Electrical synapses in rod and cone pathways of the mouse retina

小鼠视网膜视杆细胞和视锥细胞通路中的电突触

• 批准号: 270305961
• 负责人: Professorin Dr. Karin Dedek
• 金额: --
• 依托单位: Arbeitsgruppe Neurobiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/270305961?language=en
• 关键词: Electrical; synapses; rod; cone; pathways

The mammalian retina is able to encode visual information over ~10 log units of light intensities. It therefore has evolved two types of photoreceptors: rods for vision under dim light and cones for vision under bright light and color vision. Electrical synapses (gap junctions) built from connexin proteins play an essential role in the most sensitive rod pathway, the primary rod pathway, and in cone pathways. In the primary rod pathway, dim light signals are mediated from rods to rod bipolar cells, which in turn contact AII amacrine cells. AII cells form homocellular gap junctions among each other, thereby optimizing signal-to-noise ratio when photons are scarce. AII cells send the rod signal via glycinergic synapses to OFF cone bipolar cells and via heterocellular gap junctions to ON cone bipolar cells. Interestingly, the rectification of these electrical synapses becomes weaker during light adaptation favoring signal flow from ON bipolar to AII amacrine cells in bright light.AII-AII gap junctions differ in ultrastructure and sensitivity to neuromodulators from AII-ON cone bipolar cell gap junctions although the structural basis for these differences is only partially understood. While it is believed that AII-AII gap junctions are composed of connexin36 (Cx36), composition and regulation of AII-ON cone bipolar cell gap junctions are still debated. We have evidence now that AII cells not only express Cx36 but also another connexin. We hypothesize that this connexin is involved in heterocellular AII gap junctions and makes these junctions sensitive to modulators, which may induce changes in synapse rectification in a light-dependent manner. Moreover, we recently found AII-AII and AII-ON cone bipolar cell gap junctions to deviate in their assembly mechanisms although the basis for this difference is not known so far. In this project, we thus aim to determine the molecular basis for the differences in structure, assembly, and light-dependent modulation of homo- and heterocellular AII gap junctions.Electrical synapses are also essential for cone pathways. Together with colleagues, we recently found that ON bipolar cells are not only coupled to the AII amacrine cell but also to another glycinergic small-field amacrine cell. Whether this coupling is light-dependent and which connexins underlie the coupling is not known so far. Thus, we aim to analyze the regulation of the coupling and to identify the connexins involved.To achieve our goals, various connexin-deficient mouse lines and mouse lines expressing EGFP-tagged connexins will be used for co-immunoprecipitation, tracer coupling experiments under different light conditions, and superresolution microscopy-based localization analyses. This will help to understand how electrically coupled retinal neurons are able to establish electrical synapses with different synaptic partners and how these synapses can be differentially modulated depending on ambient light levels.

哺乳动物视网膜能够编码超过约10个对数单位的光强度的视觉信息。因此，它进化出两种类型的光感受器：在昏暗光线下的视觉杆和在明亮光线下的视觉和色觉的视锥。由连接蛋白蛋白构建的电突触（间隙连接）在最敏感的视杆细胞通路、初级视杆细胞通路和视锥细胞通路中起重要作用。在初级视杆细胞通路中，昏暗的光信号从视杆细胞传递到视杆双极细胞，后者又与AII无长突细胞接触。所有的细胞之间形成同源细胞间隙连接，从而在光子稀少时优化信噪比。所有细胞通过甘氨酸能突触将视杆信号发送到OFF锥双极细胞，并通过异细胞间隙连接发送到ON锥双极细胞。有趣的是，这些电突触的整流变弱，有利于信号流从ON双极到AII无长突细胞在明亮的light.AII-AII间隙连接不同的超微结构和敏感性的神经调质从AII-ON锥双极细胞间隙连接，虽然这些差异的结构基础是只有部分理解。虽然认为AII-AII间隙连接由连接蛋白36（Cx 36）组成，但AII-ON锥双极细胞间隙连接的组成和调节仍有争议。我们现在有证据表明，AII细胞不仅表达Cx 36，而且还表达另一种连接蛋白。我们假设，这种连接蛋白参与异细胞AII间隙连接，使这些路口敏感的调制器，这可能会引起突触整流的变化，在光依赖性的方式。此外，我们最近发现AII-AII和AII-ON锥双极细胞间隙连接偏离其组装机制，尽管这种差异的基础目前尚不清楚。因此，在这个项目中，我们的目标是确定同源和异源细胞AII间隙连接的结构，组装和光依赖性调制的差异的分子基础。与同事一起，我们最近发现ON双极细胞不仅与AII无长突细胞偶联，而且与另一种甘氨酸能小视野无长突细胞偶联。这种耦合是否是光依赖性的，以及哪些连接蛋白是耦合的基础，目前还不清楚。因此，我们的目标是分析调控的耦合，并确定connexins involved.To实现我们的目标，各种connexin缺陷的小鼠品系和小鼠品系表达EGFP标记的connexins将用于免疫共沉淀，示踪剂耦合实验在不同的光条件下，和超分辨率显微镜为基础的定位分析。这将有助于理解电耦合的视网膜神经元如何能够与不同的突触伙伴建立电突触，以及这些突触如何根据环境光水平进行差异调制。

项目成果

Localization of Retinal Ca2+/Calmodulin-Dependent Kinase II-β (CaMKII-β) at Bipolar Cell Gap Junctions and Cross-Reactivity of a Monoclonal Anti-CaMKII-β Antibody With Connexin36

视网膜 Ca2 /钙调蛋白依赖性激酶 II-β (CaMKII-β) 在双极细胞间隙连接处的定位以及单克隆抗 CaMKII-β 抗体与 Connexin36 的交叉反应性

• DOI: 10.3389/fnmol.2019.00206
• 发表时间: 2019
• 期刊: Frontiers in Molecular Neuroscience
• 影响因子: 4.8
• 作者: Tetenborg;Stephan;Shubhash Chandra;Brüggen;Bianca;Georg R;Hormuzdi;Sheriar G;Monyer;Hannah;van Woerden;Geeske M;Janssen-Bienhold;Ulrike
• 通讯作者: Ulrike

Phenotyping of Gap-Junctional Coupling in the Mouse Retina.

小鼠视网膜间隙连接耦合的表型分析

• DOI: 10.1007/978-1-4939-7720-8_17
• 发表时间: 2018
• 期刊: Methods in molecular biology
• 作者: Meyer A;Yadav SC;Dedek K
• 通讯作者: Dedek K

Gap Junctions in A8 Amacrine Cells Are Made of Connexin36 but Are Differently Regulated Than Gap Junctions in AII Amacrine Cells

A8 无长突细胞中的间隙连接由 Connexin36 组成，但其调节方式与 AII 无长突细胞中的间隙连接不同

• DOI: 10.3389/fnmol.2019.00099
• 发表时间: 2019
• 期刊: Frontiers in Molecular Neuroscience
• 影响因子: 4.8
• 作者: Yadav SC;Tetenborg S;Dedek K
• 通讯作者: Dedek K