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Hellevik AM, Mardoum P, Hahn J, Kölsch Y, D'Orazi FD, Suzuki SC, Godinho L, Lawrence O, Rieke F, Shekhar K, Sanes JR, Baier H, Baden T, Wong RO, Yoshimatsu T. Ancient origin of the rod bipolar cell pathway in the vertebrate retina. Nat Ecol Evol 2024; 8:1165-1179. [PMID: 38627529 DOI: 10.1038/s41559-024-02404-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/20/2024] [Indexed: 04/30/2024]
Abstract
Vertebrates rely on rod photoreceptors for vision in low-light conditions. The specialized downstream circuit for rod signalling, called the primary rod pathway, is well characterized in mammals, but circuitry for rod signalling in non-mammals is largely unknown. Here we demonstrate that the mammalian primary rod pathway is conserved in zebrafish, which diverged from extant mammals ~400 million years ago. Using single-cell RNA sequencing, we identified two bipolar cell types in zebrafish that are related to mammalian rod bipolar cell (RBCs), the only bipolar type that directly carries rod signals from the outer to the inner retina in the primary rod pathway. By combining electrophysiology, histology and ultrastructural reconstruction of the zebrafish RBCs, we found that, similar to mammalian RBCs, both zebrafish RBC types connect with all rods in their dendritic territory and provide output largely onto amacrine cells. The wiring pattern of the amacrine cells postsynaptic to one RBC type is strikingly similar to that of mammalian RBCs and their amacrine partners, suggesting that the cell types and circuit design of the primary rod pathway emerged before the divergence of teleost fish and mammals. The second RBC type, which forms separate pathways, was either lost in mammals or emerged in fish.
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Affiliation(s)
- Ayana M Hellevik
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Philip Mardoum
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Joshua Hahn
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA, USA
| | - Yvonne Kölsch
- Department Genes - Circuits - Behavior, Max Planck Institute for Biological Intelligence, Martinsried, Germany
| | - Florence D D'Orazi
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Sachihiro C Suzuki
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Leanne Godinho
- Institute of Neuronal Cell Biology, Technische Universität München, Munich, Germany
| | - Owen Lawrence
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA
- Vision Science Center, University of Washington, Seattle, WA, USA
| | - Karthik Shekhar
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology, and Center for Brain Science, Harvard University, Cambridge, MA, USA
| | - Herwig Baier
- Department Genes - Circuits - Behavior, Max Planck Institute for Biological Intelligence, Martinsried, Germany
| | - Tom Baden
- School of Life Sciences, University of Sussex, Brighton, UK
- Institute of Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Takeshi Yoshimatsu
- Department of Ophthalmology and Visual Sciences, Washington University in St Louis School of Medicine, St Louis, MO, USA.
- BioRTC, Yobe State University, Damatsuru, Yobe, Nigeria.
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2
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Felder-Schmittbuhl MP, Hicks D, Ribelayga CP, Tosini G. Melatonin in the mammalian retina: Synthesis, mechanisms of action and neuroprotection. J Pineal Res 2024; 76:e12951. [PMID: 38572848 DOI: 10.1111/jpi.12951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 02/09/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024]
Abstract
Melatonin is an important player in the regulation of many physiological functions within the body and in the retina. Melatonin synthesis in the retina primarily occurs during the night and its levels are low during the day. Retinal melatonin is primarily synthesized by the photoreceptors, but whether the synthesis occurs in the rods and/or cones is still unclear. Melatonin exerts its influence by binding to G protein-coupled receptors named melatonin receptor type 1 (MT1) and type 2 (MT2). MT1 and MT2 receptors activate a wide variety of signaling pathways and both receptors are present in the vertebrate photoreceptors where they may form MT1/MT2 heteromers (MT1/2h). Studies in rodents have shown that melatonin signaling plays an important role in the regulation of retinal dopamine levels, rod/cone coupling as well as the photopic and scotopic electroretinogram. In addition, melatonin may play an important role in protecting photoreceptors from oxidative stress and can protect photoreceptors from apoptosis. Critically, melatonin signaling is involved in the modulation of photoreceptor viability during aging and other studies have implicated melatonin in the pathogenesis of age-related macular degeneration. Hence melatonin may represent a useful tool in the fight to protect photoreceptors-and other retinal cells-against degeneration due to aging or diseases.
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Affiliation(s)
- Marie Paule Felder-Schmittbuhl
- Centre National de la Recherche Scientifique, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Université de Strasbourg, Strasbourg, France
| | - David Hicks
- Centre National de la Recherche Scientifique, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Université de Strasbourg, Strasbourg, France
| | - Christophe P Ribelayga
- Department of Vision Sciences, College of Optometry, University of Houston, Houston, Texas, USA
| | - Gianluca Tosini
- Department of Pharmacology & Toxicology, Neuroscience Institute, Morehouse School of Medicine, Atlanta, Georgia, USA
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3
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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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Bhoi JD, Goel M, Ribelayga CP, Mangel SC. Circadian clock organization in the retina: From clock components to rod and cone pathways and visual function. Prog Retin Eye Res 2023; 94:101119. [PMID: 36503722 PMCID: PMC10164718 DOI: 10.1016/j.preteyeres.2022.101119] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 08/22/2022] [Accepted: 08/25/2022] [Indexed: 12/13/2022]
Abstract
Circadian (24-h) clocks are cell-autonomous biological oscillators that orchestrate many aspects of our physiology on a daily basis. Numerous circadian rhythms in mammalian and non-mammalian retinas have been observed and the presence of an endogenous circadian clock has been demonstrated. However, how the clock and associated rhythms assemble into pathways that support and control retina function remains largely unknown. Our goal here is to review the current status of our knowledge and evaluate recent advances. We describe many previously-observed retinal rhythms, including circadian rhythms of morphology, biochemistry, physiology, and gene expression. We evaluate evidence concerning the location and molecular machinery of the retinal circadian clock, as well as consider findings that suggest the presence of multiple clocks. Our primary focus though is to describe in depth circadian rhythms in the light responses of retinal neurons with an emphasis on clock control of rod and cone pathways. We examine evidence that specific biochemical mechanisms produce these daily light response changes. We also discuss evidence for the presence of multiple circadian retinal pathways involving rhythms in neurotransmitter activity, transmitter receptors, metabolism, and pH. We focus on distinct actions of two dopamine receptor systems in the outer retina, a dopamine D4 receptor system that mediates circadian control of rod/cone gap junction coupling and a dopamine D1 receptor system that mediates non-circadian, light/dark adaptive regulation of gap junction coupling between horizontal cells. Finally, we evaluate the role of circadian rhythmicity in retinal degeneration and suggest future directions for the field of retinal circadian biology.
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Affiliation(s)
- Jacob D Bhoi
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, UTHEALTH-The University of Texas Health Science Center at Houston, Houston, TX, USA; Neuroscience Honors Research Program, William Marsh Rice University, Houston, TX, USA
| | - Manvi Goel
- Department of Neuroscience, Wexner Medical Center, College of Medicine, The Ohio State University, Columbus, OH, 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; Neuroscience Honors Research Program, William Marsh Rice University, Houston, TX, USA.
| | - Stuart C Mangel
- Department of Neuroscience, Wexner Medical Center, College of Medicine, The Ohio State University, Columbus, OH, USA.
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Brown-Panton CA, Sabour S, Zoidl GSO, Zoidl C, Tabatabaei N, Zoidl GR. Gap junction Delta-2b ( gjd2b/Cx35.1) depletion causes hyperopia and visual-motor deficiencies in the zebrafish. Front Cell Dev Biol 2023; 11:1150273. [PMID: 36936688 PMCID: PMC10017553 DOI: 10.3389/fcell.2023.1150273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/15/2023] [Indexed: 03/06/2023] Open
Abstract
The zebrafish is a powerful model to investigate the developmental roles of electrical synapses because many signaling pathways that regulate the development of the nervous system are highly conserved from fish to humans. Here, we provide evidence linking the mammalian connexin-36 (Cx36) ortholog gjd2b/Cx35.1, a major component of electrical synapses in the zebrafish, with a refractive error in the context of morphological, molecular, and behavioral changes of zebrafish larvae. Two abnormalities were identified. The optical coherence tomography analysis of the adult retina confirmed changes to the refractive properties caused by eye axial length reduction, leading to hyperopic shifts. The gjd2b/Cx35.1 depletion was also correlated with morphological changes to the head and body ratios in larvae. The differential expression of Wnt/ß-catenin signaling genes, connexins, and dopamine receptors suggested a contribution to the observed phenotypic differences. The alteration of visual-motor behavioral responses to abrupt light transitions was aggravated in larvae, providing evidence that cone photoreceptor cell activity was enhanced when gjd2b/Cx35.1 was depleted. The visual disturbances were reversed under low light conditions in gjd2b -/- /Cx35.1-/- larvae. Since qRT-PCR data demonstrated that two rhodopsin genes were downregulated, we speculated that rod photoreceptor cells in gjd2b/Cx35.1-/- larvae were less sensitive to bright light transitions, thus providing additional evidence that a cone-mediated process caused the VMR light-ON hyperactivity after losing Cx35.1 expression. Together, this study provides evidence for the role of gjd2b/Cx35.1 in the development of the visual system and visually guided behaviors.
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Affiliation(s)
- Cherie A. Brown-Panton
- Department of Biology, York University, Toronto, ON, Canada
- Center for Vision Research, York University, Toronto, ON, Canada
- *Correspondence: Cherie A. Brown-Panton, ; Georg R. Zoidl,
| | - Shiva Sabour
- Department of Mechanical Engineering, York University, Toronto, ON, Canada
| | - Georg S. O. Zoidl
- Department of Biology, York University, Toronto, ON, Canada
- Center for Vision Research, York University, Toronto, ON, Canada
| | - Christiane Zoidl
- Department of Biology, York University, Toronto, ON, Canada
- Center for Vision Research, York University, Toronto, ON, Canada
| | - Nima Tabatabaei
- Center for Vision Research, York University, Toronto, ON, Canada
- Department of Mechanical Engineering, York University, Toronto, ON, Canada
| | - Georg R. Zoidl
- Department of Biology, York University, Toronto, ON, Canada
- Center for Vision Research, York University, Toronto, ON, Canada
- Department of Psychology, York University, Toronto, ON, Canada
- *Correspondence: Cherie A. Brown-Panton, ; Georg R. Zoidl,
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Gölz L, Baumann L, Pannetier P, Braunbeck T, Knapen D, Vergauwen L. AOP Report: Thyroperoxidase Inhibition Leading to Altered Visual Function in Fish Via Altered Retinal Layer Structure. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2022; 41:2632-2648. [PMID: 35942927 DOI: 10.1002/etc.5452] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
Thyroid hormones (THs) are involved in the regulation of many important physiological and developmental processes, including vertebrate eye development. Thyroid hormone system-disrupting chemicals (THSDCs) may have severe consequences, because proper functioning of the visual system is a key factor for survival in wildlife. However, the sequence of events leading from TH system disruption (THSD) to altered eye development in fish has not yet been fully described. The development of this adverse outcome pathway (AOP) was based on an intensive literature review of studies that focused on THSD and impacts on eye development, mainly in fish. In total, approximately 120 studies (up to the end of 2021) were used in the development of this AOP linking inhibition of the key enzyme for TH synthesis, thyroperoxidase (TPO), to effects on retinal layer structure and visual function in fish (AOP-Wiki, AOP 363). In a weight-of-evidence evaluation, the confidence levels were overall moderate, with ample studies showing the link between reduced TH levels and altered retinal layer structure. However, some uncertainties about the underlying mechanism(s) remain. Although the current weight-of-evidence evaluation is based on fish, the AOP is plausibly applicable to other vertebrate classes. Through the re-use of several building blocks, this AOP is connected to the AOPs leading from TPO and deiodinase inhibition to impaired swim bladder inflation in fish (AOPs 155-159), together forming an AOP network describing THSD in fish. This AOP network addresses the lack of thyroid-related endpoints in existing fish test guidelines for the evaluation of THSDCs. Environ Toxicol Chem 2022;41:2632-2648. © 2022 SETAC.
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Affiliation(s)
- Lisa Gölz
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Lisa Baumann
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Pauline Pannetier
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology Research Group, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
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7
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Bolstad K, Novales Flamarique I. Chromatic organization of retinal photoreceptors during eye migration of Atlantic halibut (Hippoglossus hippoglossus). J Comp Neurol 2022; 531:256-280. [PMID: 36217253 DOI: 10.1002/cne.25423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 09/14/2022] [Accepted: 09/19/2022] [Indexed: 11/08/2022]
Abstract
The retinas of fishes often have single and double cone photoreceptors that are organized in lattice-like mosaics. In flatfishes experiencing eye migration (i.e., the metamorphic process whereby one eye migrates to the other side of the head), the hexagonal lattice of single cones present in the larva undergoes major restructuring resulting in a dominant square mosaic postmetamorphosis consisting of four double cones surrounding each single cone. The expression of different opsin types during eye migration has not been examined despite its importance in understanding photoreceptor plasticity and whether cell fate (in terms of spectral phenotype) could influence square mosaic formation. Here, we probed the retina of Atlantic halibut undergoing eye migration for opsin expression using two antibodies, AHblue and AB5407, that labeled short wavelength sensitive 2 (SWS2) opsin and longer wavelength (predominantly middle wavelength sensitive, RH2) opsins, respectively. Throughout the retina, double and triple cones labeled with AB5407 exclusively, whereas the vast majority of single cones labeled with AHblue. A minority (<5%) of single cones in the square mosaic of the centroventral retina labeled with AB5407. In regions of mosaic transition and near peripheral growth zones, some single cones co-expressed at least two opsins as they labeled with both antibodies. Short wavelength (SWS2 expressing, or S) cones formed a nonrandom mosaic gradient from central to dorsal retina in a region dominated by the larval single cone mosaic. Our results demonstrate the expression of at least two opsins throughout the postmetamorphic retina and suggest opsin switching as a mechanism to create new cone spectral phenotypes. In addition, the S cone gradient at the onset of eye migration may underlie a plastic, cell induction mechanism by which a cone's phenotype determines that of its neighbors and the formation of the square mosaic.
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Affiliation(s)
- Kennedy Bolstad
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Iñigo Novales Flamarique
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.,Department of Biology, University of Victoria, Victoria, British Columbia, Canada
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Myles WE, McFadden SA. Analytical methods for assessing retinal cell coupling using cut-loading. PLoS One 2022; 17:e0271744. [PMID: 35853039 PMCID: PMC9295955 DOI: 10.1371/journal.pone.0271744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 07/06/2022] [Indexed: 11/25/2022] Open
Abstract
Electrical coupling between retinal neurons contributes to the functional complexity of visual circuits. “Cut-loading” methods allow simultaneous assessment of cell-coupling between multiple retinal cell-types, but existing analysis methods impede direct comparison with gold standard direct dye injection techniques. In the current study, we both improved an existing method and developed two new approaches to address observed limitations. Each method of analysis was applied to cut-loaded dark-adapted Guinea pig retinae (n = 29) to assess coupling strength in the axonless horizontal cell type (‘a-type’, aHCs). Method 1 was an improved version of the standard protocol and described the distance of dye-diffusion (space constant). Method 2 adjusted for the geometric path of dye-transfer through cut-loaded cells and extracted the rate of dye-transfer across gap-junctions in terms of the coupling coefficient (kj). Method 3 measured the diffusion coefficient (De) perpendicular to the cut-axis. Dye transfer was measured after one of five diffusion times (1–20 mins), or with a coupling inhibitor, meclofenamic acid (MFA) (50–500μM after 20 mins diffusion). The standard protocol fits an exponential decay function to the fluorescence profile of a specified retina layer but includes non-specific background fluorescence. This was improved by measuring the fluorescence of individual cell soma and excluding from the fit non-horizontal cells located at the cut-edge (p<0.001) (Method 1). The space constant (Method 1) increased with diffusion time (p<0.01), whereas Methods 2 (p = 0.54) and 3 (p = 0.63) produced consistent results across all diffusion times. Adjusting distance by the mean cell-cell spacing within each tissue reduced the incidence of outliers across all three methods. Method 1 was less sensitive to detecting changes induced by MFA than Methods 2 (p<0.01) and 3 (p<0.01). Although the standard protocol was easily improved (Method 1), Methods 2 and 3 proved more sensitive and generalisable; allowing for detailed assessment of the tracer kinetics between different populations of gap-junction linked cell networks and direct comparison to dye-injection techniques.
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Affiliation(s)
- William E. Myles
- College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, Australia
- * E-mail:
| | - Sally A. McFadden
- College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, Australia
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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: 0.5] [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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Zang J, Gesemann M, Keim J, Samardzija M, Grimm C, Neuhauss SCF. Circadian regulation of vertebrate cone photoreceptor function. eLife 2021; 10:e68903. [PMID: 34550876 PMCID: PMC8494479 DOI: 10.7554/elife.68903] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 09/20/2021] [Indexed: 12/16/2022] Open
Abstract
Eukaryotes generally display a circadian rhythm as an adaption to the reoccurring day/night cycle. This is particularly true for visual physiology that is directly affected by changing light conditions. Here we investigate the influence of the circadian rhythm on the expression and function of visual transduction cascade regulators in diurnal zebrafish and nocturnal mice. We focused on regulators of shut-off kinetics such as Recoverins, Arrestins, Opsin kinases, and Regulator of G-protein signaling that have direct effects on temporal vision. Transcript as well as protein levels of most analyzed genes show a robust circadian rhythm-dependent regulation, which correlates with changes in photoresponse kinetics. Electroretinography demonstrates that photoresponse recovery in zebrafish is delayed in the evening and accelerated in the morning. Functional rhythmicity persists in continuous darkness, and it is reversed by an inverted light cycle and disrupted by constant light. This is in line with our finding that orthologous gene transcripts from diurnal zebrafish and nocturnal mice are often expressed in an anti-phasic daily rhythm.
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Affiliation(s)
- Jingjing Zang
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Matthias Gesemann
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Jennifer Keim
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
| | - Marijana Samardzija
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of ZurichZurichSwitzerland
| | - Christian Grimm
- Lab for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of ZurichZurichSwitzerland
| | - Stephan CF Neuhauss
- University of Zurich, Department of Molecular Life SciencesZurichSwitzerland
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11
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Günther A, Dedek K, Haverkamp S, Irsen S, Briggman KL, Mouritsen H. Double Cones and the Diverse Connectivity of Photoreceptors and Bipolar Cells in an Avian Retina. J Neurosci 2021; 41:5015-5028. [PMID: 33893221 PMCID: PMC8197639 DOI: 10.1523/jneurosci.2495-20.2021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 03/03/2021] [Accepted: 04/01/2021] [Indexed: 12/24/2022] Open
Abstract
Double cones are the most common photoreceptor cell type in most avian retinas, but their precise functions remain a mystery. Among their suggested functions are luminance detection, polarized light detection, and light-dependent, radical pair-based magnetoreception. To better understand the function of double cones, it will be crucial to know how they are connected to the neural network in the avian retina. Here we use serial sectioning, multibeam scanning electron microscopy to investigate double-cone anatomy and connectivity with a particular focus on their contacts to other photoreceptor and bipolar cells in the chicken retina. We found that double cones are highly connected to neighboring double cones and with other photoreceptor cells through telodendria-to-terminal and telodendria-to-telodendria contacts. We also identified 15 bipolar cell types based on their axonal stratifications, photoreceptor contact pattern, soma position, and dendritic and axonal field mosaics. Thirteen of these 15 bipolar cell types contacted at least one or both members of the double cone. All bipolar cells were bistratified or multistratified. We also identified surprising contacts between other cone types and between rods and cones. Our data indicate a much more complex connectivity network in the outer plexiform layer of the avian retina than originally expected.SIGNIFICANCE STATEMENT Like in humans, vision is one of the most important senses for birds. Here, we present the first serial section multibeam scanning electron microscopy dataset from any bird retina. We identified many previously undescribed rod-to-cone and cone-to-cone connections. Surprisingly, of the 15 bipolar cell types we identified, 11 received input from rods and 13 of 15 received at least part of their input from double cones. Therefore, double cones seem to play many different and important roles in avian retinal processing, and the neural network and thus information processing in the outer retina are much more complex than previously expected. These fundamental findings will be very important for several fields of science, including vertebrate vision, avian magnetoreception, and comparative neuroanatomy.
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Affiliation(s)
- Anja Günther
- Neurosensorics/Animal Navigation, Institute for Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
| | - Karin Dedek
- Neurosensorics/Animal Navigation, Institute for Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
- Research Center for Neurosensory Sciences, Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
| | - Silke Haverkamp
- Department of Computational Neuroethology, Center of Advanced European Studies and Reasearch (caesar), 53175 Bonn, Germany
| | - Stephan Irsen
- Electron Microscopy and Analytics, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
| | - Kevin L Briggman
- Department of Computational Neuroethology, Center of Advanced European Studies and Reasearch (caesar), 53175 Bonn, Germany
| | - Henrik Mouritsen
- Neurosensorics/Animal Navigation, Institute for Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
- Research Center for Neurosensory Sciences, Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
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12
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Quint WH, Tadema KCD, de Vrieze E, Lukowicz RM, Broekman S, Winkelman BHJ, Hoevenaars M, de Gruiter HM, van Wijk E, Schaeffel F, Meester-Smoor M, Miller AC, Willemsen R, Klaver CCW, Iglesias AI. Loss of Gap Junction Delta-2 (GJD2) gene orthologs leads to refractive error in zebrafish. Commun Biol 2021; 4:676. [PMID: 34083742 PMCID: PMC8175550 DOI: 10.1038/s42003-021-02185-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 05/04/2021] [Indexed: 12/20/2022] Open
Abstract
Myopia is the most common developmental disorder of juvenile eyes, and it has become an increasing cause of severe visual impairment. The GJD2 locus has been consistently associated with myopia in multiple independent genome-wide association studies. However, despite the strong genetic evidence, little is known about the functional role of GJD2 in refractive error development. Here, we find that depletion of gjd2a (Cx35.5) or gjd2b (Cx35.1) orthologs in zebrafish, cause changes in the biometry and refractive status of the eye. Our immunohistological and scRNA sequencing studies show that Cx35.5 (gjd2a) is a retinal connexin and its depletion leads to hyperopia and electrophysiological changes in the retina. These findings support a role for Cx35.5 (gjd2a) in the regulation of ocular biometry. Cx35.1 (gjd2b) has previously been identified in the retina, however, we found an additional lenticular role. Lack of Cx35.1 (gjd2b) led to a nuclear cataract that triggered axial elongation. Our results provide functional evidence of a link between gjd2 and refractive error. Quint et al. use zebrafish lines deficient in one of two orthologs of the Gap Junction Delta-2 (GJD2) gene, which is associated with myopia by genome-wide association studies. They link gjd2 with refractive error and report evidence to suggest that gjd2a plays a role in ocular biometry whilst gjd2b, previously found in the retina, possesses an additional lenticular role.
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Affiliation(s)
- Wim H Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands. .,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands.
| | - Kirke C D Tadema
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Erik de Vrieze
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Rachel M Lukowicz
- Institute of Neuroscience, University of Oregon, Eugene, United States
| | - Sanne Broekman
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Beerend H J Winkelman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Cerebellar Coordination and Cognition, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Melanie Hoevenaars
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Erwin van Wijk
- Department of Otorhinolaryngology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, Netherlands
| | - Frank Schaeffel
- Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany.,Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland
| | - Magda Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Adam C Miller
- Institute of Neuroscience, University of Oregon, Eugene, United States
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C W Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, 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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13
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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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14
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Zoidl GR, Spray DC. The Roles of Calmodulin and CaMKII in Cx36 Plasticity. Int J Mol Sci 2021; 22:4473. [PMID: 33922931 PMCID: PMC8123330 DOI: 10.3390/ijms22094473] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/17/2021] [Accepted: 04/20/2021] [Indexed: 01/07/2023] Open
Abstract
Anatomical and electrophysiological evidence that gap junctions and electrical coupling occur between neurons was initially confined to invertebrates and nonmammals and was thought to be a primitive form of synaptic transmission. More recent studies revealed that electrical communication is common in the mammalian central nervous system (CNS), often coexisting with chemical synaptic transmission. The subsequent progress indicated that electrical synapses formed by the gap junction protein connexin-36 (Cx36) and its paralogs in nonmammals constitute vital elements in mammalian and fish synaptic circuitry. They govern the collective activity of ensembles of coupled neurons, and Cx36 gap junctions endow them with enormous adaptive plasticity, like that seen at chemical synapses. Moreover, they orchestrate the synchronized neuronal network activity and rhythmic oscillations that underlie the fundamental integrative processes, such as memory and learning. Here, we review the available mechanistic evidence and models that argue for the essential roles of calcium, calmodulin, and the Ca2+/calmodulin-dependent protein kinase II in integrating calcium signals to modulate the strength of electrical synapses through interactions with the gap junction protein Cx36.
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Affiliation(s)
- Georg R. Zoidl
- Department of Biology & Center for Vision Research (CVR), York University, Toronto, ON M3J 1P3, Canada
| | - David C. Spray
- Dominick P. Purpura Department of Neuroscience & Department of Medicine (Cardiology), Albert Einstein College of Medicine, New York, NY 10461, USA;
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15
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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: 6.0] [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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16
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Zang J, Neuhauss SCF. Biochemistry and physiology of zebrafish photoreceptors. Pflugers Arch 2021; 473:1569-1585. [PMID: 33598728 PMCID: PMC8370914 DOI: 10.1007/s00424-021-02528-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/25/2021] [Accepted: 01/28/2021] [Indexed: 02/06/2023]
Abstract
All vertebrates share a canonical retina with light-sensitive photoreceptors in the outer retina. These photoreceptors are of two kinds: rods and cones, adapted to low and bright light conditions, respectively. They both show a peculiar morphology, with long outer segments, comprised of ordered stacks of disc-shaped membranes. These discs host numerous proteins, many of which contribute to the visual transduction cascade. This pathway converts the light stimulus into a biological signal, ultimately modulating synaptic transmission. Recently, the zebrafish (Danio rerio) has gained popularity for studying the function of vertebrate photoreceptors. In this review, we introduce this model system and its contribution to our understanding of photoreception with a focus on the cone visual transduction cascade.
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Affiliation(s)
- Jingjing Zang
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland
| | - Stephan C F Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrase 190, CH - 8057, Zürich, Switzerland.
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17
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Cao J, Ribelayga CP, Mangel SC. A Circadian Clock in the Retina Regulates Rod-Cone Gap Junction Coupling and Neuronal Light Responses via Activation of Adenosine A 2A Receptors. Front Cell Neurosci 2021; 14:605067. [PMID: 33510619 PMCID: PMC7835330 DOI: 10.3389/fncel.2020.605067] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/15/2020] [Indexed: 12/26/2022] Open
Abstract
Adenosine, a major neuromodulator in the central nervous system (CNS), is involved in a variety of regulatory functions such as the sleep/wake cycle. Because exogenous adenosine displays dark- and night-mimicking effects in the vertebrate retina, we tested the hypothesis that a circadian (24 h) clock in the retina uses adenosine to control neuronal light responses and information processing. Using a variety of techniques in the intact goldfish retina including measurements of adenosine overflow and content, tracer labeling, and electrical recording of the light responses of cone photoreceptor cells and cone horizontal cells (cHCs), which are post-synaptic to cones, we demonstrate that a circadian clock in the retina itself-but not activation of melatonin or dopamine receptors-controls extracellular and intracellular adenosine levels so that they are highest during the subjective night. Moreover, the results show that the clock increases extracellular adenosine at night by enhancing adenosine content so that inward adenosine transport ceases. Also, we report that circadian clock control of endogenous cone adenosine A2A receptor activation increases rod-cone gap junction coupling and rod input to cones and cHCs at night. These results demonstrate that adenosine and A2A receptor activity are controlled by a circadian clock in the retina, and are used by the clock to modulate rod-cone electrical synapses and the sensitivity of cones and cHCs to very dim light stimuli. Moreover, the adenosine system represents a separate circadian-controlled pathway in the retina that is independent of the melatonin/dopamine pathway but which nevertheless acts in concert to enhance the day/night difference in rod-cone coupling.
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Affiliation(s)
- Jiexin Cao
- Department of Neuroscience, The Ohio State University College of Medicine, Columbus, OH, United States
| | - Christophe P Ribelayga
- Department of Neuroscience, The Ohio State University College of Medicine, Columbus, OH, United States
| | - Stuart C Mangel
- Department of Neuroscience, The Ohio State University College of Medicine, Columbus, OH, United States
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18
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Campbell JR, Li H, Wang Y, Kozhemyakin M, Hunt AJ, Liu X, Janz R, Heidelberger R. Phosphorylation of the Retinal Ribbon Synapse Specific t-SNARE Protein Syntaxin3B Is Regulated by Light via a Ca 2 +-Dependent Pathway. Front Cell Neurosci 2020; 14:587072. [PMID: 33192329 PMCID: PMC7606922 DOI: 10.3389/fncel.2020.587072] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 09/11/2020] [Indexed: 12/27/2022] Open
Abstract
Neurotransmitter release at retinal ribbon-style synapses utilizes a specialized t-SNARE protein called syntaxin3B (STX3B). In contrast to other syntaxins, STX3 proteins can be phosphorylated in vitro at T14 by Ca2+/calmodulin-dependent protein kinase II (CaMKII). This modification has the potential to modulate SNARE complex formation required for neurotransmitter release in an activity-dependent manner. To determine the extent to which T14 phosphorylation occurs in vivo in the mammalian retina and characterize the pathway responsible for the in vivo phosphorylation of T14, we utilized quantitative immunofluorescence to measure the levels of STX3 and STX3 phosphorylated at T14 (pSTX3) in the synaptic terminals of mouse retinal photoreceptors and rod bipolar cells (RBCs). Results demonstrate that STX3B phosphorylation at T14 is light-regulated and dependent upon the elevation of intraterminal Ca2+. In rod photoreceptor terminals, the ratio of pSTX3 to STX3 was significantly higher in dark-adapted mice, when rods are active, than in light-exposed mice. By contrast, in RBC terminals, the ratio of pSTX3 to STX3 was higher in light-exposed mice, when these terminals are active, than in dark-adapted mice. These results were recapitulated in the isolated eyecup preparation, but only when Ca2+ was included in the external medium. In the absence of external Ca2+, pSTX3 levels remained low regardless of light/dark exposure. Using the isolated RBC preparation, we next showed that elevation of intraterminal Ca2+ alone was sufficient to increase STX3 phosphorylation at T14. Furthermore, both the non-specific kinase inhibitor staurosporine and the selective CaMKII inhibitor AIP inhibited the Ca2+-dependent increase in the pSTX3/STX3 ratio in isolated RBC terminals, while in parallel experiments, AIP suppressed RBC depolarization-evoked exocytosis, measured using membrane capacitance measurements. Our data support a novel, illumination-regulated modulation of retinal ribbon-style synapse function in which activity-dependent Ca2+ entry drives the phosphorylation of STX3B at T14 by CaMKII, which in turn, modulates the ability to form SNARE complexes required for exocytosis.
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Affiliation(s)
- Joseph R Campbell
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Hongyan Li
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Yanzhao Wang
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Maxim Kozhemyakin
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Albert J Hunt
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Xiaoqin Liu
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Roger Janz
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
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19
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Martin EA, Lasseigne AM, Miller AC. Understanding the Molecular and Cell Biological Mechanisms of Electrical Synapse Formation. Front Neuroanat 2020; 14:12. [PMID: 32372919 PMCID: PMC7179694 DOI: 10.3389/fnana.2020.00012] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/09/2020] [Indexed: 12/20/2022] Open
Abstract
In this review article, we will describe the recent advances made towards understanding the molecular and cell biological mechanisms of electrical synapse formation. New evidence indicates that electrical synapses, which are gap junctions between neurons, can have complex molecular compositions including protein asymmetries across joined cells, diverse morphological arrangements, and overlooked similarities with other junctions, all of which indicate new potential roles in neurodevelopmental disease. Aquatic organisms, and in particular the vertebrate zebrafish, have proven to be excellent models for elucidating the molecular mechanisms of electrical synapse formation. Zebrafish will serve as our main exemplar throughout this review and will be compared with other model organisms. We highlight the known cell biological processes that build neuronal gap junctions and compare these with the assemblies of adherens junctions, tight junctions, non-neuronal gap junctions, and chemical synapses to explore the unknown frontiers remaining in our understanding of the critical and ubiquitous electrical synapse.
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Affiliation(s)
- E Anne Martin
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - Abagael M Lasseigne
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - Adam C Miller
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
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20
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Sánchez OF, Rodríguez AV, Velasco-España JM, Murillo LC, Sutachan JJ, Albarracin SL. Role of Connexins 30, 36, and 43 in Brain Tumors, Neurodegenerative Diseases, and Neuroprotection. Cells 2020; 9:E846. [PMID: 32244528 PMCID: PMC7226843 DOI: 10.3390/cells9040846] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 02/15/2020] [Accepted: 02/24/2020] [Indexed: 02/07/2023] Open
Abstract
Gap junction (GJ) channels and their connexins (Cxs) are complex proteins that have essential functions in cell communication processes in the central nervous system (CNS). Neurons, astrocytes, oligodendrocytes, and microglial cells express an extraordinary repertory of Cxs that are important for cell to cell communication and diffusion of metabolites, ions, neurotransmitters, and gliotransmitters. GJs and Cxs not only contribute to the normal function of the CNS but also the pathological progress of several diseases, such as cancer and neurodegenerative diseases. Besides, they have important roles in mediating neuroprotection by internal or external molecules. However, regulation of Cx expression by epigenetic mechanisms has not been fully elucidated. In this review, we provide an overview of the known mechanisms that regulate the expression of the most abundant Cxs in the central nervous system, Cx30, Cx36, and Cx43, and their role in brain cancer, CNS disorders, and neuroprotection. Initially, we focus on describing the Cx gene structure and how this is regulated by epigenetic mechanisms. Then, the posttranslational modifications that mediate the activity and stability of Cxs are reviewed. Finally, the role of GJs and Cxs in glioblastoma, Alzheimer's, Parkinson's, and Huntington's diseases, and neuroprotection are analyzed with the aim of shedding light in the possibility of using Cx regulators as potential therapeutic molecules.
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Affiliation(s)
- Oscar F. Sánchez
- Department of Nutrition and Biochemistry, Pontificia Universidad Javeriana, 110911 Bogota, Colombia; (A.V.R.); (J.M.V.-E.); (L.C.M.); (J.-J.S.)
| | | | | | | | | | - Sonia-Luz Albarracin
- Department of Nutrition and Biochemistry, Pontificia Universidad Javeriana, 110911 Bogota, Colombia; (A.V.R.); (J.M.V.-E.); (L.C.M.); (J.-J.S.)
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21
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Li L. Circadian Vision in Zebrafish: From Molecule to Cell and from Neural Network to Behavior. J Biol Rhythms 2019; 34:451-462. [DOI: 10.1177/0748730419863917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Most visual system functions, such as opsin gene expression, retinal neural transmission, light perception, and visual sensitivity, display robust day-night rhythms. The rhythms persist in constant lighting conditions, suggesting the involvement of endogenous circadian clocks. While the circadian pacemakers that control the rhythms of animal behaviors are mostly found in the forebrain and midbrain, self-sustained circadian oscillators are also present in the neural retina, where they play important roles in the regulation of circadian vision. This review highlights some of the correlative studies of the circadian control of visual system functions in zebrafish. Because zebrafish maintain a high evolutionary proximity to mammals, the findings from zebrafish research may provide insights for a better understanding of the mechanisms of circadian vision in other vertebrate species including humans.
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Affiliation(s)
- Lei Li
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana
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22
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Felder-Schmittbuhl MP, Buhr ED, Dkhissi-Benyahya O, Hicks D, Peirson SN, Ribelayga CP, Sandu C, Spessert R, Tosini G. Ocular Clocks: Adapting Mechanisms for Eye Functions and Health. Invest Ophthalmol Vis Sci 2019; 59:4856-4870. [PMID: 30347082 PMCID: PMC6181243 DOI: 10.1167/iovs.18-24957] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Vision is a highly rhythmic function adapted to the extensive changes in light intensity occurring over the 24-hour day. This adaptation relies on rhythms in cellular and molecular processes, which are orchestrated by a network of circadian clocks located within the retina and in the eye, synchronized to the day/night cycle and which, together, fine-tune detection and processing of light information over the 24-hour period and ensure retinal homeostasis. Systematic or high throughput studies revealed a series of genes rhythmically expressed in the retina, pointing at specific functions or pathways under circadian control. Conversely, knockout studies demonstrated that the circadian clock regulates retinal processing of light information. In addition, recent data revealed that it also plays a role in development as well as in aging of the retina. Regarding synchronization by the light/dark cycle, the retina displays the unique property of bringing together light sensitivity, clock machinery, and a wide range of rhythmic outputs. Melatonin and dopamine play a particular role in this system, being both outputs and inputs for clocks. The retinal cellular complexity suggests that mechanisms of regulation by light are diverse and intricate. In the context of the whole eye, the retina looks like a major determinant of phase resetting for other tissues such as the retinal pigmented epithelium or cornea. Understanding the pathways linking the cell-specific molecular machineries to their cognate outputs will be one of the major challenges for the future.
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Affiliation(s)
- Marie-Paule Felder-Schmittbuhl
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Ethan D Buhr
- Department of Ophthalmology, University of Washington Medical School, Seattle, Washington, United States
| | - Ouria Dkhissi-Benyahya
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, Bron, France
| | - David Hicks
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Christophe P Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, United States
| | - Cristina Sandu
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives (UPR 3212), Strasbourg, France
| | - Rainer Spessert
- Institute of Functional and Clinical Anatomy, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gianluca Tosini
- Neuroscience Institute and Department of Pharmacology & Toxicology, Morehouse School of Medicine, Atlanta, Georgia, United States
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23
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Alcamí P, Pereda AE. Beyond plasticity: the dynamic impact of electrical synapses on neural circuits. Nat Rev Neurosci 2019; 20:253-271. [DOI: 10.1038/s41583-019-0133-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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24
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O'Brien J, Bloomfield SA. Plasticity of Retinal Gap Junctions: Roles in Synaptic Physiology and Disease. Annu Rev Vis Sci 2018; 4:79-100. [DOI: 10.1146/annurev-vision-091517-034133] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrical synaptic transmission via gap junctions underlies direct and rapid neuronal communication in the central nervous system. The diversity of functional roles played by electrical synapses is perhaps best exemplified in the vertebrate retina, in which gap junctions are expressed by each of the five major neuronal types. These junctions are highly plastic; they are dynamically regulated by ambient illumination and circadian rhythms acting through light-activated neuromodulators. The networks formed by electrically coupled neurons provide plastic, reconfigurable circuits positioned to play key and diverse roles in the transmission and processing of visual information at every retinal level. Recent work indicates gap junctions also play a role in the progressive cell death and aberrant activity seen in various pathological conditions of the retina. Gap junctions thus form potential targets for novel neuroprotective therapies in the treatment of neurodegenerative retinal diseases such as glaucoma and ischemic retinopathies.
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Affiliation(s)
- John O'Brien
- Department of Ophthalmology and Visual Science, University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Stewart A. Bloomfield
- Department of Biological and Vision Sciences, State University of New York College of Optometry, New York, NY 10036, USA
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25
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Welzel G, Schuster S. Long-term potentiation in an innexin-based electrical synapse. Sci Rep 2018; 8:12579. [PMID: 30135467 PMCID: PMC6105662 DOI: 10.1038/s41598-018-30966-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 08/09/2018] [Indexed: 11/08/2022] Open
Abstract
Electrical synapses are formed by two unrelated gap junction protein families, the primordial innexins (invertebrates) or the connexins (vertebrates). Although molecularly different, innexin- and connexin-based electrical synapses are strikingly similar in their membrane topology. However, it remains unclear if this similarity extends also to more sophisticated functions such as long-term potentiation which is only known in connexin-based synapses. Here we show that this capacity is not unique to connexin-based synapses. Using a method that allowed us to quantitatively measure gap-junction conductance we provide the first and unequivocal evidence of long-term potentiation in an innexin-based electrical synapse. Our findings suggest that long-term potentiation is a property that has likely existed already in ancestral gap junctions. They therefore could provide a highly potent system to dissect shared molecular mechanisms of electrical synapse plasticity.
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Affiliation(s)
- Georg Welzel
- Department of Animal Physiology, University of Bayreuth, 95440, Bayreuth, Germany.
| | - Stefan Schuster
- Department of Animal Physiology, University of Bayreuth, 95440, Bayreuth, Germany.
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26
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Aasen T, Johnstone S, Vidal-Brime L, Lynn KS, Koval M. Connexins: Synthesis, Post-Translational Modifications, and Trafficking in Health and Disease. Int J Mol Sci 2018; 19:ijms19051296. [PMID: 29701678 PMCID: PMC5983588 DOI: 10.3390/ijms19051296] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/20/2018] [Accepted: 04/21/2018] [Indexed: 02/06/2023] Open
Abstract
Connexins are tetraspan transmembrane proteins that form gap junctions and facilitate direct intercellular communication, a critical feature for the development, function, and homeostasis of tissues and organs. In addition, a growing number of gap junction-independent functions are being ascribed to these proteins. The connexin gene family is under extensive regulation at the transcriptional and post-transcriptional level, and undergoes numerous modifications at the protein level, including phosphorylation, which ultimately affects their trafficking, stability, and function. Here, we summarize these key regulatory events, with emphasis on how these affect connexin multifunctionality in health and disease.
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Affiliation(s)
- Trond Aasen
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
| | - Scott Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, P.O. Box 801394, Charlottesville, VI 22908, USA.
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TT, UK.
| | - Laia Vidal-Brime
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
| | - K Sabrina Lynn
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Michael Koval
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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27
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Hoshi H, Sato F. The morphological characterization of orientation-biased displaced large-field ganglion cells in the central part of goldfish retina. J Comp Neurol 2018; 526:243-261. [PMID: 28921532 DOI: 10.1002/cne.24331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/01/2017] [Accepted: 09/04/2017] [Indexed: 11/10/2022]
Abstract
The vertebrate retina has about 30 subtypes of ganglion cells. Each ganglion cell receives synaptic inputs from specific types of bipolar and amacrine cells ramifying at the same depth of the inner plexiform layer (IPL), each of which is thought to process a specific aspect of visual information. Here, we identified one type of displaced ganglion cell in the goldfish retina which had a large and elongated dendritic field. As a population, all of these ganglion cells were oriented in the horizontal axis and perpendicular to the dorsal-ventral axis of the goldfish eye in the central part of retina. This ganglion cell has previously been classified as Type 1.2. However, the circuit elements which synapse with this ganglion cell are not yet characterized. We found that this displaced ganglion cell was directly tracer-coupled only with homologous ganglion cells at sites containing Cx35/36 puncta. We further illustrated that the processes of dopaminergic neurons often terminated next to intersections between processes of ganglion cells, close to where dopamine D1 receptors were localized. Finally, we showed that Mb1 ON bipolar cells had ribbon synapses in the axonal processes passing through the IPL and made ectopic synapses with this displaced ganglion cell that stratified into stratum 1 of the IPL. These results suggest that the displaced ganglion cell may synapse with both Mb1 cells using ectopic ribbon synapses and OFF cone bipolar cells with regular ribbon synapses in the IPL to function in both scotopic and photopic light conditions.
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Affiliation(s)
- Hideo Hoshi
- Department of Anatomy, School of Medicine, Toho University, Tokyo, Japan
| | - Fumi Sato
- Department of Anatomy, School of Medicine, Toho University, Tokyo, Japan
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28
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Noel NCL, Allison WT. Connectivity of cone photoreceptor telodendria in the zebrafish retina. J Comp Neurol 2017; 526:609-625. [PMID: 29127712 DOI: 10.1002/cne.24354] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Revised: 10/26/2017] [Accepted: 10/27/2017] [Indexed: 01/29/2023]
Abstract
The connectivity amongst photoreceptors is critical to their function, as it underpins lateral inhibition and effective translation of stimuli into neural signals. Despite much work characterizing second-order interneurons in the outer retina, the synapses directly connecting photoreceptors have often been overlooked. Telodendria are fine processes that connect photoreceptor pedicles. They have been observed in diverse vertebrate groups, yet their roles in vision remain speculative. Here, we visualize telodendria via fluorescent protein expression in photoreceptor subtypes. We characterized short wavelength cone telodendria in adult and larval zebrafish retina. Additionally, in the larval retina, we investigated rod telodendria and UV cone telodendria in mutant and transgenic retinas with altered complements of cone types. In the adult retina, telodendria are twice as abundant and branch almost twice as often on blue cones compared to UV cones. Pedicles of neighboring UV and blue cones typically converge into contiguous pairs, despite the regular spacing of their cell bodies. In contrast to adults, larval UV cone telodendria are more numerous (1.3 times) than blue cone telodendria. UV cone telodendria are not detectably affected by ablation of blue cones, and are reduced twofold in mutant larval retina with few UV cones. We thus saw no evidence that telodendria increase in number in the absence of their typical cellular neighbors. We also found that larval rod telodendria are less abundant than short wavelength cone telodendria. In summary, we describe the development and morphology of zebrafish photoreceptor synaptic connectivity toward appreciating the function of telodendria in visual signal processing.
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Affiliation(s)
- Nicole C L Noel
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - W Ted Allison
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, Alberta, Canada
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
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29
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O'Brien J. Design principles of electrical synaptic plasticity. Neurosci Lett 2017; 695:4-11. [PMID: 28893590 DOI: 10.1016/j.neulet.2017.09.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/09/2017] [Accepted: 09/01/2017] [Indexed: 01/19/2023]
Abstract
Essentially all animals with nervous systems utilize electrical synapses as a core element of communication. Electrical synapses, formed by gap junctions between neurons, provide rapid, bidirectional communication that accomplishes tasks distinct from and complementary to chemical synapses. These include coordination of neuron activity, suppression of voltage noise, establishment of electrical pathways that define circuits, and modulation of high order network behavior. In keeping with the omnipresent demand to alter neural network function in order to respond to environmental cues and perform tasks, electrical synapses exhibit extensive plasticity. In some networks, this plasticity can have dramatic effects that completely remodel circuits or remove the influence of certain cell types from networks. Electrical synaptic plasticity occurs on three distinct time scales, ranging from milliseconds to days, with different mechanisms accounting for each. This essay highlights principles that dictate the properties of electrical coupling within networks and the plasticity of the electrical synapses, drawing examples extensively from retinal networks.
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Affiliation(s)
- John O'Brien
- McGovern Medical School, The University of Texas Health Science Center at Houston, 6431 Fannin St., MSB 7.024, Houston, TX 77030, USA.
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30
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Miller AC, Whitebirch AC, Shah AN, Marsden KC, Granato M, O'Brien J, Moens CB. A genetic basis for molecular asymmetry at vertebrate electrical synapses. eLife 2017; 6. [PMID: 28530549 PMCID: PMC5462537 DOI: 10.7554/elife.25364] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 05/20/2017] [Indexed: 01/18/2023] Open
Abstract
Neural network function is based upon the patterns and types of connections made between neurons. Neuronal synapses are adhesions specialized for communication and they come in two types, chemical and electrical. Communication at chemical synapses occurs via neurotransmitter release whereas electrical synapses utilize gap junctions for direct ionic and metabolic coupling. Electrical synapses are often viewed as symmetrical structures, with the same components making both sides of the gap junction. By contrast, we show that a broad set of electrical synapses in zebrafish, Danio rerio, require two gap-junction-forming Connexins for formation and function. We find that one Connexin functions presynaptically while the other functions postsynaptically in forming the channels. We also show that these synapses are required for the speed and coordination of escape responses. Our data identify a genetic basis for molecular asymmetry at vertebrate electrical synapses and show they are required for appropriate behavioral performance. DOI:http://dx.doi.org/10.7554/eLife.25364.001
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Affiliation(s)
- Adam C Miller
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Alex C Whitebirch
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Arish N Shah
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Kurt C Marsden
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, United States
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, United States
| | - John O'Brien
- Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Sciences Center at Houston, Houston, United States
| | - Cecilia B Moens
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
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31
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Miller AC, Pereda AE. The electrical synapse: Molecular complexities at the gap and beyond. Dev Neurobiol 2017; 77:562-574. [PMID: 28170151 DOI: 10.1002/dneu.22484] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022]
Abstract
Gap junctions underlie electrical synaptic transmission between neurons. Generally perceived as simple intercellular channels, "electrical synapses" have demonstrated to be more functionally sophisticated and structurally complex than initially anticipated. Electrical synapses represent an assembly of multiple molecules, consisting of channels, adhesion complexes, scaffolds, regulatory machinery, and trafficking proteins, all required for their proper function and plasticity. Additionally, while electrical synapses are often viewed as strictly symmetric structures, emerging evidence has shown that some components forming electrical synapses can be differentially distributed at each side of the junction. We propose that the molecular complexity and asymmetric distribution of proteins at the electrical synapse provides rich potential for functional diversity. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 562-574, 2017.
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Affiliation(s)
- Adam C Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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32
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Siu RCF, Smirnova E, Brown CA, Zoidl C, Spray DC, Donaldson LW, Zoidl G. Structural and Functional Consequences of Connexin 36 (Cx36) Interaction with Calmodulin. Front Mol Neurosci 2016; 9:120. [PMID: 27917108 PMCID: PMC5114276 DOI: 10.3389/fnmol.2016.00120] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 10/26/2016] [Indexed: 11/26/2022] Open
Abstract
Functional plasticity of neuronal gap junctions involves the interaction of the neuronal connexin36 with calcium/calmodulin-dependent kinase II (CaMKII). The important relationship between Cx36 and CaMKII must also be considered in the context of another protein partner, Ca2+ loaded calmodulin, binding an overlapping site in the carboxy-terminus of Cx36. We demonstrate that CaM and CaMKII binding to Cx36 is calcium-dependent, with Cx36 able to engage with CaM outside of the gap junction plaque. Furthermore, Ca2+ loaded calmodulin activates Cx36 channels, which is different to other connexins. The NMR solution structure demonstrates that CaM binds Cx36 in its characteristic compact state with major hydrophobic contributions arising from W277 at anchor position 1 and V284 at position 8 of Cx36. Our results establish Cx36 as a hub binding Ca2+ loaded CaM and they identify this interaction as a critical step with implications for functions preceding the initiation of CaMKII mediated plasticity at electrical synapses.
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Affiliation(s)
| | | | | | - Christiane Zoidl
- Biology Program, York University, TorontoON, Canada
- Psychology Program, York University, TorontoON, Canada
| | - David C. Spray
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New YorkNY, USA
| | | | - Georg Zoidl
- Biology Program, York University, TorontoON, Canada
- Psychology Program, York University, TorontoON, Canada
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33
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Vila A, Whitaker CM, O'Brien J. Membrane-associated guanylate kinase scaffolds organize a horizontal cell synaptic complex restricted to invaginating contacts with photoreceptors. J Comp Neurol 2016; 525:850-867. [PMID: 27558197 DOI: 10.1002/cne.24101] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/02/2016] [Accepted: 08/15/2016] [Indexed: 12/21/2022]
Abstract
Synaptic processes and plasticity of synapses are mediated by large suites of proteins. In most cases, many of these proteins are tethered together by synaptic scaffold proteins. Scaffold proteins have a large number and typically a variety of protein interaction domains that allow many different proteins to be assembled into functional complexes. Because each scaffold protein has a different set of protein interaction domains and a unique set of interacting partners, the presence of synaptic scaffolds can provide insight into the molecular mechanisms that regulate synaptic processes. In studies of rabbit retina, we found SAP102 and Chapsyn110 selectively localized in the tips of B-type horizontal cell processes, where they contact cone and rod photoreceptors. We further identified some known SAP102 binding partners, kainate receptor GluR6/7 and inward rectifier potassium channel Kir2.1, closely associated with SAP102 in photoreceptor invaginations. The kainate receptor occupies a position distinct from that of the majority of AMPA receptors that dominate the horizontal cell postsynaptic response. GluR6/7 and Kir2.1 presumably are involved in synaptic processes that govern cell-to-cell communication and could both contribute in different ways to synaptic currents that mediate feedback signaling. Notably, we failed to find evidence for the presence of Cx57 or Cx59 that might be involved in ephaptic feedback signaling in this complex. The presence of SAP102 and its binding partners in both cone and rod invaginating synapses suggests that whatever mechanism is supported by this protein complex is present in both types of photoreceptors. J. Comp. Neurol. 525:850-867, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Alejandro Vila
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas, 77030.,University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas, 77030
| | - Christopher M Whitaker
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas, 77030
| | - John O'Brien
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas, 77030.,University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas, 77030
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34
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Yoshikawa S, Vila A, Segelken J, Lin YP, Mitchell CK, Nguyen D, O'Brien J. Zebrafish connexin 79.8 (Gja8a): A lens connexin used as an electrical synapse in some neurons. Dev Neurobiol 2016; 77:548-561. [PMID: 27402207 DOI: 10.1002/dneu.22418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/23/2016] [Accepted: 07/05/2016] [Indexed: 11/07/2022]
Abstract
In the mammalian central nervous system, a remarkably small number of connexins is used in electrical synapses, with the majority formed from Cx36. A larger number has been detected in teleosts, with some seeming to serve restricted roles. Here, we report the discovery of a new connexin expressed in the zebrafish lens and a limited set of neurons. Zebrafish cx79.8 (gja8a), previously annotated incorrectly as cx50.5 based on a partial cDNA sequence, is a homologue of mammalian Cx50 (Gja8). We examined its expression through transgenic promoter-reporter constructs, in situ hybridization, and immunolabeling, and examined regulation of coupling in transfected HeLa cells. cx79.8 was expressed most strongly in the lens, but expression was also found in several groups of neurons in the cerebellum and related areas at the midbrain-hindbrain boundary, in cone photoreceptors, and in neurons in the retinal inner nuclear and ganglion cell layers. Labeling in the retina with antibodies against two C-terminal epitopes revealed numerous small punctate spots in the inner plexiform layer and along the somata of cones. Abundant gap junctions were labeled in the outer 1/3 of the lens, but were absent from the center, suggesting that the epitopes or the entire protein was absent from the center. Cx79.8 tracer coupling was strongly regulated by phosphorylation, and was extremely low in control conditions in HeLa cells due to protein phosphatase 2A activity. These properties allow coupling to be strongly restricted in situ, a frequently observed property for electrical synapses. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 548-561, 2017.
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Affiliation(s)
- Shunichi Yoshikawa
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas
| | - Alejandro Vila
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas.,University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas
| | - Jasmin Segelken
- Visual Neuroscience, Faculty of Medicine and Health Sciences, University of Oldenburg, Oldenburg, Germany
| | - Ya-Ping Lin
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas
| | - Cheryl K Mitchell
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas
| | - Duc Nguyen
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas
| | - John O'Brien
- Richard S. Ruiz M.D., Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, Texas.,University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas
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35
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Pogoda K, Kameritsch P, Retamal MA, Vega JL. Regulation of gap junction channels and hemichannels by phosphorylation and redox changes: a revision. BMC Cell Biol 2016; 17 Suppl 1:11. [PMID: 27229925 PMCID: PMC4896245 DOI: 10.1186/s12860-016-0099-3] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Post-translational modifications of connexins play an important role in the regulation of gap junction and hemichannel permeability. The prerequisite for the formation of functional gap junction channels is the assembly of connexin proteins into hemichannels and their insertion into the membrane. Hemichannels can affect cellular processes by enabling the passage of signaling molecules between the intracellular and extracellular space. For the intercellular communication hemichannels from one cell have to dock to its counterparts on the opposing membrane of an adjacent cell to allow the transmission of signals via gap junctions from one cell to the other. The controlled opening of hemichannels and gating properties of complete gap junctions can be regulated via post-translational modifications of connexins. Not only channel gating, but also connexin trafficking and assembly into hemichannels can be affected by post-translational changes. Recent investigations have shown that connexins can be modified by phosphorylation/dephosphorylation, redox-related changes including effects of nitric oxide (NO), hydrogen sulfide (H2S) or carbon monoxide (CO), acetylation, methylation or ubiquitination. Most of the connexin isoforms are known to be phosphorylated, e.g. Cx43, one of the most studied connexin at all, has 21 reported phosphorylation sites. In this review, we provide an overview about the current knowledge and relevant research of responsible kinases, connexin phosphorylation sites and reported effects on gap junction and hemichannel regulation. Regarding the effects of oxidants we discuss the role of NO in different cell types and tissues and recent studies about modifications of connexins by CO and H2S.
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Affiliation(s)
- Kristin Pogoda
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany. .,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, München, Germany.
| | - Petra Kameritsch
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, München, Germany
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - José L Vega
- Experimental Physiology Laboratory (EPhyL), Antofagasta Institute, Universidad de Antofagasta, Antofagasta, Chile
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36
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Abstract
Electrical synapses are an omnipresent feature of nervous systems, from the simple nerve nets of cnidarians to complex brains of mammals. Formed by gap junction channels between neurons, electrical synapses allow direct transmission of voltage signals between coupled cells. The relative simplicity of this arrangement belies the sophistication of these synapses. Coupling via electrical synapses can be regulated by a variety of mechanisms on times scales ranging from milliseconds to days, and active properties of the coupled neurons can impart emergent properties such as signal amplification, phase shifts and frequency-selective transmission. This article reviews the biophysical characteristics of electrical synapses and some of the core mechanisms that control their plasticity in the vertebrate central nervous system.
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Affiliation(s)
- Sebastian Curti
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
| | - John O'Brien
- Department of Ophthalmology & Visual Science, University of Texas Health Science Center, Houston, TX, USA.
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37
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Firsov ML, Astakhova LA. The Role of Dopamine in Controlling Retinal Photoreceptor Function in Vertebrates. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/s11055-015-0210-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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38
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Wang HY, Lin YP, Mitchell CK, Ram S, O'Brien J. Two-color fluorescent analysis of connexin 36 turnover: relationship to functional plasticity. J Cell Sci 2015; 128:3888-97. [PMID: 26359298 PMCID: PMC4647165 DOI: 10.1242/jcs.162586] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 09/04/2015] [Indexed: 01/14/2023] Open
Abstract
Gap junctions formed of connexin 36 (Cx36, also known as Gjd2) show tremendous functional plasticity on several time scales. Changes in connexin phosphorylation modify coupling in minutes through an order of magnitude, but recent studies also imply involvement of connexin turnover in regulating cell-cell communication. We utilized Cx36 with an internal HaloTag to study Cx36 turnover and trafficking in cultured cells. Irreversible, covalent pulse-chase labeling with fluorescent HaloTag ligands allowed clear discrimination of newly formed and pre-existing Cx36. Cx36 in junctional plaques turned over with a half-life of 3.1 h, and the turnover rate was unchanged by manipulations of protein kinase A (PKA) activity. In contrast, changes in PKA activity altered coupling within 20 min. New Cx36 in cargo vesicles was added directly to existing gap junctions and newly made Cx36 was not confined to points of addition, but diffused throughout existing gap junctions. Existing connexins also diffused into photobleached areas with a half-time of less than 2 s. In conclusion, studies of Cx36-HaloTag revealed novel features of connexin trafficking and demonstrated that phosphorylation-based changes in coupling occur on a different time scale than turnover.
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Affiliation(s)
- Helen Yanran Wang
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Ya-Ping Lin
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Cheryl K Mitchell
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Sripad Ram
- Carl Zeiss Microscopy LLC, Thornwood, NY 10594, USA
| | - John O'Brien
- Ruiz Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
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Bolte P, Herrling R, Dorgau B, Schultz K, Feigenspan A, Weiler R, Dedek K, Janssen-Bienhold U. Expression and Localization of Connexins in the Outer Retina of the Mouse. J Mol Neurosci 2015; 58:178-92. [PMID: 26453550 DOI: 10.1007/s12031-015-0654-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 09/08/2015] [Indexed: 01/30/2023]
Abstract
The identification of the proteins that make up the gap junction channels between rods and cones is of crucial importance to understand the functional role of photoreceptor coupling within the retinal network. In vertebrates, connexin proteins constitute the structural components of gap junction channels. Connexin36 is known to be expressed in cones whereas extensive investigations have failed to identify the corresponding connexin expressed in rods. Using immunoelectron microscopy, we demonstrate that connexin36 (Cx36) is present in gap junctions of cone but not rod photoreceptors in the mouse retina. To identify the rod connexin, we used nested reverse transcriptase polymerase chain reaction and tested retina and photoreceptor samples for messenger RNA (mRNA) expression of all known connexin genes. In addition to connexin36, we detected transcripts for connexin32, connexin43, connexin45, connexin50, and connexin57 in photoreceptor samples. Immunohistochemistry showed that connexin43, connexin45, connexin50, and connexin57 proteins are expressed in the outer plexiform layer. However, none of these connexins was detected at gap junctions between rods and cones as a counterpart of connexin36. Therefore, the sought-after rod protein must be either an unknown connexin sequence, a connexin36 splice product not detected by our antibodies, or a protein from a further gap junction protein family.
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Affiliation(s)
- Petra Bolte
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Animal Navigation, University of Oldenburg, 26111, Oldenburg, Germany
| | - Regina Herrling
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany
| | - Birthe Dorgau
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
| | - Konrad Schultz
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany
| | - Andreas Feigenspan
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Animal Physiology, FAU Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Reto Weiler
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany
| | - Karin Dedek
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany. .,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany.
| | - Ulrike Janssen-Bienhold
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany. .,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany.
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Moore KB, O'Brien J. Connexins in neurons and glia: targets for intervention in disease and injury. Neural Regen Res 2015; 10:1013-7. [PMID: 26330808 PMCID: PMC4541216 DOI: 10.4103/1673-5374.160092] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2015] [Indexed: 01/13/2023] Open
Abstract
Both neurons and glia throughout the central nervous system are organized into networks by gap junctions. Among glia, gap junctions facilitate metabolic homeostasis and intercellular communication. Among neurons, gap junctions form electrical synapses that function primarily for communication. However, in neurodegenerative states due to disease or injury gap junctions may be detrimental to survival. Electrical synapses may facilitate hyperactivity and bystander killing among neurons, while gap junction hemichannels in glia may facilitate inflammatory signaling and scar formation. Advances in understanding mechanisms of plasticity of electrical synapses and development of molecular therapeutics to target glial gap junctions and hemichannels offer new hope to pharmacologically limit neuronal degeneration and enhance recovery.
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Affiliation(s)
- Keith B Moore
- Richard S. Ruiz, M.D. Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, TX, USA
| | - John O'Brien
- Richard S. Ruiz, M.D. Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, TX, USA ; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA
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41
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Activation of Group I and Group II Metabotropic Glutamate Receptors Causes LTD and LTP of Electrical Synapses in the Rat Thalamic Reticular Nucleus. J Neurosci 2015; 35:7616-25. [PMID: 25972185 DOI: 10.1523/jneurosci.3688-14.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Compared with the extensive characterization of chemical synaptic plasticity, electrical synaptic plasticity remains poorly understood. Electrical synapses are strong and prevalent among the GABAergic neurons of the rodent thalamic reticular nucleus. Using paired whole-cell recordings, we show that activation of Group I metabotropic glutamate receptors (mGluRs) induces long-term depression of electrical synapses. Conversely, activation of the Group II mGluR, mGluR3, induces long-term potentiation of electrical synapses. By testing downstream targets, we show that modifications induced by both mGluR groups converge on the same signaling cascade--adenylyl cyclase to cAMP to protein kinase A--but with opposing effects. Furthermore, the magnitude of modification is inversely correlated to baseline coupling strength. Thus, electrical synapses, like their chemical counterparts, undergo both strengthening and weakening forms of plasticity, which should play a significant role in thalamocortical function.
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42
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Deming JD, Shin JA, Lim K, Lee EJ, Van Craenenbroeck K, Craft CM. Dopamine receptor D4 internalization requires a beta-arrestin and a visual arrestin. Cell Signal 2015; 27:2002-13. [PMID: 26169958 DOI: 10.1016/j.cellsig.2015.06.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 06/30/2015] [Indexed: 11/25/2022]
Abstract
PURPOSE The G-protein coupled receptor (GPCR) Dopamine Receptor D4 (DRD4) plays an essential role in cAMP regulation and gap junctional coupling in the photoreceptors, where DRD4 expression is under circadian control. Previous in vitro transfection studies of human DRD4 desensitization have reported that DRD4 is not internalized upon dopamine stimulation when beta-arrestin is co-transfected with DRD4. We hypothesized that the visual arrestins, ARR1 and ARR4, play a modulatory role in DRD4 desensitization in the photoreceptors. METHODS To test this hypothesis, immunohistochemistry analysis of mouse retinas was used to determine the cellular localization of beta-arrestins and DRD4 in photoreceptors. In vitro studies were performed in HEK293T cells transiently transfected with human DRD4 and arrestins. First, co-immunoprecipitation experiments were executed to test protein-protein interactions and to investigate the effect of dopamine stimulation. Second, immunohistochemistry analysis was implemented to study DRD4 internalization and translocation of ARR4. RESULTS Immunohistochemistry studies of mouse retinas confirmed the expression of beta-arrestin 2, ARR1 and ARR4, as well as DRD4 in mouse cone photoreceptor inner segments. Co-immunoprecipitation experiments revealed a dopamine-dependent protein-protein interaction between human DRD4 and ARR4. In vitro internalization experiments showed that no detectable internalization of DRD4 was observed with any single arrestin co-transfected. However, a dopamine-dependent internalization of DRD4 was observed with three out of six sets of two arrestins co-transfected with DRD4. Each of these pairs of arrestins contained one visual arrestin and one beta-arrestin, and no internalization was observed with either two visual arrestins or two beta-arrestins. Additional time-course experiments revealed that in vitro, ARR4 translocates to co-localize with DRD4 at the plasma membrane in response to 30min of dopamine stimulation. CONCLUSIONS The results have functional implications and we hypothesize that the desensitization and internalization of DRD4 in photoreceptors are synergistically mediated by both visual and beta-arrestins. These results are additionally unique because they demonstrate for the first time that at least one G-protein coupled receptor, DRD4, requires two arrestins for desensitization and internalization, and opens up the possibility that other G-protein coupled receptors may require more than one arrestin for desensitization and/or internalization.
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Affiliation(s)
- Janise D Deming
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Annex 215, Los Angeles, CA 90033, USA.
| | - Jung-A Shin
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Annex 215, Los Angeles, CA 90033, USA; Department of Anatomy, School of Medicine, Ewha Womans University, Seoul 158-710, Republic of Korea.
| | - Kayleen Lim
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Annex 215, Los Angeles, CA 90033, USA.
| | - Eun-Jin Lee
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Annex 215, Los Angeles, CA 90033, USA; Department of Biomedical Engineering, University of Southern California Viterbi School of Engineering, 1042 Downey Way, Los Angeles, CA 90089-1111, USA.
| | - Kathleen Van Craenenbroeck
- Laboratory of GPCR Expression and Signal Transduction (L-GEST), Ghent University-UGent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium.
| | - Cheryl Mae Craft
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Annex 215, Los Angeles, CA 90033, USA; Department of Cell & Neurobiology, Keck School of Medicine of the University of Southern California, 2250 Alcazar Street, Clinical Science Center 135H, Los Angeles, CA 90033, USA.
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43
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Jin NG, Chuang AZ, Masson PJ, Ribelayga CP. Rod electrical coupling is controlled by a circadian clock and dopamine in mouse retina. J Physiol 2015; 593:1597-631. [PMID: 25616058 PMCID: PMC4386962 DOI: 10.1113/jphysiol.2014.284919] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 01/19/2015] [Indexed: 11/08/2022] Open
Abstract
Rod single-photon responses are critical for vision in dim light. Electrical coupling via gap junction channels shapes the light response properties of vertebrate photoreceptors, but the regulation of rod coupling and its impact on the single-photon response have remained unclear. To directly address these questions, we developed a perforated patch-clamp recording technique and recorded from single rod inner segments in isolated intact neural mouse retinae, maintained by superfusion. Experiments were conducted at different times of the day or under constant environmental conditions, at different times across the circadian cycle. We show that rod electrical coupling is regulated by a circadian clock and dopamine, so that coupling is weak during the day and strong at night. Altogether, patch-clamp recordings of single-photon responses in mouse rods, tracer coupling, receptive field measurements and pharmacological manipulations of gap junction and dopamine receptor activity provide compelling evidence that rod coupling is modulated in a circadian manner. These data are consistent with computer modelling. At night, single-photon responses are smaller due to coupling, but the signal-to-noise ratio for a dim (multiphoton) light response is increased at night because of signal averaging between coupled rods.
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Affiliation(s)
- Nan Ge Jin
- Ruiz Department of Ophthalmology and Visual Science, Medical School, The University of Texas Health Science Centre at Houston6431 Fannin Street, Suite MSB 7.024, Houston, TX, 77030, USA
| | - Alice Z Chuang
- Ruiz Department of Ophthalmology and Visual Science, Medical School, The University of Texas Health Science Centre at Houston6431 Fannin Street, Suite MSB 7.024, Houston, TX, 77030, USA
| | - Philippe J Masson
- Department of Mechanical Engineering, Cullen College of Engineering, University of HoustonN207 Engineering Building 1, Suite W204, Houston, TX, 77204, USA
| | - Christophe P Ribelayga
- Ruiz Department of Ophthalmology and Visual Science, Medical School, The University of Texas Health Science Centre at Houston6431 Fannin Street, Suite MSB 7.024, Houston, TX, 77030, USA
- Graduate School of Biomedical Sciences, The University of Texas Health Science Centre at Houston, 6767 Bertner Avenue, Mitchell BuildingBSRB Suite 3.8344, Houston, TX, 77030, USA
- Neuroscience Graduate Program, The University of Texas Health Science Centre at Houston, Medical School6431 Fannin Street, Suite MSB 7.262, Houston, TX, 77030, USA
- Neuroscience Research Centre, The University of Texas Health Science Centre at HoustonHouston, 6431 Fannin Street, Suite MSB 7.046, TX, 77030, USA
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44
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Regulation of photoreceptor gap junction phosphorylation by adenosine in zebrafish retina. Vis Neurosci 2015; 31:237-43. [PMID: 24844306 DOI: 10.1017/s095252381300062x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Electrical coupling of photoreceptors through gap junctions suppresses voltage noise, routes rod signals into cone pathways, expands the dynamic range of rod photoreceptors in high scotopic and mesopic illumination, and improves detection of contrast and small stimuli. In essentially all vertebrates, connexin 35/36 (gene homologs Cx36 in mammals, Cx35 in other vertebrates) is the major gap junction protein observed in photoreceptors, mediating rod-cone, cone-cone, and possibly rod-rod communication. Photoreceptor coupling is dynamically controlled by the day/night cycle and light/dark adaptation, and is directly correlated with phosphorylation of Cx35/36 at two sites, serine110 and serine 276/293 (homologous sites in teleost fish and mammals, respectively). Activity of protein kinase A (PKA) plays a key role during this process. Previous studies have shown that activation of dopamine D4 receptors on photoreceptors inhibits adenylyl cyclase, down-regulates cAMP and PKA activity, and leads to photoreceptor uncoupling, imposing the daytime/light condition. In this study, we explored the role of adenosine, a nighttime signal with a high extracellular concentration at night and a low concentration in the day, in regulating photoreceptor coupling by examining photoreceptor Cx35 phosphorylation in zebrafish retina. Adenosine enhanced photoreceptor Cx35 phosphorylation in daytime, but with a complex dose-response curve. Selective pharmacological manipulations revealed that adenosine A2a receptors provide a potent positive drive to phosphorylate photoreceptor Cx35 under the influence of endogenous adenosine at night. A2a receptors can be activated in the daytime as well by micromolar exogenous adenosine. However, the higher affinity adenosine A1 receptors are also present and have an antagonistic though less potent effect. Thus, the nighttime/darkness signal adenosine provides a net positive drive on Cx35 phosphorylation at night, working in opposition to dopamine to regulate photoreceptor coupling via a push-pull mechanism. However, the lower concentration of adenosine present in the daytime actually reinforces the dopamine signal through action on the A1 receptor.
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45
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Zhang Z, Li H, Liu X, O’Brien J, Ribelayga CP. Circadian clock control of connexin36 phosphorylation in retinal photoreceptors of the CBA/CaJ mouse strain. Vis Neurosci 2015; 32:E009. [PMID: 26241696 PMCID: PMC4760741 DOI: 10.1017/s0952523815000061] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The gap-junction-forming protein connexin36 (Cx36) represents the anatomical substrate of photoreceptor electrical coupling in mammals. The strength of coupling is directly correlated to the phosphorylation of Cx36 at two regulatory sites: Ser110 and Ser293. Our previous work demonstrated that the extent of biotinylated tracer coupling between photoreceptor cells, which provides an index of the extent of electrical coupling, depends on the mouse strain. In the C57Bl/6J strain, light or dopamine reduces tracer coupling and Cx36 phosphorylation in photoreceptors. Conversely, darkness or a dopaminergic antagonist increases tracer coupling and Cx36 phosphorylation, regardless of the daytime. In the CBA/CaJ strain, photoreceptor tracer coupling is not only regulated by light and dopamine, but also by a circadian clock, a type of oscillator with a period close to 24 h and intrinsic to the retina, so that under prolonged dark-adapted conditions tracer coupling is broader at night compared to daytime. In the current study, we examined whether the modulation of photoreceptor coupling by a circadian clock in the CBA/CaJ mouse photoreceptors reflected a change in Cx36 protein expression and/or phosphorylation. We found no significant change in Cx36 expression or in the number of Cx36 gap junction among the conditions examined. However, we found that Cx36 phosphorylation is higher under dark-adapted conditions at night than in the daytime, and is the lowest under prolonged illumination at any time of the day/night cycle. Our observations are consistent with the view that the circadian clock regulation of photoreceptor electrical coupling is mouse strain-dependent and highlights the critical position of Cx36 phosphorylation in the control of photoreceptor coupling.
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Affiliation(s)
- Zhijing Zhang
- Richard S. Ruiz Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Medical School, Houston, TX
| | - Hongyan Li
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Medical School, Houston, TX
| | - Xiaoqin Liu
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Medical School, Houston, TX
| | - John O’Brien
- Richard S. Ruiz Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Medical School, Houston, TX
- Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, TX
- Program in Neuroscience, Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, TX
- Neuroscience Research Center, The University of Texas Health Science Center at Houston, Houston, TX
| | - Christophe P. Ribelayga
- Richard S. Ruiz Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Medical School, Houston, TX
- Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, TX
- Program in Neuroscience, Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, TX
- Neuroscience Research Center, The University of Texas Health Science Center at Houston, Houston, TX
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Palacios-Muñoz A, Escobar MJ, Vielma A, Araya J, Astudillo A, Valdivia G, García IE, Hurtado J, Schmachtenberg O, Martínez AD, Palacios AG. Role of connexin channels in the retinal light response of a diurnal rodent. Front Cell Neurosci 2014; 8:249. [PMID: 25202238 PMCID: PMC4142540 DOI: 10.3389/fncel.2014.00249] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 08/05/2014] [Indexed: 01/02/2023] Open
Abstract
Several studies have shown that connexin channels play an important role in retinal neural coding in nocturnal rodents. However, the contribution of these channels to signal processing in the retina of diurnal rodents remains unclear. To gain insight into this problem, we studied connexin expression and the contribution of connexin channels to the retinal light response in the diurnal rodent Octodon degus (degu) compared to rat, using in vivo ERG recording under scotopic and photopic light adaptation. Analysis of the degu genome showed that the common retinal connexins present a high degree of homology to orthologs expressed in other mammals, and expression of Cx36 and Cx43 was confirmed in degu retina. Cx36 localized mainly to the outer and inner plexiform layers (IPLs), while Cx43 was expressed mostly in cells of the retinal pigment epithelium. Under scotopic conditions, the b-wave response amplitude was strongly reduced by 18-β-glycyrrhetinic acid (β-GA) (−45.1% in degu, compared to −52.2% in rat), suggesting that connexins are modulating this response. Remarkably, under photopic adaptation, β-GA increased the ERG b-wave amplitude in degu (+107.2%) while reducing it in rat (−62.3%). Moreover, β-GA diminished the spontaneous action potential firing rate in ganglion cells (GCs) and increased the response latency of ON and OFF GCs. Our results support the notion that connexins exert a fine-tuning control of the retinal light response and have an important role in retinal neural coding.
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Affiliation(s)
- Angelina Palacios-Muñoz
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Maria J Escobar
- Departamento de Electrónica, Universidad Técnico Federico Santa María Valparaíso, Chile
| | - Alex Vielma
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Joaquín Araya
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Aland Astudillo
- Departamento de Electrónica, Universidad Técnico Federico Santa María Valparaíso, Chile
| | - Gonzalo Valdivia
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Isaac E García
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - José Hurtado
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile ; Instituto de Sistemas Complejos de Valparaíso Valparaíso, Chile
| | - Oliver Schmachtenberg
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Agustín D Martínez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Adrian G Palacios
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile ; Instituto de Sistemas Complejos de Valparaíso Valparaíso, Chile
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47
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Serrano-Velez JL, Rodriguez-Alvarado M, Torres-Vazquez II, Fraser SE, Yasumura T, Vanderpool KG, Rash JE, Rosa-Molinar E. Abundance of gap junctions at glutamatergic mixed synapses in adult Mosquitofish spinal cord neurons. Front Neural Circuits 2014; 8:66. [PMID: 25018700 PMCID: PMC4072101 DOI: 10.3389/fncir.2014.00066] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Accepted: 05/28/2014] [Indexed: 11/13/2022] Open
Abstract
"Dye-coupling", whole-mount immunohistochemistry for gap junction channel protein connexin 35 (Cx35), and freeze-fracture replica immunogold labeling (FRIL) reveal an abundance of electrical synapses/gap junctions at glutamatergic mixed synapses in the 14th spinal segment that innervates the adult male gonopodium of Western Mosquitofish, Gambusia affinis (Mosquitofish). To study gap junctions' role in fast motor behavior, we used a minimally-invasive neural-tract-tracing technique to introduce gap junction-permeant or -impermeant dyes into deep muscles controlling the gonopodium of the adult male Mosquitofish, a teleost fish that rapidly transfers (complete in <20 mS) spermatozeugmata into the female reproductive tract. Dye-coupling in the 14th spinal segment controlling the gonopodium reveals coupling between motor neurons and a commissural primary ascending interneuron (CoPA IN) and shows that the 14th segment has an extensive and elaborate dendritic arbor and more gap junctions than do other segments. Whole-mount immunohistochemistry for Cx35 results confirm dye-coupling and show it occurs via gap junctions. Finally, FRIL shows that gap junctions are at mixed synapses and reveals that >50 of the 62 gap junctions at mixed synapses are in the 14th spinal segment. Our results support and extend studies showing gap junctions at mixed synapses in spinal cord segments involved in control of genital reflexes in rodents, and they suggest a link between mixed synapses and fast motor behavior. The findings provide a basis for studies of specific roles of spinal neurons in the generation/regulation of sex-specific behavior and for studies of gap junctions' role in regulating fast motor behavior. Finally, the CoPA IN provides a novel candidate neuron for future studies of gap junctions and neural control of fast motor behaviors.
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Affiliation(s)
| | | | | | - Scott E Fraser
- Molecular and Computational Biology Section, University of Southern California Los Angeles, CA, USA
| | - Thomas Yasumura
- Department of Biomedical Sciences, Colorado State University Fort Collins, CO, USA
| | | | - John E Rash
- Department of Biomedical Sciences, Colorado State University Fort Collins, CO, USA ; Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University Fort Collins, CO, USA
| | - Eduardo Rosa-Molinar
- Biological Imaging Group, University of Puerto Rico San Juan, PR, USA ; Institute of Neurobiology, School of Medicine, University of Puerto Rico San Juan, PR, USA
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48
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The ever-changing electrical synapse. Curr Opin Neurobiol 2014; 29:64-72. [PMID: 24955544 DOI: 10.1016/j.conb.2014.05.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 05/30/2014] [Indexed: 12/26/2022]
Abstract
A wealth of research has revealed that electrical synapses in the central nervous system exhibit a high degree of plasticity. Several recent studies, particularly in the retina and inferior olive, highlight this plasticity. Three classes of mechanisms can alter electrical coupling over time courses ranging from milliseconds to days. Changes of membrane conductance through synaptic input or spiking activity shunt current and decouple neurons on the millisecond time scale. Such activity can also alter coupling symmetry, rectifying electrical synapses. More stable rectification can be accomplished through molecular asymmetry of the synapse itself. On the minutes time scale, changes in connexin phosphorylation can change coupling quasi-stably with an order of magnitude dynamic range. On the hours to days time scale, changes in expression level of connexins alter coupling through the course of circadian time, over developmental time, or in response to tissue injury. Combined, all of these mechanisms allow electrical coupling to be highly dynamic, changing in response to demands at the whole network level, in small portions of a network, or at the level of an individual synapse.
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49
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Nick TA. Models of vocal learning in the songbird: Historical frameworks and the stabilizing critic. Dev Neurobiol 2014; 75:1091-113. [PMID: 24841478 DOI: 10.1002/dneu.22189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/07/2014] [Accepted: 05/05/2014] [Indexed: 11/10/2022]
Abstract
Birdsong is a form of sensorimotor learning that involves a mirror-like system that activates with both song hearing and production. Early models of song learning, based on behavioral measures, identified key features of vocal plasticity, such as the requirements for memorization of a tutor song and auditory feedback during song practice. The concept of a comparator, which compares the memory of the tutor song to auditory feedback, featured prominently. Later models focused on linking anatomically-defined neural modules to behavioral concepts, such as the comparator. Exploiting the anatomical modularity of the songbird brain, localized lesions illuminated mechanisms of the neural song system. More recent models have integrated neuronal mechanisms identified in other systems with observations in songbirds. While these models explain multiple aspects of song learning, they must incorporate computational elements based on unknown biological mechanisms to bridge the motor-to-sensory delay and/or transform motor signals into the sensory domain. Here, I introduce the stabilizing critic hypothesis, which enables sensorimotor learning by (1) placing a purely sensory comparator afferent of the song system and (2) endowing song system disinhibitory interneuron networks with the capacity both to bridge the motor-sensory delay through prolonged bursting and to stabilize song segments selectively based on the comparator signal. These proposed networks stabilize an otherwise variable signal generated by both putative mirror neurons and a cortical-basal ganglia-thalamic loop. This stabilized signal then temporally converges with a matched premotor signal in the efferent song motor cortex, promoting spike-timing-dependent plasticity in the premotor circuitry and behavioral song learning.
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Affiliation(s)
- Teresa A Nick
- Department of Neuroscience, Graduate Program in Neuroscience, Center for Neurobehavioral Development, Center for Neuroengineering, The University of Minnesota, Twin Cities, Minneapolis, Minnesota, 55455
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Transmission from the dominant input shapes the stereotypic ratio of photoreceptor inputs onto horizontal cells. Nat Commun 2014; 5:3699. [PMID: 24832361 PMCID: PMC4061492 DOI: 10.1038/ncomms4699] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 03/20/2014] [Indexed: 11/21/2022] Open
Abstract
Many neurons receive synapses in stereotypic proportions from converging but functionally distinct afferents. However, developmental mechanisms regulating synaptic convergence are not well understood. Here we describe a heterotypic mechanism by which one afferent controls synaptogenesis of another afferent, but not vice-versa. Like other CNS circuits, zebrafish retinal H3 horizontal cells undergo an initial period of remodeling, establishing synapses with UV and blue cones while eliminating red and green cone contacts. As development progresses, the horizontal cells selectively synapse with UV cones to generate a 5:1 UV-to-blue cone synapse ratio. Blue cone synaptogenesis increases in mutants lacking UV cones, and when transmitter release or visual stimulation of UV cones is perturbed. Connectivity is unaltered when blue cone transmission is suppressed. Moreover, there is no homotypic regulation of cone synaptogenesis by neurotransmission. Thus, biased connectivity in this circuit is established by an unusual activity-dependent, unidirectional control of synaptogenesis exerted by the dominant input.
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