title: Connexin50 couples axon terminals of mouse horizontal cells by homotypic gap junctions.
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 feedback and feedforward 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 the 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 wildtype 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.
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.|Institute of Genetic Medicine, Newcastle University, Newcastle, UK.
authors.forename: Birthe
authors.initials: B
authors.lastname: Dorgau
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Herrling
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.
authors.forename: Konrad
authors.initials: K
authors.lastname: Schultz
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Greb
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Segelken
authors.affiliation: Institute of Genetic Medicine, Newcastle University, Newcastle, UK.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ströh
authors.affiliation: Institute of Genetic Medicine, Newcastle University, Newcastle, UK.|Animal Navigation, University of Oldenburg, Oldenburg, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Bolte
authors.forename: Reto
authors.initials: R
authors.lastname: Weiler
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111, Oldenburg, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Dedek
authors.forename: Ulrike
authors.initials: U
authors.lastname: Janssen-Bienhold
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D015153:Blotting, Western; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological / Q000502:physiology; D017629:Gap Junctions / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051248:Retinal Horizontal Cells / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection; D000099264:Connexin 50
chemical_list: D017630:Connexins; D012333:RNA, Messenger; D000099264:Connexin 50; C119811:Gja10 protein, mouse
keywords: RRID:AB-631776; RRID:AB_10000340; RRID:AB_10562715; RRID:AB_10563566; RRID:AB_11125547; RRID:AB_1163387; RRID:AB_2307331; RRID:AB_2336183; RRID:AB_2338689; RRID:AB_2490076; RRID:AB_477272; RRID:AB_477593; RRID:AB_87122; RRID:IMSR_EM:01644; RRID:IMSR_JAX007677; RRID:SciEx_12797; RRID:SciRes_000137; RRID:SciRes_000161; RRID:nif_0000_00462; RRID:nif_0000_30076; RRID:nlx_84530; RRID:rid_000081; connexin; electron microscopy; gap junction; horizontal cell; mouse; retina