Department of Ophthalmology and Visual Science, University of Texas Medical School at Houston, Houston, Texas 77030, USA.
J Comp Neurol. 2012 Jul 1;520(10):2256-74. doi: 10.1002/cne.23060.
In the rabbit retina there are two types of horizontal cell (HC). A-type HCs (AHC) are axonless and extensively coupled via connexin (Cx)50 gap junctions. The B-type HC (BHC) is axon-bearing; the somatic dendrites form a second network coupled by gap junctions while the axon terminals (ATs) form a third independent network in the outer plexiform layer (OPL). The mouse retina has only one type of HC, which is morphologically similar to the B-type HC of the rabbit. Previous work suggested that mouse HCs express Cx57 (Hombach et al. [2004] Eur J Neurosci 19:2633-2640). Therefore, we cloned rabbit Cx57 and raised an antibody to determine the distribution of Cx57 gap junctions among rabbit HCs. Dye injection methods were used to obtain detailed fills for all three HC networks for analysis by confocal microscopy. We found that Cx57 was associated with the B-type AT plexus. Cx57 plaques were anticorrelated with the B-type somatic dendrites and the A-type HC network. Furthermore, there was no colocalization between Cx50 and Cx57. We conclude that in the rabbit retina, Cx57 is only found on BHC-AT processes. Thus, in species where there are two types of HC, different connexins are expressed. The absence of Cx57 labeling in the somatic dendrites of B-type HCs suggests the possibility of an additional unidentified HC connexin in the rabbit.
在兔视网膜中有两种类型的水平细胞（HC）。A型 HC（AHC）无轴突，通过缝隙连接（Cx）50 广泛偶联。B 型 HC（BHC）有轴突；体细胞树突形成第二个通过缝隙连接偶联的网络，而轴突末梢（AT）在外丛状层（OPL）中形成第三个独立的网络。小鼠视网膜只有一种 HC，其形态与兔的 B 型 HC 相似。先前的工作表明，小鼠 HC 表达 Cx57（Hombach 等人，[2004]Eur J Neurosci 19:2633-2640）。因此，我们克隆了兔 Cx57 并制备了抗体来确定兔 HC 中 Cx57 缝隙连接的分布。通过染料注射方法获得了所有三种 HC 网络的详细填充，以便通过共聚焦显微镜进行分析。我们发现 Cx57 与 B 型 AT 丛相关。Cx57 斑与 B 型体细胞树突和 A 型 HC 网络呈反相关。此外，Cx50 和 Cx57 之间没有共定位。我们得出结论，在兔视网膜中，Cx57 仅存在于 BHC-AT 过程中。因此，在存在两种类型的 HC 的物种中，表达不同的连接蛋白。B 型 HC 体细胞树突中缺乏 Cx57 标记表明兔中可能存在另一种未识别的 HC 连接蛋白。
