The role of APOE and Bone Morphogenic protein 4 (BMP4) in early cellular pathophysiology of Alzheimer's Disease

项目摘要 阿尔茨海默氏病（AD）是一种异质性神经退行性疾病，临床上分为早期阿尔茨海默病（AD）和晚期阿尔茨海默病（AD）。 学习和记忆的缺陷，逐渐发展为严重的痴呆症。虽然家庭形式的 虽然AD是由特定基因突变引起的，但大多数AD是零星发生的（sAD）。最强 sAD诊断的风险因素是年龄，这意味着在整个生命周期中发生的生化变化， 致病易感性在人类和啮齿类动物的大脑中，随着年龄的增长， BMP4信号的增加，与认知能力下降显著负相关， 小鼠模型的空间记忆力下降。散发性阿尔茨海默病最强的遗传风险因素 是载脂蛋白E（APOE）基因型; APOE ε 4亚型在AD人群中明显更普遍， 与疾病进展加快和发病年龄提前有关。之前在凯斯勒实验室的工作 结果显示，与APOE ε 3同基因对照神经元相比，APOE ε 4神经元表达水平增加， 磷酸化的tau蛋白，并且具有响应于外部应激源（例如， 离子霉素目前的建议旨在了解增加的BMP 4和APOE ε 4之间的相互作用， 在细胞水平上表达，以了解早期sAD疾病的发病机制。为了回答这个问题，我们 一个实验室已经从散发性AD患者中产生了诱导多能干细胞（iPSC）， CRISPR-/Cas9编辑APOE ε 3/4细胞以创建同基因APOE ε 3/3系。然后这些细胞分化为 以确定涉及的细胞自主和非细胞自主细胞病理学 增加BMP 4信号和APOE ε 4表达。第一个目的是检验增加的BMP 4 与APOE ε 4表达串联引起累加效应，负性改变星形胶质细胞表达， 自我平衡功能为了验证这一假设，转录组学将用于确定差异基因 表达和随后的研究将用于解决蛋白质表达和功能变化， 发生.第二个目标将利用iPSC患者来源的神经元和星形胶质细胞的共培养物， 错配的等基因对，以确定由于BMP 4增加而发生的非细胞自主变化 信号和APOE ε 4基因型，检验APOE ε 4星形胶质细胞，沿着增加的BMP 4 信号传导，夸大神经元中的病理级联反应，导致存活力降低，随后细胞死亡， 神经元第一个目标的目的是确定星形胶质细胞，其营养支持是必要的， 神经元活力，改变响应sAD危险因素的稳态功能。第二个目标将揭示如何 星形胶质细胞中的这些细胞自主变化最终改变了神经元中的早期疾病病理学。整体 长期目标是确定早期有针对性的机制，以便成功地干预这一毁灭性疾病。

Project Summary Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disorder categorized clinically by premature deficits in learning and memory that gradually progress to severe dementia. Although familial forms of the disease are caused by mutations in specific genes, the majority of AD occurs sporadically (sAD). The strongest risk factor for sAD diagnosis is age, implicating biochemical changes that occur across lifespan that increase pathogenic susceptibility. One of the changes that occur throughout aging in both human and rodent brains is an increase in BMP4 signaling, in a manner that is significantly negatively correlated with cognitive decline and decreased spatial memory in mouse models. The strongest genetic risk factor for sporadic Alzheimer’s disease is apolipoprotein E (APOE) genotype; the APOEε4 isoform is significantly more prevalent in AD populations and has been linked to increased disease progression and earlier age of onset. Previous work in the Kessler lab has shown that APOEε4 neurons, compared to APOEε3 isogenic control neurons, express increased levels of phosphorylated tau and have greater predisposition to cell death in response to external stressors such as ionomycin. The current proposal seeks to understand the interaction between increased BMP4 and APOEε4 expression at the cellular level to understand early sAD disease pathogenesis. To answer this question, our laboratory has generated induced pluripotent stem cells (iPSCs) from patients with sporadic AD and used CRISPR-/Cas9 editing of APOEε3/4 cells to create isogenic APOEε3/3 lines. These cells are then differentiated into neurons and astrocytes to determine cell-autonomous and non-cell autonomous cellular pathology involved in increased BMP4 signaling and APOEε4 expression. The first aim will test the hypothesis that increased BMP4 in tandem with APOEε4 expression elicit additive effects that negatively alters astrocytic expression and homeostatic functions. To test this hypothesis, transcriptomics will be used to determine differential gene expression and subsequent studies will be used to address protein expression and functional changes may occur. The second aim will utilize iPSC patient-derived cocultures of neurons and astrocytes in matched or mismatched isogenic pairs to determine non-cell autonomous changes that occur as a result of increased BMP4 signaling and APOEε4 genotype, testing the hypothesis that APOEε4 astrocytes, along with increased BMP4 signaling, exaggerate pathological cascades in neurons, leading to decreased viability subsequent cell death of neurons. The purpose of the first aim is to determine how astrocytes, whose trophic support is necessary for neuronal viability, alter homeostatic functions in response to sAD risk factors. The second aim will uncover how these cell-autonomous changes in astrocytes ultimately modify early disease pathology in neurons. The overall long-term goal is to identify early targetable mechanisms for successful intervention in this devastating disease.