Enhancing microglia-dependent plaque clearance in the Alzheimer disease brain by targeting Ifi27l2a expression

摘要 阿尔茨海默病(AD)和脑淀粉样血管病(CAA)是与衰老相关的破坏性疾病 涉及脑内淀粉样β蛋白(Aβ)病理性沉积的神经退行性疾病 软脑膜血管系统周围的薄壁组织。小胶质细胞(MG)摄取β显著 随着年龄的增长而减少，这可能导致淀粉样蛋白清除减少和斑块增加 积累。最近，一种新的MG亚群具有明显的基因表达特征(“疾病- 相关的小胶质细胞“；DAM)在AD患者吞噬Aβ的过程中起着关键作用。vbl.使用 单细胞RNA测序的无偏分析(ScRNAseq)，我们发现干扰素-α- 诱导蛋白27样蛋白2a(Ifi27l2a)是MG中表达最高的基因，仅次于 缺血性卒中，随着年龄的增加而增加。利用这一发现作为起点，我们随后检查了 在AD和CAA条件下是否出现类似的上调。我们随后发现Ifi27l2a的mRNA 有症状的TgSwDI小鼠的大脑表达显著升高-这是一种 同时发展血管和实质Aβ沉积。在人类大脑样本中，我们发现 确诊为CAA和AD患者的MG切片中Ifi27l2a蛋白表达升高 病理对照和年龄匹配的非疾病对照。我们还在一名人类体内发现了Ifi27l2a的上调。 炎性刺激后的小胶质细胞系(HMC3)。我们对MG的scRNAseq分析 人群中ifi27l2a的表达与炎症基因和a 与吞噬(和DAM识别)基因呈负相关。鉴于我们关于以下方面的新发现 Ifi27l2a在MG/DAM表型中的作用以及已知的MG在β清除中的作用 Ifi27l2a在调节MG吞噬功能和β清除中的新作用 同时显示血管和实质淀粉样斑块形成的模型(TgSwDI)。 我们将测试我们的模型，在该模型中，MG患者Ifi27l2a表达增加促进吞噬能力下降 从而损害了Aβ的清除。在目标1中，我们将研究转录后的潜在机制。 如果是27l2a的规定。我们将使用原代MG(从老龄小鼠脑培养)和人MG细胞系 确定两个电子预测的microRNAs对Ifi27l2a水平的贡献及其结果 吞噬功能。在目标2中，我们将在体内演示Ifi27l2a在调节MG/DAM中的作用 吞噬细胞表型和确定Ifi27l2a下调促进增强的可能性 血管和实质Aβ斑块的清除。在这些研究中，我们将使用TgSwDI小鼠 Aβ期，血管沉积和实质斑块明显。如果成功，这些研究 将为增强Aβ聚集体在大脑中的清除提供新的方法基础。

Abstract Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA) are devastating aging-associated neurodegenerative diseases which involve pathological deposition of amyloid-beta (Aβ) in the brain parenchyma and around the leptomeningeal vasculature. Aβ uptake in microglia (MG) is strikingly reduced with age, which may contribute to reduced amyloid clearance and increased plaque accumulation. Recently, a novel subset of MG with a distinct gene expression signature (“disease- associated microglia”; DAM) have emerged as a critical player in phagocytosis of Aβ in AD. Using unbiased analysis of single-cell RNA sequencing (scRNAseq), we discovered that Interferon alpha- inducible protein 27-like protein 2A (Ifi27l2a) is the most highly upregulated gene in MG following ischemic stroke, with a greater increase in aging. Using this finding as a launch point, we then examined if similar upregulation occurred in conditions of AD and CAA. We subsequently found that Ifi27l2a mRNA expression is significantly elevated in the brain of symptomatic TgSwDI mice – a mouse model which develops both vascular and parenchymal Aβ deposits. In human brain samples, we found significantly elevated Ifi27l2a protein expression in MG in sections from patients with confirmed CAA and AD pathology versus non-disease age-matched controls. We also found upregulation of Ifi27l2a in a human microglial cell line (HMC3) following inflammatory challenge. Our scRNAseq analysis of the MG population showed a positive correlation between Ifi27l2a expression and inflammatory genes and a negative correlation with phagocytic (and DAM-identifying) genes. In light of our new findings regarding the role of Ifi27l2a in MG/DAM phenotype and the known role of MG in Aβ clearance, we now propose to explore the novel role of Ifi27l2a in regulating MG phagocytic function and Aβ clearance using a mouse model which demonstrates both vascular and parenchymal amyloid plaque formation (TgSwDI). We will test our model in which elevated Ifi27l2a expression in MG promotes reduced phagocytic capacity and thus impaired clearance of Aβ. In aim 1, we will examine potential mechanisms of post-transcriptional Ifi27l2a regulation. We will use primary MG (cultured from aged mouse brain) and a human MG cell line to determine the contribution of two in silico predicted microRNAs on Ifi27l2a level and on resulting phagocytic function. In aim 2, we will demonstrate the in vivo role of Ifi27l2a in regulating MG/DAM phagocytic phenotype and determine the potential for Ifi27l2a down-regulation to promote enhanced clearance of vascular and parenchymal Aβ plaques. For these studies, we will use TgSwDI mice at a stage where Aβ vascular deposits and parenchymal plaques are evident. If successful, these studies would provide the basis for new approaches for enhancing clearance of Aβ aggregates in the brain.