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FMRP regulation of local and long-range neocortical circuits in the mouse: Links with EEG phenotypes

FMRP 对小鼠局部和远程新皮质回路的调节：与 EEG 表型的联系

基本信息

批准号：
10453464
负责人：
KIMBERLY M. HUBER
金额：
$ 42.67万
依托单位：
CINCINNATI CHILDRENS HOSP MED CTR
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-25 至 2025-06-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10453464
关键词：
Acute Area Behavior Biochemical Brain CNR1 gene Cholecystokinin Clinical Collaborations Contralateral Coupling Cre driver Data Defect Electroencephalography Endocannabinoids Environment Excitatory Synapse FMR1 FMRP Fragile X Syndrome Frequencies Functional disorder Genetic Glutamates Human Knock-out Knockout Mice Link Measures Mediating Methods Molecular Mus Neurons Outcome Parvalbumins Pharmacology Phenotype Positioning Attribute Process Proteins RNA Regulation Research Personnel Rest Ribosomes Role Sensory Slice Somatosensory Cortex Synapses Testing Thalamic structure Touch sensation Translating base behavioral phenotyping cell type experience experimental study genetic manipulation hippocampal pyramidal neuron in vivo inhibitory neuron loss of function mouse model neocortical neurophysiology optogenetics postnatal receptor response sensory cortex somatosensory sound targeted treatment transcriptome transcriptome sequencing translational medicine translatome

项目摘要

Project 1 (P1) investigators have identified cortical EEG phenotypes in humans with Fragile X Syndrome (FXS), such as enhanced resting state gamma power, that correlate with clinical outcomes. Remarkably, many human EEG phenotypes are conserved in the mouse model of FXS, the Fmr1 knockout (KO), as discovered by Project 2 (P2) investigators. The across-species conservation of EEG phenotypes strongly suggest similarly dysfunctional cortical circuits in mice and humans with loss of function of Fmr1. Thus, our proposed studies to understand and correct circuit dysfunction in the Fmr1 KO mouse will likely be highly relevant to humans with FXS. We have identified two major functional circuit defects in primary sensory cortex of the Fmr1 KO mouse that likely contribute to specific EEG phenotypes in Fmr1 KO mice and humans with FXS – 1) hyperexcitability of “local” circuits within a cortical region and 2) reduced functional excitatory long- range connections between cortical regions. Hyperexcitability of local circuits is observed ex vivo in brain slices with 2 key measures: 1) Prolonged Circuit Activation (PCA) of neocortical circuits, either spontaneously or in response to sensory stimulation and 2) enhanced gamma power. We hypothesize that hyperexcitability of local neocortical microcircuits underlies the increased resting state gamma power and alterations in sensory-evoked gamma entrainment of the EEG observed in Fmr1 KO mice and humans with FXS. We test this hypothesis in mice through mechanistic conservation. Using ex vivo neocortical slices of Fmr1 KO mice we have discovered 3 synaptic microcircuit changes likely to give rise to hyperexcitable local circuits; 1) Hyperconnectivity of excitatory synapses between pyramidal neurons 2) Reduced excitatory synaptic drive onto Parvalbumin-positive (PV) inhibitory neurons 3) enhanced endocannabinoid suppression of inhibitory synaptic drive – likely from Cholecystokinin-positive (CCK) neurons. In Aims 1 and 2, in close collaboration with P2, we will use optogenetic, chemogenetic, and pharmacological approaches to manipulate PV and CCK inhibitory circuits in order to determine how their dysfunction contributes to hyperexcitability of local cortical circuits, abnormal EEG phenotypes, and related behaviors in Fmr1 KO mice. In addition to hyperexcitable local circuits, our new findings reveal weak excitatory connectivity between cortical regions in Fmr1 KO mice - specifically between homotopic contralateral cortical areas (callosal connections). Dysfunctional long-range synaptic connectivity likely contributes to the abnormal long-range functional coupling between cortical areas as observed by EEG in humans with FXS). In Aims 3 and 4, we propose experiments to determine the underlying synaptic and molecular mechanisms as well as the functional circuit level consequences of these weak long- range excitatory connections. Results of Project 3 (P3) are expected to determine the specific dysfunctional cell- types, microcircuits, and biochemical mechanisms that likely mediate human relevant EEG phenotypes in FXS and provide a rationale for specific, targeted therapeutic strategies.

项目 1 (P1) 的研究人员已经确定了患有脆性 X 综合征 (FXS) 的人类皮质脑电图表型，例如与临床结果相关的增强的静息态伽玛能量。值得注意的是，许多人类 Project 发现，脑电图表型在 FXS（Fmr1 敲除 (KO)）小鼠模型中是保守的 2 (P2) 调查员。脑电图表型的跨物种保守性强烈表明类似的情况 Fmr1 功能丧失的小鼠和人类皮质回路功能失调。因此，我们提出的研究了解并纠正 Fmr1 KO 小鼠的电路功能障碍可能与人类高度相关 FXS。我们已经确定了 Fmr1 KO 初级感觉皮层的两个主要功能电路缺陷可能对 Fmr1 KO 小鼠和患有 FXS 的人类的特定脑电图表型有贡献的小鼠 – 1) 皮质区域内“局部”回路的过度兴奋性和 2）功能性兴奋性长程降低皮质区域之间的范围连接。在大脑离体观察到局部电路的过度兴奋具有 2 个关键指标的切片：1) 新皮质回路的延长回路激活 (PCA)，无论是自发的还是响应感官刺激和 2) 增强的伽马功率。我们假设过度兴奋局部新皮质微电路是静息态伽马功率增加和变化的基础在 Fmr1 KO 小鼠和患有 FXS 的人类中观察到 EEG 的感觉诱发伽马夹带。我们通过机械守恒定律在小鼠身上检验这一假设。使用 Fmr1 KO 小鼠的离体新皮质切片我们发现了 3 种突触微电路变化可能导致局部电路过度兴奋； 1）锥体神经元之间兴奋性突触的超连接 2) 减少兴奋性突触驱动小清蛋白阳性 (PV) 抑制性神经元 3) 增强内源性大麻素对抑制性突触的抑制驱动力——可能来自胆囊收缩素阳性（CCK）神经元。在目标 1 和 2 中，我们与 P2 密切合作将使用光遗传学、化学遗传学和药理学方法来操纵 PV 和 CCK 抑制以确定其功能障碍如何导致局部皮质回路过度兴奋， Fmr1 KO 小鼠脑电图异常表型和相关行为。除了过度兴奋的局部电路外，我们的新发现揭示了 Fmr1 KO 小鼠皮质区域之间的兴奋性连接较弱 - 特别是同伦对侧皮质区域（胼胝体连接）之间。功能失调的长程突触连接性可能导致皮质区域之间异常的远程功能耦合，例如通过脑电图在患有 FXS 的人类中观察到）。在目标 3 和 4 中，我们提出实验来确定潜在的突触和分子机制以及这些弱长链的功能电路水平后果范围兴奋性连接。项目 3 (P3) 的结果预计将确定特定的功能障碍细胞 - FXS 中可能介导人类相关脑电图表型的类型、微电路和生化机制并为具体的、有针对性的治疗策略提供理由。