Targeting the miR-155 signaling pathway to induce beneficial disease associated microglia subtypes in Alzheimer's Disease

摘要 阿尔茨海默病(AD)是目前世界上最常见的神经退行性疾病， 预计到2050年，病例数量将增加两倍。来自全基因组的多项病理研究和数据 关联研究发现小胶质细胞和小胶质细胞特有的基因是重要的媒介。 阿尔茨海默病的发病机制和进展。几个实验室已经确定了小胶质细胞的遗传特征 与阿尔茨海默病和其他神经退行性疾病有关，这些疾病被称为“相关疾病” “小胶质细胞”(DAM)或“小胶质细胞退行性变”(MGnD)。目前还不清楚这些大坝/MGnD是不是 对阿尔茨海默病病理有利或有害。一种流行的理论是，阻止大坝/MGnD形成可能 在AD的情况下产生有益的影响，这已经在其他动物模型中得到证明 神经退行性变。为了在AD患者中验证这一假设，我们选择性地删除了microRNA 155，一种microRNA 被证明是从动态平衡小胶质细胞到DAM/MGnD的主要信号成分，在 阿尔茨海默病模型小鼠的小胶质细胞。令人惊讶的是，我们的数据表明miR-155同时缺失 与吞噬作用相关的几个典型的DAM/MGnD基因的表达增强，并被抑制 与炎症和细胞因子分泌相关的通路的活性。这一令人惊讶的变化导致了 淀粉样蛋白病理的改善和认知能力的增强。为了解释 获得这个签名后，我们评估了miR-155分子靶标的转录数据 在遗传学研究中对AD发病的意义，是我们所看到的差异基因的上游调节因子 在我们的miR-155消融研究数据中表达或倾向于差异表达。两个MIR-155目标， SHIP1和PU.1已被AD Gwas研究确定为AD发病的首选基因，并且是转录的 分别是炎症和吞噬作用的调节剂。综上所述，这些数据让我得出了我的假设 DAM/MGnD征象由吞噬和炎性“亚特征”组成 可通过SHIP1和PU.1的增强独立调制。我还假设消融 MiR-155的突变将导致人类小胶质细胞发生类似的转录变化，因为 小鼠和人类之间的MIR-155。在本提案的目标1中，我建议过度表达SHIP1和PU.1 使用慢病毒载体在AD小鼠模型的小胶质细胞中。这种方法代表了一种非常新颖的 以及可翻译地使用基因治疗技术来解决小胶质细胞功能的分子机制。在……里面 目的2，我建议重述在我们的小胶质细胞特异性miR-155消融小鼠中观察到的基因特征 实验对人小胶质细胞样细胞诱导分化为多能干细胞的意义 这些发现和这一假设给人类的健康和疾病带来了影响。

ABSTRACT Alzheimer’s Disease (AD) is currently the most prevalent neurodegenerative disorder in the world, with the number of cases expected to triple by 2050. Multiple pathological studies and data from genome wide association studies (GWAS) have identified microglia and genes specific to microglia as prominent mediators of AD pathogenesis and progression. Several laboratories have identified a genetic signature of microglia associated with AD and other neurodegenerative disorders, which have been dubbed “Disease Associated Microglia” (DAM) or “Microglia Neurodegenerative” (MGnD). It is still unknown whether these DAM/MGnD are beneficial or detrimental to AD pathology. One popular theory is that blocking DAM/MGnD formation may result in a beneficial effect in the context of AD, as this has been demonstrated in other animal models of neurodegeneration. To test this hypothesis in AD we selectively deleted microRNA 155, a microRNA demonstrated to be a major signaling component for the switch from homeostatic microglia to DAM/MGnD, in the microglia of mouse models of AD. Surprisingly, our data indicate that miR-155 deletion simultaneously enhanced expression of several canonical DAM/MGnD genes associated with phagocytosis, and dampened activity of pathways associated with inflammation and cytokine secretion. This surprising change resulted in an improvement of amyloid pathology and enhanced cognitive performance. To explain the mechanism for the acquisition of this signature, we assessed our transcriptomic data for molecular targets of miR-155 that have significance to AD onset in genetic studies and are upstream regulators of the genes we see differentially expressed or trending towards differential expression in our miR-155 ablation study data. Two miR-155 targets, SHIP1 and PU.1, have been identified by AD GWAS studies as top hits for AD onset and are transcriptional regulators of inflammation and phagocytosis, respectively. Taken together, these data led me to my hypothesis that the DAM/MGnD signatures are comprised of phagocytic and inflammatory “sub-features” which can be independently modulated by augmentation of SHIP1 and PU.1. I also hypothesize that the ablation of miR-155 will result in a similar transcriptional change in human microglia, given the identical conservation of miR-155 between mice and humans. In Aim 1 of this proposal, I propose to overexpress both SHIP1 and PU.1 in the microglia of AD mouse models using lentiviral vectors. This approach represents an extremely novel and translatable use of gene therapy technologies to address molecular mechanisms of microglial function. In Aim 2, I propose to recapitulate the gene signature observed in our microglia specific miR-155 ablation mouse experiments in human microglia like cells derived from induced pluripotent stem cells to tie the significance of these findings and this hypothesis to human health and disease.