Connexin50 Couples Axon Terminals of Mouse Horizontal Cells by Homotypic Gap Junctions
Connexin50 Couples Axon Terminals of Mouse Horizontal Cells by Homotypic Gap Junctions
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DOI：
10.1002/cne.23779
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发表时间：
2015-10-01
影响因子：
2.5
通讯作者：
Janssen-Bienhold, Ulrike
中科院分区：
文献类型：
--
作者：
Dorgau, Birthe;Herrling, Regina;Janssen-Bienhold, Ulrike
小鼠视网膜中的水平细胞是具有轴突的B型细胞，并且通过分别向光感受器和双极细胞提供反馈和前馈信号而有助于光感受器的增益控制和双极细胞的中心-环绕组织。水平细胞形成两个独立的网络，通过由连接蛋白57（Cx 57）组成的树突-树突和轴-轴间隙连接偶联。在Cx 57缺陷型小鼠中，偶尔观察到水平细胞胞体的残留示踪剂偶联。此外，从水平细胞到光感受器的负反馈，可能由连接蛋白半通道介导，似乎不受影响。这些结果表明小鼠水平细胞中存在第二种连接蛋白的表达。我们研究了Cx 50的表达，这是最近发现的无轴突的A型水平细胞的兔视网膜。在小鼠视网膜中，Cx 50免疫反应斑点主要定位于水平细胞的大轴突终末。电子显微镜没有发现任何Cx 50免疫标记的水平细胞尖端的膜内陷感光细胞终端，排除了Cx 50的负反馈的参与。此外，Cx 50共定位只有很少与Cx 57水平的细胞过程中，表明这两个连接蛋白形成同型，而不是异型或异聚间隙连接。为了检查当Cx 57缺乏时Cx 50的表达是否改变，我们比较了野生型和Cx 57缺陷型小鼠中Cx 50的表达。然而，在Cx 57缺陷小鼠中Cx 50表达不受影响。总之，我们的研究结果表明，水平细胞轴突终末形成两个独立的组的同型间隙连接，这可能是重要的光适应视网膜的功能。(C)2015 Wiley Periodicals，Inc.
Horizontal cells in the mouse retina are of the axon-bearing B-type and contribute to the gain control of photoreceptors and to the center-surround organization of bipolar cells by providing feedback and feedforward signals to photoreceptors and bipolar cells, respectively. Horizontal cells form two independent networks, coupled by dendro-dendritic and axo-axonal gap junctions composed of connexin57 (Cx57). In Cx57-deficient mice, occasionally the residual tracer coupling of horizontal cell somata was observed. Also, negative feedback from horizontal cells to photoreceptors, potentially mediated by connexin hemichannels, appeared unaffected. These results point to the expression of a second connexin in mouse horizontal cells. We investigated the expression of Cx50, which was recently identified in axonless A-type horizontal cells of the rabbit retina. In the mouse retina, Cx50-immunoreactive puncta were predominantly localized on large axon terminals of horizontal cells. Electron microscopy did not reveal any Cx50-immunolabeling at the membrane of horizontal cell tips invaginating photoreceptor terminals, ruling out the involvement of Cx50 in negative feedback. Moreover, Cx50 colocalized only rarely with Cx57 on horizontal cell processes, indicating that both connexins form homotypic rather than heterotypic or heteromeric gap junctions. To check whether the expression of Cx50 is changed when Cx57 is lacking, we compared the Cx50 expression in wildtype and Cx57-deficient mice. However, Cx50 expression was unaffected in Cx57-deficient mice. In summary, our results indicate that horizontal cell axon terminals form two independent sets of homotypic gap junctions, a feature which might be important for light adaptation in the retina. (C) 2015 Wiley Periodicals, Inc.