Pruning of Motor Neuronal Arbors

描述（由申请人提供）：本研究的长期目标是了解功能性突触形成期间运动神经元和肌纤维之间细胞间通讯的细胞和分子机制。具体来说，我们想解决如何运动神经元在成人神经系统的发展过程中重塑。我们使用果蝇（成年）背纵（飞行）肌突触作为模型。我们以前表明，基本的神经肌肉模式的DLMs的发展在第一天的变态，并描述了重塑持久的幼虫运动神经元支配成人肌肉的目标。这项建议的重点是蛹期的剩余3天，并研究如何修剪和稳定的成年特定的运动神经元乔木，以产生成熟的成年DLM突触。在这个过程中明显的突触可塑性比幼虫突触生长过程中发生的变化更明显，并且与脊椎动物神经系统中的突触细化有惊人的相似之处。我们希望证明（成人）DLM突触具有许多脊椎动物突触的特征。提出了三个主要目标：a）确定外周运动神经元乔木修剪发生的精确时间段。B）利用遗传学和电生理学方法来研究电活动在修剪中的作用。c）使用突触特异性标记物和超微结构方法跟踪神经肌肉接触成熟为功能性突触。大多数关于果蝇突触形成和成熟的研究都集中在胚胎和幼虫系统，而成年突触的发育仍然有待于同样详细的探索。由于持久的幼虫运动神经元被重新指定为成年运动神经元，我们的研究修剪变态过程中将描述一个额外的水平，这些运动神经元的突触可塑性发生在成人（第二）阶段的突触。胚胎和成人NMJ的形成以前曾在隔离研究。我们的研究将有助于加强果蝇生命周期中两个显著不同阶段之间的连续性，并为进一步研究突触发生差异和相似性的分子基础奠定基础。通过这样做，我们希望更好地了解突触前和突触后细胞之间的细胞通讯（逆行和顺行信号）的性质，这是突触可塑性表现的核心。这些研究将有助于更好地理解癫痫、精神分裂症和Rett综合征等疾病的神经发育基础，这些疾病被认为是有缺陷的。

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand the cellular and molecular mechanisms of cell-cell communication between a motor neuron and muscle fiber during the formation of a functional synapse. Specifically, we want to address how motor neurons are remodeled during the development of an adult nervous system. We use the (adult) Dorsal Longitudinal (flight) Muscle synapse of Drosophila as a model. We previously showed that the basic neuromuscular pattern of the DLMs develops during the first day of metamorphosis, and described the remodeling of persistent larval motor neurons to innervate adult muscle targets. This proposal focuses on the remaining 3 days of the pupal phase, and examines how adult-specific motor neuronal arbors are pruned back and stabilized to give rise to the mature adult DLM synapse. The synaptic plasticity evident during this process is more pronounced than changes such as those occurring during larval synaptic growth, and bears striking similarities to synapse refinement seen in vertebrate nervous systems. We hope to demonstrate that the (adult) DLM synapse has many characteristics of its vertebrate counterpart. Three main objectives are presented: a) Identify the precise time period during which pruning of peripheral motor neuronal arbors occurs. b) Use genetic and electrophysiological approaches to examine the role of electrical activity in pruning. c) Follow the maturation of neuromuscular contacts into functional synapses using synapse-specific markers and ultrastructural approaches. Most of the studies on synapse formation and maturation in Drosophila have focused on the embryonic and the larval system while development of the adult synapse remains to be explored in the same detail. Since persistent larval motor neurons are respecified to become adult motor neurons, our studies of pruning during metamorphosis will describe an additional level of synaptic plasticity of these motor neurons that occurs during the adult (second) phase of synaptogenesis. Embryonic and adult NMJ formation have previously been studied in isolation. Our studies will serve to strengthen the continuity between the two remarkably distinct stages in the Drosophila life cycle, and serve as a basis for further studies on understanding the molecular bases of the differences and similarities with respect to synaptogenesis. In doing so, we hope to better understand the nature of cell-communication between pre- and post-synaptic cells (retrograde and anterograde signaling) that is central to the manifestation of synaptic plasticity. These studies will have implications for better understanding the neurodevelopmental basis of diseases such as epilepsy, schizophrenia and Rett's syndrome, where pruning is thought to be defective.