Visual system synapses and circuits

描述(申请人提供)：我们将分析调节果蝇中光感受器突触如何形成和功能的基因的作用，以及这些基因如何对果蝇视觉系统中的神经元电路做出贡献。项目重点放在第一和第二神经鞘、板层和髓质中的光感受器靶标神经元，这是视网膜外层和内丛状层的功能对应。一个长期的目标是了解苍蝇光感受器四分体突触的多接触突触(如二联体和三联体)的组织。最近的目标是了解这些物质是如何形成的，然后对视觉系统的突触微电路做出贡献。目前的目标是研究轴突在光感受器突触发生之前的靶向，以及面包屑在引导生长锥轨迹中的作用。将利用基因试剂在EM水平标记和识别参与神经元的反馈光感受器突触的数量和类型，以及Kirre和Irrec样蛋白以及Dscam细胞黏附分子在确定L2和L4两种板层反馈中间神经元之间突触的特异性以及调节它们之间的相互作用中的作用。这些项目使用相应基因的突变和敲除，以及其他遗传试剂。突触功能将从改变光感受器突触小泡表型的突变体中检测，或者改变其末端的靶向，以及通过β-丙氨酰结合途径的神经递质组胺的循环。光感受器反馈的通路强度将从不同突触背景中的突触数量来评估，以揭示突触回路的网络调节。这些项目使用先进的连续切片和免疫-EM方法以及熟练的人员来实施这些检查突变的光感受器。对复杂延髓中的突触电路的分析将继续进行，使用序列-EM来识别识别出的神经元之间的实际电路，这些神经元是潜在的光谱识别通路。这些数据将被用来研究颜色视觉的神经基础；识别电路设计和突触电路中网络基元的频率；并检查当贡献神经元被消除或基因转化时，这些基元在板层和延髓中经历的调节。这项拟议的研究将确定视觉系统中突触功能和组织的细胞机制，以及这些机制在视网膜的功能和疾病状态下所经历的重排，并将在与视网膜有显著相似之处的模型视觉系统中从它们的遗传基础中进行识别。

DESCRIPTION (provided by applicant): We will analyze the actions of genes that regulate how photoreceptor synapses in Drosophila form and function, and how these contribute to circuits of neurons in the fly's visual system. Projects focus on the photoreceptor target interneuron in the first and second neuropils, the lamina and medulla, functional counterparts to the outer and inner plexiform layers of the retina. A long-term objective is to understand the organization of multiple-contact synapses (such as dyads and triads) from the fly's photoreceptor tetrad synapses. More recent objectives are to understand how these form and then contribute to the visual system's synaptic microcircuits. Current objectives are to study axon targeting prior to photoreceptor synaptogenesis, and the action of crumbs in directing growth cone trajectories. The numbers and types of feedback photoreceptor synapses will be studied using genetic reagents to label and identify participating neurons at EM level, and the involvement of Kirre and Irrec-like proteins as well as Dscam cell adhesion molecules in establishing the specificity of synapses between two types of lamina feedback interneuron, L2 and L4, as well as in regulating reciprocity between these. The projects use mutants and knockdowns of the corresponding genes, and other genetic reagents. Synaptic function will be examined from mutants that alter the synaptic vesicle phenotype of photoreceptors, or the targeting of their terminals, as well as the recycling of neurotransmitter, histamine, through a beta-alanyl conjugation pathway. Pathway strength for photoreceptor feedback will be evaluated from synapse numbers in different mutant backgrounds to reveal the network regulation of synaptic circuits. These projects examine mutant photoreceptors using advanced methods of serial-section and immuno-EM, and skilled personnel to implement these. Analysis of synaptic circuits in the complex medulla will continue, using serial-EM to identify actual circuits between identified neurons of the pathways underlying spectral discrimination. These data will be used to examine the neural basis of color vision; to identify circuit design and the frequencies of network motifs in synaptic circuits; and to examine the regulation that these undergo in both the lamina and medulla when contributing neurons are eliminated or genetically transformed. The proposed studies will identify the cellular mechanisms for synaptic function and organization in visual systems, and the rearrangements these undergo in functional and disease states of the retina, and will be identified from their genetic bases in a model visual system with marked similarities to the retina.