Kántor Orsolya, Varga Alexandra, Nitschke Roland, Naumann Angela, Énzsöly Anna, Lukáts Ákos, Szabó Arnold, Németh János, Völgyi Béla
Department of Neuroanatomy, Faculty of Medicine, Institute for Anatomy and Cell Biology, University of Freiburg, 79104, Freiburg, Germany.
MTA-PTE NAP B Retinal Electrical Synapses Research Group, Pécs, 7624, Hungary.
Brain Struct Funct. 2017 Aug;222(6):2603-2624. doi: 10.1007/s00429-016-1360-4. Epub 2017 Jan 10.
Connexin36 (Cx36) constituent gap junctions (GJ) throughout the brain connect neurons into functional syncytia. In the retina they underlie the transmission, averaging and correlation of signals prior conveying visual information to the brain. This is the first study that describes retinal bipolar cell (BC) GJs in the human inner retina, whose function is enigmatic even in the examined animal models. Furthermore, a number of unique features (e.g. fovea, trichromacy, midget system) necessitate a reexamination of the animal model results in the human retina. Well-preserved postmortem human samples of this study are allowed to identify Cx36 expressing BCs neurochemically. Results reveal that both rod and cone pathway interneurons display strong Cx36 expression. Rod BC inputs to AII amacrine cells (AC) appear in juxtaposition to AII GJs, thus suggesting a strategic AII cell targeting by rod BCs. Cone BCs serving midget, parasol or koniocellular signaling pathways display a wealth of Cx36 expression to form homologously coupled arrays. In addition, they also establish heterologous GJ contacts to serve an exchange of information between parallel signaling streams. Interestingly, a prominent Cx36 expression was exhibited by midget system BCs that appear to maintain intimate contacts with bistratified BCs serving other pathways. These findings suggest that BC GJs in parallel signaling streams serve both an intra- and inter-pathway exchange of signals in the human retina.
连接蛋白36（Cx36）在整个大脑中构成间隙连接（GJ），将神经元连接成功能合胞体。在视网膜中，它们是在将视觉信息传递到大脑之前对信号进行传输、平均和关联的基础。这是第一项描述人眼内视网膜中视网膜双极细胞（BC）间隙连接的研究，其功能即使在已研究的动物模型中也很神秘。此外，一些独特的特征（如中央凹、三色视觉、侏儒系统）使得有必要重新审视动物模型在人类视网膜中的研究结果。本研究中保存良好的死后人体样本能够通过神经化学方法鉴定表达Cx36的双极细胞。结果显示，视杆和视锥通路的中间神经元均表现出强烈的Cx36表达。视杆双极细胞向AII无长突细胞（AC）的输入与AII间隙连接并列出现，因此表明视杆双极细胞对AII细胞有策略性的靶向作用。服务于侏儒、伞状或小细胞信号通路的视锥双极细胞表现出丰富的Cx36表达，形成同源耦合阵列。此外，它们还建立异源间隙连接接触，以在平行信号流之间进行信息交换。有趣的是，侏儒系统双极细胞表现出显著的Cx36表达，它们似乎与服务于其他通路的双分层双极细胞保持密切接触。这些发现表明，平行信号流中的双极细胞间隙连接在人类视网膜中既服务于信号在通路内的交换也服务于通路间的交换。
