Astrocyte Regulation of Dendritic Spines in Vivo

描述（由申请人提供）：星形胶质细胞是大脑中最丰富的细胞类型。历史上，星形胶质细胞被认为主要作为神经元的支持细胞。然而，越来越多的证据表明，星形胶质细胞以多种方式积极参与脑功能，从成人的神经干细胞到调节突触的形成和活动。此外，已经表明，经典的多种神经系统疾病 被认为是神经元功能障碍的结果，例如Rett综合征、脆性X染色体和肌萎缩侧索硬化，具有星形胶质细胞成分。更全面地了解调节神经回路和连接的机制对于开发治疗方法至关重要。 治疗神经系统疾病，而且越来越清楚的是， 整合了星形胶质细胞的作用。 本研究旨在探讨星形胶质细胞在调节成年小鼠新皮层树突棘动态变化中的作用。棘是神经元之间突触后通讯的主要场所，成年人大脑中的棘的子集经历持续的更新。脊椎的持续重组促进了突触连接的变化，这种可塑性被认为是学习和记忆的结构基础，以及脑损伤后的恢复。星形胶质细胞积极监测和响应突触活动，它们的过程包裹树突棘，指出星形胶质细胞在调节棘动力学中的直接作用。在这项研究中，一个子集的星形胶质细胞表达的转录因子，Gli1，将被标记，并确定在皮层，和超微结构之间的关系Gli1表达星形胶质细胞和棘将被检查。然后将选择性靶向表达Gli1的星形胶质细胞进行消融，并使用双光子激光扫描显微镜在体内对棘重复成像，以研究星形胶质细胞消融后基础和活性依赖性棘周转是否受损。Gli1表达在暴露于高水平的Sonic hedgehog（Shh）信号传导后被刺激。为了研究星形胶质细胞介导的棘动力学调节的分子机制，将在星形胶质细胞中选择性地破坏Shh活性，并检查基础和活性依赖性棘动力学。本研究将为星形胶质细胞在结构可塑性调节中的作用提供新的认识，并进一步揭示星形胶质细胞Shh信号的功能意义。)

DESCRIPTION (provided by applicant): Astrocytes are the most abundant cell type in the brain. Historically, astrocytes were thought to act primarily as support cells to neurons. However increasing evidence indicates that astrocytes actively participate in brain function in a variety o ways, from serving as neural stem cells in the adult, to regulating synaptic formation and activity. In addition, it has been shown that multiple neurological disorders that have classically been considered to be a result of neuronal dysfunction, such as Rett Syndrome, Fragile X, and amyotrophic lateral sclerosis, have astrocytic components. A more complete understanding of the mechanisms regulating neural circuitry and connectivity is critical to developing therapies for treating neurological disorders, and it is becoming increasingly clear that it will be necessary to incorporate the role of astrocytes. This study proposes to examine the role of astrocytes in mediating the dynamics of dendritic spines in the neocortex of adult mice. Spines are the primary site of postsynaptic communication between neurons, and a subset of spines in the adult brain undergo continued turnover. The continual reorganization of spines facilitates changes in synaptic connectivity, and this plasticity is thought to be the structural basis of learning and memory, as well as recovery after brain injury. Astrocytes actively monitor and respond to synaptic activity, and their processes ensheath dendritic spines, pointing to a direct role for astrocytes in regulating spine dynamics. In this study, a subset of astrocytes expressing the transcription factor, Gli1, will be marked and identified in the cortex, and the ultrastructura relationships between Gli1-expressing astrocytes and spines will be examined. Gli1-expressing astrocytes will then be selectively targeted for ablation, and spines will be repeatedly imaged in vivo using 2 photon laser scanning microscopy to investigate whether basal and activity-dependent spine turnover are impaired following astrocyte ablation. Gli1 expression is stimulated upon exposure to high levels of Sonic hedgehog (Shh) signaling. In order to examine the molecular mechanisms underlying astrocyte-mediated regulation of spine dynamics, Shh activity will be disrupted selectively in astrocytes, and basal and activity-dependent spine dynamics will be examined. This study will provide novel insight into the role of astrocytes in regulating structural plasticity, and further, will reveal the functional significance of Shh signaing in astrocytes. )