PSD-95 deficiency alters glutamatergic synapses during development in the prefrontal cortex

项目总结/摘要 突触后密度蛋白-95（Postsynaptic density protein-95，PSD-95）是一种分布于树突状细胞的高度丰富的支架蛋白 兴奋性突触的棘，并参与N-甲基-D- 天冬氨酸受体（NMDAR）和α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体 在突触成熟过程中，AMPAR（AMPAR）与突触后膜结合。此前的研究表明， 在海马体中，PSD-95缺陷导致“沉默突触”的形成，这可能与 在精神分裂症（SCZ）和自闭症的神经障碍中观察到的病理学。然而， 前额叶皮层（PFC）中的PSD-95缺乏症，这是一个延迟成熟的大脑区域， 研究了前额叶皮层位于额叶前部，负责认知、工作记忆、 情绪控制和社交能力它也与神经发育障碍高度相关，特别是 精神分裂症我们假设PSD-95缺陷会破坏年龄依赖性突触成熟。 由于NMDAR/AMPAR-神经递质传递增加，导致PFC受损 发展和功能。在这项研究中，我们使用PSD-95-/-小鼠来建立PSD-95缺陷的模型，并研究 内侧前额叶皮层（mPFC）内的NMDA和AMPA受体特性。我们探索蛋白质 NMDAR和AMPAR-亚基和其他相关支架蛋白的表达水平。另外我们 检查NMDAR/AMPAR传输来表征沉默突触，因此，我们将检查 工作记忆功能和社会互动来衡量社会新奇性和探索性。此外，基于 我们的初步发现增加NMDA/AMPA比率在皮质皮层传入，我们将检查 mPFC的主要输入-内侧背丘脑（MD），负责发育和 mPFC的功能通过由突触能传递介导的相互连接。我们进一步 假设PSD-95缺乏将通过破坏丘脑-皮层神经元投射损害丘脑-皮层投射 传递，导致传入特定的突触功能和神经发育缺陷的变化， 导致生理和行为功能障碍的mPFC。我们将注射腺相关病毒（AAV） 在MD内表达通道视紫红质-2（ChR 2）的载体，并使用光遗传学来特异性激活MD 输入到mPFC以记录兴奋性突触后电流。这些数据将提供更大的 了解PSD-95如何影响谷氨酸受体的组成和传输，因为它涉及 mPFC的发展和功能。

Project Summary/Abstract Postsynaptic density protein-95 (PSD-95) is a highly abundant scaffolding protein located at the dendritic spines of excitatory synapses and is involved in the recruitment, trafficking, and stabilization of N-methyl-D- aspartic acid receptors (NMDAR’s) and α-amino-3-hydroxy-5-methyl-4-isox-azoleproprionic acid receptors (AMPAR's) to the postsynaptic membrane during synaptic maturation. Previous studies have shown that within the hippocampus, PSD-95 deficiency causes “silent synapse” formation that may be associated with the pathology observed in the neurological disorders of schizophrenia (SCZ) and autism. However, the effects of PSD-95 deficiency within the prefrontal cortex (PFC), a brain region with delayed maturation, have yet to be investigated. The PFC, located anterior of the frontal lobe, is responsible for cognition, working memory, emotional control, and sociability. It is also highly associated with neurodevelopmental disorders, especially schizophrenia. We hypothesize that PSD-95 deficiency will disrupt synaptic maturation in an age-dependent manner due to an increase in NMDAR/AMPAR-glutamatergic transmission that leads to impairments in PFC development and function. In this study we use a PSD-95-/- mouse to model PSD-95 deficiency and investigate NMDA and AMPA-receptor properties within the medial prefrontal cortex (mPFC). We explore protein expression levels of NMDAR and AMPAR-subunits and other relevant scaffolding proteins. Additionally, we examine NMDAR/AMPAR-transmission to characterize silent synapses, and accordingly, we will examine working memory function and social interaction to measure social novelty and exploration. Furthermore, based on our preliminary finding of increased NMDA/AMPA ratio in corticocortical afferents, we will examine the major inputs of the mPFC − the mediodorsal thalamus (MD), which is responsible for the development and function of the mPFC via reciprocal connections mediated by glutamatergic transmission. We further hypothesize that PSD-95 deficiency will impair thalamocortical projections via disrupted glutamatergic transmission, resulting in afferent-specific changes in synaptic function and neurodevelopmental deficits of the mPFC that lead to physiological and behavioral dysfunctions. We will inject an adeno-associated virus (AAV) vector expressing channelrhodopsin-2 (ChR2) within the MD and use optogenetics to specifically activate MD inputs to mPFC to record excitatory postsynaptic currents. Together, this data will provide a greater understanding of how PSD-95 affects the glutamate receptor composition and transmission as it relates to mPFC development and function.