG in our tauopathy model will have similar pathway alterations and could thus be partially responsible for microglial contributions to neurodegeneration. To assess the relevance of these findings to humans, we will stain postmortem human AD brain samples for any promising mouse LD-MG markers. To elucidate the functional roles of LD-MG in the progression of tauopathy, we will utilize a new mouse model that allows for the inducible, microglial-specific knockout of the diacylglycerol acyltransferase (DGAT) enzymes, which have been demonstrated to be required for LD biogenesis in multiple biological contexts. A substantial amount of literature supports a role for lipid droplets in sequestering potentially toxic lipids and we hypothesize that crippling the ability of MG to form LDs via DGAT KO will accelerate tauopathy progression, which we will assess using a combination of immunohistochemical, scRNAseq, and lipidomic analyses. Our studies will characterize an understudied subset of microglia, increase our knowledge of the diversity of myeloid functional states, and evaluate the potential of modulating microglial lipid metabolism for the treatment of Alzheimer disease.