Contributions of cell type and exosome signaling to prodromal synaptic and circuit changes in Alzheimer's Disease models

阿尔茨海默病(AD)的特征是突触丢失，导致认知功能下降。这个 阿尔茨海默病的病理学日益被认识到涉及神经元与其他脑细胞类型的相互作用，值得注意的是 小胶质细胞和星形胶质细胞。细胞外小泡(EV)由大脑中的所有细胞分泌，携带蛋白质和 核糖核酸货物。EVS具有从供体细胞向脑组织内受体细胞发出信号并修饰细胞的能力 功能，如癌症和多种神经系统疾病所显示的。EV致病蛋白的繁殖 至少在AD病理的某些方面，脑细胞之间的相互作用是一种强有力的候选机制， 提示不同的EV病毒不仅可以作为疾病的生物标志物，而且可以直接诱发 对病理疾病状态的脆弱性或保护性。然而，人们对电动汽车货运的多样性和 与阿尔茨海默病有关的关键脑细胞类型的生物活性。此外，遗传易感基因座或 其他因素，如性别，尚未确定关于EV含量、EV生物活性或 神经元对EVS的反应。为了克服这些障碍，我们建议使用IPSC和直接重新编程来 从与AD相关的IPSCs中获得纯化的人类神经元、星形胶质细胞和小胶质细胞的培养 遗传背景或预期的易感性。因为APOE的变异对两种AD风险都有很强的影响 (ApoE4)和保护(APOE2)我们将从每个APOE基因的同基因IPSCs中分析EV货物的EV 使用最先进的蛋白质组学和RNA-Seq方法。同时，我们将解决功能后果 EV在人诱导神经元上的生物活性的两个灵敏读数：成像神经元连接和 突触动力学和无偏转录侧写。这些合作研究将建立一种新的 基于细胞类型的电动汽车货物多样性和信号生物活性概况目录。比较电动汽车的内容来自 病理风险和保护性变异有可能揭示与细胞到细胞相关的新机制 传播致病或保护性信号，并确定候选生物标志物以在人类临床样本中进行测试 AD患者。

Alzheimer’s Disease (AD) is characterized by loss of synapses, resulting in decline of cognitive function. The pathology of AD is increasingly recognized to involve neuronal interactions with other brain cell types, notably microglia and astrocytes. Extracellular vesicles (EVs) are secreted by all cells in the brain, and carry protein and RNA cargo. EVs have the capacity to signal from donor to recipient cells within brain tissue and modify cell functions, as shown in cancers and multiple neurological diseases. EV propagation of pathologic proteins between cells in the brain is a strong candidate mechanism underlying at least some aspects of AD pathology, suggesting that distinct EV cargos may not only serve as biomarkers for disease but also directly induce vulnerability to or protection from pathologic disease states. Yet, little is known about EV cargo diversity and bioactivity from key brain cell types implicated in AD. Furthermore, the impact of genetic susceptibility loci or other factors such as gender has not been determined with respect to EV content, EV bioactivity or variation in neuronal responses to EVs. To overcome these barriers, we propose to use iPSCs and direct reprogramming to generate purified cultures of human neurons, astrocytes and microglia from iPSCs that vary by their AD-related genetic background or expected susceptibility. Because variation at APOE has a strong effect on both AD risk (APOE4) and protection (APOE2) we will profile EV cargos of EVs from isogenic iPSCs of each APOE genotype using state-of-the-art proteomic and RNA-Seq methods. In parallel, we will address the functional consequences of EV bioactivity on human induced neurons with two sensitive readouts: imaging neuronal connectivity and synaptic dynamics and unbiased transcriptomic profiling. These collaborative studies will establish a novel catalog of cell-type based profiles of EV cargo diversity and signaling bioactivity. Comparing EV contents from pathologic risk and protective variants has the potential to uncover novel mechanisms related to cell-to-cell spread of pathogenic or protective signals, and identify candidate biomarkers to test in clincal samples of human AD patients.