Astrocyte Regulation of Dendritic Spines in Vivo

描述(申请人提供)：星形胶质细胞是大脑中最丰富的细胞类型。在历史上，星形胶质细胞被认为主要是神经元的支持细胞。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，从在成人中作为神经干细胞，到调节突触的形成和活动。此外，已有研究表明，典型的多发性神经紊乱 被认为是神经元功能障碍的结果，如Rett综合征、脆性X和肌萎缩侧索硬化症，都有星形细胞成分。更全面地了解调节神经回路和连接的机制对于开发治疗高血压的方法至关重要。 治疗神经系统疾病，而且越来越明显的是，有必要 结合星形胶质细胞的作用。这项研究建议研究星形胶质细胞在成年小鼠新皮质树突棘动态调节中的作用。脊椎是神经元之间突触后交流的主要场所，成人大脑中的一部分脊椎经历了持续的更替。脊椎的持续重组有助于突触连接的改变，这种可塑性被认为是学习和记忆以及脑损伤后恢复的结构基础。星形胶质细胞主动监测和响应突触活动，它们的突起包裹树突棘，表明星形胶质细胞在调节脊柱动力学方面起着直接作用。在这项研究中，将在皮质中标记和鉴定表达转录因子Gli1的星形胶质细胞亚群，并研究表达Gli1的星形胶质细胞与脊椎之间的超微结构关系。然后选择性地以表达Gli1的星形胶质细胞为靶点进行消融，并使用双光子激光扫描显微镜在体内重复成像，以调查星形胶质细胞消融后基础和活动依赖的脊柱翻转是否受到损害。Gli1的表达在暴露于高水平的Sonic hedgehog(Shh)信号时被刺激。为了研究星形胶质细胞介导的脊柱动力学调控的分子机制，我们将选择性地干扰星形胶质细胞中的Shh活性，并检测基础和活动依赖的脊柱动力学。这项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见解，并进一步揭示Shh信号在星形胶质细胞中的功能意义。)

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. )