New Models For Astrocyte Function in Genetic Mouse Models of Autism Spectrum Diso

描述(由申请人提供)：自闭症谱系障碍(ASD)是以社交和沟通障碍为突出表现的精神障碍。这些复杂的行为变化是由特定大脑区域的突触功能改变引起的。此前的研究主要集中在神经元发育和成熟的改变上。除了这些神经元的变化，最近的研究还表明，星形胶质细胞是大脑中的主要神经胶质细胞，是自闭症发病的主要因素。星形胶质细胞是三体突触的组成部分。在该模型中，星形胶质细胞突起围绕和/或结合突触前和突触后成分，调节神经递质的动态平衡和循环，为神经元代谢提供基础底物，隔离钙离子，促进突触发生和突触重塑。星形胶质细胞也与遗传性人类ASD动物模型的发病有关；这些动物模型包括缺乏甲基CpG结合蛋白2(MeCP2)或脆性X智力低下1(FMR1)基因的小鼠。虽然星形胶质细胞的多样性已经被认识了一个多世纪，但在体内支持这种多样性的分子和细胞机制以及对精神障碍的后果仍然知之甚少。这项建议的目的是在两种ASDS小鼠模型中表征灰质星形胶质细胞亚群中星形胶质细胞的多样性。我们的实验得到了两项技术进步的推动，这两项技术进步允许在ASD动物模型中识别和分子表征星形胶质细胞。首先，我们培育了一种新的转基因小鼠品系(BT4-mEGFP)，在该品系中，星形胶质细胞表面的膜从胚胎发育开始就被荧光标记。将这些荧光标记的星形胶质细胞培育成ASD的遗传模型，将允许通过荧光激活细胞分选和随后的基因图谱分离星形胶质细胞。我们将确定这些基因缺陷如何改变星形胶质细胞的发育，星形胶质细胞与突触的联系，以及基因图谱研究中确定的星形胶质细胞蛋白的表达。这些数据将通过使用自动连续电子显微镜确定星形胶质细胞和突触之间的三维关联来扩展。我们的研究基于星形胶质细胞在ASD中扮演两个关键角色的总体假设。首先，它们与突触有异常的联系，这会导致神经递质稳态改变和神经元异常电活动。其次，它们改变了线粒体的功能，缺乏ATP的产生和钙离子的缓冲，这降低了它们向神经元提供基本营养的能力。这些研究将阐明星形胶质细胞在ASD中以前未知的作用，并将为未来针对星形胶质细胞在治疗或预防ASD中的功能的治疗策略的开发提供一个关键的遗传和超微结构框架。

DESCRIPTION (provided by applicant): Autism spectrum disorders (ASDs) are psychiatric disorders highlighted by social and communicative dysfunction. These complex behavioral changes are caused by altered synaptic functioning in select brain regions. Studies have previously focused on altered neuronal development and maturation. In addition to these neuronal changes, more recent studies have implicated astrocytes, the major glial cell in the brain, as major contributors to the pathogenesis of ASDs. Astrocytes are integral components of the tripartite synapse. In this model astrocyte processes surround and/or associate with pre- and post-synaptic components and regulate neurotransmitter homeostasis and recycling, provide basic substrates for neuronal metabolism, sequester Ca2+ ions and promote synaptogenesis and synaptic remodeling. Astrocytes have also been implicated in the pathogenesis of animal models of inherited human ASDs; these include mice lacking methyl-CpG-binding protein 2 (MeCP2) or the fragile X mental retardation 1 (FMR1) gene. While astrocyte diversity has been recognized for over a century, the molecular and cellular mechanisms underpinning this diversity in vivo and the consequences for psychiatric disorders remain poorly understood. The purpose of this proposal is to characterize astrocyte diversity in subpopulations of gray matter astrocytes in two mouse models of ASDs. Our experiments are facilitated by two technical advances that permit the identification and molecular characterization of astrocytes in animal models of ASDs. First, we have produced a novel transgenic mouse line (BT4-mEGFP) in which astrocyte surface membranes are fluorescently tagged from embryonic development onward. Breeding of these fluorescently tagged astrocytes into genetic models of ASDs will permit astrocyte isolation by fluorescent activated cell sorting and subsequent gene profiling. We will establish how these gene defects alter the development of astrocytes, the association of astrocytes with synapses and the expression of astrocyte proteins identified in the gene profiling studies. These data will be extended by determining the three dimensional associations between astrocytes and synapses using automated serial electron microscopy. Our studies are based upon the overall hypotheses that astrocytes play two key roles in ASDs. First, they have abnormal associations with synapses, which results in altered neurotransmitter homeostasis and abnormal neuronal electrical activity. Second they have altered mitochondrial functions, deficient ATP production and Ca2+ buffering, which reduces their ability to provide basic nutrition to neurons. These studies will elucidate previousl unidentified roles of astrocytes in ASDs and will provide a critical genetic and ultrastructural framework for the development of future therapeutic strategies that target astrocyte function in treating or preventing ASDs.