AGRIN GENE EXPRESSION

AGRIN 基因表达

• 批准号: 6624809
• 负责人: MARTIN A SMITH
• 金额: $ 33.36万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-01 至 2004-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6624809
• 关键词: RNA splicing; agrin; developmental neurobiology; electron microscopy; gene expression; gene mutation; glutamate receptor; hippocampus; immunocytochemistry; in situ hybridization; neuromuscular junction; neurotransmitter receptor; polymerase chain reaction; protein binding; protein biosynthesis; protein structure function; protooncogene; receptor expression; synapses; synaptogenesis; tissue /cell culture

DESCRIPTION (Verbatim from Applicant's Abstract): Normal brain function depends on the rapid transfer of information between neurons at highly specialized structures known as synapses. Understanding the mechanisms that direct the formation of synapses during development and their maintenance in the adult are, therefore, fundamental problems in neurobiology. Most of what we know about the development of chemical synapses comes from studies of the neuromuscular junction, where signals exchanged between motor neurons and the skeletal muscle fibers they innervate coordinate differentiation of the motor nerve terminal and postsynaptic apparatus in the muscle fiber. Compelling evidence now exists to show that one such signal is an extracellular matrix molecule called agrin, which plays a key role in the motor neuron induced organization of synaptic components in the muscle fiber. In contrast to the neuromuscular junction, relatively little is known about the mechanisms that direct neuron-neuron synapse formation in the central nervous system. We have shown that agrin is expressed in mammalian brain, consistent with a role for agrin in neuron-neuron synapse formation. Surprisingly, early stages of synaptogenesis between cortical neurons cultured from agrin knock-out mice appear normal, raising the question of what, if any, function agrin serves in brain. We have addressed this issue using expression of the immediate early gene c-fos and neural injury to monitor neuronal activity and show that agrin-deficient cultured cortical neurons exhibit reduced sensitivity to excitatory amino acids. These studies are the first to establish a CNS neuronal phenotype for a mutation in the agrin gene and suggest an important role for agrin in regulating glutamate receptor expression or function. Experiments are proposed that seek to test this hypothesis and identify the cellular defect caused by the mutation. Evidence that agrin is required for normal development of cortical neurons predicts the existence of a neuronal signal transduction pathway for agrin. Preliminary data confirm this hypothesis showing that agrin induces a dose-dependent saturable increase in Fos levels in cultured cortical neurons. Biochemical studies indicate that agrin induction of c-fos is similar to but distinct from signals mediating agrin-induced clustering of acetylcholine receptors in muscle. Additional experiments are proposed to explore these observations in more detail, culminating with cloning the receptor for agrin that regulates the neuronal signal transduction pathway. The results of these studies will contribute to our understanding of neural development and synapse formation in the brain. This knowledge will be directly relevant to the management of brain disorders characterized by cognitive deterioration such as Alzheimer disease, as well as regeneration following traumatic injury.

描述（逐字摘自申请人摘要）：正常的大脑功能取决于 高度专业化的神经元之间的信息快速传递 称为突触的结构。了解指导机制 发育过程中突触的形成及其在成人中的维持 因此，这是神经生物学的基本问题。大多数我们所知道的 关于化学突触发展的研究来自于 神经肌肉接头，运动神经元和神经元之间交换信号的地方 骨骼肌纤维 它们支配运动的协调分化 肌纤维中的神经末梢和突触后装置。引人注目 现在有证据表明这样的信号之一是细胞外基质 称为集聚蛋白的分子，在运动神经元诱导的运动中起关键作用 肌纤维中突触成分的组织。相比之下 对于神经肌肉接头的作用机制，人们知之甚少 中枢神经系统中直接神经元-神经元突触的形成。我们有 研究表明集聚蛋白在哺乳动物大脑中表达，与 集聚蛋白在神经元-神经元突触形成中的作用。令人惊讶的是，早期阶段 Agrin 敲除小鼠皮层神经元之间的突触发生 看起来正常，这就提出了一个问题：agrin 的功能是什么（如果有） 脑。 我们利用立即早期基因 c-fos 的表达解决了这个问题 和神经损伤来监测神经元活动并表明集聚蛋白缺乏 培养的皮质神经元对兴奋性氨基酸的敏感性降低 酸。这些研究首次建立了中枢神经系统神经元表型 集聚蛋白基因的突变表明集聚蛋白在 调节谷氨酸受体的表达或功能。建议进行实验 试图检验这一假设并确定由 突变。有证据表明 agrin 是正常发育所必需的 皮质神经元预测神经元信号转导的存在 集聚蛋白途径。初步数据证实了这一假设，表明 agrin 诱导培养皮质中 Fos 水平呈剂量依赖性饱和增加 神经元。生化研究表明集聚蛋白对 c-fos 的诱导作用相似 与介导集聚蛋白诱导的聚集的信号不同 肌肉中的乙酰胆碱受体。建议进行额外的实验 更详细地探索这些观察结果，最终克隆 调节神经元信号转导途径的集聚蛋白受体。这 这些研究的结果将有助于我们对神经网络的理解 大脑中的发育和突触形成。这些知识将直接 与以认知为特征的脑部疾病的管理相关 恶化，例如阿尔茨海默病，以及随后的再生 外伤。