Circuit-based mechanisms of neuronal vulnerability in the adult EC

成人内皮细胞神经元脆弱性的基于回路的机制

• 批准号: 10615015
• 负责人: Caleb Wood
• 金额: $ 4.77万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-15 至 2024-04-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10615015
• 关键词: Action Potentials; Address; Adult; Alzheimer' s Disease; Apoptosis; Apoptotic; Automobile Driving; Axon; Binding; Brain; Brain region; Cell Death; Cell Death Induction; Cells; Cessation of life; Chloride Channels; Chronic; Code; Cognitive deficits; Communication; Cytoplasmic Granules; Data; Development; Developmental Process; Disease; Disparity; Electrophysiology (science); Engineering; Excision; Exhibits; Fire - disasters; Functional disorder; Future; Generations; Genetic; Genetic Models; Gliosis; Glutamates; Glycine; Goals; Hippocampus; Infusion procedures; Injury; Ivermectin; Life; Ligands; Mediating; Memory; Modeling; Morphologic artifacts; Mus; Nerve Degeneration; Neurodegenerative Disorders; Neurons; Neurotransmitters; Pathway interactions; Pattern; Perforant Pathway; Population; Predisposition; Process; Signal Transduction; Sodium Channel; Symptoms; Synapses; Synaptic plasticity; Testing; Tetanus Toxin; Tetrodotoxin; Traction; competitive environment; critical period; dentate gyrus; entorhinal cortex; experimental study; genetic approach; granule cell; in vivo; insight; mouse model; neuron loss; neuronal survival; neurotransmitter release; pharmacologic; postnatal; postnatal development; postnatal period; postsynaptic; prevent; pro-apoptotic protein; response; way finding

Project summary/abstract. Entorhinal cortex layer II (ECII) neurons are some of the first cells to degenerate in Alzheimer’s Disease (AD). ECII axons form the perforant pathway and are the major cortical input into the hippocampus. The perforant pathway supports memory formation and spatial navigation throughout life, and loss of this input is consistent with the cognitive deficits that present early in AD. To mimic the loss of this input in AD, the Jankowsky lab created a chemogenetic mouse model of perforant pathway disruption in which a subset of ECII neurons express an engineered chloride channel (GlyCl) to prevent the generation of action potentials. We unexpectedly discovered that entorhinal neurons were highly vulnerable to silencing. Shortly after being inactivated, many ECII neurons retract their axons from the dentate gyrus, express pro- apoptotic proteins, and then are eliminated from the circuit. We observed similar neurodegeneration after eliminating neurotransmitter release with tetanus toxin (TeTX), confirming that neuronal loss is not an artifact of GlyCl activation. Further, this silencing-induced degeneration is not shared by other brain regions, as neither the pre/parasubiculum nor retrosplenial cortex exhibit cell loss after neuronal inactivation. This suggests that specific features of the entorhinal cortex may confer neuronal vulnerability to inactivity. One possible vulnerability could be related to the formation of entorhinal-hippocampal circuit. We noted that the pattern of ECII degeneration after silencing was strikingly similar to the processes that guide to refinement of the perforant pathway during development. In early post-natal periods, inactive ECII neurons are pruned from the circuit in a process that is mediated by local differences in activity, referred to as activity- dependent competition. Projections are only pruned when neurons are sparsely inactive - when all cells are equally inactive, none are removed. This proposal will test two hypotheses about the cellular mechanism driving neuronal death in the mature entorhinal cortex. Aim 1 will determine whether activity-dependent competition persists in the adult ECII. Pharmacological and genetic approaches will be used to modulate relative activity levels to determine how cell death is influenced by activity differences between neighboring cells. Aim 2 will determine whether post-synaptic partners promote the survival of ECII neurons. Our preliminary data suggests that eliminating neurotransmitter release from ECII neurons – without blocking action potentials - is sufficient to induce degeneration. I will therefore use pharmacological and genetic approaches to both reduce neurotransmitter binding in dentate granule cells and eliminate their ability to fire action potentials in response to ECII input. This will test whether neurotransmitter-mediate signaling, or post-synaptic activity itself, is required for ECII neuron survival. Data from these aims will determine how activity disruption may mediate cell death in the adult brain. Further, these data may suggest that mechanisms which drive cell death during postnatal development are not necessarily limited to critical periods but may persist into adulthood within certain pathways. Understanding these mechanisms may inform future studies on neurodegenerative disease and how circuit disruption may contribute to neuronal loss.

项目概要/摘要。 内嗅皮层第二层（ECII）神经元是阿尔茨海默病（AD）中最早退化的细胞之一。ECII 轴突形成穿通通路并且是进入海马的主要皮质输入。穿支通路支持 记忆形成和空间导航贯穿一生，这种输入的丧失与认知缺陷一致 在AD早期出现。为了模拟AD中这种输入的丢失，Jankowsky实验室创建了一个化学遗传小鼠模型 其中ECII神经元的子集表达工程氯离子通道（GlyCl）， 防止动作电位的产生。我们意外地发现，内嗅神经元非常容易受到 沉默在失活后不久，许多ECII神经元从齿状回撤回它们的轴突，表达pro-mRNA。 凋亡蛋白，然后从电路中消除。我们观察到类似的神经变性后，消除 神经递质释放与破伤风毒素（TeTX），证实神经元损失不是GlyCl激活的假象。 此外，这种沉默诱导的变性不被其他大脑区域共享，因为前/旁隐核和前/旁隐核都不存在。 压后皮质在神经元失活后表现出细胞损失。这表明，内嗅的具体特点， 皮质可赋予神经元对不活动的脆弱性。一个可能的脆弱性可能与形成 内鼻-海马回路我们注意到，沉默后ECII退化的模式与沉默后ECII退化的模式惊人地相似。 在发育过程中指导穿孔通路的完善的过程。在出生后早期，不活跃的ECII 神经元在一个过程中从回路中被修剪，该过程由活动的局部差异介导，称为活动- 依赖竞争。只有当神经元稀疏不活跃时，投射才会被修剪--当所有细胞都是平等的时候。 不活动，没有删除任何内容。这项建议将测试两个假设的细胞机制驱动神经元死亡， 成熟的内嗅皮层目的1将确定活动依赖性竞争是否持续在成人ECII。 药理学和遗传学方法将用于调节相对活性水平，以确定细胞死亡是如何发生的。 受相邻细胞之间活动差异的影响。AIM 2将决定突触后伴侣是否 促进ECII神经元的存活。我们的初步数据表明，消除ECII释放的神经递质 神经元-没有阻断动作电位-足以诱导变性。因此，我将使用药理学 以及基因方法来减少齿状颗粒细胞中的神经递质结合并消除它们的放电能力 响应ECII输入的动作电位。这将测试是否神经递质介导的信号，或突触后 活动本身是ECII神经元存活所必需的。来自这些目标的数据将决定活动中断如何可能 介导成年人大脑中的细胞死亡。此外，这些数据可能表明，细胞死亡的驱动机制， 出生后发育不一定局限于关键时期，但可能持续到成年， 途径。了解这些机制可能会为未来的神经退行性疾病研究提供信息， 破坏可能导致神经元损失。