Influence of the constitutive, conditional and inducible astroglia-derived tenascin-C ablation on synaptic function

来源于胶质细胞的细胞外基质分子已被证明是发育过程中神经元-胶质相互作用的重要介质。它们最近也被证明是受伤神经系统再生和成年哺乳动物突触可塑性的关键成分。其中一种细胞外基质分子是腱蛋白- c，在大脑发育的早期阶段，星形胶质细胞显著表达，在某些大脑区域，也在成人中表达。本研究旨在探讨tenascin-C对幼龄成年小鼠海马突触可塑性的影响。这些研究将在组成性的、有条件的（在人GFAP启动子的控制下）和他莫非芬诱导消融的小鼠中进行。利用表达绿色荧光蛋白的转基因小鼠，在人类GFAP启动子和Dil标记的控制下，通过双光子显微镜研究这些突变体星形胶质细胞过程和树突棘形态的动态特征。常规的免疫细胞化学将用于监测神经元和神经元亚群及其相对于星形胶质细胞的比例和定位。电子显微镜将用于立体监测突触的精细结构和相关的星形细胞过程。这些发现和广泛的电生理测量将与CA1和CA3海马体相关的行为参数有关，如痕量恐惧条件反射、模式完成、工作记忆和降压回避，代表了更高水平的星形胶质细胞-突触相互作用。

Extracellular matrix molecules derived from glial cells have been shown to be important mediators of neuron-glia interactions during development. They have recently also been shown to be crucial ingredients in regeneration of the injured nervous system and in synaptic plasticity of adult mammals. One of these extracellular matrix molecules is tenascin-C that is prominently expressed by astrocytes at early stages of brain development and, in some brain regions, also in the adult. The aim of our study is to investigate how tenascin-C may affect synaptic plasticity in the hippocampus of young adult mice. These studies will be conducted with constitutively, conditionally (under the control of the human GFAP promoter) and tamofixen inducibly-ablated mice. The dynamic features of astroglial process and dendritic spine morphology will be studied in these mutants by 2-photon microscopy using transgenic mice expressing green fluorescent protein under the control of the human GFAP promoter and Dil labeling of spines. Conventional immunocytochemistry will be carried out to monitor neurons and subpopulations of neurons and their relative proportions and localization with respect to astrocytes. Electron microscopy will be used to stereologically monitor the fine structure of synapses and associated astrocytic processes. These finings and extensive electrophysiological measurements will be related to CA1 and CA3 hippocampus-associated behavioral parameters, such as trace fear conditioning, pattern completion, working memory and step-down avoidance, representing higher levels of astrocyte-synapse interactions.