A tale of two synapses: The development of neurotransmitter phenotype in motor ne

描述（由申请人提供）：两个突触的故事：运动神经元中神经递质表型的发展。虽然人们已经知道运动神经元在神经肌肉连接处释放乙酰胆碱60年了，但越来越多的证据表明，运动神经元也在其他神经元的突触上释放一种兴奋性氨基酸递质。最近的几项研究提供了证据，证明运动神经元在它们形成的不同类型的突触（外周神经肌肉连接和脊髓神经元间突触）之间以空间分离的方式释放多种神经递质。我们的实验室和其他人最近发表的研究表明，从胚胎中分离出来的运动神经元在不与肌肉细胞接触的情况下培养，培养中的兴奋性神经传递完全通过谷氨酸，没有检测到胆碱能神经传递。最近可获得的光遗传学小鼠模型允许可逆的、实时的和细胞自主的乙酰胆碱释放神经元的光激活，为研究运动神经元中神经递质表型的发展提供了一个很好的工具。本研究的目的是利用电生理学、共聚焦成像和光遗传学方法对培养和脊髓切片中的运动神经元进行研究，以确定运动神经元在其他神经元上形成的突触的神经递质表型，并研究运动神经元与肌肉细胞的接触、神经肌肉连接的形成以及可能的乙酰胆碱酯酶如何影响神经递质释放。了解神经元如何被引导在不同的目标上形成不同类型的突触，包括发展多种神经递质的空间分离释放，对于理解神经元发育至关重要。运动神经元形成的两类突触在结构、功能和位置上有明显的差异，是研究突触差异发育的理想模型系统。了解与肌肉的相互作用如何完成运动神经元的发育，将有助于深入了解神经肌肉疾病的病理生理学，包括发育性运动神经元疾病，如脊髓性肌萎缩症和肌肉萎缩症。此外，随着越来越多的研究人员探索利用分化的多能细胞来替代因疾病或损伤而失去的运动神经元，对运动神经元分化和突触生理学的全面了解将对推进这一研究至关重要。这个项目是R15支持的理想选择，因为特拉华州立大学是一所历史上以黑人为主的本科院校，大约80%的非裔美国人入学。资助本研究将增加少数民族本科生和研究生通过参与重要科学研究直接体验科学过程的机会。

DESCRIPTION (provided by applicant): A tale of two synapses: the development of neurotransmitter phenotype in motor neurons. While it has been known for 60 years that motor neurons release acetylcholine at neuromuscular junctions, evidence has been accumulating that motor neurons also release an excitatory amino acid transmitter at synapses on other neurons. Several recent studies provide evidence that motor neurons release multiple neurotransmitters in a spatially segregated way between the distinct types of synapses they make - neuromuscular junctions in the periphery and inter- neuronal synapses in the spinal cord. Recently published work from our lab and others has shown that in cultures of motor neurons isolated from embryos and grown in the absence of contact with muscle cells, excitatory neurotransmission in the culture is entirely through glutamate with no detectable cholinergic neurotransmission. The recent availability of an optogenetic mouse model that allows reversible, real-time and cell-autonomous photo-activation of acetylcholine-releasing neurons provides an excellent tool to investigate the development of neurotransmitter phenotype in motor neurons. The objective of the proposed study is to use electrophysiology, confocal imaging and optogenetic approaches with motor neurons grown in culture and in spinal cord slices to determine the neurotransmitter phenotype of synapses formed by motor neurons on other neurons, and investigate how contact with muscle cells, the formation of neuromuscular junctions, and possibly acetylcholinesterase influence the neurotransmitter released. Insight into how neurons are guided to make different types of synapses on different targets, including developing spatially segregated release of multiple neurotransmitters, is crucial for understanding neuronal development. Motor neurons, which make two types of synapses clearly differentiated in structure, function and location, are an ideal model system in which to investigate differential synaptic development. Understanding how interaction with muscle completes the development of motor neurons will lead to insights into the pathophysiology of neuromuscular disorders including developmental motor neuron diseases such as spinal muscular atrophy and muscular dystrophy. In addition, as more researchers explore the use of differentiated pluripotent cells for potential replacement of motor neurons lost to disease or injury, a complete understanding of motor neuron differentiation and synaptic physiology will be crucial to advancing that research. This project is ideal for R15 support as Delaware State University is an Historically Black, predominantly undergraduate institution with approximately 80% African-American enrollment. Funding this research will increase opportunities for minority undergraduate and graduate students to directly experience the scientific process by taking part in important scientific research.