Role of Arc in synaptic/experience-dependent plasticity in mouse visual cortex

描述（由申请人提供）：神经科学的一个主要挑战是了解神经元网络如何通过经验进行修改，以及蛋白质/基因如何有助于电路修改。神经回路在发育过程中通过活性依赖性基因和蛋白质表达而得到完善。类似的大分子合成对于突触可塑性的长期形式如长时程增强（LTP）和抑制（LTD）是必不可少的。对这些可塑性分子的识别工作揭示了一组以兴奋性突触为目标的基因。其中，Arc与神经元回路中的行为信息编码耦合最紧密。Arc通过直接与内吞机制相互作用来稳态调节表面AMPA型谷氨酸受体（AMPAR）。然而，Arc在神经元回路水平的功能或其在体内介导信息存储的确切作用知之甚少。视觉皮层是探索这些问题的理想准备，因为视觉体验可以被调节以诱导神经元活动的总体变化。该提案的总体目标是研究Arc在响应视觉体验而修改神经回路中的作用的机制，以及这些过程在神经系统疾病中如何被破坏。在先前的实验中，我们发现Arc在小鼠视觉皮层（V1）的经验依赖性可塑性中起着基础性作用。Arc基因敲除小鼠表现出眼优势可塑性的缺陷，以及一种新发现的经验依赖性可塑性，刺激特异性反应增强的形式。我们还发现了一个经验和弧依赖的组成部分，建立对侧同侧的比例。Arc如何调节视觉皮层中的经验依赖可塑性？目的1的目标是通过利用V1皮层切片中的切片电生理学并研究Arc在3种不同类型的突触可塑性中的作用来研究这些表型的机制; LTD，LTP和突触缩放。体内电生理学提供了一个强大的工具来评估经验依赖的可塑性，但很难确定特定的网络的个别细胞。目的2的目标是使用体内双光子钙成像在单细胞水平上研究Arc在经验依赖性可塑性中的作用，该成像可以以空间精度测量许多细胞中的神经元活性。目标3将直接测试Arc是否通过其在AMPAR运输中的作用介导可塑性。最后，目的4旨在测试Arc水平对于正常突触稳态是关键的并且异常Arc水平有助于在神经障碍（包括阿尔茨海默病、脆性X染色体和Angelman Syndrome）中观察到的突触功能障碍的想法。 公共卫生相关性：这个建议的总体目标是在分子和细胞水平上理解经验如何塑造和修改大脑。我们将研究活动依赖基因Arc在小鼠视皮层突触和经验依赖信息存储中的作用。我们还将测试的假设，即正常的Arc水平是至关重要的脑功能和Arc表达的异常调节有助于神经系统疾病中观察到的突触功能障碍。

DESCRIPTION (provided by applicant): A major challenge in neuroscience is to understand how neuronal networks are modified through experience and how proteins/genes contribute to circuit modification. Neural circuits are refined during development through activity-dependent gene and protein expression. Similar macromolecular synthesis is essential for long-term forms of synaptic plasticity such as long-term potentiation (LTP) and depression (LTD). Efforts to identify molecules that underlie these forms of plasticity have revealed a set of genes that target to excitatory synapses. Among these, Arc is the most tightly coupled to behavioral encoding of information in neuronal circuits. Arc homeostatically regulates surface AMPA type glutamate receptors (AMPARs) by directly interacting with the endocytic machinery. However, very little is known about Arc's function at the level of neuronal circuits or its precise in vivo role in mediating information storage. The visual cortex is an ideal preparation to probe these questions as visual experience can be modulated to induce gross changes in neuronal activity. The overall goal of this proposal is to investigate the mechanisms that underlie Arc's role in modifying neural circuits in response to visual experience and how these processes are disrupted in neurological disorders. In previous experiments, we find that Arc plays a fundamental role in experience- dependent plasticity in mouse visual cortex (V1). Arc knocks out mice exhibit deficits in ocular dominance plasticity and in a newly discovered form of experience-dependent plasticity, stimulus-specific response potentiation. We also uncover an experience and Arc-dependent component to establishing the contralateral to ipsilateral ratio. How does Arc regulate experience-dependent plasticity in the visual cortex? The goal of aim 1 is to investigate the mechanisms underlying these phenotypes by utilizing slice electrophysiology in V1 cortical slices and investigating the role of Arc in 3 different types of synaptic plasticity; LTD, LTP and synaptic scaling. In vivo electrophysiology provides a powerful tool to assess experience-dependent plasticity, but it is difficult to identify specific networks of individual cells. The goal of aim 2 is to investigate the role of Arc in experience- dependent plasticity at the single cell level using 2-photon calcium imaging in vivo, which can measure neuronal activity in many cells with spatial precision. Aim 3 will directly test whether Arc mediates plasticity through its role in AMPAR trafficking. Finally, aim 4 intends to test the idea that Arc levels are critical for normal synaptic homeostasis and that abnormal Arc levels contribute to the synaptic dysfunction observed in neurological disorders, including Alzheimer's disease, Fragile X and Angelman Syndromes. PUBLIC HEALTH RELEVANCE: The overall goal of this proposal is to understand, at the molecular and cellular level, how experience shapes and modifies the brain. We will investigate the role of the activity-dependent gene Arc in synaptic and experience-dependent information storage in mouse visual cortex. We will also test the hypothesis that normal Arc levels are critical for brain function and that abnormal regulation of Arc expression contributes to the synaptic dysfunction observed in neurological disorders.