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

项目总结 感觉过敏是自闭症和脆性X综合征(FXS)的常见症状，被认为是 大脑皮层回路失调的结果。FXS患者和FXS小鼠模型Fmr1的脑电研究 Ko，揭示了皮层回路的超兴奋性和同步性缺陷，如增强的静息状态功率。 伽马频段和减少的感官驱动的同步性。在急性脑片中，这种过度兴奋可以观察到 延长持续活动状态，称为UP状态，并在UP状态期间增加伽马频段功率。我 假设新皮质中介导过度兴奋和延长UP状态的回路机制 可能与FXS的脑电表型有关。使用正负变构调节剂(PAMS/NAMS) 对于NMDA受体的GluN2C/D亚基，我已经揭示了GluN2C/D功能在 FMR1 KO皮层，有助于回路过度兴奋。具体地说，GluN2C/D PAM增加了UP状态 持续时间和在UP状态期间的伽马功率，而NAMS拯救UP状态持续时间。值得注意的是，这些 干预措施只影响Fmr1KO，而不影响它们的野生型(WT)产仔，这表明GluN2C/D功能 在Fmr1KO中上调，并导致皮质回路功能障碍。通常，GluN2C/D亚基是 表达于皮质抑制神经元和星形胶质细胞。因为我的结果与 抑制性神经元，GluN2C/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 在Fmr1 KO中。我假设GluN2C/D的表达和/或功能在兴奋性增加 Fmr1KO小鼠的神经元和/或星形胶质细胞，这有助于过度兴奋和改变 大脑皮层回路的同步性。拟议项目的目标是检验这一假设，并确定 Glu2C/D的表达和功能变化可能与皮质的过度兴奋性和同步性有关 遵循三个具体目标。目的1.测定大脑皮层蛋白质和RNA表达水平的变化 作为GluN2C/D亚基在Fmr1KO皮层的细胞特异性表达。目的2.确定细胞特异性功能 GluN2C/D亚基在WT和Fmr1KO皮层NMDA介导电流中的作用目标3.确定 GluN2C/D NMDAR在体内感觉驱动回路兴奋性和同步性改变中的作用 多电极阵列脑电与Fmr1 KO小鼠听源性惊厥的测量 加州大学河滨分校的德文·宾德博士。这些实验不仅将提供对分子和细胞的洞察 GluN2C/D在皮质回路功能障碍中的作用基础，但也检测GluN2C/D亚基作为潜在的 使用翻译生物标记物进行治疗开发的目标。

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.