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Kindig K, Gibbs E, Seiferth D, Biggin PC, Chakrapani S. Mechanisms underlying modulation of human GlyRα3 receptors by Zn 2+ and pH. SCIENCE ADVANCES 2024; 10:eadr5920. [PMID: 39693447 DOI: 10.1126/sciadv.adr5920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Accepted: 11/11/2024] [Indexed: 12/20/2024]
Abstract
Glycine receptors (GlyRs) regulate motor control and pain processing in the central nervous system through inhibitory synaptic signaling. The subtype GlyRα3 expressed in nociceptive sensory neurons of the spinal dorsal horn is a key regulator of physiological pain perception. Disruption of spinal glycinergic inhibition is associated with chronic inflammatory pain states, making GlyRα3 an attractive target for pain treatment. GlyRα3 activity is modulated by numerous endogenous and exogenous ligands that consequently affect pain sensitization. To understand the mechanism of two such endogenous modulators, Zn2+ and protons, we have used cryo-electron microscopy to determine structures of full-length human GlyRα3 in various functional states. Whereas acidic pH reduces peak glycine response, Zn2+ displays biphasic modulation in a concentration-dependent manner. Our findings reveal the effector sites and also capture intermediate conformations in the gating cycle. Combined with molecular dynamics simulations and electrophysiology, this work provides important insights into GlyRα3 activation and regulation.
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Affiliation(s)
- Kayla Kindig
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
- Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
| | - Eric Gibbs
- Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
| | - David Seiferth
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
- Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4970, USA
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Wu SM, Pang JJ. Effects of elevated intraocular pressure on alpha ganglion cells in experimental glaucoma mice. Vision Res 2024; 224:108475. [PMID: 39217910 DOI: 10.1016/j.visres.2024.108475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Revised: 08/08/2024] [Accepted: 08/09/2024] [Indexed: 09/04/2024]
Abstract
Glaucoma is a leading cause of blindness worldwide and glaucoma patients exhibit an early diffuse loss of retinal sensitivity followed by focal loss of RGCs. Combining some previous published results and some new data, this paper provides our current view on how high IOP (H-IOP) affects the light response sensitivity of a subset of RGCs, the alpha-ganglion cells (αGCs), as well as their presynaptic bipolar cells (DBCs and HBCs) and A2 amacrine cells (AIIACs) in dark-adapted mouse retinas. Our data demonstrate that H-IOP in experimental glaucoma mice significantly decreases light-evoked spike response sensitivity of sONαGCs and sOFFαGCs (i.e., raises thresholds by 1.5-2.5 log units), but not that of the tONαGCs and tOFFαGCs. The sensitivity loss in sONαGCs and sOFFαGCs is mediated by a H-IOP induced suppression of AIIAC response which is caused by a decrease of transmission efficacy of the DBCR→AIIAC synapse. We also provide evidence supporting the hypothesis that BK channels in the A17AC→DBCR feedback synapse are the H-IOP sensor that regulates the DBCR→AIIAC synaptic efficacy, as BK channel blocker IBTX mimics the action of H-IOP. Our results provide useful information for designing strategies for early detection and possible treatments of glaucoma as physiological changes occur before irreversible structural damage.
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Affiliation(s)
- Samuel M Wu
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, United States.
| | - Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, United States
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3
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Zhou Y, Zhou W, Rao Y, He J, Huang Y, Zhao P, Li J. Dysregulated energy and protein homeostasis and the loss of GABAergic amacrine cells in aging retina. Exp Eye Res 2024; 245:109985. [PMID: 38945518 DOI: 10.1016/j.exer.2024.109985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 05/30/2024] [Accepted: 06/27/2024] [Indexed: 07/02/2024]
Abstract
Aging is a major risk factor for the development or the worsening of retinal degenerative conditions. The intricate network of the neural retina determined that the retinal aging is a complicated process. The aim of this study is to delineate the transcriptomic changes of major retinal neurons during aging in C57BL/6 mice at single-cell level. We analyzed the transcriptional profiles of the photoreceptor, bipolar, amacrine, and Müller glial cells of 1.5-2 and 24-30 months old mice using single-cell RNA sequencing technique. We selectively confirmed the differences in gene expression using immunofluorescence staining and RNA in situ hybridization analysis. We found that each retinal cell type had unique changes upon aging. However, they all showed signs of dysregulated glucose and energy metabolism, and perturbed proteostasis. In particular, old Müller glia exhibited the most profound changes, including the upregulation of cell metabolism, stress-responses, antigen-presentation and immune responses and metal ion homeostasis. The dysregulated gliogenesis and differentiation was confirmed by the presence of Müller glia expressing rod-specific genes in the inner nuclear layer and the outer plexiform layer of the old retina. We further pinpointed the specific loss of GABAergic amacrine cells in old retina. Our study emphasized changes of amacrine and Müller glia during retinal aging, provided resources for further research on the molecular and cellular regulatory mechanisms underlying aging-associated retinal deterioration.
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Affiliation(s)
- Yutong Zhou
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China
| | - Wenchuan Zhou
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China
| | - Yuqing Rao
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China
| | - Jincan He
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China
| | - Yue Huang
- Department of Ophthalmology, Chongming Hospital Affiliated to Shanghai University of Medicine and Health Sciences, Shanghai, 202150, China
| | - Peiquan Zhao
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.
| | - Jing Li
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.
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Ebert S, Buffet T, Sermet BS, Marre O, Cessac B. Temporal pattern recognition in retinal ganglion cells is mediated by dynamical inhibitory synapses. Nat Commun 2024; 15:6118. [PMID: 39033142 PMCID: PMC11271269 DOI: 10.1038/s41467-024-50506-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 07/10/2024] [Indexed: 07/23/2024] Open
Abstract
A fundamental task for the brain is to generate predictions of future sensory inputs, and signal errors in these predictions. Many neurons have been shown to signal omitted stimuli during periodic stimulation, even in the retina. However, the mechanisms of this error signaling are unclear. Here we show that depressing inhibitory synapses shape the timing of the response to an omitted stimulus in the retina. While ganglion cells, the retinal output, responded to an omitted flash with a constant latency over many frequencies of the flash sequence, we found that this was not the case once inhibition was blocked. We built a simple circuit model and showed that depressing inhibitory synapses were a necessary component to reproduce our experimental findings. A new prediction of our model is that the accuracy of the constant latency requires a sufficient amount of flashes in the stimulus, which we could confirm experimentally. Depressing inhibitory synapses could thus be a key component to generate the predictive responses observed in the retina, and potentially in many brain areas.
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Affiliation(s)
- Simone Ebert
- INRIA Biovision Team, Université Côte d'Azur, Valbonne, France.
- Institute for Modeling in Neuroscience and Cognition (NeuroMod), Université Côte d'Azur, Nice, France.
- Sorbonne Université, INSERM, CNRS, Institut De La Vision, Paris, France.
| | - Thomas Buffet
- Sorbonne Université, INSERM, CNRS, Institut De La Vision, Paris, France
| | - B Semihcan Sermet
- Sorbonne Université, INSERM, CNRS, Institut De La Vision, Paris, France
- Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Olivier Marre
- Sorbonne Université, INSERM, CNRS, Institut De La Vision, Paris, France
| | - Bruno Cessac
- INRIA Biovision Team, Université Côte d'Azur, Valbonne, France
- Institute for Modeling in Neuroscience and Cognition (NeuroMod), Université Côte d'Azur, Nice, France
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Holden JM, Wareham LK, Calkins DJ. Morphological and electrophysiological characterization of a novel displaced astrocyte in the mouse retina. Glia 2024; 72:1356-1370. [PMID: 38591270 PMCID: PMC11081821 DOI: 10.1002/glia.24536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 03/08/2024] [Accepted: 03/30/2024] [Indexed: 04/10/2024]
Abstract
Astrocytes throughout the central nervous system are heterogeneous in both structure and function. This diversity leads to tissue-specific specialization where morphology is adapted to the surrounding neuronal circuitry, as seen in Bergman glia of the cerebellum and Müller glia of the retina. Because morphology can be a differentiating factor for cellular classification, we recently developed a mouse where glial-fibrillary acidic protein (GFAP)-expressing cells stochastically label for full membranous morphology. Here we utilize this tool to investigate whether morphological and electrophysiological features separate types of mouse retinal astrocytes. In this work, we report on a novel glial population found in the inner plexiform layer and ganglion cell layer which expresses the canonical astrocyte markers GFAP, S100β, connexin-43, Sox2 and Sox9. Apart from their retinal layer localization, these cells are unique in their radial distribution. They are notably absent from the mid-retina but are heavily concentrated near the optic nerve head, and to a lesser degree the peripheral retina. Additionally, their morphology is distinct from both nerve fiber layer astrocytes and Müller glia, appearing more similar to amacrine cells. Despite this structural similarity, these cells lack protein expression of common neuronal markers. Additionally, they do not exhibit action potentials, but rather resemble astrocytes and Müller glia in their small amplitude, graded depolarization to both light onset and offset. Their structure, protein expression, physiology, and intercellular connections suggest that these cells are astrocytic, displaced from their counterparts in the nerve fiber layer. As such, we refer to these cells as displaced retinal astrocytes.
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Affiliation(s)
- Joseph Matthew Holden
- Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical Center, Nashville, TN 37212
- Vanderbilt Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37212
| | - Lauren Katie Wareham
- Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical Center, Nashville, TN 37212
| | - David John Calkins
- Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical Center, Nashville, TN 37212
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Yuan C, Gerhards L, Solov'yov IA, Dedek K. Biotin-cGMP and -cAMP are able to permeate through the gap junctions of some amacrine cells in the mouse retina despite their large size. FRONTIERS IN OPHTHALMOLOGY 2024; 3:1334602. [PMID: 38983094 PMCID: PMC11182161 DOI: 10.3389/fopht.2023.1334602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/22/2023] [Indexed: 07/11/2024]
Abstract
Gap junctions transmit electrical signals in neurons and serve metabolic coupling and chemical communication. Gap junctions are made of intercellular channels with large pores, allowing ions and small molecules to permeate. In the mammalian retina, intercellular coupling fulfills many vital functions in visual signal processing but is also implicated in promoting cell death after insults, such as excitotoxicity or hypoxia. Conversely, some studies also suggested a role for retinal gap junctions in neuroprotection. Recently, gap junctions were also advocated as conduits for therapeutic drug delivery in neurodegenerative disorders. This requires the permeation of rather large molecules through retinal gap junctions. However, the permeability of retinal networks for molecules >0.6 kDa has not been tested systematically. Here, we used the cut-loading method and probed gap junctional networks in the mouse retina for their permeability to cGMP and cAMP coupled to Biotin, using the well-characterized tracer Neurobiotin as control. Biotin-cGMP and -cAMP have a molecular weight of >0.8 kDa. We show that they cannot pass the gap junctions of horizontal cells but can permeate through the gap junctions of specific amacrine cells in the inner retina. These amacrine cells do not comprise AII amacrine cells and nitric oxide-releasing amacrine cells but some unknown type. In summary, we show that some retinal gap junctions are large enough to let molecules >0.8 kDa pass, making the intercellular delivery of therapeutic agents - already successfully exploited, for example, in cancer - also feasible in neurodegenerative diseases.
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Affiliation(s)
- Chunxu Yuan
- Animal Navigation, Institute for Biology and Environmental Sciences, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
| | - Luca Gerhards
- Institute of Physics, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
| | - Ilia A Solov'yov
- Institute of Physics, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
- CeNaD - Center for Nanoscale Dynamics, University of Oldenburg, Oldenburg, Germany
| | - Karin Dedek
- Animal Navigation, Institute for Biology and Environmental Sciences, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
- Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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Park SJ, Lei W, Pisano J, Orpia A, Minehart J, Pottackal J, Hanke-Gogokhia C, Zapadka TE, Clarkson-Paredes C, Popratiloff A, Ross SE, Singer JH, Demb JB. Molecular identification of wide-field amacrine cells in mouse retina that encode stimulus orientation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.28.573580. [PMID: 38234775 PMCID: PMC10793454 DOI: 10.1101/2023.12.28.573580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Visual information processing is sculpted by a diverse group of inhibitory interneurons in the retina called amacrine cells. Yet, for most of the >60 amacrine cell types, molecular identities and specialized functional attributes remain elusive. Here, we developed an intersectional genetic strategy to target a group of wide-field amacrine cells (WACs) in mouse retina that co-express the transcription factor Bhlhe22 and the Kappa Opioid Receptor (KOR; B/K WACs). B/K WACs feature straight, unbranched dendrites spanning over 0.5 mm (∼15° visual angle) and produce non-spiking responses to either light increments or decrements. Two-photon dendritic population imaging reveals Ca 2+ signals tuned to the physical orientations of B/K WAC dendrites, signifying a robust structure-function alignment. B/K WACs establish divergent connections with multiple retinal neurons, including unexpected connections with non-orientation-tuned ganglion cells and bipolar cells. Our work sets the stage for future comprehensive investigations of the most enigmatic group of retinal neurons: WACs.
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Dharmarajan S, Carrillo C, Qi Z, Wilson JM, Baucum AJ, Sorenson CM, Sheibani N, Belecky-Adams TL. Retinal inflammation in murine models of type 1 and type 2 diabetes with diabetic retinopathy. Diabetologia 2023; 66:2170-2185. [PMID: 37670018 PMCID: PMC10541343 DOI: 10.1007/s00125-023-05995-4] [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: 01/04/2023] [Accepted: 06/28/2023] [Indexed: 09/07/2023]
Abstract
AIMS/HYPOTHESIS The loss of pericytes surrounding the retinal vasculature in early diabetic retinopathy underlies changes to the neurovascular unit that lead to more destructive forms of the disease. However, it is unclear which changes lead to loss of retinal pericytes. This study investigated the hypothesis that chronic increases in one or more inflammatory factors mitigate the signalling pathways needed for pericyte survival. METHODS Loss of pericytes and levels of inflammatory markers at the mRNA and protein levels were investigated in two genetic models of diabetes, Ins2Akita/+ (a model of type 1 diabetes) and Leprdb/db (a model of type 2 diabetes), at early stages of diabetic retinopathy. In addition, changes that accompany gliosis and the retinal vasculature were determined. Finally, changes in retinal pericytes chronically incubated with vehicle or increasing amounts of IFNγ were investigated to determine the effects on pericyte survival. The numbers of pericytes, microglia, astrocytes and endothelial cells in retinal flatmounts were determined by immunofluorescence. Protein and mRNA levels of inflammatory factors were determined using multiplex ELISAs and quantitative reverse transcription PCR (qRT-PCR). The effects of IFNγ on the murine retinal pericyte survival-related platelet-derived growth factor receptor β (PDGFRβ) signalling pathway were investigated by western blot analysis. Finally, the levels of cell death-associated protein kinase C isoform delta (PKCδ) and cleaved caspase 3 (CC3) in pericytes were determined by western blot analysis and immunocytochemistry. RESULTS The essential findings of this study were that both type 1 and 2 diabetes were accompanied by a similar progression of retinal pericyte loss, as well as gliosis. However, inflammatory factor expression was dissimilar in the two models of diabetes, with peak expression occurring at different ages for each model. Retinal vascular changes were more severe in the type 2 diabetes model. Chronic incubation of murine retinal pericytes with IFNγ decreased PDGFRβ signalling and increased the levels of active PKCδ and CC3. CONCLUSIONS/INTERPRETATION We conclude that retinal inflammation is involved in and sustains pericyte loss as diabetic retinopathy progresses. Moreover, IFNγ plays a critical role in reducing pericyte survival in the retina by reducing activation of the PDGFRβ signalling pathway and increasing PKCδ levels and pericyte apoptosis.
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Affiliation(s)
- Subramanian Dharmarajan
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA
| | - Casandra Carrillo
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA
| | - Zhonghua Qi
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Jonathan M Wilson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
| | - Anthony J Baucum
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Christine M Sorenson
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Nader Sheibani
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Teri L Belecky-Adams
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA.
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9
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Pang JJ, Gao F, Wu SM. Light responses and amacrine cell modulation of morphologically-identified retinal ganglion cells in the mouse retina. Vision Res 2023; 205:108187. [PMID: 36758452 PMCID: PMC11349081 DOI: 10.1016/j.visres.2023.108187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 01/21/2023] [Accepted: 01/23/2023] [Indexed: 02/10/2023]
Abstract
By analyzing light-evoked spike responses, cation currents (ΔIC) and chloride currents (ΔICl) of over 100 morphologically-identified retinal ganglion cells (GCs) in dark-adapted mouse retina, we found there are at least 14 functionally- and morphologically-distinct types of RGCs. These cells can be divided into 5 groups based on their patterns of spike response to whole field light steps (SRWFLS), a GC identification scheme commonly used in studies with extracellular recording techniques. We also found that all GCs in the mouse retina express strychnine-sensitive glycine receptors, and receive light-elicited chloride current (ΔICl) accompanied by a conductance increase from narrow-field, glycinergic amacrine cells. As the dark membrane potential of RGC are near the chloride-equilibrium potential, mouse GCs' spike responses are mediated primarily by bipolar cells inputs, and modulated by "shunting inhibition" from narrow-field amacrine cells. Analysis of strychnine actions on light-evoked cation current ΔIC (bipolar cell inputs) in GCs suggests that narrow-field amacrine cells modulate GCs by sending ON-OFF crossover feedback signals to presynaptic bipolar cell axon terminals via sign-inverting glycinergic synapses, and the feedback signals are synergistic to the bipolar cell light responses. Therefore narrow-field amacrine cells enhance light-evoked bipolar cell inputs to GCs by presynaptic "synergistic addition", besides the abovementioned postsynaptic "shunting inhibition" in GCs.
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Affiliation(s)
- Ji-Jie Pang
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, United States
| | - Fan Gao
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, United States
| | - Samuel M Wu
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, United States.
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Gibbs E, Klemm E, Seiferth D, Kumar A, Ilca SL, Biggin PC, Chakrapani S. Conformational transitions and allosteric modulation in a heteromeric glycine receptor. Nat Commun 2023; 14:1363. [PMID: 36914669 PMCID: PMC10011588 DOI: 10.1038/s41467-023-37106-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/02/2023] [Indexed: 03/16/2023] Open
Abstract
Glycine Receptors (GlyRs) provide inhibitory neuronal input in the spinal cord and brainstem, which is critical for muscle coordination and sensory perception. Synaptic GlyRs are a heteromeric assembly of α and β subunits. Here we present cryo-EM structures of full-length zebrafish α1βBGlyR in the presence of an antagonist (strychnine), agonist (glycine), or agonist with a positive allosteric modulator (glycine/ivermectin). Each structure shows a distinct pore conformation with varying degrees of asymmetry. Molecular dynamic simulations found the structures were in a closed (strychnine) and desensitized states (glycine and glycine/ivermectin). Ivermectin binds at all five interfaces, but in a distinct binding pose at the β-α interface. Subunit-specific features were sufficient to solve structures without a fiduciary marker and to confirm the 4α:1β stoichiometry recently observed. We also report features of the extracellular and intracellular domains. Together, our results show distinct compositional and conformational properties of α1βGlyR and provide a framework for further study of this physiologically important channel.
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Affiliation(s)
- Eric Gibbs
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Emily Klemm
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - David Seiferth
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Arvind Kumar
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Serban L Ilca
- New York Structural Biology Center, New York, NY, 10027, USA
- Simons Electron Microscopy Center, New York, NY, 10027, USA
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
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11
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Chen X, Wilson KA, Schaefer N, De Hayr L, Windsor M, Scalais E, van Rijckevorsel G, Stouffs K, Villmann C, O’Mara ML, Lynch JW, Harvey RJ. Loss, Gain and Altered Function of GlyR α2 Subunit Mutations in Neurodevelopmental Disorders. Front Mol Neurosci 2022; 15:886729. [PMID: 35571374 PMCID: PMC9103196 DOI: 10.3389/fnmol.2022.886729] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/07/2022] [Indexed: 12/11/2022] Open
Abstract
Glycine receptors (GlyRs) containing the α2 subunit govern cell fate, neuronal migration and synaptogenesis in the developing cortex and spinal cord. Rare missense variants and microdeletions in the X-linked GlyR α2 subunit gene (GLRA2) have been associated with human autism spectrum disorder (ASD), where they typically cause a loss-of-function via protein truncation, reduced cell-surface trafficking and/or reduced glycine sensitivity (e.g., GLRA2Δex8-9 and extracellular domain variants p.N109S and p.R126Q). However, the GlyR α2 missense variant p.R323L in the intracellular M3-M4 domain results in a gain-of-function characterized by slower synaptic decay times, longer duration active periods and increases in channel conductance. This study reports the functional characterization of four missense variants in GLRA2 associated with ASD or developmental disorders (p.V-22L, p.N38K, p.K213E, p.T269M) using a combination of bioinformatics, molecular dynamics simulations, cellular models of GlyR trafficking and electrophysiology in artificial synapses. The GlyR α2V–22L variant resulted in altered predicted signal peptide cleavage and a reduction in cell-surface expression, suggestive of a partial loss-of-function. Similarly, GlyR α2N38K homomers showed reduced cell-surface expression, a reduced affinity for glycine and a reduced magnitude of IPSCs in artificial synapses. By contrast, GlyR α2K213E homomers showed a slight reduction in cell-surface expression, but IPSCs were larger, with faster rise/decay times, suggesting a gain-of-function. Lastly, GlyR α2T269M homomers exhibited a high glycine sensitivity accompanied by a substantial leak current, suggestive of an altered function that could dramatically enhance glycinergic signaling. These results may explain the heterogeneity of clinical phenotypes associated with GLRA2 mutations and reveal that missense variants can result in a loss, gain or alteration of GlyR α2 function. In turn, these GlyR α2 missense variants are likely to either negatively or positively deregulate cortical progenitor homeostasis and neuronal migration in the developing brain, leading to changes in cognition, learning, and memory.
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Affiliation(s)
- Xiumin Chen
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Katie A. Wilson
- Research School of Chemistry, The Australian National University, Canberra, ACT, Australia
| | - Natascha Schaefer
- Institute of Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Lachlan De Hayr
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia
- Sunshine Coast Health Institute, Birtinya, QLD, Australia
| | - Mark Windsor
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia
- Sunshine Coast Health Institute, Birtinya, QLD, Australia
| | - Emmanuel Scalais
- Neurologie Pédiatrique, Centre Hospitalier de Luxembourg, Luxembourg, Luxembourg
| | | | - Katrien Stouffs
- Center for Medical Genetics, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels, Belgium
| | - Carmen Villmann
- Institute of Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Megan L. O’Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT, Australia
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD, Australia
| | - Joseph W. Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Robert J. Harvey
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia
- Sunshine Coast Health Institute, Birtinya, QLD, Australia
- *Correspondence: Robert J. Harvey,
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12
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Reh M, Lee M, Zeck G. Expression of Channelrhodopsin‐2 in Rod Bipolar Cells Restores ON and OFF Responses at High Spatial Resolution in Blind Mouse Retina. ADVANCED THERAPEUTICS 2022. [DOI: 10.1002/adtp.202100164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Miriam Reh
- Neurophysics NMI Natural and Medical Sciences Institute at the University of Tübingen 72770 Reutlingen Germany
- Graduate School of Neural Information Processing/ International Max Planck Research School Tübingen Germany
| | - Meng‐Jung Lee
- Neurophysics NMI Natural and Medical Sciences Institute at the University of Tübingen 72770 Reutlingen Germany
- Graduate School of Neural Information Processing/ International Max Planck Research School Tübingen Germany
| | - Günther Zeck
- Neurophysics NMI Natural and Medical Sciences Institute at the University of Tübingen 72770 Reutlingen Germany
- Institute of Biomedical Electronics TU Wien 1040 Vienna Austria
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13
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Sundberg CA, Lakk M, Paul S, Figueroa KP, Scoles DR, Pulst SM, Križaj D. The RNA-binding protein and stress granule component ATAXIN-2 is expressed in mouse and human tissues associated with glaucoma pathogenesis. J Comp Neurol 2022; 530:537-552. [PMID: 34350994 PMCID: PMC8716417 DOI: 10.1002/cne.25228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 07/06/2021] [Indexed: 02/03/2023]
Abstract
Polyglutamine repeat expansions in the Ataxin-2 (ATXN2) gene were first implicated in Spinocerebellar Ataxia Type 2, a disease associated with degeneration of motor neurons and Purkinje cells. Recent studies linked single nucleotide polymorphisms in the gene to elevated intraocular pressure in primary open angle glaucoma (POAG); yet, the localization of ATXN2 across glaucoma-relevant tissues of the vertebrate eye has not been thoroughly examined. This study characterizes ATXN2 expression in the mouse and human retina, and anterior eye, using an antibody validated in ATXN2-/- retinas. ATXN2-ir was localized to cytosolic sub compartments in retinal ganglion cell (RGC) somata and proximal dendrites in addition to GABAergic, glycinergic, and cholinergic amacrine cells in the inner plexiform layer (IPL) and displaced amacrine cells. Human, but not mouse retinas showed modest immunolabeling of bipolar cells. ATXN2 immunofluorescence was prominent in the trabecular meshwork and pigmented and nonpigmented cells of the ciliary body, with analyses of primary human trabecular meshwork cells confirming the finding. The expression of ATXN2 in key POAG-relevant ocular tissues supports the potential role in autophagy and stress granule formation in response to ocular hypertension.
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Affiliation(s)
- Chad A. Sundberg
- Department of Ophthalmology & Visual Sciences, University of Utah, Salt Lake City, Utah, USA
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Monika Lakk
- Department of Ophthalmology & Visual Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Sharan Paul
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Karla P. Figueroa
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Daniel R. Scoles
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Stefan M. Pulst
- Department of Neurology, University of Utah, Salt Lake City, Utah, USA
| | - David Križaj
- Department of Ophthalmology & Visual Sciences, University of Utah, Salt Lake City, Utah, USA
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA
- Department of Neurobiology & Anatomy, University of Utah, Salt Lake City, Utah, USA
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14
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Glycine Release Is Potentiated by cAMP via EPAC2 and Ca 2+ Stores in a Retinal Interneuron. J Neurosci 2021; 41:9503-9520. [PMID: 34620721 PMCID: PMC8612479 DOI: 10.1523/jneurosci.0670-21.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 09/28/2021] [Accepted: 09/30/2021] [Indexed: 11/21/2022] Open
Abstract
Neuromodulation via the intracellular second messenger cAMP is ubiquitous at presynaptic nerve terminals. This modulation of synaptic transmission allows exocytosis to adapt to stimulus levels and reliably encode information. The AII amacrine cell (AII-AC) is a central hub for signal processing in the mammalian retina. The main apical dendrite of the AII-AC is connected to several lobular appendages that release glycine onto OFF cone bipolar cells and ganglion cells. However, the influence of cAMP on glycine release is not well understood. Using membrane capacitance measurements from mouse AII-ACs to directly measure exocytosis, we observe that intracellular dialysis of 1 mm cAMP enhances exocytosis without affecting the L-type Ca2+ current. Responses to depolarizing pulses of various durations show that the size of the readily releasable pool of vesicles nearly doubles with cAMP, while paired-pulse depression experiments suggest that release probability does not change. Specific agonists and antagonists for exchange protein activated by cAMP 2 (EPAC2) revealed that the cAMP-induced enhancement of exocytosis requires EPAC2 activation. Furthermore, intact Ca2+ stores were also necessary for the cAMP potentiation of exocytosis. Postsynaptic recordings from OFF cone bipolar cells showed that increasing cAMP with forskolin potentiated the frequency of glycinergic spontaneous IPSCs. We propose that cAMP elevations in the AII-AC lead to a robust enhancement of glycine release through an EPAC2 and Ca2+ store signaling pathway. Our results thus contribute to a better understanding of how AII-AC crossover inhibitory circuits adapt to changes in ambient luminance.SIGNIFICANCE STATEMENT The mammalian retina operates over a wide dynamic range of light intensities and contrast levels. To optimize the signal-to-noise ratio of processed visual information, both excitatory and inhibitory synapses within the retina must modulate their gain in synaptic transmission to adapt to different levels of ambient light. Here we show that increases of cAMP concentration within AII amacrine cells produce enhanced exocytosis from these glycinergic interneurons. Therefore, we propose that light-sensitive neuromodulators may change the output of glycine release from AII amacrine cells. This novel mechanism may fine-tune the amount of tonic and phasic synaptic inhibition received by bipolar cell terminals and, consequently, the spiking patterns that ganglion cells send to the upstream visual areas of the brain.
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15
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Yu H, Bai XC, Wang W. Characterization of the subunit composition and structure of adult human glycine receptors. Neuron 2021; 109:2707-2716.e6. [PMID: 34473954 DOI: 10.1016/j.neuron.2021.08.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 07/23/2021] [Accepted: 08/16/2021] [Indexed: 11/27/2022]
Abstract
The strychnine-sensitive pentameric glycine receptor (GlyR) mediates fast inhibitory neurotransmission in the mammalian nervous system. Only heteromeric GlyRs mediate synaptic transmission, as they contain the β subunit that permits clustering at the synapse through its interaction with scaffolding proteins. Here, we show that α2 and β subunits assemble with an unexpected 4:1 stoichiometry to produce GlyR with native electrophysiological properties. We determined structures in multiple functional states at 3.6-3.8 Å resolutions and show how 4:1 stoichiometry is consistent with the structural features of α2β GlyR. Furthermore, we show that one single β subunit in each GlyR gives rise to the characteristic electrophysiological properties of heteromeric GlyR, while more β subunits render GlyR non-conductive. A single β subunit ensures a univalent GlyR-scaffold linkage, which means the scaffold alone regulates the cluster properties.
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Affiliation(s)
- Hailong Yu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiao-Chen Bai
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Weiwei Wang
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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16
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Harsing LG, Szénási G, Zelles T, Köles L. Purinergic-Glycinergic Interaction in Neurodegenerative and Neuroinflammatory Disorders of the Retina. Int J Mol Sci 2021; 22:ijms22126209. [PMID: 34201404 PMCID: PMC8228622 DOI: 10.3390/ijms22126209] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/03/2021] [Accepted: 06/04/2021] [Indexed: 12/26/2022] Open
Abstract
Neurodegenerative–neuroinflammatory disorders of the retina seriously hamper human vision. In searching for key factors that contribute to the development of these pathologies, we considered potential interactions among purinergic neuromodulation, glycinergic neurotransmission, and microglia activity in the retina. Energy deprivation at cellular levels is mainly due to impaired blood circulation leading to increased release of ATP and adenosine as well as glutamate and glycine. Interactions between these modulators and neurotransmitters are manifold. First, P2Y purinoceptor agonists facilitate reuptake of glycine by glycine transporter 1, while its inhibitors reduce reverse-mode operation; these events may lower extracellular glycine levels. The consequential changes in extracellular glycine concentration can lead to parallel changes in the activity of NR1/NR2B type NMDA receptors of which glycine is a mandatory agonist, and thereby may reduce neurodegenerative events in the retina. Second, P2Y purinoceptor agonists and glycine transporter 1 inhibitors may indirectly inhibit microglia activity by decreasing neuronal or glial glycine release in energy-compromised retina. These inhibitions may have a role in microglia activation, which is present during development and progression of neurodegenerative disorders such as glaucomatous and diabetic retinopathies and age-related macular degeneration or loss of retinal neurons caused by thromboembolic events. We have hypothesized that glycine transporter 1 inhibitors and P2Y purinoceptor agonists may have therapeutic importance in neurodegenerative–neuroinflammatory disorders of the retina by decreasing NR1/NR2B NMDA receptor activity and production and release of a series of proinflammatory cytokines from microglial cells.
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Affiliation(s)
- Laszlo G. Harsing
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary; (T.Z.); (L.K.)
- Correspondence: ; Tel.: +36-1-210-4416
| | - Gábor Szénási
- Institute of Translational Medicine, Semmelweis University, H-1089 Budapest, Hungary;
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary; (T.Z.); (L.K.)
- Department of Oral Biology, Semmelweis University, H-1089 Budapest, Hungary
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary; (T.Z.); (L.K.)
- Department of Oral Biology, Semmelweis University, H-1089 Budapest, Hungary
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17
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Chen AM, Azar SS, Harris A, Brecha NC, Pérez de Sevilla Müller L. PTEN Expression Regulates Gap Junction Connectivity in the Retina. Front Neuroanat 2021; 15:629244. [PMID: 34093139 PMCID: PMC8172595 DOI: 10.3389/fnana.2021.629244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/26/2021] [Indexed: 12/16/2022] Open
Abstract
Manipulation of the phosphatase and tensin homolog (PTEN) pathway has been suggested as a therapeutic approach to treat or prevent vision loss due to retinal disease. In this study, we investigated the effects of deleting one copy of Pten in a well-characterized class of retinal ganglion cells called α-ganglion cells in the mouse retina. In Pten +/- retinas, α-ganglion cells did not exhibit major changes in their dendritic structure, although most cells developed a few, unusual loop-forming dendrites. By contrast, α-ganglion cells exhibited a significant decrease in heterologous and homologous gap junction mediated cell coupling with other retinal ganglion and amacrine cells. Additionally, the majority of OFF α-ganglion cells (12/18 cells) formed novel coupling to displaced amacrine cells. The number of connexin36 puncta, the predominant connexin that mediates gap junction communication at electrical synapses, was decreased by at least 50% on OFF α-ganglion cells. Reduced and incorrect gap junction connectivity of α-ganglion cells will affect their functional properties and alter visual image processing in the retina. The anomalous connectivity of retinal ganglion cells would potentially limit future therapeutic approaches involving manipulation of the Pten pathway for treating ganglion cell degeneration in diseases like glaucoma, traumatic brain injury, Parkinson's, and Alzheimer's diseases.
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Affiliation(s)
- Ashley M. Chen
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
| | - Shaghauyegh S. Azar
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
| | - Alexander Harris
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
| | - Nicholas C. Brecha
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
- Stein Eye Institute, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
- CURE Digestive Diseases Research Center, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
- Veterans Administration Greater Los Angeles Health System, Los Angeles, CA, United States
| | - Luis Pérez de Sevilla Müller
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California, Los Angeles, Los Angeles, CA, United States
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18
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Sawant A, Ebbinghaus BN, Bleckert A, Gamlin C, Yu WQ, Berson D, Rudolph U, Sinha R, Hoon M. Organization and emergence of a mixed GABA-glycine retinal circuit that provides inhibition to mouse ON-sustained alpha retinal ganglion cells. Cell Rep 2021; 34:108858. [PMID: 33730586 PMCID: PMC8030271 DOI: 10.1016/j.celrep.2021.108858] [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: 05/10/2020] [Revised: 12/07/2020] [Accepted: 02/19/2021] [Indexed: 12/04/2022] Open
Abstract
In the retina, amacrine interneurons inhibit retinal ganglion cell (RGC) dendrites to shape retinal output. Amacrine cells typically use either GABA or glycine to exert synaptic inhibition. Here, we combined transgenic tools with immunohistochemistry, electrophysiology, and 3D electron microscopy to determine the composition and organization of inhibitory synapses across the dendritic arbor of a well-characterized RGC type in the mouse retina: the ON-sustained alpha RGC. We find mixed GABA-glycine receptor synapses across this RGC type, unveiling the existence of "mixed" inhibitory synapses in the retinal circuit. Presynaptic amacrine boutons with dual release sites are apposed to ON-sustained alpha RGC postsynapses. We further reveal the sequence of postsynaptic assembly for these mixed synapses: GABA receptors precede glycine receptors, and a lack of early GABA receptor expression impedes the recruitment of glycine receptors. Together our findings uncover the organization and developmental profile of an additional motif of inhibition in the mammalian retina.
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Affiliation(s)
- Abhilash Sawant
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA
| | - Briana N Ebbinghaus
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Adam Bleckert
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Clare Gamlin
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Wan-Qing Yu
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - David Berson
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Uwe Rudolph
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Raunak Sinha
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA.
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19
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Glycinergic Inhibition Targets Specific Off Cone Bipolar Cells in Primate Retina. eNeuro 2021; 8:ENEURO.0432-20.2020. [PMID: 33188005 PMCID: PMC7920536 DOI: 10.1523/eneuro.0432-20.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/06/2020] [Indexed: 11/21/2022] Open
Abstract
Adapting between scotopic and photopic illumination involves switching the routing of retinal signals between rod and cone-dominated circuits. In the daytime, cone signals pass through parallel On and Off cone bipolar cells (CBCs), that are sensitive to increments and decrements in luminance, respectively. At night, rod signals are routed into these cone-pathways via a key glycinergic interneuron, the AII amacrine cell (AII-AC). AII-ACs also provide On-pathway-driven crossover inhibition to Off-CBCs under photopic conditions. In primates, it is not known whether all Off-bipolar cell types receive functional inputs from AII-ACs. Here, we show that select Off-CBC types receive significantly higher levels of On-pathway-driven glycinergic input than others. The rise and decay kinetics of the glycinergic events are consistent with involvement of the α1 glycine receptor (GlyR) subunit, a result supported by a higher level of GLRA1 transcript in these cells. The Off-bipolar types that receive glycinergic input have sustained physiological properties and include the flat midget bipolar (FMB) cells, which provide excitatory input to the Off-midget ganglion cells (GCs; parvocellular pathway). Our results suggest that only a subset of Off-bipolar cells have the requisite receptors to respond to AII-AC input. Taken together with results in mouse retina, our findings suggest a conserved motif whereby signal output from AII-ACs is preferentially routed into sustained Off-bipolar signaling pathways.
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20
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Jiménez E, Piniella D, Giménez C, Zafra F. Regulation of the Glycine Transporter GLYT1 by microRNAs. Neurochem Res 2021; 47:138-147. [PMID: 33484385 DOI: 10.1007/s11064-021-03228-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/18/2020] [Accepted: 01/02/2021] [Indexed: 12/28/2022]
Abstract
The glycine transporter GLYT1 participates in inhibitory and excitatory neurotransmission by controlling the reuptake of this neuroactive substance from synapses. Over the past few years, microRNAs have emerged as potent negative regulators of gene expression. In this report, we investigate the possible regulation of GLYT1 by microRNAs. TargetScan software predicted the existence of multiple targets for microRNAs within the 3' UTR of the human GLYT1 (miR-7, miR-30, miR-96, miR-137 and miR-141), and as they are all conserved among mammalian orthologues, their effects on GLYT1 expression were determined experimentally. Dual reporter bioluminescent assays showed that only miR-96 and miR-137 down-regulated expression of the Renilla reporter fused to the 3' UTR of GLYT1. Mutations introduced into the target sequences blocked this inhibitory effect. Consistently, these two microRNAs downregulated the uptake of [3H]glycine into glial C6 cells, a cell line where GLYT1 is the main carrier for glycine. Moreover, the expression of endogenous GLYT1 in primary mixed cultures from rat spinal cord was decreased upon lentiviral expression of miR-96 and miR-137. Although the bulk of GLYT1 is glial, it is abundantly expressed in glycinergic neurons of the retina and in smaller amounts in glutamatergic neurons though the brain. Since miR-96 in the retina is strongly downregulated by light exposure, when rats were maintained in darkness for a few hours we observed a concomitant increase of GLYT1 expression, suggesting that at least miR-96 might be an important negative regulator of GLYT1 under physiological conditions.
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Affiliation(s)
- Esperanza Jiménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain.,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera 1, Madrid, 28049, Spain. .,IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
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21
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Hussein RA, Ahmed M, Sticht H, Breitinger HG, Breitinger U. Fine-Tuning of Neuronal Ion Channels-Mapping of Residues Involved in Glucose Sensitivity of Recombinant Human Glycine Receptors. ACS Chem Neurosci 2020; 11:3474-3483. [PMID: 33007159 DOI: 10.1021/acschemneuro.0c00566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The inhibitory glycine receptor (GlyR) mediates synaptic inhibition in the spinal cord, brain stem, and other regions of the mammalian central nervous system. Glucose was shown to potentiate α1 GlyRs by interacting with K143. Here, additional amino acids involved in glucose modulation were identified using a structure-based approach of site-directed mutagenesis followed by whole-cell patch-clamp analysis. We identified two additional lysine residues in the α1 GlyR extracellular domain, K16 and K281, that were involved in glucose modulation. Mutation of either residue to alanine abolished glucose potentiation. Residue K281 is located in the same pocket as K143 and could thus contribute to glucose binding. The double mutant K143A-K281A showed a 6-fold increase of EC50, while EC50 of both single mutants K143A and K281A was only slightly increased (1.7- and 1.3-fold, respectively). K16 is located at an analgesic binding site that is distant from the agonist or glucose sites, and the K16A mutation may generate a receptor species that is not potentiated. GlyR position α1-S267 is close to the postulated glucose binding site and known for interactions with ethanol and anesthetics. In the presence of glucose, GlyR α1 mutants S267A, S267I, and S267R showed potentiation, no effect, and reduction of current responses, respectively. This pattern follows that of ethanol modulation and suggests that the interaction sites of glucose and ethanol are identical or located close to each other. Our results support the presence of a distinct binding site for glucose on the glycine receptor, overlapping with the ivermectin/ethanol binding pocket near the transmembrane region and the TM2-3 loop.
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Affiliation(s)
- Rama Ashraf Hussein
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo 11835, Egypt
| | - Marwa Ahmed
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo 11835, Egypt
| | - Heinrich Sticht
- Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, D-91054 Erlangen, Germany
| | - Hans-Georg Breitinger
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo 11835, Egypt
| | - Ulrike Breitinger
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo 11835, Egypt
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22
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Yan W, Laboulaye MA, Tran NM, Whitney IE, Benhar I, Sanes JR. Mouse Retinal Cell Atlas: Molecular Identification of over Sixty Amacrine Cell Types. J Neurosci 2020; 40:5177-5195. [PMID: 32457074 PMCID: PMC7329304 DOI: 10.1523/jneurosci.0471-20.2020] [Citation(s) in RCA: 172] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 05/07/2020] [Accepted: 05/13/2020] [Indexed: 02/01/2023] Open
Abstract
Amacrine cells (ACs) are a diverse class of interneurons that modulate input from photoreceptors to retinal ganglion cells (RGCs), rendering each RGC type selectively sensitive to particular visual features, which are then relayed to the brain. While many AC types have been identified morphologically and physiologically, they have not been comprehensively classified or molecularly characterized. We used high-throughput single-cell RNA sequencing to profile >32,000 ACs from mice of both sexes and applied computational methods to identify 63 AC types. We identified molecular markers for each type and used them to characterize the morphology of multiple types. We show that they include nearly all previously known AC types as well as many that had not been described. Consistent with previous studies, most of the AC types expressed markers for the canonical inhibitory neurotransmitters GABA or glycine, but several expressed neither or both. In addition, many expressed one or more neuropeptides, and two expressed glutamatergic markers. We also explored transcriptomic relationships among AC types and identified transcription factors expressed by individual or multiple closely related types. Noteworthy among these were Meis2 and Tcf4, expressed by most GABAergic and most glycinergic types, respectively. Together, these results provide a foundation for developmental and functional studies of ACs, as well as means for genetically accessing them. Along with previous molecular, physiological, and morphologic analyses, they establish the existence of at least 130 neuronal types and nearly 140 cell types in the mouse retina.SIGNIFICANCE STATEMENT The mouse retina is a leading model for analyzing the development, structure, function, and pathology of neural circuits. A complete molecular atlas of retinal cell types provides an important foundation for these studies. We used high-throughput single-cell RNA sequencing to characterize the most heterogeneous class of retinal interneurons, amacrine cells, identifying 63 distinct types. The atlas includes types identified previously as well as many novel types. We provide evidence for the use of multiple neurotransmitters and neuropeptides, and identify transcription factors expressed by groups of closely related types. Combining these results with those obtained previously, we proposed that the mouse retina contains ∼130 neuronal types and is therefore comparable in complexity to other regions of the brain.
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Affiliation(s)
- Wenjun Yan
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Mallory A Laboulaye
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Nicholas M Tran
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Irene E Whitney
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Inbal Benhar
- Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142
| | - Joshua R Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138
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23
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Patterson SS, Bordt AS, Girresch RJ, Linehan CM, Bauss J, Yeo E, Perez D, Tseng L, Navuluri S, Harris NB, Matthews C, Anderson JR, Kuchenbecker JA, Manookin MB, Ogilvie JM, Neitz J, Marshak DW. Wide-field amacrine cell inputs to ON parasol ganglion cells in macaque retina. J Comp Neurol 2020; 528:1588-1598. [PMID: 31845339 PMCID: PMC7153979 DOI: 10.1002/cne.24840] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 10/31/2019] [Accepted: 11/24/2019] [Indexed: 11/07/2022]
Abstract
Parasol cells are one of the major types of primate retinal ganglion cells. The goal of this study was to describe the synaptic inputs that shape the light responses of the ON type of parasol cells, which are excited by increments in light intensity. A connectome from central macaque retina was generated by serial blockface scanning electron microscopy. Six neighboring ON parasol cells were reconstructed, and their synaptic inputs were analyzed. On average, they received 21% of their input from bipolar cells, excitatory local circuit neurons receiving input from cones. The majority of their input was from amacrine cells, local circuit neurons of the inner retina that are typically inhibitory. Their contributions to the neural circuit providing input to parasol cells are not well-understood, and the focus of this study was on the presynaptic wide-field amacrine cells, which provided 17% of the input to ON parasol cells. These are GABAergic amacrine cells with long, relatively straight dendrites, and sometimes also axons, that run in a single, narrow stratum of the inner plexiform layer. The presynaptic wide-field amacrine cells were reconstructed, and two types were identified based on their characteristic morphology. One presynaptic amacrine cell was identified as semilunar type 2, a polyaxonal cell that is electrically coupled to ON parasol cells. A second amacrine was identified as wiry type 2, a type known to be sensitive to motion. These inputs likely make ON parasol cells more sensitive to stimuli that are rapidly changing outside their classical receptive fields.
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Affiliation(s)
- Sara S Patterson
- Department of Ophthalmology, University of Washington, Seattle, Washington
- Neuroscience Graduate Program, University of Washington, Seattle, Washington
| | - Andrea S Bordt
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | | | - Conor M Linehan
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Jacob Bauss
- Department of Biology, Saint Louis University, Saint Louis, Missouri
| | - Eunice Yeo
- Department of Biology, Saint Louis University, Saint Louis, Missouri
| | - Diego Perez
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | - Luke Tseng
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | - Sriram Navuluri
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | - Nicole B Harris
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | - Chaiss Matthews
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
| | - James R Anderson
- John A. Moran Eye Center, University of Utah, Salt Lake City, Utah
| | | | - Michael B Manookin
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Judith M Ogilvie
- Department of Biology, Saint Louis University, Saint Louis, Missouri
| | - Jay Neitz
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - David W Marshak
- Department of Neurobiology & Anatomy, McGovern Medical School, Houston, Texas
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Silverstein SM, Demmin DL, Schallek JB, Fradkin SI. Measures of Retinal Structure and Function as Biomarkers in Neurology and Psychiatry. Biomark Neuropsychiatry 2020. [DOI: 10.1016/j.bionps.2020.100018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Principal Neurons in the Anteroventral Cochlear Nucleus Express Cell-Type Specific Glycine Receptor α Subunits. Neuroscience 2019; 415:77-88. [PMID: 31325562 DOI: 10.1016/j.neuroscience.2019.07.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 11/21/2022]
Abstract
Signal processing in the principal neurons of the anteroventral cochlear nucleus (AVCN) is modulated by glycinergic inhibition. The kinetics of IPSCs are specific to the target neurons. It remains unclear what glycine receptor subunits are involved in generating such target-specific IPSC kinetics in AVCN principal neurons. We investigated the expression patterns of glycine receptor α (GlyRα) subunits in AVCN using immunohistochemical labeling of four isoforms of GlyRα subunits (GlyRα1-α4), and found that AVCN neurons express GlyRα1 and GlyRα4, but not GlyRα2 and GlyRα3 subunits. To further identify the cell type-specific expression patterns of GlyRα subunits, we combined whole-cell patch clamp recording with immunohistochemistry by recording from all three types of AVCN principal neurons, characterizing the synaptic properties of their glycinergic inhibition, dye-filling the neurons, and processing the slice for immunostaining of different GlyRα subunits. We found that AVCN bushy neurons express both GlyRα1 and GlyRα4 subunits that underlie their slow IPSC kinetics, whereas both T-stellate and D-stellate neurons express only GlyRα1 subunit that underlies their fast IPSC kinetics. In conclusion, AVCN principal neurons express cell-type specific GlyRα subunits that underlie their distinct IPSC kinetics, which enables glycinergic inhibition from the same source to exert target cell-specific modulation of activity to support the unique physiological function of these neurons.
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Ghinia MG, Novelli E, Sajgo S, Badea TC, Strettoi E. Brn3a and Brn3b knockout mice display unvaried retinal fine structure despite major morphological and numerical alterations of ganglion cells. J Comp Neurol 2019; 527:187-211. [PMID: 27391320 PMCID: PMC5219957 DOI: 10.1002/cne.24072] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 06/07/2016] [Accepted: 06/30/2016] [Indexed: 01/21/2023]
Abstract
Ganglion cells (GCs), the retinal output neurons, receive synaptic inputs from bipolar and amacrine cells in the inner plexiform layer (IPL) and send information to the brain nuclei via the optic nerve. Although GCs constitute less than 1% of the total retinal cells, they occur in numerous types and are the first neurons formed during retinal development. Using Brn3a and Brn3b mutant mice in which the alkaline phosphatase gene was knocked-in (Badea et al. [Neuron] 2009;61:852-864; Badea and Nathans [Vision Res] 2011;51:269-279), we studied the general effects after gene removal on the retinal neuropil together with the consequences of lack of development of large numbers of GCs onto the remaining retinal neurons of the same class. We analyzed the morphology, number, and general architecture of various neuronal types presynaptic to GCs, searching for changes secondary to the decrement in the number of their postsynaptic partners, as well as the morphology and distribution of retinal astrocytes, for their strong topographical relation to GCs. We found that, despite GC losses, retinal organization in Brn3 null mice is remarkably similar to that of wild-type controls. J. Comp. Neurol. 527:187-211, 2019. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Miruna Georgiana Ghinia
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
- Babeş Bolyai University, 400084 Cluj Napoca, Romania
| | - Elena Novelli
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
| | - Szilard Sajgo
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Tudor Constantin Badea
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Enrica Strettoi
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
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Graydon CW, Lieberman EE, Rho N, Briggman KL, Singer JH, Diamond JS. Synaptic Transfer between Rod and Cone Pathways Mediated by AII Amacrine Cells in the Mouse Retina. Curr Biol 2018; 28:2739-2751.e3. [PMID: 30122532 PMCID: PMC6133723 DOI: 10.1016/j.cub.2018.06.063] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/24/2018] [Accepted: 06/22/2018] [Indexed: 02/03/2023]
Abstract
To understand computation in a neural circuit requires a complete synaptic connectivity map and a thorough grasp of the information-processing tasks performed by the circuit. Here, we dissect a microcircuit in the mouse retina in which scotopic visual information (i.e., single photon events, luminance, contrast) is encoded by rod bipolar cells (RBCs) and distributed to parallel ON and OFF cone bipolar cell (CBC) circuits via the AII amacrine cell, an inhibitory interneuron. Serial block-face electron microscopy (SBEM) reconstructions indicate that AIIs preferentially connect to one OFF CBC subtype (CBC2); paired whole-cell patch-clamp recordings demonstrate that, depending on the level of network activation, AIIs transmit distinct components of synaptic input from single RBCs to downstream ON and OFF CBCs. These findings highlight specific synaptic and circuit-level features that allow intermediate neurons (e.g., AIIs) within a microcircuit to filter and propagate information to downstream neurons.
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Affiliation(s)
- Cole W Graydon
- Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892, USA
| | - Evan E Lieberman
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Nao Rho
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Kevin L Briggman
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892, USA
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Jeffrey S Diamond
- Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892, USA.
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Abstract
Amacrine cells are a diverse set of local circuit neurons of the inner retina, and they all release either GABA or glycine, amino acid neurotransmitters that are generally inhibitory. But some types of amacrine cells have another function besides inhibiting other neurons. One glycinergic amacrine cell, the Aii type, excites a subset of bipolar cells via extensive gap junctions while inhibiting others at chemical synapses. Many types of GABAergic amacrine cells also release monoamines, acetylcholine, or neuropeptides. There is now good evidence that another type of amacrine cell releases glycine at some of its synapses and releases the excitatory amino acid glutamate at others. The glutamatergic synapses are made onto a subset of retinal ganglion cells and amacrine cells and have the asymmetric postsynaptic densities characteristic of central excitatory synapses. The glycinergic synapses are made onto other types of ganglion cells and have the symmetric postsynaptic densities characteristic of central inhibitory synapses. These amacrine cells, which contain vesicular glutamate transporter 3, will be the focus of this brief review.
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Corelease of Inhibitory Neurotransmitters in the Mouse Auditory Midbrain. J Neurosci 2017; 37:9453-9464. [PMID: 28847813 DOI: 10.1523/jneurosci.1125-17.2017] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/07/2017] [Accepted: 08/23/2017] [Indexed: 11/21/2022] Open
Abstract
The central nucleus of the inferior colliculus (ICC) of the auditory midbrain, which integrates most ascending auditory information from lower brainstem regions, receives prominent long-range inhibitory input from the ventral nucleus of the lateral lemniscus (VNLL), a region thought to be important for temporal pattern discrimination. Histological evidence suggests that neurons in the VNLL release both glycine and GABA in the ICC, but functional evidence for their corelease is lacking. We took advantage of the GlyT2-Cre mouse line (both male and female) to target expression of ChR2 to glycinergic afferents in the ICC and made whole-cell recordings in vitro while exciting glycinergic fibers with light. Using this approach, it was clear that a significant fraction of glycinergic boutons corelease GABA in the ICC. Viral injections were used to target ChR2 expression specifically to glycinergic fibers ascending from the VNLL, allowing for activation of fibers from a single source of ascending input in a way that has not been previously possible in the ICC. We then investigated aspects of the glycinergic versus GABAergic current components to probe functional consequences of corelease. Surprisingly, the time course and short-term plasticity of synaptic signaling were nearly identical for the two transmitters. We therefore conclude that the two neurotransmitters may be functionally interchangeable and that multiple receptor subtypes subserving inhibition may offer diverse mechanisms for maintaining inhibitory homeostasis.SIGNIFICANCE STATEMENT Corelease of neurotransmitters is a common feature of the brain. GABA and glycine corelease is particularly common in the spinal cord and brainstem, but its presence in the midbrain is unknown. We show corelease of GABA and glycine for the first time in the central nucleus of the inferior colliculus of the auditory midbrain. Glycine and GABA are both inhibitory neurotransmitters involved in fast synaptic transmission, so we explored differences between the currents to establish a physiological foundation for functional differences in vivo In contrast to the auditory brainstem, coreleased GABAergic and glycinergic currents in the midbrain are strikingly similar. This apparent redundancy may ensure homeostasis if one neurotransmitter system is compromised.
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Nerlich J, Rübsamen R, Milenkovic I. Developmental Shift of Inhibitory Transmitter Content at a Central Auditory Synapse. Front Cell Neurosci 2017; 11:211. [PMID: 28769768 PMCID: PMC5516124 DOI: 10.3389/fncel.2017.00211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/03/2017] [Indexed: 12/11/2022] Open
Abstract
Synaptic inhibition in the CNS is mostly mediated by GABA or glycine. Generally, the use of the two transmitters is spatially segregated, but there are central synapses employing both, which allows for spatial and temporal variability of inhibitory mechanisms. Spherical bushy cells (SBCs) in the mammalian cochlear nucleus receive primary excitatory inputs through auditory nerve fibers arising from the organ of Corti and non-primary inhibition mediated by a dual glycine-GABA transmission. Slow kinetics IPSCs enable activity dependent tonic-like conductance build up, functioning as a gain control by filtering out small or temporally imprecise EPSPs. However, it remained elusive whether GABA and glycine are released as content of the same vesicle or from distinct presynaptic terminals. The developmental profile of quantal release was investigated with whole cell recordings of miniature inhibitory postsynaptic currents (mIPSCs) from P1–P25 SBCs of Mongolian gerbils. GABA is the initial transmitter eliciting slow-rising and -decaying events of relatively small amplitudes, occurring only during early postnatal life. Around and after hearing onset, the inhibitory quanta are predominantly containing glycine that—with maturity—triggers progressively larger and longer mIPSC. In addition, GABA corelease with glycine evokes mIPSCs of particularly large amplitudes consistently occurring across all ages, but with low probability. Together, these results suggest that GABA, as the primary transmitter released from immature inhibitory terminals, initially plays a developmental role. In maturity, GABA is contained in synaptic vesicles only in addition to glycine to increase the inhibitory potency, thereby fulfilling solely a modulatory function.
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Affiliation(s)
- Jana Nerlich
- Department of Physiology, Faculty of Medicine, Carl Ludwig Institute for Physiology, University of LeipzigLeipzig, Germany
| | - Rudolf Rübsamen
- Faculty of Biosciences, Pharmacy and Psychology, University of LeipzigLeipzig, Germany
| | - Ivan Milenkovic
- Department of Physiology, Faculty of Medicine, Carl Ludwig Institute for Physiology, University of LeipzigLeipzig, Germany
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Hannibal J, Christiansen AT, Heegaard S, Fahrenkrug J, Kiilgaard JF. Melanopsin expressing human retinal ganglion cells: Subtypes, distribution, and intraretinal connectivity. J Comp Neurol 2017; 525:1934-1961. [PMID: 28160289 DOI: 10.1002/cne.24181] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/24/2017] [Accepted: 01/25/2017] [Indexed: 12/15/2022]
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin belong to a heterogenic population of RGCs which regulate the circadian clock, masking behavior, melatonin suppression, the pupillary light reflex, and sleep/wake cycles. The different functions seem to be associated to different subtypes of melanopsin cells. In rodents, subtype classification has associated subtypes to function. In primate and human retina such classification has so far, not been applied. In the present study using antibodies against N- and C-terminal parts of human melanopsin, confocal microscopy and 3D reconstruction of melanopsin immunoreactive (-ir) RGCs, we applied the criteria used in mouse on human melanopsin-ir RGCs. We identified M1, displaced M1, M2, and M4 cells. We found two other subtypes of melanopsin-ir RGCs, which were named "gigantic M1 (GM1)" and "gigantic displaced M1 (GDM1)." Few M3 cells and no M5 subtypes were labeled. Total cell counts from one male and one female retina revealed that the human retina contains 7283 ± 237 melanopsin-ir (0.63-0.75% of the total number of RGCs). The melanopsin subtypes were unevenly distributed. Most significant was the highest density of M4 cells in the nasal retina. We identified input to the melanopsin-ir RGCs from AII amacrine cells and directly from rod bipolar cells via ribbon synapses in the innermost ON layer of the inner plexiform layer (IPL) and from dopaminergic amacrine cells and GABAergic processes in the outermost OFF layer of the IPL. The study characterizes a heterogenic population of human melanopsin-ir RGCs, which most likely are involved in different functions.
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Affiliation(s)
- Jens Hannibal
- Department of Clinical Biochemistry, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | | | - Steffen Heegaard
- Department of Ophalmology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Pathology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Jan Fahrenkrug
- Department of Clinical Biochemistry, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Jens Folke Kiilgaard
- Department of Ophalmology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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Abstract
Receptive fields (RFs) of most retinal ganglion cells (RGCs) consist of an excitatory center and suppressive surround. The RF center arises from the summation of excitatory bipolar cell glutamatergic inputs, whereas the surround arises from lateral inhibitory inputs. In the retina, both gamma amino butyric acid (GABA) and glycine are inhibitory neurotransmitters. A clear role for GABAergic inhibition modulating the RGC RF surround has been demonstrated across species. Glycinergic inhibition is more commonly associated with RF center modulation, although there is some evidence that it may contribute to the RF surround. The synaptic glycinergic chloride channels are formed by three homomeric β and two homomeric α subunits that can be glycine receptor (GlyR) α1, α2, α3, or α4. GlyRα composition is responsible for currents with distinct decay kinetics. Their expression within the inner plexiform laminae and neuronal subtypes also differ. We studied the role of GlyR subunit selective modulation of RGC RF surrounds, using mice lacking GlyRα2 (Glra2 -/-), GlyRα3 (Glra3 -/-), or both (Glra2/3 -/-). We chose this molecular genetic approach instead of pharmacological manipulation because there are no subunit selective antagonists and strychnine blocks all GlyRs. Comparisons of annulus-evoked responses among wild type (WT) and GlyRα knockouts (Glra2 -/-, Glra3 -/- and Glra2/3 -/-) show that GlyRα2 inhibition enhances RF surround suppression and post-stimulus excitation in only WT OFF RGCs. Similarities in the responses in Glra2 -/- and Glra2/3 -/- RGCs verify these conclusions. Based on previous and current data, we propose that GlyRα2-mediated input uses a crossover inhibitory circuit. Further, we suggest that GlyRα2 modulates the OFF RGC RF center and surround independently. In summary, our results define a selective GlyR subunit-specific control of RF surround suppression in OFF RGCs.
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Breitinger U, Sticht H, Breitinger HG. Modulation of Recombinant Human α1 Glycine Receptors by Mono- and Disaccharides: A Kinetic Study. ACS Chem Neurosci 2016; 7:1077-87. [PMID: 27227552 DOI: 10.1021/acschemneuro.6b00044] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Glycine receptors (GlyRs) mediate fast synaptic inhibition in spinal cord, brainstem, and higher brain centers. Recently, glucose was identified as a positive modulator of GlyR-mediated currents. Here, we investigated extent and kinetics of the positive modulation of recombinant human α1 glycine receptors by different mono- and disaccharides and sorbitol using patch-clamp recording techniques. Glucose and fructose augmented glycine-mediated whole-cell currents with an EC50 of 6-7 mM. At concentrations > 10 mM, the maximum of current enhancement was reached within ∼30 min. Kinetics of GlyR modulation resemble those of protein glycation. On-rates were <0.5 h for saturating concentrations of monosaccharides and ∼1.5 h for disaccharides. Off-rates were considerably slower (>24 h). Galactose, the C4-epimer of glucose, and the sugar alcohol sorbitol had no effect on GlyR currents. Recent cryoelectron microscopy structures were used to identify a potential binding site for saccharides near the ivermectin binding pocket with lysine 143 as possible attachment site. The GlyR mutant α1(K143A) was not potentiated by glucose, suggesting an involvement of this residue in glycine receptor modulation by saccharides.
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Affiliation(s)
- Ulrike Breitinger
- Department
of Biochemistry, The German University in Cairo, Main Entrance
of Al Tagamoa Al Khames, New Cairo 11835, Egypt
| | - Heinrich Sticht
- Bioinformatics, Institute for Biochemistry, Friedrich-Alexander-Universität Erlangen-Nümberg, Fahrstrasse 17, D-91054 Erlangen, Germany
| | - Hans-Georg Breitinger
- Department
of Biochemistry, The German University in Cairo, Main Entrance
of Al Tagamoa Al Khames, New Cairo 11835, Egypt
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Electrophysiological fingerprints of OFF bipolar cells in rat retina. Sci Rep 2016; 6:30259. [PMID: 27457753 PMCID: PMC4960551 DOI: 10.1038/srep30259] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/04/2016] [Indexed: 01/05/2023] Open
Abstract
Retinal bipolar cells (BCs) divide photoreceptor output into different channels for the parallel extraction of temporal and chromatic stimulus properties. In rodents, five types of OFF BCs have been differentiated, based on morphological and functional criteria, but their electrophysiological characterization remains incomplete. This study analyzed OFF BCs with the patch clamp technique in acute slices of rat retina. Their specific voltage-dependent currents and glutamate responses are shown to represent individual fingerprints which define the signal processing and filtering properties of each cell type and allow their unequivocal identification. Two additions to the rat BC repertoire are presented: OFF BC-2', a variation of BC-2 with wider axonal arbours and prominent Na(+) currents, is described for the first time in rodents, and OFF BC-3b, previously identified in mouse, is electrophysiologically characterized in rat. Moreover, the glutamate responses of rat OFF BCs are shown to be differentially sensitive to AMPA- and kainate-receptor blockers and to modulation by nitric oxide (NO) through a cGMP-dependent mechanism. These results contribute to our understanding of the diversity and function of bipolar cells in mammals.
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Ogino K, Hirata H. Defects of the Glycinergic Synapse in Zebrafish. Front Mol Neurosci 2016; 9:50. [PMID: 27445686 PMCID: PMC4925712 DOI: 10.3389/fnmol.2016.00050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022] Open
Abstract
Glycine mediates fast inhibitory synaptic transmission. Physiological importance of the glycinergic synapse is well established in the brainstem and the spinal cord. In humans, the loss of glycinergic function in the spinal cord and brainstem leads to hyperekplexia, which is characterized by an excess startle reflex to sudden acoustic or tactile stimulation. In addition, glycinergic synapses in this region are also involved in the regulation of respiration and locomotion, and in the nociceptive processing. The importance of the glycinergic synapse is conserved across vertebrate species. A teleost fish, the zebrafish, offers several advantages as a vertebrate model for research of glycinergic synapse. Mutagenesis screens in zebrafish have isolated two motor defective mutants that have pathogenic mutations in glycinergic synaptic transmission: bandoneon (beo) and shocked (sho). Beo mutants have a loss-of-function mutation of glycine receptor (GlyR) β-subunit b, alternatively, sho mutant is a glycinergic transporter 1 (GlyT1) defective mutant. These mutants are useful animal models for understanding of glycinergic synaptic transmission and for identification of novel therapeutic agents for human diseases arising from defect in glycinergic transmission, such as hyperekplexia or glycine encephalopathy. Recent advances in techniques for genome editing and for imaging and manipulating of a molecule or a physiological process make zebrafish more attractive model. In this review, we describe the glycinergic defective zebrafish mutants and the technical advances in both forward and reverse genetic approaches as well as in vivo visualization and manipulation approaches for the study of the glycinergic synapse in zebrafish.
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Affiliation(s)
- Kazutoyo Ogino
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University Sagamihara, Japan
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Synaptic connections of amacrine cells containing vesicular glutamate transporter 3 in baboon retinas. Vis Neurosci 2016; 32:E006. [PMID: 26241195 DOI: 10.1017/s0952523815000036] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The goals of these experiments were to describe the morphology and synaptic connections of amacrine cells in the baboon retina that contain immunoreactive vesicular glutamate transporter 3 (vGluT3). These amacrine cells had the morphology characteristic of knotty bistratified type 1 cells, and their dendrites formed two plexuses on either side of the center of the inner plexiform layer. The primary dendrites received large synapses from amacrine cells, and the higher-order dendrites were both pre- and postsynaptic to other amacrine cells. Based on light microscopic immunolabeling results, these include AII cells and starburst cells, but not the polyaxonal amacrine cells tracer-coupled to ON parasol ganglion cells. The vGluT3 cells received input from ON bipolar cells at ribbon synapses and made synapses onto OFF bipolar cells, including the diffuse DB3a type. Many synapses from vGluT3 cells onto retinal ganglion cells were observed in both plexuses. At synapses where vGluT3 cells were presynaptic, two types of postsynaptic densities were observed; there were relatively thin ones characteristic of inhibitory synapses and relatively thick ones characteristic of excitatory synapses. In the light microscopic experiments with Neurobiotin-injected ganglion cells, vGluT3 cells made contacts with midget and parasol ganglion cells, including both ON and OFF types. Puncta containing immunoreactive gephyrin, an inhibitory synapse marker, were found at appositions between vGluT3 cells and each of the four types of labeled ganglion cells. The vGluT3 cells did not have detectable levels of immunoreactive γ-aminobutyric acid (GABA) or immunoreactive glycine transporter 1. Thus, the vGluT3 cells would be expected to have ON responses to light and make synapses onto neurons in both the ON and the OFF pathways. Taken with previous results, these findings suggest that vGluT3 cells release glycine at some of their output synapses and glutamate at others.
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37
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Yan RJ, Gong HQ, Zhang PM, He SG, Liang PJ. Temporal properties of dual-peak responses of mouse retinal ganglion cells and effects of inhibitory pathways. Cogn Neurodyn 2016; 10:211-23. [PMID: 27275377 DOI: 10.1007/s11571-015-9374-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 12/08/2015] [Accepted: 12/24/2015] [Indexed: 11/26/2022] Open
Abstract
Dual-peak responses of retinal ganglion cells (RGCs) are observed in various species, previous researches suggested that both response peaks were involved in retinal information coding. In the present study, we investigated the temporal properties of the dual-peak responses recorded in mouse RGCs elicited by spatially homogeneous light flashes and the effect of the inhibitory inputs mediated by GABAergic and/or glycinergic pathways. We found that the two peaks in the dual-peak responses exhibited distinct temporal dynamics, similar to that of short-latency and long-latency single-peak responses respectively. Pharmacological studies demonstrated that the application of exogenous GABA or glycine greatly suppressed or even eliminated the second peak of the cells' firing activities, while little change was induced in the first peak. Co-application of glycine and GABA led to complete elimination of the second peak. Moreover, application of picrotoxin or strychnine induced dual-peak responses in some cells with transient responses by unmasking a second response phase. These results suggest that both GABAergic and glycinergic pathways are involved in the dual-peak responses of the mouse RGCs, and the two response peaks may arise from distinct pathways that would converge on the ganglion cells.
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Affiliation(s)
- Ru-Jia Yan
- School of Biomedical Engineering, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai, 200240 China
| | - Hai-Qing Gong
- School of Biomedical Engineering, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai, 200240 China
| | - Pu-Ming Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai, 200240 China
| | - Shi-Gang He
- School of Biomedical Engineering, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai, 200240 China
| | - Pei-Ji Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, 800 Dong-Chuan Road, Shanghai, 200240 China
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Vuong HE, Pérez de Sevilla Müller L, Hardi CN, McMahon DG, Brecha NC. Heterogeneous transgene expression in the retinas of the TH-RFP, TH-Cre, TH-BAC-Cre and DAT-Cre mouse lines. Neuroscience 2015; 307:319-37. [PMID: 26335381 PMCID: PMC4603663 DOI: 10.1016/j.neuroscience.2015.08.060] [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] [Received: 02/05/2015] [Revised: 08/21/2015] [Accepted: 08/24/2015] [Indexed: 11/29/2022]
Abstract
Transgenic mouse lines are essential tools for understanding the connectivity, physiology and function of neuronal circuits, including those in the retina. This report compares transgene expression in the retina of a tyrosine hydroxylase (TH)-red fluorescent protein (RFP) mouse line with three catecholamine-related Cre recombinase mouse lines [TH-bacterial artificial chromosome (BAC)-, TH-, and dopamine transporter (DAT)-Cre] that were crossed with a ROSA26-tdTomato reporter line. Retinas were evaluated and immunostained with commonly used antibodies including those directed to TH, GABA and glycine to characterize the RFP or tdTomato fluorescent-labeled amacrine cells, and an antibody directed to RNA-binding protein with multiple splicing to identify ganglion cells. In TH-RFP retinas, types 1 and 2 dopamine (DA) amacrine cells were identified by their characteristic cellular morphology and type 1 DA cells by their expression of TH immunoreactivity. In the TH-BAC-, TH-, and DAT-tdTomato retinas, less than 1%, ∼ 6%, and 0%, respectively, of the fluorescent cells were the expected type 1 DA amacrine cells. Instead, in the TH-BAC-tdTomato retinas, fluorescently labeled AII amacrine cells were predominant, with some medium diameter ganglion cells. In TH-tdTomato retinas, fluorescence was in multiple neurochemical amacrine cell types, including four types of polyaxonal amacrine cells. In DAT-tdTomato retinas, fluorescence was in GABA immunoreactive amacrine cells, including two types of bistratified and two types of monostratified amacrine cells. Although each of the Cre lines was generated with the intent to specifically label DA cells, our findings show a cellular diversity in Cre expression in the adult retina and indicate the importance of careful characterization of transgene labeling patterns. These mouse lines with their distinctive cellular labeling patterns will be useful tools for future studies of retinal function and visual processing.
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Affiliation(s)
- H E Vuong
- Molecular, Cellular, and Integrative Physiology Program, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
| | - L Pérez de Sevilla Müller
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
| | - C N Hardi
- Department of Psychology, College of Letters and Science, UCLA, Los Angeles, CA 90095, United States
| | - D G McMahon
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, United States
| | - N C Brecha
- Molecular, Cellular, and Integrative Physiology Program, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; CURE-Digestive Diseases Research Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, United States.
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Balakrishnan V, Puthussery T, Kim MH, Taylor WR, von Gersdorff H. Synaptic Vesicle Exocytosis at the Dendritic Lobules of an Inhibitory Interneuron in the Mammalian Retina. Neuron 2015; 87:563-75. [PMID: 26247863 DOI: 10.1016/j.neuron.2015.07.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/07/2015] [Accepted: 07/20/2015] [Indexed: 11/16/2022]
Abstract
Ribbon synapses convey sustained and phasic excitatory drive within retinal microcircuits. However, the properties of retinal inhibitory synapses are less well known. AII-amacrine cells are interneurons in the retina that exhibit large glycinergic synapses at their dendritic lobular appendages. Using membrane capacitance measurements, we observe robust exocytosis elicited by the opening of L-type Ca(2+) channels located on the lobular appendages. Two pools of synaptic vesicles were detected: a small, rapidly releasable pool and a larger and more slowly releasable pool. Depending on the stimulus, either paired-pulse depression or facilitation could be elicited. During early postnatal maturation, the coupling of the exocytosis Ca(2+)-sensor to Ca(2+) channel becomes tighter. Light-evoked depolarizations of the AII-amacrine cell elicited exocytosis that was graded to light intensity. Our results suggest that AII-amacrine cell synapses are capable of providing both phasic and sustained inhibitory input to their postsynaptic partners without the benefit of synaptic ribbons.
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Affiliation(s)
| | - Theresa Puthussery
- Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Mean-Hwan Kim
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - W Rowland Taylor
- Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Henrique von Gersdorff
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA.
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Neurotransmission plays contrasting roles in the maturation of inhibitory synapses on axons and dendrites of retinal bipolar cells. Proc Natl Acad Sci U S A 2015; 112:12840-5. [PMID: 26420868 DOI: 10.1073/pnas.1510483112] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neuronal output is modulated by inhibition onto both dendrites and axons. It is unknown whether inhibitory synapses at these two cellular compartments of an individual neuron are regulated coordinately or separately during in vivo development. Because neurotransmission influences synapse maturation and circuit development, we determined how loss of inhibition affects the expression of diverse types of inhibitory receptors on the axon and dendrites of mouse retinal bipolar cells. We found that axonal GABA but not glycine receptor expression depends on neurotransmission. Importantly, axonal and dendritic GABAA receptors comprise distinct subunit compositions that are regulated differentially by GABA release: Axonal GABAA receptors are down-regulated but dendritic receptors are up-regulated in the absence of inhibition. The homeostatic increase in GABAA receptors on bipolar cell dendrites is pathway-specific: Cone but not rod bipolar cell dendrites maintain an up-regulation of receptors in the transmission deficient mutants. Furthermore, the bipolar cell GABAA receptor alterations are a consequence of impaired vesicular GABA release from amacrine but not horizontal interneurons. Thus, inhibitory neurotransmission regulates in vivo postsynaptic maturation of inhibitory synapses with contrasting modes of action specific to synapse type and location.
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Barrera SP, Castrejon-Tellez V, Trinidad M, Robles-Escajeda E, Vargas-Medrano J, Varela-Ramirez A, Miranda M. PKC-Dependent GlyT1 Ubiquitination Occurs Independent of Phosphorylation: Inespecificity in Lysine Selection for Ubiquitination. PLoS One 2015; 10:e0138897. [PMID: 26418248 PMCID: PMC4587969 DOI: 10.1371/journal.pone.0138897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/06/2015] [Indexed: 01/08/2023] Open
Abstract
Neurotransmitter transporter ubiquitination is emerging as the main mechanism for endocytosis and sorting of cargo into lysosomes. In this study, we demonstrate PKC-dependent ubiquitination of three different isoforms of the glycine transporter 1 (GlyT1). Incubation of cells expressing transporter with the PKC activator phorbol ester induced a dramatic, time-dependent increase in GlyT1 ubiquitination, followed by accumulation of GlyT1 in EEA1 positive early endosomes. This occurred via a mechanism that was abolished by inhibition of PKC. GlyT1 endocytosis was confirmed in both retinal sections and primary cultures of mouse amacrine neurons. Replacement of only all lysines in the N-and C-termini to arginines prevented ubiquitination and endocytosis, displaying redundancy in the mechanism of ubiquitination. Interestingly, a 40–50% reduction in glycine uptake was detected in phorbol-ester stimulated cells expressing the WT-GlyT1, whereas no significant change was for the mutant protein, demonstrating that endocytosis participates in the reduction of uptake. Consistent with previous findings for the dopamine transporter DAT, ubiquitination of GlyT1 tails functions as sorting signal to deliver transporter into the lysosome and removal of ubiquitination sites dramatically attenuated the rate of GlyT1 degradation. Finally, we showed for the first time that PKC-dependent GlyT1 phosphorylation was not affected by removal of ubiquitination sites, suggesting separate PKC-dependent signaling events for these posttranslational modifications.
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Affiliation(s)
- Susana P. Barrera
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Vicente Castrejon-Tellez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Margarita Trinidad
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Elisa Robles-Escajeda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Javier Vargas-Medrano
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Armando Varela-Ramirez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Manuel Miranda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
- * E-mail:
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Some Operational Characteristics of Glycine Release in Rat Retina: The Role of Reverse Mode Operation of Glycine Transporter Type-1 (GlyT-1) in Ischemic Conditions. Neurochem Res 2015; 41:73-85. [PMID: 26364050 DOI: 10.1007/s11064-015-1713-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/26/2015] [Accepted: 08/28/2015] [Indexed: 10/23/2022]
Abstract
Rat posterior eyecups containing the retina were prepared, loaded with [(3)H]glycine and superfused in order to determine its release originated from glycinergic amacrine cells and/or glial cells. Deprivation of oxygen and glucose from the Krebs-bicarbonate buffer used for superfusion evoked a marked increase of [(3)H]glycine release, an effect that was found to be external Ca(2+)-independent. Whereas oxygen and glucose deprivation increased [(3)H]glycine release, its uptake was reduced suggesting that energy deficiency shifts glycine transporter type-1 operation from normal to reverse mode. The increased release of [(3)H]glycine evoked by oxygen and glucose deprivation was suspended by addition of the non-competitive glycine transporter type-1 inhibitor NFPS and the competitive inhibitor ACPPB further suggesting the involvement of this transporter in the mediation of [(3)H]glycine release. Oxygen and glucose deprivation also evoked [(3)H]glutamate release from rat retina and the concomitantly occurring release of the NMDA receptor agonist glutamate and the coagonist glycine makes NMDA receptor pathological overstimulation possible in hypoxic conditions. [(3)H]Glutamate release was suspended by addition of the excitatory amino acid transporter inhibitor TBOA. Sarcosine, a substrate inhibitor of glycine transporter type-1, also increased [(3)H]glycine release probably by heteroexchange shifting transporter operation into reverse mode. This effect of sarcosine was also external Ca(2+)-independent and could be suspended by NFPS. Energy deficiency in retina induced by ouabain, an inhibitor of the Na(+)-K(+)-dependent ATPase, and by rotenone, a mitochondrial complex I inhibitor added with the glycolytic inhibitor 2-deoxy-D-glucose, led to increase of retinal [(3)H]glycine efflux. These effects of ouabain and rotenone/2-deoxy-D-glucose could also be blocked by NFPS pointed to the preferential reverse mode operation of glycine transporter type-1 as a consequence of impaired cellular energy homeostasis. Immunohistochemical studies revealed that glycine transporter type-1, of which reverse mode operation assures [(3)H]glycine release, is expressed in amacrine cells in the inner nuclear and plexiform layers of the retina and also in Müller macroglia cells. We conclude that disruption of the balanced normal/reverse mode operation of glycine transporter type-1 is likely a significant factor contributing to neurotoxic processes of the retina. The possibility to inhibit glycine transporter type-1 mediated glycine efflux by drugs more potently than glycine uptake might offer some therapeutic potential for the treatment of various neurodegenerative disorders of the retina.
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Tkatchenko AV, Tkatchenko TV, Guggenheim JA, Verhoeven VJM, Hysi PG, Wojciechowski R, Singh PK, Kumar A, Thinakaran G, Williams C. APLP2 Regulates Refractive Error and Myopia Development in Mice and Humans. PLoS Genet 2015; 11:e1005432. [PMID: 26313004 PMCID: PMC4551475 DOI: 10.1371/journal.pgen.1005432] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 07/07/2015] [Indexed: 11/19/2022] Open
Abstract
Myopia is the most common vision disorder and the leading cause of visual impairment worldwide. However, gene variants identified to date explain less than 10% of the variance in refractive error, leaving the majority of heritability unexplained (“missing heritability”). Previously, we reported that expression of APLP2 was strongly associated with myopia in a primate model. Here, we found that low-frequency variants near the 5’-end of APLP2 were associated with refractive error in a prospective UK birth cohort (n = 3,819 children; top SNP rs188663068, p = 5.0 × 10−4) and a CREAM consortium panel (n = 45,756 adults; top SNP rs7127037, p = 6.6 × 10−3). These variants showed evidence of differential effect on childhood longitudinal refractive error trajectories depending on time spent reading (gene x time spent reading x age interaction, p = 4.0 × 10−3). Furthermore, Aplp2 knockout mice developed high degrees of hyperopia (+11.5 ± 2.2 D, p < 1.0 × 10−4) compared to both heterozygous (-0.8 ± 2.0 D, p < 1.0 × 10−4) and wild-type (+0.3 ± 2.2 D, p < 1.0 × 10−4) littermates and exhibited a dose-dependent reduction in susceptibility to environmentally induced myopia (F(2, 33) = 191.0, p < 1.0 × 10−4). This phenotype was associated with reduced contrast sensitivity (F(12, 120) = 3.6, p = 1.5 × 10−4) and changes in the electrophysiological properties of retinal amacrine cells, which expressed Aplp2. This work identifies APLP2 as one of the “missing” myopia genes, demonstrating the importance of a low-frequency gene variant in the development of human myopia. It also demonstrates an important role for APLP2 in refractive development in mice and humans, suggesting a high level of evolutionary conservation of the signaling pathways underlying refractive eye development. Gene variants identified by GWAS studies to date explain only a small fraction of myopia cases because myopia represents a complex disorder thought to be controlled by dozens or even hundreds of genes. The majority of genetic variants underlying myopia seems to be of small effect and/or low frequency, which makes them difficult to identify using classical genetic approaches, such as GWAS, alone. Here, we combined gene expression profiling in a monkey model of myopia, human GWAS, and a gene-targeted mouse model of myopia to identify one of the “missing” myopia genes, APLP2. We found that a low-frequency risk allele of APLP2 confers susceptibility to myopia only in children exposed to large amounts of daily reading, thus, providing an experimental example of the long-hypothesized gene-environment interaction between nearwork and genes underlying myopia. Functional analysis of APLP2 using an APLP2 knockout mouse model confirmed functional significance of APLP2 in refractive development and implicated a potential role of synaptic transmission at the level of glycinergic amacrine cells of the retina for the development of myopia. Furthermore, mouse studies revealed that lack of Aplp2 has a dose-dependent suppressive effect on susceptibility to form-deprivation myopia, providing a potential gene-specific target for therapeutic intervention to treat myopia.
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Affiliation(s)
- Andrei V. Tkatchenko
- Department of Ophthalmology, Columbia University, New York, New York, United States of America
- Department of Pathology and Cell Biology, Columbia University, New York, New York, United States of America
- * E-mail:
| | - Tatiana V. Tkatchenko
- Department of Ophthalmology, Columbia University, New York, New York, United States of America
| | - Jeremy A. Guggenheim
- School of Optometry & Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Virginie J. M. Verhoeven
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, Netherlands
| | - Pirro G. Hysi
- Department of Twin Research and Genetic Epidemiology, King’s College London School of Medicine, London, United Kingdom
| | - Robert Wojciechowski
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- Statistical Genetics Section, Inherited Disease Research Branch, National Human Genome Research Institute (NIH), Baltimore, Maryland, United States of America
| | - Pawan Kumar Singh
- Department of Ophthalmology, Wayne State University, Detroit, Michigan, United States of America
| | - Ashok Kumar
- Department of Ophthalmology, Wayne State University, Detroit, Michigan, United States of America
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States of America
| | - Gopal Thinakaran
- Departments of Neurobiology, Neurology, and Pathology, University of Chicago, Chicago, Illinois, United States of America
| | | | - Cathy Williams
- School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom
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Lee SCS, Meyer A, Schubert T, Hüser L, Dedek K, Haverkamp S. Morphology and connectivity of the small bistratified A8 amacrine cell in the mouse retina. J Comp Neurol 2015; 523:1529-47. [PMID: 25630271 DOI: 10.1002/cne.23752] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 01/22/2015] [Accepted: 01/24/2015] [Indexed: 01/23/2023]
Abstract
Amacrine cells comprise ∼ 30 morphological types in the mammalian retina. The synaptic connectivity and function of a few γ-aminobutyric acid (GABA)ergic wide-field amacrine cells have recently been studied; however, with the exception of the rod pathway-specific AII amacrine cell, the connectivity of glycinergic small-field amacrine cells has not been investigated in the mouse retina. Here, we studied the morphology and connectivity pattern of the small-field A8 amacrine cell. A8 cells in mouse retina are bistratified with lobular processes in the ON sublamina and arboreal dendrites in the OFF sublamina of the inner plexiform layer. The distinct bistratified morphology was first visible at postnatal day 8, reaching the adult shape at P13, around eye opening. The connectivity of A8 cells to bipolar cells and ganglion cells was studied by double and triple immunolabeling experiments by using various cell markers combined with synaptic markers. Our data suggest that A8 amacrine cells receive glutamatergic input from both OFF and ON cone bipolar cells. Furthermore, A8 cells are coupled to ON cone bipolar cells by gap junctions, and provide inhibitory input via glycine receptor (GlyR) subunit α1 to OFF cone bipolar cells and to ON A-type ganglion cells. Measurements of spontaneous glycinergic postsynaptic currents and GlyR immunolabeling revealed that A8 cells express GlyRs containing the α2 subunit. The results show that the bistratified A8 cell makes very similar synaptic contacts with cone bipolar cells as the rod pathway-specific AII amacrine cell. However, unlike AII cells, A8 amacrine cells provide glycinergic input to ON A-type ganglion cells.
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Affiliation(s)
- Sammy C S Lee
- Max Planck Institute for Brain Research, 60438, Frankfurt am Main, Germany.,University of Sydney-Save Sight Institute, Sydney, New South Wales, 2000, Australia
| | - Arndt Meyer
- Department of Neurobiology, University of Oldenburg, 26129, Oldenburg, Germany
| | - Timm Schubert
- Werner Reichardt Center for Integrative Neuroscience (CIN)/Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany
| | - Laura Hüser
- Max Planck Institute for Brain Research, 60438, Frankfurt am Main, Germany
| | - Karin Dedek
- Department of Neurobiology, University of Oldenburg, 26129, Oldenburg, Germany.,Research Center for Neurosensory Science, University of Oldenburg, 26129, Oldenburg, Germany
| | - Silke Haverkamp
- Max Planck Institute for Brain Research, 60438, Frankfurt am Main, Germany
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Zhang Y, Dixon CL, Keramidas A, Lynch JW. Functional reconstitution of glycinergic synapses incorporating defined glycine receptor subunit combinations. Neuropharmacology 2015; 89:391-7. [DOI: 10.1016/j.neuropharm.2014.10.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/16/2014] [Accepted: 10/26/2014] [Indexed: 10/24/2022]
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46
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Zhang C, Rompani SB, Roska B, McCall MA. Adeno-associated virus-RNAi of GlyRα1 and characterization of its synapse-specific inhibition in OFF alpha transient retinal ganglion cells. J Neurophysiol 2014; 112:3125-37. [PMID: 25231618 DOI: 10.1152/jn.00505.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the central nervous system, inhibition shapes neuronal excitation. In spinal cord glycinergic inhibition predominates, whereas GABAergic inhibition predominates in the brain. The retina uses GABA and glycine in approximately equal proportions. Glycinergic crossover inhibition, initiated in the On retinal pathway, controls glutamate release from presynaptic OFF cone bipolar cells (CBCs) and directly shapes temporal response properties of OFF retinal ganglion cells (RGCs). In the retina, four glycine receptor (GlyR) α-subunit isoforms are expressed in different sublaminae and their synaptic currents differ in decay kinetics. GlyRα1, expressed in both On and Off sublaminae of the inner plexiform layer, could be the glycinergic isoform that mediates On-to-Off crossover inhibition. However, subunit-selective glycine contributions remain unknown because we lack selective antagonists or cell class-specific subunit knockouts. To examine the role of GlyRα1 in direct inhibition in mature RGCs, we used retrogradely transported adeno-associated virus (AAV) that performed RNAi and eliminated almost all glycinergic spontaneous and visually evoked responses in PV5 (OFFα(Transient)) RGCs. Comparisons of responses in PV5 RGCs infected with AAV-scrambled-short hairpin RNA (shRNA) or AAV-Glra1-shRNA confirm a role for GlyRα1 in crossover inhibition in cone-driven circuits. Our results also define a role for direct GlyRα1 inhibition in setting the resting membrane potential of PV5 RGCs. The absence of GlyRα1 input unmasked a serial and a direct feedforward GABA(A)ergic modulation in PV5 RGCs, reflecting a complex interaction between glycinergic and GABA(A)ergic inhibition.
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Affiliation(s)
- C Zhang
- Department of Ophthalmology and Visual Science, University of Louisville, Louisville, Kentucky; Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky; and
| | - S B Rompani
- Neural Circuit Laboratories, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - B Roska
- Neural Circuit Laboratories, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - M A McCall
- Department of Ophthalmology and Visual Science, University of Louisville, Louisville, Kentucky; Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky; and
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Hoon M, Okawa H, Della Santina L, Wong ROL. Functional architecture of the retina: development and disease. Prog Retin Eye Res 2014; 42:44-84. [PMID: 24984227 DOI: 10.1016/j.preteyeres.2014.06.003] [Citation(s) in RCA: 359] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/08/2014] [Accepted: 06/22/2014] [Indexed: 12/22/2022]
Abstract
Structure and function are highly correlated in the vertebrate retina, a sensory tissue that is organized into cell layers with microcircuits working in parallel and together to encode visual information. All vertebrate retinas share a fundamental plan, comprising five major neuronal cell classes with cell body distributions and connectivity arranged in stereotypic patterns. Conserved features in retinal design have enabled detailed analysis and comparisons of structure, connectivity and function across species. Each species, however, can adopt structural and/or functional retinal specializations, implementing variations to the basic design in order to satisfy unique requirements in visual function. Recent advances in molecular tools, imaging and electrophysiological approaches have greatly facilitated identification of the cellular and molecular mechanisms that establish the fundamental organization of the retina and the specializations of its microcircuits during development. Here, we review advances in our understanding of how these mechanisms act to shape structure and function at the single cell level, to coordinate the assembly of cell populations, and to define their specific circuitry. We also highlight how structure is rearranged and function is disrupted in disease, and discuss current approaches to re-establish the intricate functional architecture of the retina.
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Affiliation(s)
- Mrinalini Hoon
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Haruhisa Okawa
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Luca Della Santina
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Rachel O L Wong
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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Carvajal-González A, Leite MI, Waters P, Woodhall M, Coutinho E, Balint B, Lang B, Pettingill P, Carr A, Sheerin UM, Press R, Press R, Lunn MP, Lim M, Maddison P, Meinck HM, Vandenberghe W, Vincent A. Glycine receptor antibodies in PERM and related syndromes: characteristics, clinical features and outcomes. ACTA ACUST UNITED AC 2014; 137:2178-92. [PMID: 24951641 PMCID: PMC4107739 DOI: 10.1093/brain/awu142] [Citation(s) in RCA: 324] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
See Martinez-Martinez et al. (doi:10.1093/brain/awu153) for a scientific commentary on this article. Carvajal-González et al. describe the first prospective cohort of patients with glycine receptor antibodies. The majority have progressive encephalomyelitis with rigidity and myoclonus. The antibodies bind to extracellular determinants on glycine receptor-α1 and to glycine receptors on spinal cord and brainstem neurons. The patients make a good recovery with immunotherapies. The clinical associations of glycine receptor antibodies have not yet been described fully. We identified prospectively 52 antibody-positive patients and collated their clinical features, investigations and immunotherapy responses. Serum glycine receptor antibody endpoint titres ranged from 1:20 to 1:60 000. In 11 paired samples, serum levels were higher than (n = 10) or equal to (n = 1) cerebrospinal fluid levels; there was intrathecal synthesis of glycine receptor antibodies in each of the six pairs available for detailed study. Four patients also had high glutamic acid decarboxylase antibodies (>1000 U/ml), and one had high voltage-gated potassium channel-complex antibody (2442 pM). Seven patients with very low titres (<1:50) and unknown or alternative diagnoses were excluded from further study. Three of the remaining 45 patients had newly-identified thymomas and one had a lymphoma. Thirty-three patients were classified as progressive encephalomyelitis with rigidity and myoclonus, and two as stiff person syndrome; five had a limbic encephalitis or epileptic encephalopathy, two had brainstem features mainly, two had demyelinating optic neuropathies and one had an unclear diagnosis. Four patients (9%) died during the acute disease, but most showed marked improvement with immunotherapies. At most recent follow-up, (2–7 years, median 3 years, since first antibody detection), the median modified Rankin scale scores (excluding the four deaths) decreased from 5 at maximal severity to 1 (P < 0.0001), but relapses have occurred in five patients and a proportion are on reducing steroids or other maintenance immunotherapies as well as symptomatic treatments. The glycine receptor antibodies activated complement on glycine receptor-transfected human embryonic kidney cells at room temperature, and caused internalization and lysosomal degradation of the glycine receptors at 37°C. Immunoglobulin G antibodies bound to rodent spinal cord and brainstem co-localizing with monoclonal antibodies to glycine receptor-α1. Ten glycine receptor antibody positive samples were also identified in a retrospective cohort of 56 patients with stiff person syndrome and related syndromes. Glycine receptor antibodies are strongly associated with spinal and brainstem disorders, and the majority of patients have progressive encephalomyelitis with rigidity and myoclonus. The antibodies demonstrate in vitro evidence of pathogenicity and the patients respond well to immunotherapies, contrasting with earlier studies of this syndrome, which indicated a poor prognosis. The presence of glycine receptor antibodies should help to identify a disease that responds to immunotherapies, but these treatments may need to be sustained, relapses can occur and maintenance immunosuppression may be required.
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Affiliation(s)
| | - M Isabel Leite
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Patrick Waters
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Mark Woodhall
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Ester Coutinho
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Bettina Balint
- 2 Department of Neurology, INF 400, 69120 Heidelberg, Germany
| | - Bethan Lang
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Philippa Pettingill
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Aisling Carr
- 3 Department of Clinical Neurology, Royal Victoria Hospital, Belfast, Northern Ireland, BT12 6BA
| | - Una-Marie Sheerin
- 4 Department of Clinical Neurosciences, Charing Cross Hospital, Imperial College, London UK
| | | | - Raomand Press
- 5 Clinical Neuroscience, Karolinska Institute, Department of Neurology, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Michael P Lunn
- 6 Centre for Neuromuscular Disease, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Ming Lim
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Paul Maddison
- 7 Department of Clinical Neurology, Queen's Medical Centre, Nottingham, NG7 2UH, UK
| | - H-M Meinck
- 2 Department of Neurology, INF 400, 69120 Heidelberg, Germany
| | - Wim Vandenberghe
- 8 Department of Neurology, University Hospitals Leuven; Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Angela Vincent
- 1 Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK
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Jiang Z, Yang J, Purpura LA, Liu Y, Ripps H, Shen W. Glycinergic feedback enhances synaptic gain in the distal retina. J Physiol 2014; 592:1479-92. [PMID: 24421349 DOI: 10.1113/jphysiol.2013.265785] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Glycine input originates with interplexiform cells, a group of neurons situated within the inner retina that transmit signals centrifugally to the distal retina. The effect on visual function of this novel mechanism is largely unknown. Using gramicidin-perforated patch whole cell recordings, intracellular recordings and specific antibody labelling techniques, we examined the effects of the synaptic connections between glycinergic interplexiform cells, photoreceptors and bipolar cells. To confirm that interplexiform cells make centrifugal feedback on bipolar cell dendrites, we recorded the postsynaptic glycine currents from axon-detached bipolar cells while stimulating presynaptic interplexiform cells. The results show that glycinergic interplexiform cells activate bipolar cell dendrites that express the α3 subunit of the glycine receptor, as well as a subclass of unidentified receptors on photoreceptors. By virtue of their synaptic contacts, glycine centrifugal feedback increases glutamate release from photoreceptors and suppresses the uptake of glutamate by the type 2A excitatory amino acid transporter on photoreceptors. The net effect is a significant increase in synaptic gain between photoreceptors and their second-order neurons.
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Affiliation(s)
- Zheng Jiang
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA.
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50
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Nivison-Smith L, Chua J, Tan SS, Kalloniatis M. Amino acid signatures in the developing mouse retina. Int J Dev Neurosci 2013; 33:62-80. [PMID: 24368173 DOI: 10.1016/j.ijdevneu.2013.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 12/13/2013] [Indexed: 11/29/2022] Open
Abstract
This study characterizes the developmental patterns of seven key amino acids: glutamate, γ-amino-butyric acid (GABA), glycine, glutamine, aspartate, alanine and taurine in the mouse retina. We analyze amino acids in specific bipolar, amacrine and ganglion cell sub-populations (i.e. GABAergic vs. glycinergic amacrine cells) and anatomically distinct regions of photoreceptors and Müller cells (i.e. cell bodies vs. endfeet) by extracting data from previously described pattern recognition analysis. Pattern recognition statistically classifies all cells in the retina based on their neurochemical profile and surpasses the previous limitations of anatomical and morphological identification of cells in the immature retina. We found that the GABA and glycine cellular content reached adult-like levels in most neurons before glutamate. The metabolic amino acids glutamine, aspartate and alanine also reached maturity in most retinal cells before eye opening. When the overall amino acid profiles were considered for each cell group, ganglion cells and GABAergic amacrine cells matured first, followed by glycinergic amacrine cells and finally bipolar cells. Photoreceptor cell bodies reached adult-like amino acid profiles at P7 whilst Müller cells acquired typical amino acid profiles in their cell bodies at P7 and in their endfeet by P14. We further compared the amino acid profiles of the C57Bl/6J mouse with the transgenic X-inactivation mouse carrying the lacZ gene on the X chromosome and validated this animal model for the study of normal retinal development. This study provides valuable insight into normal retinal neurochemical maturation and metabolism and benchmark amino acid values for comparison with retinal disease, particularly those which occur during development.
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Affiliation(s)
- Lisa Nivison-Smith
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
| | - Jacqueline Chua
- Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
| | - Seong-Seng Tan
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Michael Kalloniatis
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia; Department of Optometry and Vision Science, University of Auckland, Auckland, New Zealand; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia; Centre for Eye Health, Sydney, Australia.
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