Dystroglycan regulates cerebellar synapse function

项目摘要 肌营养不良聚糖是由跨膜β亚基和非共价连接的蛋白质组成的支架分子。 结合的细胞外α亚基α亚基经历重糖基化， Dystroglycan与细胞外结合伴侣形成蛋白质-碳水化合物相互作用的聚糖链。一 不能正确地糖基化肌营养不良聚糖导致称为肌营养不良聚糖病的一种形式的肌营养不良。 在肌营养不良症中看到的肌肉缺陷通常伴有神经缺陷。而 肌营养不良聚糖在肌肉完整性中的作用已得到充分描述，其在疾病的神经方面的作用 仍在研究中。已知神经上皮细胞中的肌营养不良聚糖是正常迁移所必需的。 神经元在发育过程中的作用，但Dystroglycan在整个生命过程中保持在高水平，这表明它的作用超越了 发展已经表明，神经元营养不良聚糖与某些抑制性糖基化的标志物共定位。 突触，并可以与neurexins相互作用，neurexins是一种在突触前支架分子， 个脑袋总之，这表明肌营养不良聚糖在抑制性免疫缺陷的亚类的发展中的潜在作用。 突触，充当突触后支架分子。 最近的研究表明，海马锥体神经元中的肌营养不良聚糖是海马神经元的功能所必需的。 研究人员已经发现了抑制性篮状突触子集的功能，但其他大脑区域仍然未被探索。本研究将 专注于小脑中的抑制性突触，其中Dystroglycan在小脑中以特别高的水平存在， 浦肯野神经元。拟议的实验将利用小鼠遗传学，成像和切片生理学来解剖 肌营养不良聚糖促进突触形成和/或维持抑制性突触的机制 在小脑皮层目的1将确定存在肌营养不良聚糖的突触子集，并将描述 Dystroglycan在这些突触功能中的重要性。目标2然后将试图剖析 Dystroglycan在突触形成和维持中的作用，并将测试基因治疗的可行性，以挽救 观察突触表型。目的3探讨Dystroglycan各结构域在突触中的作用 功能：来自β亚基C-尾的细胞内信号传导以及与细胞外结合的相互作用 通过α亚基的糖基化来结合伴侣。这项工作将是第一次探索在体内功能 Dystroglycan在大脑突触中的作用。此外，这些实验将提供理解， 关于肌营养不良聚糖缺陷如何导致患有以下疾病的人类患者的认知缺陷： 这将有助于开发基因疗法来治疗这种认知缺陷。

Project Summary Dystroglycan is a scaffolding molecule composed of a transmembrane beta subunit and a non-covalently bonded extracellular alpha subunit. The alpha subunit undergoes heavy glycosylation and it is through these glycan chains that Dystroglycan forms protein-carbohydrate interactions with extracellular binding partners. A failure to properly glycosylate Dystroglycan results in a form of muscular dystrophy termed dystroglycanopathy. The muscular defects seen in dystroglycanopathies are often accompanied by neurological defects. While the role of Dystroglycan in muscle integrity has been well described, its role in the neurological aspects of the disease remains understudied. It is known that Dystroglycan in neuroepithelial cells is necessary for the proper migration of neurons during development, but Dystroglycan remains at high levels throughout life, suggesting a role beyond development. It has been shown that neuronal Dystroglycan co-localizes with certain markers of inhibitory synapses and can interact with neurexins, a well described class of presynaptic scaffolding molecules in the brain. Together, this suggests a potential role for Dystroglycan in the development of a subset of inhibitory synapses, acting as a postsynaptic scaffolding molecule. Recent work has shown that Dystroglycan in pyramidal neurons of the hippocampus is required for the function of a subset of inhibitory basket synapses, but other brain regions remain unexplored. This study will focus on inhibitory synapses in the cerebellum, where Dystroglycan is present at particularly high levels in Purkinje neurons. The proposed experiments will utilize mouse genetics, imaging, and slice physiology to dissect the mechanism by which Dystroglycan promotes synapse formation and/or maintenance of inhibitory synapses in cerebellar cortex. Aim 1 will identify the subset of synapses at which Dystroglycan is present and will describe the importance of Dystroglycan in the function of these synapses. Aim 2 will then seek to dissect the role of Dystroglycan in synapse formation and maintenance and will test the feasibility of gene therapy to rescue the observed synaptic phenotype. Aim 3 will investigate the roles of the various domains of Dystroglycan in synapse function: intracellular signaling from the C-tail of the beta subunit and the interaction with extracellular binding partners via glycosylation of the alpha subunit. This work will be among the first to explore the in vivo functional role of Dystroglycan at synapses in the brain. Furthermore, these experiments will provide understanding with regards to how defects in Dystroglycan results in cognitive deficits in human patients suffering from dystroglycanopathies and will aid in the development of gene therapies to treat such cognitive defects.