Deciphering molecular pathways of inhibitory interneuron dysfunction in Alzheimer's disease

自从Ramon y Cajal提出大脑不是一个单一的网状单位，而是包含离散和独立的细胞， 尽管神经科学家们一直在努力阐明不同脑细胞类型的功能特性。这 细胞异质性，这是由细胞类型特异性基因表达程序引起的， 是神经元群体对神经退行性疾病的选择性脆弱性的基础。然而，在这方面， 缺乏有效的工具来进行特定细胞类型的分子分析和操作阻碍了进展 在确定脆弱细胞群体的疾病机制和开发细胞类型特异性疗法方面。作为 开发了新的技术平台来分析神经系统中的特定细胞类型，包括 BacTRAP和单细胞RNA-seq，以及操纵特定神经元中基因或活性的遗传工具 人群，包括依赖铬和通道视紫红质系统，新的机会正在出现 以实验方式解决体内细胞类型异质性和选择性脆弱性。我们将采取 最新技术的优势，以确定与抑制性中间神经元相关的分子改变， 在阿尔茨海默病（AD）小鼠模型和患有AD的人类中的认知损害。我们将特别关注抑制性中间神经元，因为它们可能对早期脑网络改变（例如，活动过度和失活缺陷）、淀粉样蛋白-β（Aβ）沉积和AD患者及相关模型的认知改变。在这里，我们建议通过使用BacTRAP和单细胞RNA-seq的转录组分析来识别AD，J20和APP-KI小鼠的两种小鼠模型中的中间神经元细胞类型中的认知相关分子改变，验证我们在人类AD样本中的发现，并在小鼠模型中进行机制研究以确定所识别的分子改变的功能和治疗相关性。具体而言，目标1将确定遗传上确定的内源性和移植的抑制性细胞类型（Mafb-和Dlx 1-BacTRAP细胞）的RNA-seq转录组谱以及行为表征的NTG、J20和APP-KI小鼠的皮质和海马的大量RNA-seq转录组。目的2将确定J20和APP-KI小鼠中中间神经元亚型的全部多样性的单细胞RNA-seq转录组谱（目的2a），并在AD的人类样品中验证它（目的2b）。目的3将通过cre依赖性缺失或过表达调节J20小鼠中鉴定的分子/途径改变的表达水平，以确定其对J20小鼠脑网络和认知功能障碍的因果贡献，从而在功能上验证J20小鼠中鉴定的分子/途径改变。与我们的初步结果一致，我们预测中间神经元对AD诱导的变化具有细胞类型特异性的脆弱性，其中一些改变与J20小鼠的认知能力下降有因果关系。我们预测这项研究将 产生重大的科学贡献，这将有助于我们了解AD中的网络异常和中间神经元功能障碍。

Since Ramon y Cajal proposed that the brain is not a single reticular unit but contains discrete and independent brain cells, neuroscientists have struggled to elucidate the functional properties of distinct brain cell types. This cellular heterogeneity, which arises from cell-type-specific gene expression programs, probably underlies the selective vulnerability of neuronal populations to neurodegenerative disorders. However, the lack of effective tools for molecular profiling and manipulation of specific cell types has hampered progress in identifying disease mechanisms of vulnerable cell populations and developing cell-type specific therapies. As new technology platforms are developed to profile specific cell types in the nervous system, including BacTRAP and single-cell RNA-seq, and genetic tools to manipulate genes or activity in specific neuronal populations, including cre-dependent and channelrhodopsin systems, new opportunities are emerging to experimentally address cell-type heterogeneity and selective vulnerability in vivo. We will take advantage of the latest technologies to identify molecular alterations in inhibitory interneurons associated with cognitive impairment in mouse models of Alzheimer's disease (AD) and humans with AD. We will particularly focus on inhibitory interneurons since they may critically contribute to early brain network alterations (e.g., hyperactivity and deactivation deficits), amyloid-β (Aβ) deposition, and cognitive alterations in humans with AD and related models. Here, we propose to identify cognitive-relevant molecular alterations in interneuron cell types in two mouse models of AD, J20 and APP-KI mice, by transcriptome profiling using BacTRAP and single-cell RNA-seq, validate our findings in human AD samples, and perform mechanistic studies in mouse models to determine the functional and therapeutic relevance of the identified molecular alterations. Specifically, Aim 1 will determine the RNA-seq transcriptome profile of genetically defined endogenous and transplanted inhibitory cell types (Mafb- and Dlx1-BacTRAP cells) and bulk RNA-seq transcriptome of the cortex and hippocampus of behaviorally characterized NTG, J20, and APP-KI mice. Aim 2 will determine the single-cell RNA-seq transcriptome profile of the full diversity of interneuron sub-types in J20 and APP-KI mice (Aim 2a) and validate it in human samples of AD (Aim 2b). Aim 3 will functionally validate the identified molecular/pathway alterations in J20 mice by modulating their expression levels by cre-dependent deletions or overexpression to determine their causal contribution to brain network and cognition dysfunction in J20 mice. Consistent with our preliminary results, we predict that interneurons have cell-type-specific vulnerability to AD-induced changes and some of those alterations are causally linked to cognitive decline in J20 mice. we predict this research will generate major scientific contributions that will help us to understand network abnormalities and interneuron dysfunction in AD.