Cell and Network Disruptions and Associated Pathogenenesis in Tauopathy and Down Syndrome

我们的研究目的是更好地了解tau蛋白传递和神经元过度兴奋驱动阿尔茨海默病（AD）相关痴呆神经退行性变进展的机制 （ADRD），其包括由21号染色体三体（Ts 21）引起的唐氏综合征（DS）。我们的研究是一致的 与RFA PAR-18-706的目标一致，因为我们将专注于理解“电路中tau细胞间扩散的选择性细胞敏感性的潜在机制”。我们研究的基础是tau蛋白是ADRD（如DS）发病机制的罪魁祸首，因为tau蛋白是DS脑中神经元缠结的主要成分，tau基因MAPT多态性增加Ts 21患者AD和AD的风险。ADRD中的神经病理学遵循脑中的时间和空间进展，并且越来越多的证据表明ADRD中的进行性神经变性是由于tau经由连接的神经元的跨突触扩散。除tau蛋白外，神经元过度兴奋可发生在ADRD的早期阶段，有些人提出网络功能障碍可能是ADRD中神经变性的驱动力。我们将研究由于Ts 21引起的淀粉样前体蛋白（APP）过度表达而导致的神经元活性改变是否有助于tau的跨突触扩散，从而增加神经变性的速率。我们将使用多学科的方法来研究ADRD中发现的APP过表达如何影响tau的传递并影响人脑回路。我们将共培养类器官并移植来自ADRD患者（tauP 301 L或Ts 21）的人类iPSC衍生的皮质神经元与对照人类皮质类器官或人类胎儿皮质切片，并使用新型延时成像平台四维机器人显微镜（4DRM）监测对神经元回路的影响。4DRM将在数周内跟踪人类初级脑切片中4D个体神经元的功能特性，以深入了解APP过度表达，过度兴奋和tau蛋白传递如何相互作用导致神经退行性变。纵向监测类器官和人脑切片中神经元回路的能力在研究可能由tau蛋白传递诱导的缓慢退行性过程中具有创新性和关键性。我们将使用4DRM结合多变量考克斯比例风险分析，以确定网络过度兴奋和tau聚集对神经元存活是否有害、有益或无关紧要。为了补充这些体外研究，我们开发了一种tau蛋白病的体内整体动物模型，其中转基因斑马鱼幼虫在其神经系统中过表达人tauP 301 L，并使用4DRM来监测活体动物中的神经元回路。GFP-tauP 301 L斑马鱼模型显示p-tau增加，但没有明显的神经元功能障碍或神经变性。当过度兴奋被诱导时，鱼显示出对神经元死亡和神经变性的行为迹象的敏感性。利用该模型，我们将研究过度兴奋对tau蛋白聚集的影响， Tau在体内的传递机制。通过了解tau蛋白的传递机制，我们可以制定策略来阻止神经病理学的传播，以减缓AD的进展。

The goal of our studies is to better understand the mechanisms by which tau transmission and neuronal hyperexcitability drive the progression of neurodegeneration in Alzheimer's Disease (AD) Related Dementias (ADRD) that include Down Syndrome (DS) caused by trisomy of chromosome 21 (Ts21). Our studies are in line with the goals of RFA PAR-18-706 because we will focus on understanding “mechanisms underlying selective cell sensitivity to tau cell-to-cell spread in circuitry.” The foundation of our studies is that tau is a prime culprit in pathogenesis of ADRDs such as DS because tau is a major component of neurofibrillary tangles in DS brains and polymorphisms in the tau gene MAPT increase risk of AD and AD in Ts21 patients. Neuropathology in ADRD follows a temporal and spatial progression in brain, and there is growing evidence that the progressive neurodegeneration in ADRD is due to transsynaptic spread of tau via connected neurons. In addition to tau, neuronal hyperexcitability can occur at early stages of ADRD, and some have proposed that network dysfunction may be a driving force for neurodegeneration in ADRDs. We will investigate if altered neuronal activity due to overexpression of amyloid precursor protein (APP) caused by Ts21 contributes to the transsynaptic spread of tau, increasing the rate of neurodegeneration. We will use a multidisciplinary approach to study how APP overexpression found in ADRDs affects transmission of tau and impacts human brain circuitry. We will co-culture organoids and transplant human iPSC-derived cortical neurons from ADRD patients (tauP301L or Ts21) with control human cortical organoids or human fetal cortical slices and monitor the impact on neuronal circuits using a novel time lapse, imaging platform, four-dimensional robotic microscopy (4DRM). 4DRM will track functional properties of individual neurons in 4D in human primary brain slices over weeks, to give insight into how APP overexpression, hyperexcitability, and tau transmission interact to cause neurodegeneration. The ability to monitor neuronal circuitry in organoids and human brain slices longitudinally is innovative and critical in studying the slow degenerative processes that may be induced by tau transmission. We will use 4DRM in combination with multivariate Cox proportional hazards analysis to determine if network hyperexcitability and tau aggregation is detrimental, beneficial or inconsequential towards neuronal survival. To complement these in vitro studies, we developed an in vivo whole animal model of tauopathy in which transgenic zebrafish larvae overexpress human tauP301L in their nervous system and use 4DRM to monitor neuronal circuitry in the living animals. The GFP-tauP301L zebrafish model shows increased p-tau but no overt neuronal dysfunction, or neurodegeneration. When hyperexcitability is induced, the fish display sensitivity to neuronal death and behavioral signs of neurodegeneration. With this model, we will investigate the effect of hyperexcitability on aggregation of tau and mechanisms of tau transmission in vivo. By understanding mechanisms of tau transmission, we can develop strategies to block spread of neuropathology to slow the progression of AD.