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）研究人员已经确定了患有脆弱X综合征（FXS）的人类的皮质EEG表型，例如增强的静息状态γ功率，与临床结果相关。值得注意的是，许多人 EEG表型在FXS的小鼠模型，FMR1敲除（KO）中保守，如Project所发现 2（P2）调查人员。脑电图表型的跨物种保护强烈建议类似地表明小鼠和人类功能丧失FMR1的功能失调的皮质回路。那，我们提出的研究在FMR1 KO鼠标中了解并纠正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的主要感觉皮层中的两个主要功能电路缺陷可能有助于FMR1 KO小鼠和人类具有FXS的特定脑电图表型的小鼠 - 1）皮质区域内“局部”电路的过度兴奋和2）功能性兴奋性长期降低皮质区域之间的范围连接。观察到局部电路的过度兴奋性在大脑中离体具有2个关键措施的切片：1）新皮层电路的长时间电路激活（PCA），要么赞助或响应感官刺激和2）增强的伽马功率。我们假设局部新皮层微电路是增加静息状态伽马功率和改变的基础在FMR1 KO小鼠和带有FXS的人类中观察到的脑电图的感官诱发的伽马入口。我们通过机械保护在小鼠中检验这一假设。使用FMR1 KO小鼠的体内新皮层切片我们发现3种突触微电路变化可能导致过度可见的本地电路。 1）锥体神经元之间的兴奋性突触的高连接性2）将兴奋性突触驱动降低到白蛋白阳性（PV）抑制性神经元3）增强内源性大麻素抑制抑制性突触驱动 - 可能来自胆囊化蛋白阳性（CCK）神经元。在AIMS 1和2中，与P2密切合作，我们将使用光遗传学，化学遗传和药物方法来操纵PV和CCK抑制电路以确定其功能障碍如何促进局部皮质电路过度兴奋的性能， FMR1 KO小鼠中的异常脑电图表型和相关行为。除了过度可见的本地电路外，我们的新发现表明，FMR1 KO小鼠的皮质区域之间的兴奋性弱 - 特别是在同位对侧皮质区域（Callosal连接）之间。功能失调的远程突触连通性可能有助于皮质区域之间的异常远程功能耦合由脑电图在患有FXS的人类中观察到）。在目标3和4中，我们提出了实验以确定基础突触和分子机制以及这些弱长的功能电路水平的后果范围兴奋连接。项目3（P3）的结果有望确定特定功能失调的细胞 - 类型，微电路和生化机制可能介导FX中的人类相关的EEG表型并为特定有针对性的治疗策略提供理由。