Wiring direction-selective circuits in the mouse retina

小鼠视网膜中的布线方向选择电路

• 批准号: 8982323
• 负责人: Rebecca Ellen James
• 金额: $ 5.42万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-16 至 2017-12-15
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8982323
• 关键词: Ablation; Address; Axon; Binding; Biological; Biological Assay; Candidate Disease Gene; Cells; Cues; Dendrites; Detection; Development; Disease; Distal; Environment; Event; Excision; Eye; Gene Expression; Genetic; Goals; Image; In Vitro; Individual; Inner Plexiform Layer; Interneurons; Label; Ligands; Light; Molecular; Molecular Profiling; Motion; Mus; Neurons; Output; Pathway interactions; Pattern; Phenotype; Population; Property; RNA Sequences; Radial; Retina; Retinal; Role; Signal Pathway; Signal Transduction; Signaling Molecule; Sister; Source; Specific qualifier value; Staging; Stratification; Synapses; Testing; Transgenes; Varicosity; Visual; Work; design; differential expression; ganglion cell; in vivo; induced pluripotent stem cell; mutant; nerve supply; neuronal circuitry; neurotransmission; neurotransmitter release; plexin; postsynaptic; presynaptic; protein distribution; public health relevance; receptor; response; segregation; starburst amacrine cell; synaptogenesis; transcriptome sequencing

 DESCRIPTION (provided by applicant): Starburst amacrine cells (SACs) are radially symmetric inhibitory interneurons essential to confer the direction- selective (DS) properties of DS visual circuits in the mammalian retina, which impart image motion detection, a critical function for organismal survival. SACs have evolved to release neurotransmitter from varicosities in their distal dendritic arbors, since they lack axons. The principles that govern circuit assembly of neurons that lack clearly distinguishable axonal-dendritic compartments, and therefore discrete regions of specialization, are poorly defined. In the mouse retina, signaling through the guidance cue semaphorin6A (Sema6A) and its receptor is required for proper SAC circuit assembly. Two mirror populations of SACs exist that respond to either increases (ON) or decreases (OFF) in light. SAC are initially intermingled in the developing retina, but then stratif into the ON and OFF SAC circuits. Sema6A-PlexA2 signaling drives not only ON and OFF SAC stratification, but also establishes appropriate radial symmetry of individual ON SACs, which is necessary for accurate DS visual responses. Sema6A is also required for proper light (i.e. visual cue) evoked inhibitory postsynaptic responses in ON SACs. How the Sema6A-PlexA2 signaling pathway elicits such disparate cellular responses is unclear. This proposal is designed to study the mechanisms that distinguish these branches of guidance cue signaling within single SACs, and to define the range of guidance cues that contribute to DS SAC wiring. The specific aims of this study are to 1) assess the directionality of Sema6A-PlexA2 signaling pathways during retinal development with respect to segregation of the ON and OFF SAC circuits and development of SAC symmetry; 2) probe the mechanism underlying improper SAC inhibition in Sema6A mutants; and 3) to ask if other class 6 Semas and/or class A Plexins contribute to wiring DS circuitry. I will address these basic biological questions by 1) conditional removal of either Sema6A or PlexA2 in single SACs to determine the directionality of signaling; 2) examining the localization of synapses in Sema6A and PlexA2 mutant SACs, to ask if inappropriate synapse formation contributes to improper SAC inhibitory input; and 3) phenotypic analysis of class 6 Sema and class A double mutant combinations, to ask if any of these molecules regulates SAC stratification or elaboration of SAC symmetry. The answers to these questions have the potential to reveal general principles that guide CNS circuit assembly, especially in contexts where neurons lack axodendritic polarity. Since these molecules also contribute to wiring other circuits in the developing CNS, in addition to wiring DS circuits in the retina, understanding the directionality of their signaling and the mechanisms by which they direct distinct aspects of circuit refinement in the retina will have significant implications for treating developmental neuronal circuitry disorders where these and related signaling molecules are non-functional.

 描述（由应用程序提供）：Starburst Amacrine细胞（SACS）是径向对称的抑制性中间神经元，对于在哺乳动物视网膜中赋予DS视觉电路的方向选择性（DS）特性所必需的抑制性中间神经元，它赋予了图像运动检测，这是有机存活的关键功能。 SAC已演变为从其独特的树突弧菌中的静脉曲张中释放神经递质，因为它们缺乏轴突。在缺乏明显区分轴突树突室的神经元电路组装的原理，因此是离散的专业化区域的定义很差。在小鼠视网膜中，通过指导提示信号量信号（SEMA6A）发出信号及其接收器是正确的SAC电路组件。存在两个镜面囊群，以响应在光线下增加（ON）或减少（关闭）。 SAC最初是在发育中的视网膜中混合的，但随后分层进入囊囊电路。 SEMA6A-PLEXA2信号传导不仅在SAC分层内外驱动，还可以在SAC上建立适当的径向对称性，这对于精确的DS视觉响应是必不可少的。还需要SEMA6A才能在囊中诱发抑制性突触后反应（即视觉提示）。 SEMA6A-PLEXA2信号通路如何引起这种不同的细胞反应尚不清楚。该建议旨在研究区分单个囊中这些指导提示信号传导的机制，并定义有助于DS SAC接线的指导线索范围。这项研究的具体目的是1）评估视网膜开发过程中SEMA6A-PLEXA2信号通路的方向性在开关和关闭囊电路的分离和SAC对称性的发展方面； 2）探测SEMA6A突变体中SAC抑制的机制； 3）询问其他6类SEMAS和/或A类丛生是否有助于接线DS电路。我将通过1）在单个SAC中有条件地去除SEMA6A或PLEXA2来解决这些基本的生物学问题，以确定信号传导的方向性； 2）检查突触在SEMA6A和PLEXA2突变囊中的定位，以询问不适当的突触形成是否导致SAC抑制输入不当； 3）6类SEMA和A类双重突变体组合的表型分析，以询问这些分子中的任何一个是否调节SAC分层或阐述SAC对称性。这些问题的答案有可能揭示指导中枢神经系统电路组装的一般原则，尤其是在神经元缺乏轴突极性的情况下。由于这些分子还有助于在发育中的CNS中接线其他电路，除了接线DS电路 视网膜，了解其信号的方向性以及视网膜中电路细化的不同方面的机制将对处理这些和相关信号分子无功能的发育神经元电路疾病具有重要意义。