title: Complexity of gap junctions between horizontal cells of the carp retina.
abstract: In the vertebrate retina, horizontal cells (HCs) reveal homologous coupling by gap junctions (gj), which are thought to consist of different connexins (Cx). However, recent studies in mouse, rabbit and zebrafish retina indicate that individual HCs express more than one connexin. To provide further insights into the composition of gj connecting HCs and to determine whether HCs express multiple connexins, we examined the molecular identity and distribution of gj between HCs of the carp retina. We have cloned four carp connexins designated Cx49.5, Cx55.5, Cx52.6 and Cx53.8 with a close relationship to connexins previously reported in HCs of mouse, rabbit and zebrafish, respectively. Using in situ hybridization, Cx49.5 expression was detected in different subpopulations of retinal neurons including HCs, whereas the Cx52.6 transcript was localized exclusively in HCs. Using specific antibodies, Cx55.5 and Cx53.8 were detected on dendrites of all four HC subtypes and axon terminals. Immunoelectron microscopy confirmed the presence of Cx55.5 and Cx53.8 in gap junctions between these processes and Cx55.5 was additionally observed in HC dendrites invaginating cone pedicles, suggesting its participation in the modulation of photoreceptor output in the carp retina. Furthermore, using single-cell RT-PCR, all four connexins were detected in different subtypes of HCs, suggesting overlapping expression patterns. Thus, the composition of gj mediating homologous coupling between subtypes of carp HCs appears to be more complex than expected. Moreover, BLAST searches of the preliminary carp genome, using novel sequences as query, suggest that most of the analyzed connexin genes are duplicated in carp.
authors: Visual Neuroscience, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: H
authors: H
authors: Greb
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: S
authors: S
authors: Hermann
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: P
authors: P
authors: Dirks
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: G
authors: G
authors: Ommen
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany; Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg University of Mainz, D-55128 Mainz, Germany.
authors: V
authors: V
authors: Kretschmer
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: K
authors: K
authors: Schultz
authors: Department of Psychology, Faculty of Health, York University, Toronto, Canada.
authors: G
authors: G
authors: Zoidl
authors: Neurobiology, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, D-26111 Oldenburg, Germany.
authors: R
authors: R
authors: Weiler
authors: Visual Neuroscience, Department of Neuroscience, University of Oldenburg, D-26111 Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, D-26111 Oldenburg, Germany. Electronic address: ulrike.janssen.bienhold@uni-oldenburg.de.
authors: U
authors: U
authors: Janssen-Bienhold
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism; D015153:Blotting, Western; D002347:Carps / Q000033:anatomy & histology* / Q000378:metabolism*; D045744:Cell Line, Tumor; D017630:Connexins / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism; D029941:Fish Proteins / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D016253:Microscopy, Immunoelectron; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms; D051248:Retinal Horizontal Cells / Q000166:cytology* / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D017630:Connexins; D029941:Fish Proteins; D020033:Protein Isoforms
keywords: Connexin49.5; Connexin52.6; Connexin53.8; Connexin55.5; electrical synapse; hemichannel