Imaging visual plasticity in vivo.

描述(申请人提供)：在发育过程中，皮层网络因视觉经验而重塑依赖于突触结构和功能的特定和局部变化，其进展和机制仍然知之甚少。虽然细胞内信号传递一直是大多数视皮层研究的重点，但细胞外环境在限制视觉可塑性方面起着至关重要的作用。我们假设，细胞外通路被认为仅限于受伤或患病的大脑，令人惊讶的是，在视觉皮质可塑性期间，细胞外通路也很活跃，并允许单个突触的结构重建。利用成像技术，我们可以在活体内实时可视化细胞形态，我们可以首次在单个突触水平上可视化视觉操作过程中皮质网络的重新连接，并直接检查这种重新连接的全新机制。使用这些方法，我们将测试以下场景：单眼剥夺导致细胞外蛋白酶活性，导致小胶质细胞激活和细胞外基质降解，进而实现结构和功能的可塑性。在目标1中，我们将量化这种结构性突触可塑性的关键方面，并确定其突触轨迹。在目标2中，我们将分析小胶质细胞参与视觉可塑性，在目标3中，我们将阐明导致小胶质细胞激活和细胞外基质重塑的细胞外途径。我们将使用体内功能和结构4D成像与组织学、分子和遗传学工具的组合，将提供对视觉皮质可塑性潜在的细胞外机制的独特见解。由于在神经发育和神经退行性疾病中观察到广泛的形态和功能突触缺陷，实现这些目标也将为此类疾病的新治疗途径提供见解。公共卫生相关性：突触的结构对神经系统的正常运作至关重要：在大脑发育、学习以及包括自闭症、癫痫和阿尔茨海默病在内的许多神经疾病中，都会观察到这种结构的变化。在这个提案中，我们将研究自然刺激如何在完整的大脑中调节突触结构，并确定介导突触变化的机制。这项研究将为理解和治疗人类神经疾病提供具有广泛意义的信息。

DESCRIPTION (provided by applicant): Remodeling of cortical networks in response to visual experience during development relies on specific and localized changes in synaptic structure and function, the progression and mechanisms of which are still poorly understood. While intracellular signaling has been the focus of most studies of the visual cortex, the extracellular environment plays a crucial role in limiting visual plasticity. We hypothesize that extracellular pathways, which are believed to be restricted to the injured or diseased brain, are surprisingly also active during plasticity in the visual cortex and allow structural remodeling at single synapses. Using imaging techniques which allow real time visualization of cellular morphology in vivo, we can, for the first time, visualize the rewiring of cortical networks during manipulations of vision at the level of a single synapse and directly examine entirely novel mechanisms of this rewiring. Using these methods, we will test the following scenario: monocular deprivation leads to extracellular protease activity resulting in microglial activation and extracellular matrix degradation, which in turn implement structural and functional plasticity. In aim 1 we will quantify key aspects of this structural synaptic plasticity and determine its synaptic locus. In aim 2, we will assay microglial involvement in visual plasticity and in aim 3 we will elucidate the extracellular pathway that leads to microglial activation and extracellular matrix remodeling. We will use a combination of in vivo functional and structural 4D imaging with histological, molecular and genetic tools which will provide unique insights into the extracellular mechanisms underlying plasticity in the visual cortex. Because of the broad range of morphological and functional synaptic deficits observed in neurodevelopmental and neurodegenerative disorders, accomplishing these aims will also provide insights into new treatment avenues for such diseases. PUBLIC HEALTH RELEVANCE: The structure of synapses is crucial to the proper functioning of the nervous system: changes in this structure are observed during brain development, learning and in many neurological disorders, including autism, epilepsy and Alzheimer's disease. In this proposal we will study how synapse structure is modulated by natural stimuli in the intact brain and identify mechanisms mediating synaptic changes. This study will provide information with broad implications for understanding and treating a large spectrum of human neurological disorders.