The regulation of the microglial response to amyloid-beta plaques by the polycomb repressive complex 2

项目总结/摘要 我们对阿尔茨海默病（AD）背后的病理生理学的理解存在差距，这导致了 几乎没有治疗选择。最近的研究已经确定了小胶质细胞，先天免疫细胞的 大脑，作为对AD反应的关键参与者，可以帮助我们填补这一空白。具体来说，小胶质细胞似乎在 对与含淀粉样蛋白斑块相关的毒性具有保护作用。通过激活 触发髓样细胞中表达的受体2（TREM 2）信号通路，小胶质细胞向 在这些斑块周围，同时诱导一种独特的转录特征，称为疾病相关性， 小胶质细胞（DAM）表型。一个重要的悬而未决的问题是小胶质细胞如何调节这种状态， 转录和功能上。我们的实验室以前已经确定了polycomb抑制复合物2（PRC 2）。 作为脑区特异性小胶质细胞亚群的重要表观遗传调节因子。PRC 2是表观遗传的 该复合物参与基因沉默，并且也被认为是免疫细胞中的信号调节剂。 值得注意的是，我们发现PRC 2缺陷型小胶质细胞下调了TREM 2信号通路中的许多基因。我 假设PRC 2控制小胶质细胞对TREM 2中含有淀粉样蛋白的斑块的反应， 依赖机制为了支持这一点，我建立了一个PRC 2缺陷型小胶质细胞小鼠系， AD的5xFAD淀粉样蛋白模型，并显示PRC 2缺陷导致斑块相关小胶质细胞的损失， 类似于TREM 2缺陷模型。这可能是由于TREM 2途径的转录调控，或 直接调节TREM 2信号传导。为了进一步研究我的假设，我将首先描述 PRC 2在5xFAD小胶质细胞中发挥的表观遗传和转录作用。存在多种TREM 2依赖性 可能导致斑块相关小胶质细胞减少的机制-无法感知斑块，增加 斑块处死亡或缺乏向斑块的迁移。为了确定PRC 2是否调节这些 在TREM 2依赖的方式表型，我将培养原代小鼠小胶质细胞和胶质细胞， 抑制PRC 2，随后诱导TREM 2信号传导。用这个模型，我将分析TREM 2依赖性 感知、生存和迁移。该提案的结果将揭示PRC 2是否是 小胶质细胞通过控制TREM 2信号对含有AD淀粉样蛋白的斑块的反应， 转录或通过信号传导途径的直接调节。这些数据对于进一步推动我们 了解小胶质细胞的功能状态是如何调节的，为开发 有效治疗阿尔茨海默病

Project Summary/Abstract A gap exists in our understanding of the pathophysiology behind Alzheimer’s Disease (AD), which has led to virtually nonexistent treatment options. Recent studies have identified microglia, the innate immune cells of the brain, as key players in the response to AD that may help us fill this gap. Specifically, microglia appear to play a protective role against toxicity associated with amyloid-ß containing plaques. Through activation of the triggering receptor expressed in myeloid cells 2 (TREM2) signaling pathway, microglia migrate towards and surround these plaques while inducing a distinct transcriptional signature known as the Disease Associated Microglia (DAM) phenotype. An important outstanding question is how microglia regulate this state, both transcriptionally and functionally. Our lab has previously identified the polycomb repressive complex 2 (PRC2) as an important epigenetic regulator of brain region specific microglia subpopulations. PRC2 is an epigenetic complex involved in gene silencing and has also been implicated as a signaling regulator in immune cells. Notably, we found that PRC2 deficient microglia downregulate many genes in the TREM2 signaling pathway. I hypothesize that PRC2 controls the microglial response to amyloid-ß containing plaques in a TREM2- dependent mechanism. In support of this, I generated a PRC2-deficient microglia mouse line crossed to the 5xFAD amyloid model of AD and showed that PRC2-deficiency leads to loss of plaque associated microglia, similar to TREM2-deficient models. This could be due to transcriptional regulation of the TREM2 pathway or direct modulation of TREM2 signaling. To further investigate my hypothesis, I will first characterize the epigenetic and transcriptional role PRC2 plays in 5xFAD microglia. There are multiple TREM2-dependent mechanisms that could lead to decreased plaque associated microglia – inability to sense plaques, increased death at the plaques, or lack of migration towards the plaques. To determine if PRC2 regulates these phenotypes in a TREM2-dependent manner, I will culture primary mouse microglia and pharmacologically inhibit PRC2, followed by induction of TREM2 signaling. With this model, I will assay TREM2-dependent sensing, survival, and migration. The results of this proposal will reveal whether PRC2 is a master regulator of the microglial response to AD amyloid-ß containing plaques through its control of TREM2 signaling, either transcriptionally or through direct regulation of the signaling pathway. These data are critical to furthering our understanding of how microglial functional states are regulated, opening avenues for the development of effective treatments against Alzheimer’s Disease.