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Ribelayga CP, O’Brien J. When microscopy and electrophysiology meet connectomics-Steve Massey's contribution to unraveling the structure and function of the rod/cone gap junction. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1305131. [PMID: 38983007 PMCID: PMC11182179 DOI: 10.3389/fopht.2023.1305131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 10/31/2023] [Indexed: 07/11/2024]
Abstract
Electrical synapses, formed of gap junctions, are ubiquitous components of the central nervous system (CNS) that shape neuronal circuit connectivity and dynamics. In the retina, electrical synapses can create a circuit, control the signal-to-noise ratio in individual neurons, and support the coordinated neuronal firing of ganglion cells, hence, regulating signal processing at the network, single-cell, and dendritic level. We, the authors, and Steve Massey have had a long interest in gap junctions in retinal circuits, in general, and in the network of photoreceptors, in particular. Our combined efforts, based on a wide array of techniques of molecular biology, microscopy, and electrophysiology, have provided fundamental insights into the molecular structure and properties of the rod/cone gap junction. Yet, a full understanding of how rod/cone coupling controls circuit dynamics necessitates knowing its operating range. It is well established that rod/cone coupling can be greatly reduced or eliminated by bright-light adaptation or pharmacological treatment; however, the upper end of its dynamic range has long remained elusive. This held true until Steve Massey's recent interest for connectomics led to the development of a new strategy to assess this issue. The effort proved effective in establishing, with precision, the connectivity rules between rods and cones and estimating the theoretical upper limit of rod/cone electrical coupling. Comparing electrophysiological measurements and morphological data indicates that under pharmacological manipulation, rod/cone coupling can reach the theoretical maximum of its operating range, implying that, under these conditions, all the gap junction channels present at the junctions are open. As such, channel open probability is likely the main determinant of rod/cone coupling that can change momentarily in a time-of-day- and light-dependent manner. In this article we briefly review our current knowledge of the molecular structure of the rod/cone gap junction and of the mechanisms behind its modulation, and we highlight the recent work led by Steve Massey. Steve's contribution has been critical toward asserting the modulation depth of rod/cone coupling as well as elevating the rod/cone gap junction as one of the most suitable models to examine the role of electrical synapses and their plasticity in neural processing.
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Affiliation(s)
- Christophe P. Ribelayga
- Department of Vision Sciences, University of Houston College of Optometry, Houston, TX, United States
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Ishibashi M, Keung J, Morgans CW, Aicher SA, Carroll JR, Singer JH, Jia L, Li W, Fahrenfort I, Ribelayga CP, Massey SC. Analysis of rod/cone gap junctions from the reconstruction of mouse photoreceptor terminals. eLife 2022; 11:73039. [PMID: 35471186 PMCID: PMC9170248 DOI: 10.7554/elife.73039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 04/25/2022] [Indexed: 12/14/2022] Open
Abstract
Electrical coupling, mediated by gap junctions, contributes to signal averaging, synchronization, and noise reduction in neuronal circuits. In addition, gap junctions may also provide alternative neuronal pathways. However, because they are small and especially difficult to image, gap junctions are often ignored in large-scale 3D reconstructions. Here, we reconstruct gap junctions between photoreceptors in the mouse retina using serial blockface-scanning electron microscopy, focused ion beam-scanning electron microscopy, and confocal microscopy for the gap junction protein Cx36. An exuberant spray of fine telodendria extends from each cone pedicle (including blue cones) to contact 40-50 nearby rod spherules at sites of Cx36 labeling, with approximately 50 Cx36 clusters per cone pedicle and 2-3 per rod spherule. We were unable to detect rod/rod or cone/cone coupling. Thus, rod/cone coupling accounts for nearly all gap junctions between photoreceptors. We estimate a mean of 86 Cx36 channels per rod/cone pair, which may provide a maximum conductance of ~1200 pS, if all gap junction channels were open. This is comparable to the maximum conductance previously measured between rod/cone pairs in the presence of a dopamine antagonist to activate Cx36, suggesting that the open probability of gap junction channels can approach 100% under certain conditions.
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Affiliation(s)
- Munenori Ishibashi
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Joyce Keung
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Catherine W Morgans
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - Sue A Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - James R Carroll
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, College Park, United States
| | - Li Jia
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Wei Li
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Iris Fahrenfort
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Christophe P Ribelayga
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Stephen C Massey
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
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3
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Cangiano L, Asteriti S. Interphotoreceptor coupling: an evolutionary perspective. Pflugers Arch 2021; 473:1539-1554. [PMID: 33988778 PMCID: PMC8370920 DOI: 10.1007/s00424-021-02572-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/13/2021] [Accepted: 04/23/2021] [Indexed: 12/16/2022]
Abstract
In the vertebrate retina, signals generated by cones of different spectral preference and by highly sensitive rod photoreceptors interact at various levels to extract salient visual information. The first opportunity for such interaction is offered by electrical coupling of the photoreceptors themselves, which is mediated by gap junctions located at the contact points of specialised cellular processes: synaptic terminals, telodendria and radial fins. Here, we examine the evolutionary pressures for and against interphotoreceptor coupling, which are likely to have shaped how coupling is deployed in different species. The impact of coupling on signal to noise ratio, spatial acuity, contrast sensitivity, absolute and increment threshold, retinal signal flow and colour discrimination is discussed while emphasising available data from a variety of vertebrate models spanning from lampreys to primates. We highlight the many gaps in our knowledge, persisting discrepancies in the literature, as well as some major unanswered questions on the actual extent and physiological role of cone-cone, rod-cone and rod-rod communication. Lastly, we point toward limited but intriguing evidence suggestive of the ancestral form of coupling among ciliary photoreceptors.
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Affiliation(s)
- Lorenzo Cangiano
- Dept. of Translational Research, University of Pisa, Via San Zeno 31, 56123, Pisa, Italy.
| | - Sabrina Asteriti
- Dept. of Translational Research, University of Pisa, Via San Zeno 31, 56123, Pisa, Italy
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4
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Li Y, Cohen ED, Qian H. Rod and Cone Coupling Modulates Photopic ERG Responses in the Mouse Retina. Front Cell Neurosci 2020; 14:566712. [PMID: 33100974 PMCID: PMC7546330 DOI: 10.3389/fncel.2020.566712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/31/2020] [Indexed: 11/13/2022] Open
Abstract
Light adaptation changes both the sensitivity and maximum amplitude (Rmax) of the mouse photopic electroretinogram (ERG) b-wave. Using the ERG, we examined how modulation of gap junctional coupling between rod and cones alters the light-adapted ERG. To measure changes, a b-wave light adaptation enhancement factor (LAEF), was defined as the ratio of Rmax after 15 min light adaptation to Rmax recorded at the onset of an adapting light. For wild-type mice (WT), the LAEF averaged 2.64 ± 0.29, however, it was significantly reduced (1.06 ± 0.04) for connexin 36 knock out (Cx36KO) mice, which lack electrical coupling between photoreceptors. Wild type mice intraocularly injected with meclofenamic acid (MFA), a gap junction blocker, also showed a significantly reduced LAEF. Degeneration of rod photoreceptors significantly alters the effects of light adaptation on the photopic ERG response. Rd10 mice at P21, with large portions of their rod photoreceptors present in the retina, exhibited a similar b-wave enhancement as wildtype controls, with a LAEF of 2.55 ± 0.19. However, by P31 with most of their rod photoreceptors degenerated, rd10 mice had a much reduced b-wave enhancement during light-adaptation (LAEF of 1.54 ± 0.12). Flicker ERG responses showed a higher temporal amplitude in mesopic conditions for WT than those of Cx36KO mice, suggesting rod-cone coupling help high-frequency signals to pass from rods to cone pathways in the retina. In conclusion, our study provides a novel method to noninvasively measure the dynamics and modulation by the light adaptation for rod-cone gap junctional coupling in intact eyes.
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Affiliation(s)
- Yichao Li
- Visual Function Core, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, United States
| | - Ethan D Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, United States
| | - Haohua Qian
- Visual Function Core, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, United States
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Jin N, Zhang Z, Keung J, Youn SB, Ishibashi M, Tian LM, Marshak DW, Solessio E, Umino Y, Fahrenfort I, Kiyama T, Mao CA, You Y, Wei H, Wu J, Postma F, Paul DL, Massey SC, Ribelayga CP. Molecular and functional architecture of the mouse photoreceptor network. SCIENCE ADVANCES 2020; 6:eaba7232. [PMID: 32832605 PMCID: PMC7439306 DOI: 10.1126/sciadv.aba7232] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
Mouse photoreceptors are electrically coupled via gap junctions, but the relative importance of rod/rod, cone/cone, or rod/cone coupling is unknown. Furthermore, while connexin36 (Cx36) is expressed by cones, the identity of the rod connexin has been controversial. We report that FACS-sorted rods and cones both express Cx36 but no other connexins. We created rod- and cone-specific Cx36 knockout mice to dissect the photoreceptor network. In the wild type, Cx36 plaques at rod/cone contacts accounted for more than 95% of photoreceptor labeling and paired recordings showed the transjunctional conductance between rods and cones was ~300 pS. When Cx36 was eliminated on one side of the gap junction, in either conditional knockout, Cx36 labeling and rod/cone coupling were almost abolished. We could not detect direct rod/rod coupling, and cone/cone coupling was minor. Rod/cone coupling is so prevalent that indirect rod/cone/rod coupling via the network may account for previous reports of rod coupling.
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Affiliation(s)
- Nange Jin
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Zhijing Zhang
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Joyce Keung
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Sean B. Youn
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Undergraduate Program, William Marsh Rice University, Houston, TX, USA
| | - Munenori Ishibashi
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Lian-Ming Tian
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - David W. Marshak
- Department of Neurobiology and Anatomy, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Eduardo Solessio
- Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Yumiko Umino
- Center for Vision Research and SUNY Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Iris Fahrenfort
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Takae Kiyama
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Chai-An Mao
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Yanan You
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Haichao Wei
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Jiaqian Wu
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- The Vivian L. Smith Department of Neurosurgery, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Stem Cell and Regenerative Medicine, The University of Texas Brown Foundation Institute of Molecular Medicine, Houston, TX, USA
| | - Friso Postma
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, USA
| | - David L. Paul
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, USA
| | - Stephen C. Massey
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Elizabeth Morford Distinguished Chair in Ophthalmology and Research Director, Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Christophe P. Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Summer Research Program, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Neuroscience Research Center, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Neuroscience, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Program in Biochemistry and Cellular Biology, Graduate School of Biomedical Sciences, MD Anderson Cancer Center/UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
- Bernice Weingarten Chair in Ophthalmology, Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA
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6
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Smedowski A, Akhtar S, Liu X, Pietrucha‐Dutczak M, Podracka L, Toropainen E, Alkanaan A, Ruponen M, Urtti A, Varjosalo M, Kaarniranta K, Lewin‐Kowalik J. Electrical synapses interconnecting axons revealed in the optic nerve head - a novel model of gap junctions' involvement in optic nerve function. Acta Ophthalmol 2020; 98:408-417. [PMID: 31602808 PMCID: PMC7318195 DOI: 10.1111/aos.14272] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 09/14/2019] [Indexed: 01/14/2023]
Abstract
PURPOSE To characterize newly discovered electrical synapses, formed by connexin (Cx) 36 and 45, between neighbouring axons within the optic nerve head. METHODS Twenty-five Wistar rats were killed by CO2 inhalation. Proximal and distal optic nerve (ON) stumps were collected and processed for immunostainings, electron microscopy (EM) with immunogold labelling, PCR and Western blots (WB). Additional 15 animals were deeply anaesthetized, and flash visual evoked potentials (fVEP) after retrobulbar injection of saline (negative control) or 100 μm meclofenamic acid solution (gap junctions' blocker) were recorded. Human paraffin cross-sections of eyeballs for immunostainings were obtained from the Human Eye Biobank for Research. RESULTS Immunostainings of both rat and human ON revealed the presence of Cx45 and 36 colocalizing with β3-tubulin, but not with glial fibrillary acidic protein (GFAP). In WB, Cx36 content in optic nerve was approximately halved when compared with retina (0.58 ± 0.005 in proximal stump and 0.44 ± 0.02 in distal stump), Cx45 showed higher levels (0.68 ± 0.01 in proximal stump and 0.9 ± 0.07 in distal stump). In immunogold-EM of optic nerve sections, we found electric synapses (formed mostly by Cx45) directly coupling neighbouring axons. In fVEP, blocking of gap junctions with meclofenamic acid resulted in significant prolongation of the latency of P1 wave up to 160% after 30 min (p < 0.001). CONCLUSIONS Optic nerve (ON) axons are equipped with electrical synapses composed of neuronal connexins, especially Cx45, creating direct morphological and functional connections between each other. This finding could have substantial implications for understanding of the pathogenesis of various optic neuropathies and identifies a new potential target for a therapeutic approach.
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Affiliation(s)
- Adrian Smedowski
- Department of PhysiologySchool of Medicine in KatowiceMedical University of SilesiaKatowicePoland
| | - Saeed Akhtar
- Department of OptometryCollege of Applied Medical SciencesKing Saud UniversityRiyadhKingdom of Saudi Arabia
| | - Xiaonan Liu
- Institute of BiotechnologyUniversity of HelsinkiHelsinkiFinland
| | - Marita Pietrucha‐Dutczak
- Department of PhysiologySchool of Medicine in KatowiceMedical University of SilesiaKatowicePoland
| | - Lucia Podracka
- School of PharmacyUniversity of Eastern FinlandKuopioFinland
| | | | - Aljoharah Alkanaan
- Department of OptometryCollege of Applied Medical SciencesKing Saud UniversityRiyadhKingdom of Saudi Arabia
| | - Marika Ruponen
- School of PharmacyUniversity of Eastern FinlandKuopioFinland
| | - Arto Urtti
- School of PharmacyUniversity of Eastern FinlandKuopioFinland
| | | | - Kai Kaarniranta
- Department of OphthalmologyUniversity of Eastern FinlandKuopioFinland,Department of OphthalmologyKuopio University HospitalKuopioFinland
| | - Joanna Lewin‐Kowalik
- Department of PhysiologySchool of Medicine in KatowiceMedical University of SilesiaKatowicePoland
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7
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Tetenborg S, Yadav SC, Brüggen B, Zoidl GR, Hormuzdi SG, Monyer H, van Woerden GM, Janssen-Bienhold U, Dedek K. Localization of Retinal Ca 2+/Calmodulin-Dependent Kinase II-β (CaMKII-β) at Bipolar Cell Gap Junctions and Cross-Reactivity of a Monoclonal Anti-CaMKII-β Antibody With Connexin36. Front Mol Neurosci 2019; 12:206. [PMID: 31555090 PMCID: PMC6724749 DOI: 10.3389/fnmol.2019.00206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/07/2019] [Indexed: 11/13/2022] Open
Abstract
Neuronal gap junctions formed by connexin36 (Cx36) and chemical synapses share striking similarities in terms of plasticity. Ca2+/calmodulin-dependent protein kinase II (CaMKII), an enzyme known to induce memory formation at chemical synapses, has recently been described to potentiate electrical coupling in the retina and several other brain areas via phosphorylation of Cx36. The contribution of individual CaMKII isoforms to this process, however, remains unknown. We recently identified CaMKII-β at electrical synapses in the mouse retina. Now, we set out to identify cell types containing Cx36 gap junctions that also express CaMKII-β. To ensure precise description, we first tested the specificity of two commercially available antibodies on CaMKII-β-deficient retinas. We found that a polyclonal antibody was highly specific for CaMKII-β. However, a monoclonal antibody (CB-β-1) recognized CaMKII-β but also cross-reacted with the C-terminal tail of Cx36, making localization analyses with this antibody inaccurate. Using the polyclonal antibody, we identified strong CaMKII-β expression in bipolar cell terminals that were secretagogin- and HCN1-positive and thus represent terminals of type 5 bipolar cells. In these terminals, a small fraction of CaMKII-β also colocalized with Cx36. A similar pattern was observed in putative type 6 bipolar cells although there, CaMKII expression seemed less pronounced. Next, we tested whether CaMKII-β influenced the Cx36 expression in bipolar cell terminals by quantifying the number and size of Cx36-immunoreactive puncta in CaMKII-β-deficient retinas. However, we found no significant differences between the genotypes, indicating that CaMKII-β is not necessary for the formation and maintenance of Cx36-containing gap junctions in the retina. In addition, in wild-type retinas, we observed frequent association of Cx36 and CaMKII-β with synaptic ribbons, i.e., chemical synapses, in bipolar cell terminals. This arrangement resembled the composition of mixed synapses found for example in Mauthner cells, in which electrical coupling is regulated by glutamatergic activity. Taken together, our data imply that CaMKII-β may fulfill several functions in bipolar cell terminals, regulating both Cx36-containing gap junctions and ribbon synapses and potentially also mediating cross-talk between these two types of bipolar cell outputs.
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Affiliation(s)
- Stephan Tetenborg
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Shubhash Chandra Yadav
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Bianca Brüggen
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Georg R Zoidl
- Department of Biology & Center for Vision Research, York University, Toronto, ON, Canada
| | - Sheriar G Hormuzdi
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom
| | | | - Geeske M van Woerden
- Department of Neuroscience, Erasmus MC University Medical Center, Rotterdam, Netherlands
| | - Ulrike Janssen-Bienhold
- Department of Neuroscience, Visual Neuroscience, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - Karin Dedek
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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8
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Telkes I, Kóbor P, Orbán J, Kovács-Öller T, Völgyi B, Buzás P. Connexin-36 distribution and layer-specific topography in the cat retina. Brain Struct Funct 2019; 224:2183-2197. [PMID: 31172263 PMCID: PMC6591202 DOI: 10.1007/s00429-019-01876-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 04/11/2019] [Indexed: 11/29/2022]
Abstract
Connexin-36 (Cx36) is the major constituent of mammalian retinal gap junctions positioned in key signal pathways. Here, we examined the laminar and large-scale topographical distribution of Cx36 punctate immunolabels in the retina of the cat, a classical model of the mammalian visual system. Calretinin-immunoreactive (CaR-IR) cell populations served to outline the nuclear and plexiform layers and to stain specific neuronal populations. CaR-IR cells included horizontal cells in the outer retina, numerous amacrine cells, and scattered cells in the ganglion cell layer. Cx36-IR plaques were found among horizontal cell dendrites albeit without systematic colocalization of the two labels. Diffuse Cx36 immunoreactivity was found in the cytoplasm of AII amacrine cells, but no colocalization of Cx36 plaques was observed with either the perikarya or the long varicose dendrites of the CaR-IR non-AII amacrine cells. Cx36 puncta were seen throughout the entire inner plexiform layer showing their highest density in the ON sublamina. The densities of AII amacrine cell bodies and Cx36 plaques in the ON sublamina were strongly correlated across a wide range of eccentricities suggesting their anatomical association. However, the high number of plaques per AII cell suggests that a considerable fraction of Cx36 gap junctions in the ON sublamina is formed by other cell types than AII amacrine cells drawing attention to extensive but less studied electrically coupled networks.
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Affiliation(s)
- Ildikó Telkes
- Institute of Physiology, Medical School, University of Pécs, Szigeti út 12, Pécs, 7624, Hungary
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary
- Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - Péter Kóbor
- Institute of Physiology, Medical School, University of Pécs, Szigeti út 12, Pécs, 7624, Hungary
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary
- Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - József Orbán
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary
- Department of Biophysics, Medical School, University of Pécs, Pécs, 7624, Hungary
| | - Tamás Kovács-Öller
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary
- Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, 7624, Hungary
- Retinal Electrical Synapses Research Group, MTA-PTE NAP-2, University of Pécs, Pécs, 7624, Hungary
- Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - Béla Völgyi
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary
- Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, 7624, Hungary
- Retinal Electrical Synapses Research Group, MTA-PTE NAP-2, University of Pécs, Pécs, 7624, Hungary
- Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary
| | - Péter Buzás
- Institute of Physiology, Medical School, University of Pécs, Szigeti út 12, Pécs, 7624, Hungary.
- Szentágothai Research Centre, University of Pécs, Pécs, 7624, Hungary.
- Centre for Neuroscience, University of Pécs, Pécs, 7624, Hungary.
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9
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Abstract
We have long known that rod and cone signals interact within the retina and can even contribute to color vision, but the extent of these influences has remained unclear. New results with more powerful methods of RNA expression profiling, specific cell labeling, and single-cell recording have provided greater clarity and are showing that rod and cone signals can mix at virtually every level of signal processing. These interactions influence the integration of retinal signals and make an important contribution to visual perception.
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Affiliation(s)
- Gordon Fain
- Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095-7000, USA.,Department of Integrative Biology and Physiology, University of California Los Angeles, Terasaki Life Sciences, 610 Charles E. Young Drive South, Los Angeles, CA 90095-7239, USA
| | - Alapakkam P Sampath
- Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, University of California Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095-7000, USA
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10
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Zhang C, Kolodkin AL, Wong RO, James RE. Establishing Wiring Specificity in Visual System Circuits: From the Retina to the Brain. Annu Rev Neurosci 2017; 40:395-424. [PMID: 28460185 DOI: 10.1146/annurev-neuro-072116-031607] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The retina is a tremendously complex image processor, containing numerous cell types that form microcircuits encoding different aspects of the visual scene. Each microcircuit exhibits a distinct pattern of synaptic connectivity. The developmental mechanisms responsible for this patterning are just beginning to be revealed. Furthermore, signals processed by different retinal circuits are relayed to specific, often distinct, brain regions. Thus, much work has focused on understanding the mechanisms that wire retinal axonal projections to their appropriate central targets. Here, we highlight recently discovered cellular and molecular mechanisms that together shape stereotypic wiring patterns along the visual pathway, from within the retina to the brain. Although some mechanisms are common across circuits, others play unconventional and circuit-specific roles. Indeed, the highly organized connectivity of the visual system has greatly facilitated the discovery of novel mechanisms that establish precise synaptic connections within the nervous system.
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Affiliation(s)
- Chi Zhang
- Department of Biological Structure, University of Washington, Seattle, Washington 98195; ,
| | - Alex L Kolodkin
- Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; ,
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, Washington 98195; ,
| | - Rebecca E James
- Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; ,
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11
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Kovács-Öller T, Debertin G, Balogh M, Ganczer A, Orbán J, Nyitrai M, Balogh L, Kántor O, Völgyi B. Connexin36 Expression in the Mammalian Retina: A Multiple-Species Comparison. Front Cell Neurosci 2017; 11:65. [PMID: 28337128 PMCID: PMC5343066 DOI: 10.3389/fncel.2017.00065] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 02/23/2017] [Indexed: 11/23/2022] Open
Abstract
Much knowledge about interconnection of human retinal neurons is inferred from results on animal models. Likewise, there is a lack of information on human retinal electrical synapses/gap junctions (GJ). Connexin36 (Cx36) forms GJs in both the inner and outer plexiform layers (IPL and OPL) in most species including humans. However, a comparison of Cx36 GJ distribution in retinas of humans and popular animal models has not been presented. To this end a multiple-species comparison was performed in retinas of 12 mammals including humans to survey the Cx36 distribution. Areas of retinal specializations were avoided (e.g., fovea, visual streak, area centralis), thus observed Cx36 distribution differences were not attributed to these species-specific architecture of central retinal areas. Cx36 was expressed in both synaptic layers in all examined retinas. Cx36 plaques displayed an inhomogenous IPL distribution favoring the ON sublamina, however, this feature was more pronounced in the human, swine and guinea pig while it was less obvious in the rabbit, squirrel monkey, and ferret retinas. In contrast to the relative conservative Cx36 distribution in the IPL, the labels in the OPL varied considerably among mammals. In general, OPL plaques were rare and rather small in rod dominant carnivores and rodents, whereas the human and the cone rich guinea pig retinas displayed robust Cx36 labels. This survey presented that the human retina displayed two characteristic features, a pronounced ON dominance of Cx36 plaques in the IPL and prevalent Cx36 plaque conglomerates in the OPL. While many species showed either of these features, only the guinea pig retina shared both. The observed similarities and subtle differences in Cx36 plaque distribution across mammals do not correspond to evolutionary distances but may reflect accomodation to lifestyles of examined species.
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Affiliation(s)
- Tamás Kovács-Öller
- Department of Experimental Zoology and Neurobiology, University of PécsPécs, Hungary; János Szentágothai Research CenterPécs, Hungary; Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary
| | - Gábor Debertin
- Department of Experimental Zoology and Neurobiology, University of PécsPécs, Hungary; János Szentágothai Research CenterPécs, Hungary; Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary
| | - Márton Balogh
- Department of Experimental Zoology and Neurobiology, University of PécsPécs, Hungary; János Szentágothai Research CenterPécs, Hungary; Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary
| | - Alma Ganczer
- Department of Experimental Zoology and Neurobiology, University of PécsPécs, Hungary; János Szentágothai Research CenterPécs, Hungary; Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary
| | - József Orbán
- János Szentágothai Research CenterPécs, Hungary; Department of Biophysics, University of PécsPécs, Hungary; High-Field Terahertz Research Group, Hungarian Academy of Sciences (MTA-PTE)Pécs, Hungary
| | - Miklós Nyitrai
- János Szentágothai Research CenterPécs, Hungary; Department of Biophysics, University of PécsPécs, Hungary; Nuclear-Mitochondrial Interactions Research Group, Hungarian Academy of Sciences (MTA-PTE)Pécs, Hungary
| | - Lajos Balogh
- National Research Institute for Radiobiology and Radiohygiene Budapest, Hungary
| | - Orsolya Kántor
- Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary; Department of Anatomy, Histology and Embryology, Semmelweis UniversityBudapest, Hungary; Department of Neuroanatomy, Institute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgFreiburg, Germany
| | - Béla Völgyi
- Department of Experimental Zoology and Neurobiology, University of PécsPécs, Hungary; János Szentágothai Research CenterPécs, Hungary; Retinal Electrical Synapses Research Group, Hungarian Academy of Sciences (MTA-PTE NAP B)Pécs, Hungary; Department of Ophthalmology, New York University Langone Medical Center, New YorkNY, USA
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12
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Beheshti S, Zeinali R, Esmaeili A. Rapid upregulation of the hippocampal connexins 36 and 45 mRNA levels during memory consolidation. Behav Brain Res 2017; 320:85-90. [PMID: 27913256 DOI: 10.1016/j.bbr.2016.11.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 11/25/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022]
Abstract
Gap junction channels are implicated in learning and memory process. However, their role on each of the particular stages of memory formation has been studied less. In this study, the time profile of the expression levels of hippocampal connexins 36 and 45 (Cx36 and Cx45) mRNAs was measured during memory consolidation, in a passive avoidance paradigm. Totally 30 adult male rats were distributed into 5 groups of each 6. At different times profiles (30min, 3, 6 and 24h) following training, rats were decapitated and their hippocampi were immediately removed and frozen in liquid nitrogen. Total RNA was extracted and cDNA was synthesized, using oligo-dt primers. A quantitative real-time PCR was used to measure the levels of each of Cx36 and Cx45 mRNAs. Both connexins showed a rapid upregulation (30min) at the transcriptional level, which declined in later times and reached to the control level at 24h. The rapid up-regulation of Cx36 and Cx45 mRNAs might be accompanied with increasing intercellular coupling via gap junction channels and neuronal oscillatory activities required for memory consolidation. The results highlight the role of gap junctional coupling between hippocampal neurons during memory consolidation in the physiological conditions.
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Affiliation(s)
- Siamak Beheshti
- Division of Animal Sciences, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran.
| | - Reyhaneh Zeinali
- Division of Animal Sciences, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
| | - Abolghasem Esmaeili
- Division of Cellular and Molecular Biology, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
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13
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Baker MW, Macagno ER. Gap junction proteins and the wiring (Rewiring) of neuronal circuits. Dev Neurobiol 2017; 77:575-586. [PMID: 27512961 DOI: 10.1002/dneu.22429] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 08/01/2016] [Accepted: 08/08/2016] [Indexed: 11/11/2022]
Abstract
The unique morphology and pattern of synaptic connections made by a neuron during development arise in part by an extended period of growth in which cell-cell interactions help to sculpt the arbor into its final shape, size, and participation in different synaptic networks. Recent experiments highlight a guiding role played by gap junction proteins in controlling this process. Ectopic and overexpression studies in invertebrates have revealed that the selective expression of distinct gap junction genes in neurons and glial cells is sufficient to establish selective new connections in the central nervous systems of the leech (Firme et al. [2012]: J Neurosci 32:14265-14270), the nematode (Rabinowitch et al. [2014]: Nat Commun 5:4442), and the fruit fly (Pézier et al., 2016: PLoS One 11:e0152211). We present here an overview of this work and suggest that gap junction proteins, in addition to their synaptic/communicative functions, have an instructive role as recognition and adhesion factors. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 575-586, 2017.
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Affiliation(s)
- Michael W Baker
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California, 92093
| | - Eduardo R Macagno
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California, 92093
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14
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Asteriti S, Gargini C, Cangiano L. Connexin 36 expression is required for electrical coupling between mouse rods and cones. Vis Neurosci 2017; 34:E006. [PMID: 28965521 DOI: 10.1017/s0952523817000037] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Rod-cone gap junctions mediate the so-called "secondary rod pathway", one of three routes that convey rod photoreceptor signals across the retina. Connexin 36 (Cx36) is expressed at these gap junctions, but an unidentified connexin protein also seems to be expressed. Cx36 knockout mice have been used extensively in the quest to dissect the roles in vision of all three pathways, with the assumption, never directly tested, that rod-cone electrical coupling is abolished by deletion of this connexin isoform. We previously showed that when wild type mouse cones couple to rods, their apparent dynamic range is extended toward lower light intensities, with the appearance of large responses to dim flashes (up to several mV) originating in rods. Here we recorded from the cones of Cx36del[LacZ]/del[LacZ] mice and found that dim flashes of the same intensity evoked at most small sub-millivolt responses. Moreover, these residual responses originated in the cones themselves, since: (i) their spectral preference matched that of the recorded cone and not of rods, (ii) their time-to-peak was shorter than in coupled wild type cones, (iii) a pharmacological block of gap junctions did not reduce their amplitude. Taken together, our data show that rod signals are indeed absent in the cones of Cx36 knockout mice. This study is the first direct demonstration that Cx36 is crucial for the assembly of functional rod-cone gap junctional channels, implying that its genetic deletion is a reliable experimental approach to eliminate rod-cone coupling.
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Affiliation(s)
- Sabrina Asteriti
- Department of Translational Research,University of Pisa,Pisa,Italy
| | | | - Lorenzo Cangiano
- Department of Translational Research,University of Pisa,Pisa,Italy
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15
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Meyer A, Tetenborg S, Greb H, Segelken J, Dorgau B, Weiler R, Hormuzdi SG, Janssen-Bienhold U, Dedek K. Connexin30.2: In Vitro Interaction with Connexin36 in HeLa Cells and Expression in AII Amacrine Cells and Intrinsically Photosensitive Ganglion Cells in the Mouse Retina. Front Mol Neurosci 2016; 9:36. [PMID: 27303262 PMCID: PMC4882342 DOI: 10.3389/fnmol.2016.00036] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/09/2016] [Indexed: 11/13/2022] Open
Abstract
Electrical coupling via gap junctions is an abundant phenomenon in the mammalian retina and occurs in all major cell types. Gap junction channels are assembled from different connexin subunits, and the connexin composition of the channel confers specific properties to the electrical synapse. In the mouse retina, gap junctions were demonstrated between intrinsically photosensitive ganglion cells and displaced amacrine cells but the underlying connexin remained undetermined. In the primary rod pathway, gap junctions play a crucial role, coupling AII amacrine cells among each other and to ON cone bipolar cells. Although it has long been known that connexin36 and connexin45 are necessary for the proper functioning of this most sensitive rod pathway, differences between homocellular AII/AII gap junctions and AII/ON bipolar cell gap junctions suggested the presence of an additional connexin in AII amacrine cells. Here, we used a connexin30.2-lacZ mouse line to study the expression of connexin30.2 in the retina. We show that connexin30.2 is expressed in intrinsically photosensitive ganglion cells and AII amacrine cells. Moreover, we tested whether connexin30.2 and connexin36-both expressed in AII amacrine cells-are able to interact with each other and are deposited in the same gap junctional plaques. Using newly generated anti-connexin30.2 antibodies, we show in HeLa cells that both connexins are indeed able to interact and may form heteromeric channels: both connexins were co-immunoprecipitated from transiently transfected HeLa cells and connexin30.2 gap junction plaques became significantly larger when co-expressed with connexin36. These data suggest that connexin36 is able to form heteromeric gap junctions with another connexin. We hypothesize that co-expression of connexin30.2 and connexin36 may endow AII amacrine cells with the means to differentially regulate its electrical coupling to different synaptic partners.
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Affiliation(s)
- Arndt Meyer
- Department of Neuroscience and Neurobiology, University of Oldenburg Oldenburg, Germany
| | - Stephan Tetenborg
- Department of Neuroscience and Neurobiology, University of Oldenburg Oldenburg, Germany
| | - Helena Greb
- Department of Neuroscience and Neurobiology, University of Oldenburg Oldenburg, Germany
| | - Jasmin Segelken
- Department of Neuroscience and Neurobiology, University of Oldenburg Oldenburg, Germany
| | - Birthe Dorgau
- Department of Neuroscience and Neurobiology, University of Oldenburg Oldenburg, Germany
| | - Reto Weiler
- Department of Neuroscience and Neurobiology, University of OldenburgOldenburg, Germany; Research Center Neurosensory Science, University of OldenburgOldenburg, Germany
| | | | - Ulrike Janssen-Bienhold
- Department of Neuroscience and Neurobiology, University of OldenburgOldenburg, Germany; Research Center Neurosensory Science, University of OldenburgOldenburg, Germany
| | - Karin Dedek
- Department of Neuroscience and Neurobiology, University of OldenburgOldenburg, Germany; Research Center Neurosensory Science, University of OldenburgOldenburg, Germany
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