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Connexin50 couples axon terminals of mouse horizontal cells by homotypic gap junctions

Lookup NU author(s): Dr Birthe Hilgen

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Abstract

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 feed-back and feed-forward 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, 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 wild-type 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.


Publication metadata

Author(s): Dorgau B, Herrling R, Schultz K, Greb H, Segelken J, Ströh S, Bolte P, Weiler R, Dedek K, Janssen-Bienhold U

Publication type: Article

Publication status: Published

Journal: Journal of Comparative Neurology

Year: 2015

Volume: 523

Issue: 14

Pages: 2062-2081

Print publication date: 01/10/2015

Online publication date: 14/05/2015

Acceptance date: 24/03/2015

ISSN (print): 0021-9967

ISSN (electronic): 0092-7317

Publisher: John Wiley & Sons, Inc,

URL: http://dx.doi.org/10.1002/cne.23779

DOI: 10.1002/cne.23779


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