AII amacrine cells discriminate between heterocellular and homocellular locations when assembling connexin36-containing gap junctions

Meyer, A., Hilgen, Gerrit, Dorgau, B., Sammler, E. M., Weiler, R., Monyer, H., Dedek, K. and Hormuzdi, S. G. (2014) AII amacrine cells discriminate between heterocellular and homocellular locations when assembling connexin36-containing gap junctions. Journal of Cell Science, 127 (6). pp. 1190-1202. ISSN 0021-9533

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Abstract

Electrical synapses (gap junctions) rapidly transmit signals between neurons and are composed of connexins. In neurons, connexin36 (C×36) is the most abundant isoform; however, the mechanisms underlying formation of C×36-containing electrical synapses are unknown. We focus on homocellular and heterocellular gap junctions formed by an AII amacrine cell, a key interneuron found in all mammalian retinas. In mice lacking native C×36 but expressing a variant tagged with enhanced green fluorescent protein at the C-terminus (KO-C×36-EGFP), heterocellular gap junctions formed between AII cells and ON cone bipolar cells are fully functional, whereas homocellular gap junctions between two AII cells are not formed. A tracer injected into an AII amacrine cell spreads into ON cone bipolar cells but is excluded from other AII cells. Reconstruction of C×36-EGFP clusters on an AII cell in the KO-C×36-EGFP genotype confirmed that the number, but not average size, of the clusters is reduced - as expected for AII cells lacking a subset of electrical synapses. Our studies indicate that some neurons exhibit at least two discriminatory mechanisms for assembling C×36. We suggest that employing different gapjunction- forming mechanisms could provide the means for a cell to regulate its gap junctions in a target-cell-specific manner, even if these junctions contain the same connexin.

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