Transcriptional Dysfunction in Dentate Gyrus Cell Types: Roles of Retinoic Acid Responsive Genes in Protection Against Alzheimer's Disease Pathogenesis

项目总结/摘要 海马齿状回（DG）的过度兴奋与早期学习障碍有关。 阿尔茨海默病（AD）。AD早期DG回路内发生的因果性上游信号机制 发病机制仍然知之甚少。衰老的线粒体自由基理论提出， 线粒体，通过产生过量的活性氧（ROS），导致氧化损伤， 蛋白质、脂质和DNA的氧化应激过程称为氧化应激（OS）。抗氧化剂（AO）通常会抵消 这一过程通过清除过量的ROS，从而防止OS。抗氧化剂全反式维甲酸 （ATRA），视黄醇的活性形式，在ROS清除和转录控制中具有双重作用。 突触/神经元蛋白通过其作为视黄酸受体（RAR）激动剂的功能。的最新证据 啮齿类动物表现出海马ATRA水平的年龄依赖性下降， 肝-脑轴我们认为DG中的ATRA缺失是AD发病机制的早期事件， 导致过量ROS诱导的损伤、线粒体功能障碍和RAR的占用减少。 DG细胞类型、加速性淀粉样变性、网络过度兴奋和认知功能障碍。支持这个 在科学前提下，对人类海马转录组数据的二次分析使我们发现了一个大的 AD脑中OS和RAR敏感基因的数量失调。在J20 AD的初步研究中， 在小鼠模型中，长期用ATRA治疗使行为正常化，防止了异常抑制的形成。 DG中的回路，并使许多途径正常化，其中包括DG中的RAR和OS敏感基因 DG因此，我们的中心假设是，ATRA耗竭诱导氧化应激和 DG细胞类型中RAR敏感基因的转录控制，其可以加速或延迟 通过双向操控DG ATRA水平采用创新的多学科方法， 独特地结合了DG依赖性学习范式，单细胞转录组学和细胞/突触 分析在两个AD小鼠模型，我们将确定如何双向操纵ATRA水平改变 RAR敏感基因在DG细胞类型中的转录控制，并影响DG依赖性学习， 细胞/突触功能。SA 1检验了DG特异性逆转学习受损伴随着 通过DG细胞类型中RAR敏感基因的转录受损，OS增加， 两种AD小鼠模型的功能障碍。SA 2检验了逆转学习性能、OS水平、 在两种AD小鼠模型中，DG细胞类型和RAR敏感基因的表达依赖于饮食中视黄醇的摄入。 最后，SA 3在两个AD小鼠中检验了DG回路功能依赖于膳食视黄醇摄入的假设 模型成功完成这个项目将揭示DG相关学习障碍的新机制 并在特定细胞类型中发现新的AD生物标志物，指示ATRA缺乏。的作用的话 视黄醇在预防AD中的应用将使知识从实验室迅速传播到床边。

PROJECT SUMMARY / ABSTRACT Hyperexcitability of the hippocampal dentate gyrus (DG) is associated with impaired learning in early stages of Alzheimer’s disease (AD). Causal upstream signaling mechanisms occurring within DG circuits early in AD pathogenesis remain poorly understood. The Mitochondrial Free Radical Theory of Aging proposes that mitochondria, through the production of excess reactive oxygen species (ROS), cause oxidative damage to proteins, lipids, and DNA ¾ a process termed oxidative stress (OS). Antioxidants (AOs) normally counteract this process by scavenging excess ROS, thereby preventing OS. The antioxidant all-trans retinoic acid (ATRA), the active form of retinol, has a dual role in ROS scavenging and transcriptional control of synaptic/neuronal proteins via its function as a retinoic acid receptor (RAR) agonist. Recent evidence from rodents has demonstrated an age-dependent decline in hippocampal ATRA levels due to homeostatic collapse of the liver-brain axis. We propose that ATRA depletion in the DG is an early event in AD pathogenesis, leading to excess ROS-induced damage, mitochondrial dysfunction, and reduced occupancy of RARs across DG cell types, accelerating amyloidosis, network hyperexcitability, and cognitive dysfunction. Bolstering this scientific premise, secondary analyses of human hippocampal transcriptomic data led us to discover a large number of OS- and RAR-sensitive genes dysregulated in AD brains. In preliminary studies from the J20 AD mouse model, chronic treatment with ATRA normalized behavior, prevented the formation of aberrant inhibitory circuits in the DG, and normalized a number of pathways that included RAR- and OS-sensitive genes in the DG. Therefore, our central hypothesis is that ATRA depletion induces oxidative stress and loss of transcriptional control of RAR-sensitive genes in DG cell types, which can be accelerated or delayed by bidirectionally manipulating DG ATRA levels. Using an innovative multidisciplinary approach that uniquely combines DG-dependent learning paradigms, single cell transcriptomics, and cellular/synaptic analysis in two AD mouse models, we will determine how bidirectional manipulation of ATRA levels alters transcriptional control of RAR-sensitive genes across DG cell types and impacts DG-dependent learning and cellular/synaptic function. SA1 tests the hypothesis that impaired DG-specific reversal learning is accompanied by impaired transcription of RAR-sensitive genes in DG cell types, increased OS, and mitochondrial dysfunction in two AD mouse models. SA2 tests the hypothesis that reversal learning performance, OS levels, and RAR-sensitive gene expression in DG cell types depend on dietary retinol intake in two AD mouse models. Finally, SA3 tests the hypothesis that DG circuit function depends on dietary retinol intake in two AD mouse models. Successful completion of this project will reveal novel mechanisms of DG-related learning impairments in AD and discover new AD biomarkers in specific cell types indicative of ATRA deficiency. Determining roles of retinol in protection against AD will enable rapid dissemination of knowledge from bench to bedside.