Cell surface molecules that require arrangement of retinal neurons and arbors

需要视网膜神经元和乔木排列的细胞表面分子

• 批准号: 8387742
• 负责人: JOSHUA R SANES
• 金额: $ 39.94万
• 依托单位: HARVARD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-12-01 至 2015-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8387742
• 关键词: Adhesives; Affect; Amacrine Cells; Attention; Binding; Binding Sites; Brain; Caenorhabditis elegans; Cell Surface Proteins; Cell physiology; Cell surface; Cells; Complex; Cues; Cultured Cells; Cytoplasmic Tail; Defect; Dendrites; Development; Drosophila genus; Ectopic Expression; Ensure; Extracellular Domain; Gene Family; Genetic; Homologous Gene; In Vitro; Inner Plexiform Layer; Interneurons; Laboratory culture; Learning; Ligands; Maintenance; Mental disorders; Methods; Modeling; Molecular; Muscle fasciculation; Mutant Strains Mice; Nervous system structure; Neuraxis; Neurites; Neurons; Pattern; Phenotype; Play; Process; Protein Isoforms; Proteins; Retina; Retinal; Retinal Ganglion Cells; Role; Self-control as a personality trait; Signal Transduction; Sorting - Cell Movement; Specificity; Surface; Synapses; System; Testing; Translating; Vertebrates; Visual Fields; Work; avoidance behavior; base; cell type; horizontal cell; in vivo; insight; loss of function; mutant; neural circuit; neuronal cell body; postsynaptic; presynaptic; receptive field; receptor; response; retinal neuron

DESCRIPTION (provided by applicant): Orderly and specific connections among neurons of multiple subtypes underlie the function of neural circuits. Our own work has used retina as a model to elucidate molecules and mechanisms that underlie specificity, focusing on the matching of pre- and postsynaptic partners in particular synaptic laminae. There is another sort of order, however, that has received less attention: the arrangement of cells and their neurites in the orthogonal (x-y) plane. Processes that contribute to this arrangement include mosaic spacing of neuronal somata, tiling of dendrites, and self-avoidance of processes within a single arbor. These processes are believed to ensure uniform coverage of the visual field, precise connectivity, and appropriate receptive field size. Their molecular bases remain unknown in vertebrates. Recently, we began analyzing two sets of cell surface proteins that we suspected to be involved in laminar specificity: MEGF10 and 11, and a cluster of 22 related gamma protocadherins (Pcdhgs). Unexpectedly, preliminary results suggest that both are involved in regulating the arrangement of specific neurons and their dendrites in the x-y plane. Moreover, both affect the same cell type, starburst amacrine cells (SACs), but in different ways: MEGF10/11 regulate the mosaic arrangement of SAC somata whereas Pcdhgs are required for self-avoidance of their dendrites. We will now use these results as starting points to obtain insights into the mechanisms that underlie these common but little-studied aspects of circuit assembly. First, we will use gain- and loss-of function methods in vivo to characterize the role of MEGF10/11 in mosaic formation. We will ask whether MEGF10/11 is effective only during development, whether its effects endure, whether it can disrupt mosaics after they form, and whether the two homologues have distinct effects. Second, we will ask whether defects in self-avoidance observed in conditional Pcdhg mutant mice are cell-autonomous and whether they reflect problems in dendrite formation or refinement. We will then use genetic methods to reduce the repertoire of Pcdhg isoforms that retinal cells express. We can thereby test the role of isoform diversity in the process and learn whether different isoforms play different roles. Third, we will ask whether retinal subtypes other than SACs use MEGF10/11 or Pcdhgs to pattern their somata or arbors. Finally, we will combine studies in vitro and in vivo to initiate analyses of the signaling mechanisms by which MEGF10/11 and Pcdhgs function. We will ask whether MEGF10/11 act as receptors, as ligands, or as both ligand and receptor (that is, homophilically). For Pcdhgs, we will ask how the initially adhesive interaction that Pcdhgs appear to promote is translated into the repellent one required for self-avoidance. Together, these results will further our understanding of two poorly understood gene families and of a poorly understood set of processes important for patterning neural circuits.

描述（由申请人提供）：多个亚型的神经元之间的有序和特异性连接是神经回路功能的基础。我们自己的工作已经使用视网膜作为一个模型，以阐明分子和机制的基础特异性，侧重于匹配的前和突触后的合作伙伴，特别是突触板。然而，还有另一种秩序却很少受到关注：细胞和它们的神经突在正交（x-y）平面上的排列。过程，有助于这种安排包括马赛克间距的神经元胞体，平铺的树突，和自我回避的过程中的一个单一的乔木。这些过程被认为可以确保视野的均匀覆盖，精确的连通性和适当的感受野大小。它们的分子基础在脊椎动物中仍然未知。 最近，我们开始分析两组细胞表面蛋白，我们怀疑是参与层状特异性：MEGF 10和11，和一个集群的22个相关的γ原钙粘蛋白（Pcdhgs）。出乎意料的是，初步结果表明，两者都参与调节特定神经元及其树突在x-y平面上的排列。此外，两者都影响相同的细胞类型，星爆无长突细胞（SAC），但以不同的方式：MEGF 10/11调节SAC胞体的马赛克排列，而Pcdhgs是自我回避树突所必需的。现在，我们将使用这些结果作为出发点，以获得深入了解这些常见的，但很少研究的电路组装方面的机制。首先，我们将使用体内功能获得和丧失方法来表征MEGF 10/11在嵌合体形成中的作用。我们将询问MEGF 10/11是否仅在发育期间有效，其作用是否持久，是否可以在马赛克形成后破坏它们，以及这两种同系物是否具有不同的作用。第二，我们将询问是否在条件Pcdhg突变小鼠中观察到的自我回避缺陷是细胞自主的，以及它们是否反映了树突形成或细化的问题。然后，我们将使用遗传方法来减少视网膜细胞表达的Pcdhg亚型的库。因此，我们可以测试同种型多样性在这一过程中的作用，并了解不同的同种型是否发挥不同的作用。第三，我们将询问除了SAC之外的视网膜亚型是否使用MEGF 10/11或Pcdhgs来图案化它们的胞体或乔木。最后，我们将结合联合收割机在体外和体内的研究，启动MEGF 10/11和Pcdhgs功能的信号转导机制的分析。我们会问MEGF 10/11是否作为受体，作为配体，或作为配体和受体（即，同嗜性）。对于Pcdhgs，我们将问Pcdhgs似乎促进的最初粘附相互作用如何转化为自我回避所需的排斥性相互作用。总之，这些结果将进一步加深我们对两个知之甚少的基因家族的理解，以及对神经回路模式化重要的一组知之甚少的过程的理解。