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

我们研究的目的是更好地了解tau传递和神经元超兴奋性驱动阿尔茨海默病(AD)相关性痴呆神经变性进展的机制 (ADRD)，包括由21号染色体三体(Ts21)引起的唐氏综合征(DS)。我们的学习是一致的 与RFA PAR-18-706的目标一致，因为我们将重点了解“电路中tau细胞对细胞间扩散的选择性敏感性的潜在机制”。我们研究的基础是tau是DS等ADRDS发病的罪魁祸首，因为tau是DS脑内神经原纤维缠结的主要成分，而且tau基因MAPT的多态增加了Ts21患者AD和AD的风险。ADRD的神经病理学遵循脑内时间和空间的进程，越来越多的证据表明，ADRD的进行性神经变性是由于tau通过连接的神经元跨突触扩散所致。除tau外，ADRD早期还可出现神经元超兴奋性，一些人提出网络功能障碍可能是ADRD神经退行性变的驱动力。我们将研究Ts21引起的淀粉样前体蛋白(APP)过度表达引起的神经元活动改变是否有助于tau的跨突触扩散，从而增加神经退行性变的速度。我们将使用多学科的方法来研究在ADRDS中发现的APP过度表达如何影响tau的传递并影响人类的大脑电路。我们将ADRD患者(tauP301L或Ts21)的IPSC来源的皮质神经元与对照人类皮质器官或人胎儿皮质切片共培养并移植，并使用新型延时成像平台、四维机器人显微镜(4DRM)监测对神经元电路的影响。4DRM将在数周内跟踪人类原代脑片4D中单个神经元的功能特性，以深入了解APP过度表达、过度兴奋和tau传递如何相互作用导致神经退化。在研究tau传递可能诱导的缓慢退化过程中，纵向监测有机体和人脑切片中的神经元电路的能力是创新的和关键的。我们将使用4DRM结合多变量Cox比例风险分析来确定网络超兴奋性和tau聚集对神经元存活是有害的、有益的还是无关紧要的。为了补充这些体外研究，我们建立了一个体内整体动物模型，在该模型中，转基因斑马鱼幼虫在神经系统中过表达人类tauP301L，并使用4DRM来监测活体动物的神经元回路。GFP-tauP301L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。当诱导过度兴奋时，鱼类表现出对神经元死亡和神经变性的行为迹象的敏感性。利用这个模型，我们将研究超兴奋性对tau和tau聚集的影响。 Tau在体内的传播机制。通过了解tau的传播机制，我们可以制定策略来阻止神经病理的传播，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.