Complexity of gap junctions between horizontal cells of the carp retina. (6th January 2017)

• Record Type: Journal Article
• Authors: Greb, H.; Hermann, S.; Dirks, P.; Ommen, G.; Kretschmer, V.; Schultz, K.; Zoidl, G.; Weiler, R.; Janssen-Bienhold, U.
• Is Part Of: Neuroscience. Volume 340(2017)
• Page Start: 8
• Page End: 22
• Publication Date: 2017-01-06
• Subjects: aa amino acid -- bp base pairs -- Cx connexin -- cc Cyprinus carpio -- Da Dalton -- dr Danio rerio -- GCL ganglion cell layer -- hs Homo sapiens -- HC horizontal cell -- INL inner nuclear layer -- IPL inner plexiform layer -- mm Mus musculus -- N2a neuroblastoma 2a -- oc Oryctolagus cuniculus -- ONL outer nuclear layer -- OPL outer plexiform layer; Connexin49.5 -- Connexin52.6 -- Connexin55.5 -- Connexin53.8 -- electrical synapse -- hemichannel; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2016.10.044
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Individual carp horizontal cells express up to four different connexins. The expression of Cx49.5 and Cx52.6 in carp horizontal cells was confirmed via in situ hybridization and RT–PCR. Cx55.5 and Cx53.8 form dendro-dendritic and axo-axonal gap junctions between carp horizontal cells. Cx55.5 hemichannels are present on horizontal cell dendrites invaginating cone pedicles. Identified horizontal cell connexins are duplicated in carp. 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.