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Cen YY, Gao XL, Feng YH, Zhou C, Li CJ, Liu F, Shen JF, Zhang YY. The Double-Edged Effect of Connexins and Pannexins of Glial Cells in Central and Peripheral Nervous System After Nerve Injury. Mol Neurobiol 2025:10.1007/s12035-025-04991-6. [PMID: 40310549 DOI: 10.1007/s12035-025-04991-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2025] [Accepted: 04/21/2025] [Indexed: 05/02/2025]
Abstract
Glial cells play pivotal roles in homeostatic regulation and driving reactive pathologic changes after nerve injury. Connexins (Cxs) and pannexins (Panxs) have emerged as seminal proteins implicated in cell-cell communication, exerting a profound impact on the response processes of glial cell activation, proliferation, protein synthesis and secretion, as well as apoptosis following nerve injury. These influences are mediated through various forms, including protein monomers, hemichannel (HC), and gap junction (GJ), mainly by regulating intercellular or intracellular signaling pathways. Multiple Cx and Panx isoforms have been detected in central nervous system (CNS) or peripheral nervous system (PNS). Each isoform exhibits distinct cellular and subcellular localization, and the differential regulation and functional roles of various protein isoforms are observed post-injury. The quantitative and functional alterations of the same protein isoform in different studies remain inconsistent, attributable to factors such as the predominant mode of protein polymerization, the specific injury model, and the injury site. Similarly, the same protein isoforms have different roles in regulating the response processes after nerve injury, thus exerting a double-edged sword effect. This review describes the regulatory mechanisms and bidirectional effects of Cxs and Panxs. Additionally, it surveys the current status of research and application of drugs as therapeutic targets for neuropathic injuries. We summarize comprehensive and up-to-date information on these proteins in the glial cell response to nerve injury, providing new perspectives for future mechanistic exploration and development of targeted therapeutic approaches.
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Affiliation(s)
- Yue-Yan Cen
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
| | - Xin-Lin Gao
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
| | - Yu-Heng Feng
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
| | - Cheng Zhou
- Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, China
| | - Chun-Jie Li
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Fei Liu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China
| | - Jie-Fei Shen
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China.
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China.
| | - Yan-Yan Zhang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, National Center for Stomatology, West China School of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China.
- Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, No. 14, Section 3, Renminnan Road, Chengdu, 610041, China.
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Li YZ, Wang Y, Jiao Q, Chi J, Liang Y, Fan B, Li GY. Complexin regulation of synaptic vesicle release: mechanisms in the central nervous system and specialized retinal ribbon synapses. Cell Commun Signal 2024; 22:581. [PMID: 39627811 PMCID: PMC11613576 DOI: 10.1186/s12964-024-01942-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2024] [Accepted: 11/11/2024] [Indexed: 12/08/2024] Open
Abstract
Synaptic ribbons, recognized for their pivotal role in conveying sensory signals in the visual pathway, are intricate assemblages of presynaptic proteins. Complexin (CPX) regulates synaptic vesicle fusion and neurotransmitter release by modulating the assembly of the soluble NSF attachment protein receptor (SNARE) complex, ensuring precise signal transmission in the retina and the broader central nervous system (CNS). While CPX1 or CPX2 isoforms (CPX1/2) play crucial roles in classical CNS synapses, CPX3 or CPX4 isoforms (CPX3/4) specifically regulate retinal ribbon synapses. These isoforms are essential for sustaining synaptic plasticity related to light signaling, adapting to changes in circadian rhythms, and dynamically regulating visual function under varying light conditions. This review explores the regulation of synaptic vesicle release by CPX in both the CNS and retinal ribbon synapses, with a focus on the mechanisms governing CPX3/4 function in the retina. Additionally, by reviewing the role of CPX and ribbon synapse dysfunction in non-retinal diseases, we further hypothesize the potential mechanisms of CPX in retinal diseases and propose therapeutic strategies targeting CPX to address retinal and CNS disorders associated with synaptic dysfunction.
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Affiliation(s)
- Yun-Zhi Li
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China
| | - Yu Wang
- Department of Neurology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China
| | - Qing Jiao
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China
| | - Jing Chi
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China
| | - Yang Liang
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China
| | - Bin Fan
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China.
| | - Guang-Yu Li
- Department of Ophthalmology, The Second Norman Bethune Hospital of JiLin University, Changchun, 130041, China.
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3
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Kim YJ, Packer O, Pollreisz A, Martin PR, Grünert U, Dacey DM. Comparative connectomics reveals noncanonical wiring for color vision in human foveal retina. Proc Natl Acad Sci U S A 2023; 120:e2300545120. [PMID: 37098066 PMCID: PMC10160961 DOI: 10.1073/pnas.2300545120] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/31/2023] [Indexed: 04/26/2023] Open
Abstract
The Old World macaque monkey and New World common marmoset provide fundamental models for human visual processing, yet the human ancestral lineage diverged from these monkey lineages over 25 Mya. We therefore asked whether fine-scale synaptic wiring in the nervous system is preserved across these three primate families, despite long periods of independent evolution. We applied connectomic electron microscopy to the specialized foveal retina where circuits for highest acuity and color vision reside. Synaptic motifs arising from the cone photoreceptor type sensitive to short (S) wavelengths and associated with "blue-yellow" (S-ON and S-OFF) color-coding circuitry were reconstructed. We found that distinctive circuitry arises from S cones for each of the three species. The S cones contacted neighboring L and M (long- and middle-wavelength sensitive) cones in humans, but such contacts were rare or absent in macaques and marmosets. We discovered a major S-OFF pathway in the human retina and established its absence in marmosets. Further, the S-ON and S-OFF chromatic pathways make excitatory-type synaptic contacts with L and M cone types in humans, but not in macaques or marmosets. Our results predict that early-stage chromatic signals are distinct in the human retina and imply that solving the human connectome at the nanoscale level of synaptic wiring will be critical for fully understanding the neural basis of human color vision.
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Affiliation(s)
- Yeon Jin Kim
- Department of Biological Structure, University of Washington, Seattle, WA98195
| | - Orin Packer
- Department of Biological Structure, University of Washington, Seattle, WA98195
| | - Andreas Pollreisz
- Department of Ophthalmology, Medical University of Vienna, Vienna1090, Austria
| | - Paul R. Martin
- Save Sight Institute and Department of Ophthalmology, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW2000, Australia
| | - Ulrike Grünert
- Save Sight Institute and Department of Ophthalmology, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW2000, Australia
| | - Dennis M. Dacey
- Department of Biological Structure, University of Washington, Seattle, WA98195
- Washington National Primate Research Center, University of Washington, Seattle, WA98195
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Potential Neuroprotective Role of Calretinin-N18 and Calbindin-D28k in the Retina of Adult Zebrafish Exposed to Different Wavelength Lights. Int J Mol Sci 2023; 24:ijms24021087. [PMID: 36674603 PMCID: PMC9862630 DOI: 10.3390/ijms24021087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/26/2022] [Accepted: 12/15/2022] [Indexed: 01/08/2023] Open
Abstract
The incidence rates of light-induced retinopathies have increased significantly in the last decades because of continuous exposure to light from different electronic devices. Recent studies showed that exposure to blue light had been related to the pathogenesis of light-induced retinopathies. However, the pathophysiological mechanisms underlying changes induced by light exposure are not fully known yet. In the present study, the effects of exposure to light at different wavelengths with emission peaks in the blue light range (400-500 nm) on the localization of Calretinin-N18 (CaR-N18) and Calbindin-D28K (CaB-D28K) in adult zebrafish retina are studied using double immunofluorescence with confocal laser microscopy. CaB-D28K and CaR-N18 are two homologous cytosolic calcium-binding proteins (CaBPs) implicated in essential process regulation in central and peripheral nervous systems. CaB-D28K and CaR-N18 distributions are investigated to elucidate their potential role in maintaining retinal homeostasis under distinct light conditions and darkness. The results showed that light influences CaB-D28K and CaR-N18 distribution in the retina of adult zebrafish, suggesting that these CaBPs could be involved in the pathophysiology of retinal damage induced by the short-wavelength visible light spectrum.
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Jiang X, Xu Z, Soorma T, Tariq A, Bhatti T, Baneke AJ, Pontikos N, Leo SM, Webster AR, Williams KM, Hammond CJ, Hysi PG, Mahroo OA. Electrical responses from human retinal cone pathways associate with a common genetic polymorphism implicated in myopia. Proc Natl Acad Sci U S A 2022; 119:e2119675119. [PMID: 35594404 PMCID: PMC9173800 DOI: 10.1073/pnas.2119675119] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 04/08/2022] [Indexed: 11/25/2022] Open
Abstract
Myopia is the commonest visual impairment. Several genetic loci confer risk, but mechanisms by which they do this are unknown. Retinal signals drive eye growth, and myopia usually results from an excessively long eye. The common variant most strongly associated with myopia is near the GJD2 gene, encoding connexin-36, which forms retinal gap junctions. Light-evoked responses of retinal neurons can be recorded noninvasively as the electroretinogram (ERG). We analyzed these responses from 186 adult twin volunteers who had been genotyped at this locus. Participants underwent detailed ERG recordings incorporating international standard stimuli as well as experimental protocols aiming to separate dark-adapted rod- and cone-driven responses. A mixed linear model was used to explore association between allelic dosage at the locus and international standard ERG parameters after adjustment for age, sex, and family structure. Significant associations were found for parameters of light-adapted, but not dark-adapted, responses. Further investigation of isolated rod- and cone-driven ERGs confirmed associations with cone-driven, but not rod-driven, a-wave amplitudes. Comparison with responses to similar experimental stimuli from a patient with a prior central retinal artery occlusion, and from two patients with selective loss of ON-bipolar cell signals, was consistent with the associated parameters being derived from signals from cone-driven OFF-bipolar cells. Analysis of single-cell transcriptome data revealed strongest GJD2 expression in cone photoreceptors; bipolar cell expression appeared strongest in OFF-bipolar cells and weakest in rod-driven ON-bipolar cells. Our findings support a potential role for altered signaling in cone-driven OFF pathways in myopia development.
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Affiliation(s)
- Xiaofan Jiang
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Zihe Xu
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Talha Soorma
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
| | - Ambreen Tariq
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Taha Bhatti
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Alexander J. Baneke
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
| | - Nikolas Pontikos
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
| | - Shaun M. Leo
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Medical Retina Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
- Inherited Eye Disease Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
| | - Andrew R. Webster
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Medical Retina Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
- Inherited Eye Disease Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
| | - Katie M. Williams
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
- Medical Retina Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
- Inherited Eye Disease Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
| | - Christopher J. Hammond
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Pirro G. Hysi
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
| | - Omar A. Mahroo
- Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Department of Ophthalmology, King’s College London, London SE1 7EH, United Kingdom
- Department of Twin Research and Genetic Epidemiology, King’s College London, London SE1 7EH, United Kingdom
- Medical Retina Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
- Inherited Eye Disease Service, Moorfields Eye Hospital, London EC1V 2PD, United Kingdom
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, United Kingdom
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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: 17] [Impact Index Per Article: 5.7] [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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Rai D, Iwanami M, Takahashi Y, Komuta Y, Aoi N, Umezawa A, Seko Y. Evaluation of photoreceptor-directed fibroblasts derived from retinitis pigmentosa patients with defects in the EYS gene: a possible cost-effective cellular model for mechanism-oriented drug. Stem Cell Res Ther 2022; 13:157. [PMID: 35410372 PMCID: PMC8996485 DOI: 10.1186/s13287-022-02827-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 03/14/2022] [Indexed: 12/15/2022] Open
Abstract
Background The most common gene responsible for autosomal recessive retinitis pigmentosa (RP) is EYS. The manner of decay of genetically defective EYS gene transcripts varies depending on the type of mutation using our cellular model, which consists of induced photoreceptor-directed fibroblasts from EYS-RP patients (EYS-RP cells). However, disease-specific profiles have not been clarified in EYS-RP cells. Herein we investigated comprehensive gene expression patterns and restoration of altered expression by low molecular weight molecules in EYS-RP cells.
Methods Using induced photoreceptor-like cells by CRX, RAX, NeuroD, and OTX2, we employed qRT-PCR and DNA microarray analysis to compare expression levels of disease-related genes in EYS-RP cells. We investigated the effect of antiapoptotic or anti-endoplasmic reticulum (ER) stress/antioxidant reagents on the restoration of altered gene expression. Results Expression levels of phototransduction-related genes (blue opsin, rhodopsin, S-antigen, GNAT1, GNAT2) were lower in EYS-RP cells. CRYGD was extracted by global gene expression analysis, as a downregulated, retina-related and apoptosis-, endoplasmic reticulum (ER) stress- or aging-related gene. Pathway enrichment analysis suggested that “complement and coagulation cascades,” “ECM-receptor interaction” and “PI3K-Akt signaling pathway” could be involved in EYS-RP-associated pathogenesis. Among the matching/overlapping genes involved in those pathways, F2R was suggested as an EYS-RP-associated gene. The downregulation of CRYGD and F2R was completely restored by additional 4-PBA, an inhibitor of ER stress, and partially restored by metformin or NAC. In addition, 4-PBA normalized the expression level of cleaved caspase-3. Conclusions Our cellular model may reflect the ER stress-mediated degenerative retina and serve as a pathogenesis-oriented cost-effective rescue strategy for RP patients. Supplementary Information The online version contains supplementary material available at 10.1186/s13287-022-02827-x.
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Affiliation(s)
- Dilip Rai
- Sensory Functions Section, Research Institute, National Rehabilitation Center for Persons With Disabilities, 4-1 Namiki, Tokorozawa, 359-8555, Japan
| | - Masaki Iwanami
- Department of Ophthalmology, Hospital, National Rehabilitation Center for Persons With Disabilities, 4-1 Namiki, Tokorozawa, 359-8555, Japan.,Iwanami Eye Clinic, 7-1-3, Tsuchihashi, Miyamae-ku Kawasaki, Tokyo, 216-0005, Japan
| | - Yoriko Takahashi
- Bioscience and Healthcare Engineering Division, Mitsui Knowledge Industry Co., Ltd., 2-7-14 Higashi-Nakano, Nakano-ku, Tokyo, 164-8555, Japan
| | - Yukari Komuta
- Sensory Functions Section, Research Institute, National Rehabilitation Center for Persons With Disabilities, 4-1 Namiki, Tokorozawa, 359-8555, Japan.,Division of Bioinformation and Therapeutic Systems, National Defense Medical College, 3 Namiki, Tokorozawa, 359-0042, Japan
| | - Noriyuki Aoi
- Department of Plastic, Oral and Maxillofacial Surgery, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi, Tokyo, 173-8605, Japan.,Miyamasuzaka Clinic, SK Aoyama Bldg. 5F, 1-6-5 Shibuya, Tokyo, 150-0002, Japan
| | - Akihiro Umezawa
- National Center for Child Health and Development, Research Institute, 2-10-1 Okura, Setagaya, 157-8535, Japan
| | - Yuko Seko
- Sensory Functions Section, Research Institute, National Rehabilitation Center for Persons With Disabilities, 4-1 Namiki, Tokorozawa, 359-8555, Japan.
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8
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van der Sande E, Haarman AEG, Quint WH, Tadema KCD, Meester-Smoor MA, Kamermans M, De Zeeuw CI, Klaver CCW, Winkelman BHJ, Iglesias AI. The Role of GJD2(Cx36) in Refractive Error Development. Invest Ophthalmol Vis Sci 2022; 63:5. [PMID: 35262731 PMCID: PMC8934558 DOI: 10.1167/iovs.63.3.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 02/16/2022] [Indexed: 02/06/2023] Open
Abstract
Refractive errors are common eye disorders characterized by a mismatch between the focal power of the eye and its axial length. An increased axial length is a common cause of the refractive error myopia (nearsightedness). The substantial increase in myopia prevalence over the last decades has raised public health concerns because myopia can lead to severe ocular complications later in life. Genomewide association studies (GWAS) have made considerable contributions to the understanding of the genetic architecture of refractive errors. Among the hundreds of genetic variants identified, common variants near the gap junction delta-2 (GJD2) gene have consistently been reported as one of the top hits. GJD2 encodes the connexin 36 (Cx36) protein, which forms gap junction channels and is highly expressed in the neural retina. In this review, we provide current evidence that links GJD2(Cx36) to the development of myopia. We summarize the gap junctional communication in the eye and the specific role of GJD2(Cx36) in retinal processing of visual signals. Finally, we discuss the pathways involving dopamine and gap junction phosphorylation and coupling as potential mechanisms that may explain the role of GJD2(Cx36) in refractive error development.
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Affiliation(s)
- Emilie van der Sande
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
| | - Annechien E. G. Haarman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Wim H. Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Kirke C. D. Tadema
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Magda A. Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Maarten Kamermans
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Biomedical Physics and Biomedical Photonics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Chris I. De Zeeuw
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C. W. Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
- Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
| | - Beerend H. J. Winkelman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Adriana I. Iglesias
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
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9
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Haarman AEG, Enthoven CA, Tedja MS, Polling JR, Tideman JWL, Keunen JEE, Boon CJF, Felix JF, Raat H, Geerards AJM, Luyten GPM, van Rijn GA, Verhoeven VJM, Klaver CCW. Phenotypic Consequences of the GJD2 Risk Genotype in Myopia Development. Invest Ophthalmol Vis Sci 2021; 62:16. [PMID: 34406332 PMCID: PMC8375003 DOI: 10.1167/iovs.62.10.16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 01/26/2021] [Indexed: 12/12/2022] Open
Abstract
Purpose To study the relatively high effect of the refractive error gene GJD2 in human myopia, and to assess its relationship with refractive error, ocular biometry and lifestyle in various age groups. Methods The population-based Rotterdam Study (RS), high myopia case-control study MYopia STudy, and the birth-cohort study Generation R were included in this study. Spherical equivalent (SER), axial length (AL), axial length/corneal radius (AL/CR), vitreous depth (VD), and anterior chamber depth (ACD) were measured using standard ophthalmologic procedures. Biometric measurements were compared between GJD2 (rs524952) genotype groups; education and environmental risk score (ERS) were calculated to estimate gene-environment interaction effects, using the Synergy index (SI). Results RS adults carrying two risk alleles had a lower SER and longer AL, ACD and VD (AA versus TT, 0.23D vs. 0.70D; 23.79 mm vs. 23.52 mm; 2.72 mm vs. 2.65 mm; 16.12 mm vs. 15.87 mm; all P < 0.001). Children carrying two risk alleles had larger AL/CR at ages 6 and 9 years (2.88 vs. 2.87 and 3.00 vs. 2.96; all P < 0.001). Education and ERS both negatively influenced myopia and the biometric outcomes, but gene-environment interactions did not reach statistical significance (SI 1.25 [95% confidence interval {CI}, 0.85-1.85] and 1.17 [95% CI, 0.55-2.50] in adults and children). Conclusions The elongation of the eye caused by the GJD2 risk genotype follows a dose-response pattern already visible at the age of 6 years. These early effects are an example of how a common myopia gene may drive myopia.
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Affiliation(s)
- Annechien E G Haarman
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Epidemiology, Rotterdam, The Netherlands
| | - Clair A Enthoven
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Epidemiology, Rotterdam, The Netherlands
- Erasmus Medical Center, the Generation R Study Group, Rotterdam, The Netherlands
| | - Milly S Tedja
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Epidemiology, Rotterdam, The Netherlands
| | - Jan R Polling
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Department of Optometry and Orthoptics, Hogeschool Utrecht, University of Applied Science, Utrecht, The Netherlands
| | - J Willem L Tideman
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
| | - Jan E E Keunen
- University Medical Center St Radboud, Department of Ophthalmology, Nijmegen, The Netherlands
| | - Camiel J F Boon
- Leiden University Medical Center, Department of Ophthalmology, The Netherlands
- Amsterdam University Medical Center, Department of Ophthalmology, University of Amsterdam, The Netherlands
| | - Janine F Felix
- Erasmus Medical Center, Department of Epidemiology, Rotterdam, The Netherlands
- Erasmus Medical Center, the Generation R Study Group, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Pediatrics, Rotterdam, The Netherlands
| | - H Raat
- Erasmus University Medical Centre, Department of Public Health, Rotterdam, The Netherlands
| | | | | | - Gwyneth A van Rijn
- Leiden University Medical Center, Department of Ophthalmology, The Netherlands
| | - Virginie J M Verhoeven
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Clinical Genetics, Rotterdam, The Netherlands
| | - Caroline C W Klaver
- Erasmus Medical Center, Department of Ophthalmology, Rotterdam, The Netherlands
- Erasmus Medical Center, Department of Epidemiology, Rotterdam, The Netherlands
- University Medical Center St Radboud, Department of Ophthalmology, Nijmegen, The Netherlands
- Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
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10
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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: 0.5] [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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11
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Burger CA, Jiang D, Mackin RD, Samuel MA. Development and maintenance of vision's first synapse. Dev Biol 2021; 476:218-239. [PMID: 33848537 DOI: 10.1016/j.ydbio.2021.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/02/2021] [Accepted: 04/03/2021] [Indexed: 12/21/2022]
Abstract
Synapses in the outer retina are the first information relay points in vision. Here, photoreceptors form synapses onto two types of interneurons, bipolar cells and horizontal cells. Because outer retina synapses are particularly large and highly ordered, they have been a useful system for the discovery of mechanisms underlying synapse specificity and maintenance. Understanding these processes is critical to efforts aimed at restoring visual function through repairing or replacing neurons and promoting their connectivity. We review outer retina neuron synapse architecture, neural migration modes, and the cellular and molecular pathways that play key roles in the development and maintenance of these connections. We further discuss how these mechanisms may impact connectivity in the retina.
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Affiliation(s)
- Courtney A Burger
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Danye Jiang
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Robert D Mackin
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Melanie A Samuel
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA.
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12
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González-Casanova J, Schmachtenberg O, Martínez AD, Sanchez HA, Harcha PA, Rojas-Gomez D. An Update on Connexin Gap Junction and Hemichannels in Diabetic Retinopathy. Int J Mol Sci 2021; 22:ijms22063194. [PMID: 33801118 PMCID: PMC8004116 DOI: 10.3390/ijms22063194] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 03/06/2021] [Accepted: 03/10/2021] [Indexed: 01/10/2023] Open
Abstract
Diabetic retinopathy (DR) is one of the main causes of vision loss in the working age population. It is characterized by a progressive deterioration of the retinal microvasculature, caused by long-term metabolic alterations inherent to diabetes, leading to a progressive loss of retinal integrity and function. The mammalian retina presents an orderly layered structure that executes initial but complex visual processing and analysis. Gap junction channels (GJC) forming electrical synapses are present in each retinal layer and contribute to the communication between different cell types. In addition, connexin hemichannels (HCs) have emerged as relevant players that influence diverse physiological and pathological processes in the retina. This article highlights the impact of diabetic conditions on GJC and HCs physiology and their involvement in DR pathogenesis. Microvascular damage and concomitant loss of endothelial cells and pericytes are related to alterations in gap junction intercellular communication (GJIC) and decreased connexin 43 (Cx43) expression. On the other hand, it has been shown that the expression and activity of HCs are upregulated in DR, becoming a key element in the establishment of proinflammatory conditions that emerge during hyperglycemia. Hence, novel connexin HCs blockers or drugs to enhance GJIC are promising tools for the development of pharmacological interventions for diabetic retinopathy, and initial in vitro and in vivo studies have shown favorable results in this regard.
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Affiliation(s)
- Jorge González-Casanova
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago 8910060, Chile;
| | - Oliver Schmachtenberg
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Biología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile;
| | - Agustín D. Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (A.D.M.); (H.A.S.); (P.A.H.)
| | - Helmuth A. Sanchez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (A.D.M.); (H.A.S.); (P.A.H.)
| | - Paloma A. Harcha
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile; (A.D.M.); (H.A.S.); (P.A.H.)
| | - Diana Rojas-Gomez
- Escuela de Nutrición y Dietética, Facultad de Medicina, Universidad Andres Bello, Santiago 8370146, Chile
- Correspondence: ; Tel.: +56-2-26618559
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13
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Fournel R, Hartveit E, Veruki ML. Differential Contribution of Gap Junctions to the Membrane Properties of ON- and OFF-Bipolar Cells of the Rat Retina. Cell Mol Neurobiol 2021; 41:229-245. [PMID: 32323153 PMCID: PMC7870642 DOI: 10.1007/s10571-020-00845-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/08/2020] [Indexed: 01/31/2023]
Abstract
Gap junctions are ubiquitous within the retina, but in general, it remains to be determined whether gap junction coupling between specific cell types is sufficiently strong to mediate functionally relevant coupling via electrical synapses. From ultrastructural, tracer coupling and immunolabeling studies, there is clear evidence for gap junctions between cone bipolar cells, but it is not known if these gap junctions function as electrical synapses. Here, using whole-cell voltage-clamp recording in rat (male and female) retinal slices, we investigated whether the gap junctions of bipolar cells make a measurable contribution to the membrane properties of these cells. We measured the input resistance (RN) of bipolar cells before and after applying meclofenamic acid (MFA) to block gap junctions. In the presence of MFA, RN of ON-cone bipolar cells displayed a clear increase, paralleled by block of the electrical coupling between these cells and AII amacrine cells in recordings of coupled cell pairs. For OFF-cone and rod bipolar cells, RN did not increase in the presence of MFA. The results for rod bipolar cells are consistent with the lack of gap junctions in these cells. However, for OFF-cone bipolar cells, our results suggest that the morphologically identified gap junctions between these cells do not support a junctional conductance that is sufficient to mediate effective electrical coupling. Instead, these junctions might play a role in chemical and/or metabolic coupling between subcellular compartments.
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Affiliation(s)
- Rémi Fournel
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
| | - Espen Hartveit
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Margaret Lin Veruki
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
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14
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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: 2.0] [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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15
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Network Architecture of Gap Junctional Coupling among Parallel Processing Channels in the Mammalian Retina. J Neurosci 2020; 40:4483-4511. [PMID: 32332119 DOI: 10.1523/jneurosci.1810-19.2020] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 03/27/2020] [Accepted: 04/12/2020] [Indexed: 01/04/2023] Open
Abstract
Gap junctions are ubiquitous throughout the nervous system, mediating critical signal transmission and integration, as well as emergent network properties. In mammalian retina, gap junctions within the Aii amacrine cell-ON cone bipolar cell (CBC) network are essential for night vision, modulation of day vision, and contribute to visual impairment in retinal degenerations, yet neither the extended network topology nor its conservation is well established. Here, we map the network contribution of gap junctions using a high-resolution connectomics dataset of an adult female rabbit retina. Gap junctions are prominent synaptic components of ON CBC classes, constituting 5%-25% of all axonal synaptic contacts. Many of these mediate canonical transfer of rod signals from Aii cells to ON CBCs for night vision, and we find that the uneven distribution of Aii signals to ON CBCs is conserved in rabbit, including one class entirely lacking direct Aii coupling. However, the majority of gap junctions formed by ON CBCs unexpectedly occur between ON CBCs, rather than with Aii cells. Such coupling is extensive, creating an interconnected network with numerous lateral paths both within, and particularly across, these parallel processing streams. Coupling patterns are precise with ON CBCs accepting and rejecting unique combinations of partnerships according to robust rulesets. Coupling specificity extends to both size and spatial topologies, thereby rivaling the synaptic specificity of chemical synapses. These ON CBC coupling motifs dramatically extend the coupled Aii-ON CBC network, with implications for signal flow in both scotopic and photopic retinal networks during visual processing and disease.SIGNIFICANCE STATEMENT Electrical synapses mediated by gap junctions are fundamental components of neural networks. In retina, coupling within the Aii-ON CBC network shapes visual processing in both the scotopic and photopic networks. In retinal degenerations, these same gap junctions mediate oscillatory activity that contributes to visual impairment. Here, we use high-resolution connectomics strategies to identify gap junctions and cellular partnerships. We describe novel, pervasive motifs both within and across classes of ON CBCs that dramatically extend the Aii-ON CBC network. These motifs are highly specific with implications for both signal processing within the retina and therapeutic interventions for blinding conditions. These findings highlight the underappreciated contribution of coupling motifs in retinal circuitry and the necessity of their detection in connectomics studies.
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16
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Kovács-Öller T, Szarka G, Ganczer A, Tengölics Á, Balogh B, Völgyi B. Expression of Ca 2+-Binding Buffer Proteins in the Human and Mouse Retinal Neurons. Int J Mol Sci 2019; 20:E2229. [PMID: 31067641 PMCID: PMC6539911 DOI: 10.3390/ijms20092229] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 12/31/2022] Open
Abstract
Ca2+-binding buffer proteins (CaBPs) are widely expressed by various neurons throughout the central nervous system (CNS), including the retina. While the expression of CaBPs by photoreceptors, retinal interneurons and the output ganglion cells in the mammalian retina has been extensively studied, a general description is still missing due to the differences between species, developmental expression patterns and study-to-study discrepancies. Furthermore, CaBPs are occasionally located in a compartment-specific manner and two or more CaBPs can be expressed by the same neuron, thereby sharing the labor of Ca2+ buffering in the intracellular milieu. This article reviews this topic by providing a framework on CaBP functional expression by neurons of the mammalian retina with an emphasis on human and mouse retinas and the three most abundant and extensively studied buffer proteins: parvalbumin, calretinin and calbindin.
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Affiliation(s)
- Tamás Kovács-Öller
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
- Medical School, University of Pécs, 7624 Pécs, Hungary.
| | - Gergely Szarka
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
| | - Alma Ganczer
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
| | - Ádám Tengölics
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
| | - Boglárka Balogh
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
| | - Béla Völgyi
- János Szentágothai Research Centre, University of Pécs, 7624 Pécs, Hungary.
- Retinal Electrical Synapses Research Group, National Brain Research Program (NAP 2.0), Hungarian Academy of Sciences, 1051 Budapest, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, 7624 Pécs, Hungary.
- Medical School, University of Pécs, 7624 Pécs, Hungary.
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17
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Kántor O, Szarka G, Benkő Z, Somogyvári Z, Pálfi E, Baksa G, Rácz G, Nitschke R, Debertin G, Völgyi B. Strategic Positioning of Connexin36 Gap Junctions Across Human Retinal Ganglion Cell Dendritic Arbors. Front Cell Neurosci 2018; 12:409. [PMID: 30524239 PMCID: PMC6262005 DOI: 10.3389/fncel.2018.00409] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/22/2018] [Indexed: 11/18/2022] Open
Abstract
Connexin36 (Cx36) subunits form gap junctions (GJ) between neurons throughout the central nervous system. Such GJs of the mammalian retina serve the transmission, averaging and correlation of signals prior to conveying visual information to the brain. Retinal GJs have been exhaustively studied in various animal species, however, there is still a perplexing paucity of information regarding the presence and function of human retinal GJs. Particularly little is known about GJ formation of human retinal ganglion cells (hRGCs) due to the limited number of suitable experimental approaches. Compared to the neuronal coupling studies in animal models, where GJ permeable tracer injection is the gold standard method, the post-mortem nature of scarcely available human retinal samples leaves immunohistochemistry as a sole approach to obtain information on hRGC GJs. In this study Lucifer Yellow (LY) dye injections and Cx36 immunohistochemistry were performed in fixed short-post-mortem samples to stain hRGCs with complete dendritic arbors and locate dendritic Cx36 GJs. Subsequent neuronal reconstructions and morphometric analyses revealed that Cx36 plaques had a clear tendency to form clusters and particularly favored terminal dendritic segments.
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Affiliation(s)
- Orsolya Kántor
- Department of Neuroanatomy, Faculty of Medicine, Institute for Anatomy and Cell Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.,MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary.,Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Gergely Szarka
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary.,Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, Hungary.,Center for Neuroscience, University of Pécs, Pécs, Hungary.,János Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Zsigmond Benkő
- Complex Systems and Computational Neuroscience Group, Wigner Research Center for Physics, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zoltán Somogyvári
- Complex Systems and Computational Neuroscience Group, Wigner Research Center for Physics, Hungarian Academy of Sciences, Budapest, Hungary
| | - Emese Pálfi
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Gábor Baksa
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Gergely Rácz
- Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
| | - Roland Nitschke
- Life Imaging Center, Center for Biological Systems Analysis, Albert-Ludwigs University, Freiburg, Germany.,BIOSS Center for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, Freiburg, Germany
| | - Gábor Debertin
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary.,Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, Hungary.,Center for Neuroscience, University of Pécs, Pécs, Hungary.,János Szentágothai Research Center, University of Pécs, Pécs, Hungary
| | - Béla Völgyi
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary.,Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, Hungary.,Center for Neuroscience, University of Pécs, Pécs, Hungary.,János Szentágothai Research Center, University of Pécs, Pécs, Hungary
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18
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Tetenborg S, Yadav SC, Hormuzdi SG, Monyer H, Janssen-Bienhold U, Dedek K. Differential Distribution of Retinal Ca 2+/Calmodulin-Dependent Kinase II (CaMKII) Isoforms Indicates CaMKII-β and -δ as Specific Elements of Electrical Synapses Made of Connexin36 (Cx36). Front Mol Neurosci 2017; 10:425. [PMID: 29311815 PMCID: PMC5742114 DOI: 10.3389/fnmol.2017.00425] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 12/05/2017] [Indexed: 12/17/2022] Open
Abstract
AII amacrine cells are essential interneurons of the primary rod pathway and transmit rod-driven signals to ON cone bipolar cells to enable scotopic vision. Gap junctions made of connexin36 (Cx36) mediate electrical coupling among AII cells and between AII cells and ON cone bipolar cells. These gap junctions underlie a remarkable degree of plasticity and are modulated by different signaling cascades. In particular, Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been characterized as an important regulator of Cx36, capable of potentiating electrical coupling in AII cells. However, it is unclear which CaMKII isoform mediates this effect. To obtain a more detailed understanding of the isoform composition of CaMKII at retinal gap junctions, we analyzed the retinal distribution of all four CaMKII isoforms using confocal microscopy. These experiments revealed a differential distribution of CaMKII isoforms: CaMKII-α was strongly expressed in starburst amacrine cells, which are known to lack electrical coupling. CaMKII-β was abundant in OFF bipolar cells, which form electrical synapses in the outer and the inner retina. CaMKII-γ was diffusely distributed across the entire retina and could not be assigned to a specific cell type. CaMKII-δ labeling was evident in bipolar and AII amacrine cells, which contain the majority of Cx36-immunoreactive puncta in the inner retina. We double-labeled retinas for Cx36 and the four CaMKII isoforms and revealed that the composition of the CaMKII enzyme differs between gap junctions in the outer and the inner retina: in the outer retina, only CaMKII-β colocalized with Cx36-containing gap junctions, whereas in the inner retina, CaMKII-β and -δ colocalized with Cx36. This finding suggests that gap junctions in the inner and the outer retina may be regulated differently although they both contain the same connexin. Taken together, our study identifies CaMKII-β and -δ as Cx36-specific regulators in the mouse retina with CaMKII-δ regulating the primary rod pathway.
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Affiliation(s)
- Stephan Tetenborg
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Shubhash C Yadav
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany
| | - Sheriar G Hormuzdi
- Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom
| | | | - Ulrike Janssen-Bienhold
- Visual Neuroscience, Department of 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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Kántor O, Varga A, Nitschke R, Naumann A, Énzsöly A, Lukáts Á, Szabó A, Németh J, Völgyi B. Bipolar cell gap junctions serve major signaling pathways in the human retina. Brain Struct Funct 2017; 222:2603-2624. [PMID: 28070649 DOI: 10.1007/s00429-016-1360-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/22/2016] [Indexed: 11/26/2022]
Abstract
Connexin36 (Cx36) constituent gap junctions (GJ) throughout the brain connect neurons into functional syncytia. In the retina they underlie the transmission, averaging and correlation of signals prior conveying visual information to the brain. This is the first study that describes retinal bipolar cell (BC) GJs in the human inner retina, whose function is enigmatic even in the examined animal models. Furthermore, a number of unique features (e.g. fovea, trichromacy, midget system) necessitate a reexamination of the animal model results in the human retina. Well-preserved postmortem human samples of this study are allowed to identify Cx36 expressing BCs neurochemically. Results reveal that both rod and cone pathway interneurons display strong Cx36 expression. Rod BC inputs to AII amacrine cells (AC) appear in juxtaposition to AII GJs, thus suggesting a strategic AII cell targeting by rod BCs. Cone BCs serving midget, parasol or koniocellular signaling pathways display a wealth of Cx36 expression to form homologously coupled arrays. In addition, they also establish heterologous GJ contacts to serve an exchange of information between parallel signaling streams. Interestingly, a prominent Cx36 expression was exhibited by midget system BCs that appear to maintain intimate contacts with bistratified BCs serving other pathways. These findings suggest that BC GJs in parallel signaling streams serve both an intra- and inter-pathway exchange of signals in the human retina.
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Affiliation(s)
- Orsolya Kántor
- Department of Neuroanatomy, Faculty of Medicine, Institute for Anatomy and Cell Biology, University of Freiburg, 79104, Freiburg, Germany
- MTA-PTE NAP B Retinal Electrical Synapses Research Group, Pécs, 7624, Hungary
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
| | - Alexandra Varga
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
| | - Roland Nitschke
- Life Imaging Center, Center for Biological Systems Analysis, University of Freiburg, 79104, Freiburg, Germany
- BIOSS Centre for Biological Signaling Studies, University of Freiburg, 79104, Freiburg, Germany
| | - Angela Naumann
- Life Imaging Center, Center for Biological Systems Analysis, University of Freiburg, 79104, Freiburg, Germany
- BIOSS Centre for Biological Signaling Studies, University of Freiburg, 79104, Freiburg, Germany
| | - Anna Énzsöly
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
- Department of Ophthalmology, Semmelweis University, Budapest, 1085, Hungary
| | - Ákos Lukáts
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
| | - Arnold Szabó
- Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, 1094, Hungary
| | - János Németh
- Department of Ophthalmology, Semmelweis University, Budapest, 1085, Hungary
| | - Béla Völgyi
- MTA-PTE NAP B Retinal Electrical Synapses Research Group, Pécs, 7624, Hungary.
- Department of Experimental Zoology and Neurobiology, University of Pécs, Pécs, 7624, Hungary.
- János Szentágothai Research Center, University of Pécs, Ifjúság street 20, Pécs, 7624, Hungary.
- Department of Ophthalmology, New York University Langone Medical Center, New York, NY, 10016, USA.
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20
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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: 1.9] [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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21
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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: 3.8] [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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22
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Calcium buffer proteins are specific markers of human retinal neurons. Cell Tissue Res 2016; 365:29-50. [PMID: 26899253 DOI: 10.1007/s00441-016-2376-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 02/04/2016] [Indexed: 10/22/2022]
Abstract
Ca(2+)-buffer proteins (CaBPs) modulate the temporal and spatial characteristics of transient intracellular Ca(2+)-concentration changes in neurons in order to fine-tune the strength and duration of the output signal. CaBPs have been used as neurochemical markers to identify and trace neurons of several brain loci including the mammalian retina. The CaBP content of retinal neurons, however, varies between species and, thus, the results inferred from animal models cannot be utilised directly by clinical ophthalmologists. Moreover, the shortage of well-preserved human samples greatly impedes human retina studies at the cellular and network level. Our purpose has therefore been to examine the distribution of major CaBPs, including calretinin, calbindin-D28, parvalbumin and the recently discovered secretagogin in exceptionally well-preserved human retinal samples. Based on a combination of immunohistochemistry, Neurolucida tracing and Lucifer yellow injections, we have established a database in which the CaBP marker composition can be defined for morphologically identified cell types of the human retina. Hence, we describe the full CaBP make-up for a number of human retinal neurons, including HII horizontal cells, AII amacrine cells, type-1 tyrosine-hydroxylase-expressing amacrine cells and other lesser known neurons. We have also found a number of unidentified cells whose morphology remains to be characterised. We present several examples of the colocalisation of two or three CaBPs with slightly different subcellular distributions in the same cell strongly suggesting a compartment-specific division of labour of Ca(2+)-buffering by CaBPs. Our work thus provides a neurochemical framework for future ophthalmological studies and renders new information concerning the cellular and subcellular distribution of CaBPs for experimental neuroscience.
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