Examining the role of specific NMDA receptor subunits in cortical circuit dysfunction in Fragile X Syndrome

项目摘要 感觉超敏反应是自闭症和脆性X综合征（FXS）的常见症状，被认为是自闭症的一种表现。 大脑皮层回路失调的结果在患有FXS的人类和FXS小鼠模型中的EEG研究， KO，揭示了皮质回路过度兴奋和同步性缺陷，如增强静息状态下的功率， 伽马波段和减少的传感器驱动的同步。在急性切片中，可以观察到这种过度兴奋， 延长的持续活动状态，称为UP状态，以及在UP状态期间增加的伽马带功率。我 假设在新皮层中介导过度兴奋和延长UP状态回路机制 可能有助于FXS的EEG表型。使用正和负变构调节剂（PAM/NAM） 对于NMDA受体的GluN 2C/D亚基，我已经揭示了在NMDA受体中GluN 2C/D功能的上调。 导致回路过度兴奋的Fmr 1 KO皮质。具体地，GluN 2C/D PAM增加UP状态 UP状态期间的持续时间和伽马功率，而NAM抢救UP状态持续时间。值得注意的是，这些 干预仅影响Fmr 1 KO，而不影响其野生型（WT）同窝仔，表明GluN 2C/D功能 在Fmr 1 KO中上调并导致皮质回路功能障碍。通常，GluN 2C/D亚基是 在皮质抑制性神经元和星形胶质细胞中表达。因为我的结果与对 在抑制性神经元中，GluN 2C/D亚基可能在兴奋性神经元中错误表达或在星形胶质细胞中上调 关于FMR 1 KO我假设GluN 2C/D表达和/或功能在兴奋性脑损伤中增加。 神经元和/或星形胶质细胞，这有助于过度兴奋和改变 皮层回路的同步性该项目的目标是测试这一假设，并确定 Glun 2C/D的表达和功能变化可能导致皮质过度兴奋和同步性 三个具体目标。目标1。同时测定皮质蛋白和RNA表达水平的变化 作为Fmr 1 KO皮质中GluN 2C/D亚基的细胞特异性表达。目标2.确定细胞特异性功能 GluN 2C/D亚基对WT和Fmr 1 KO皮质中NMDA介导的电流的贡献。目标3。以确定 GluN 2C/D NMDAR对体内感觉驱动回路兴奋性和改变的同步性的贡献， 多电极阵列EEG和Fmr 1 KO小鼠中听源性癫痫发作的测量， 博士加州大学滨江分校的迪文宾德。这些实验不仅将提供对分子和细胞的深入了解， GluN 2C/D对皮层回路功能障碍的贡献的基础，但也检查了GluN 2C/D亚基作为潜在的 使用翻译生物标志物用于治疗开发的靶点。

PROJECT SUMMARY Sensory hypersensitivity is a common symptom in autism and Fragile X Syndrome (FXS) and is thought to be a result of cortical circuit dysregulation. EEG studies in humans with FXS and the FXS mouse model, the Fmr1 KO, reveal cortical circuit hyperexcitability and synchrony deficits such as enhanced resting state power in the gamma band and reduced sensory-driven synchrony. In acute slices, this hyperexcitability can be observed as prolonged persistent activity states, called UP states, and increased gamma band power during UP states. I hypothesize that circuit mechanisms that mediate hyperexcitability and prolonged UP states in the neocortex may contribute to EEG phenotypes in FXS. Using positive and negative allosteric modulators (PAMs/NAMs) specific for GluN2C/D subunits of NMDA receptors, I have revealed an upregulation of GluN2C/D function in the Fmr1 KO cortex that contributes to circuit hyperexcitability. Specifically, GluN2C/D PAMs increase UP state duration and gamma power during the UP states, while NAMs rescue UP state duration. Remarkably, these interventions only affected the Fmr1 KO, not their wildtype (WT) littermates suggesting that GluN2C/D function is upregulated in the Fmr1 KO and leads to cortical circuit dysfunction. Typically, GluN2C/D subunits are expressed in cortical inhibitory neurons and astrocytes. Since my results are not consistent with effects on inhibitory neurons, GluN2C/D subunits may be misexpressed in excitatory neurons or upregulated in astrocytes in the Fmr1 KO. I hypothesize that GluN2C/D expression and/or function is increased in excitatory neurons and/or astrocytes in Fmr1 KO mice and this contributes to hyperexcitability and altered synchrony of cortical circuits. The goal of the proposed project is to test this hypothesis and determine expressional and functional changes in Glun2C/D that may contribute to cortical hyperexcitability and synchrony following three Specific Aims. Aim 1. To determine change in cortical protein and RNA expression levels as well as cell specific expression of GluN2C/D subunits in Fmr1 KO cortex. Aim 2. To determine cell specific functional contribution of GluN2C/D subunits to NMDA-mediated currents in WT and Fmr1 KO cortex. Aim 3. To determine the contribution of GluN2C/D NMDARs to in vivo sensory driven circuit excitability and altered synchrony using multi-electrode array EEG and measurement of audiogenic seizures in the Fmr1 KO mouse in collaboration with Dr. Devin Binder at UC Riverside. These experiments will not only provide insights into the molecular and cellular basis of GluN2C/D contribution to cortical circuit dysfunction, but also examine GluN2C/D subunits as a potential target for therapeutic development using translational biomarkers.