Abstract
Gap junction-mediated electrical coupling contributes to synchronous oscillatory activities of neurons, and considerable progress has been made in defining the molecular composition of gap junction channels. In particular, cloning and functional expression of gap junction proteins (connexins (Cx)) from zebrafish retina have shown that this part of the brain possesses a high degree of connexin diversity that may account for differential functional properties of electrical synapses. Here, we report the cloning and functional characterization of a new connexin, designated zebrafish Cx52.6 (zfCx52.6). This connexin shows little similarity to known connexins from fish and higher vertebrates. By combining in situ hybridization with Laser Capture Microdissection and RT-PCR, we found that this novel fish connexin is expressed in horizontal cells in the inner nuclear layer of the retina. Functional expression of zfCx52.6 in neuroblastoma cells and Xenopus oocytes led to functional gap junctional channels and, in single oocytes, induced large non-junctional membrane currents indicative of the formation of hemichannels, which were inhibited in reversible fashion by raising extracellular Ca(2+) concentrations.
Highlights
Gap junction-mediated electrical coupling contributes to synchronous oscillatory activities of neurons, and considerable progress has been made in defining the molecular composition of gap junction channels
Cloning and functional expression of gap junction proteins (connexins (Cx)) from zebrafish retina have shown that this part of the brain possesses a high degree of connexin diversity that may account for differential functional properties of electrical synapses
By combining in situ hybridization with Laser Capture Microdissection and RT-polymerase chain reaction (PCR), we found that this novel fish connexin is expressed in horizontal cells in the inner nuclear layer of the retina
Summary
Gap junction-mediated electrical coupling contributes to synchronous oscillatory activities of neurons, and considerable progress has been made in defining the molecular composition of gap junction channels. Cloning and functional expression of gap junction proteins (connexins (Cx)) from zebrafish retina have shown that this part of the brain possesses a high degree of connexin diversity that may account for differential functional properties of electrical synapses. We report the cloning and functional characterization of a new connexin, designated zebrafish Cx52.6 (zfCx52.6). This connexin shows little similarity to known connexins from fish and higher vertebrates. Gap junction-mediated dye transfer is found between most cell types that form the neuronal retinal matrix [21,22,23,24] and a diversity of coupling patterns that is so far unmatched in any other part of the brain [25, 26]. The selective nature of neuronal coupling and its differential regulation by neuromodulators [31,32,33,34,35,36,37], as shown recently for the amacrine AII cells [23, 38, 39], supports the idea that multiple types of connexins may exist within the neuronal populations of this tissue
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