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Krüppel S, Khani MH, Schreyer HM, Sridhar S, Ramakrishna V, Zapp SJ, Mietsch M, Karamanlis D, Gollisch T. Applying Super-Resolution and Tomography Concepts to Identify Receptive Field Subunits in the Retina. PLoS Comput Biol 2024; 20:e1012370. [PMID: 39226328 DOI: 10.1371/journal.pcbi.1012370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 07/28/2024] [Indexed: 09/05/2024] Open
Abstract
Spatially nonlinear stimulus integration by retinal ganglion cells lies at the heart of various computations performed by the retina. It arises from the nonlinear transmission of signals that ganglion cells receive from bipolar cells, which thereby constitute functional subunits within a ganglion cell's receptive field. Inferring these subunits from recorded ganglion cell activity promises a new avenue for studying the functional architecture of the retina. This calls for efficient methods, which leave sufficient experimental time to leverage the acquired knowledge for further investigating identified subunits. Here, we combine concepts from super-resolution microscopy and computed tomography and introduce super-resolved tomographic reconstruction (STR) as a technique to efficiently stimulate and locate receptive field subunits. Simulations demonstrate that this approach can reliably identify subunits across a wide range of model variations, and application in recordings of primate parasol ganglion cells validates the experimental feasibility. STR can potentially reveal comprehensive subunit layouts within only a few tens of minutes of recording time, making it ideal for online analysis and closed-loop investigations of receptive field substructure in retina recordings.
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Affiliation(s)
- Steffen Krüppel
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Mohammad H Khani
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
| | - Helene M Schreyer
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
| | - Shashwat Sridhar
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
| | - Varsha Ramakrishna
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
- International Max Planck Research School for Neurosciences, Göttingen, Germany
| | - Sören J Zapp
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
| | - Matthias Mietsch
- German Primate Center, Laboratory Animal Science Unit, Göttingen, Germany
- German Center for Cardiovascular Research, Partner Site Göttingen, Göttingen, Germany
| | - Dimokratis Karamanlis
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
| | - Tim Gollisch
- University Medical Center Göttingen, Department of Ophthalmology, Göttingen, Germany
- Bernstein Center for Computational Neuroscience Göttingen, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
- Else Kröner Fresenius Center for Optogenetic Therapies, University Medical Center Göttingen, Göttingen, Germany
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Hanke-Gogokhia C, Zapadka TE, Finkelstein S, Klingeborn M, Maugel TK, Singer JH, Arshavsky VY, Demb JB. The Structural and Functional Integrity of Rod Photoreceptor Ribbon Synapses Depends on Redundant Actions of Dynamins 1 and 3. J Neurosci 2024; 44:e1379232024. [PMID: 38641407 PMCID: PMC11209669 DOI: 10.1523/jneurosci.1379-23.2024] [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: 07/21/2023] [Revised: 04/02/2024] [Accepted: 04/13/2024] [Indexed: 04/21/2024] Open
Abstract
Vertebrate vision begins with light absorption by rod and cone photoreceptors, which transmit signals from their synaptic terminals to second-order neurons: bipolar and horizontal cells. In mouse rods, there is a single presynaptic ribbon-type active zone at which the release of glutamate occurs tonically in the dark. This tonic glutamatergic signaling requires continuous exo- and endocytosis of synaptic vesicles. At conventional synapses, endocytosis commonly requires dynamins: GTPases encoded by three genes (Dnm1-3), which perform membrane scission. Disrupting endocytosis by dynamin deletions impairs transmission at conventional synapses, but the impact of disrupting endocytosis and the role(s) of specific dynamin isoforms at rod ribbon synapses are understood incompletely. Here, we used cell-specific knock-outs (KOs) of the neuron-specific Dnm1 and Dnm3 to investigate the functional roles of dynamin isoforms in rod photoreceptors in mice of either sex. Analysis of synaptic protein expression, synapse ultrastructure, and retinal function via electroretinograms (ERGs) showed that dynamins 1 and 3 act redundantly and are essential for supporting the structural and functional integrity of rod ribbon synapses. Single Dnm3 KO showed no phenotype, and single Dnm1 KO only modestly reduced synaptic vesicle density without affecting vesicle size and overall synapse integrity, whereas double Dnm1/Dnm3 KO impaired vesicle endocytosis profoundly, causing enlarged vesicles, reduced vesicle density, reduced ERG responses, synaptic terminal degeneration, and disassembly and degeneration of postsynaptic processes. Concurrently, cone function remained intact. These results show the fundamental redundancy of dynamins 1 and 3 in regulating the structure and function of rod ribbon synapses.
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Affiliation(s)
- Christin Hanke-Gogokhia
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
| | - Thomas E Zapadka
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
- Cellular & Molecular Physiology, Yale University, New Haven, Connecticut 06511
| | - Stella Finkelstein
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Mikael Klingeborn
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Timothy K Maugel
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Jonathan B Demb
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
- Cellular & Molecular Physiology, Yale University, New Haven, Connecticut 06511
- Department of Neuroscience, Yale University, New Haven, Connecticut 06511
- Wu Tsai Institute, Yale University, New Haven, Connecticut 06511
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Pan F, Massey SC. Dye coupling of horizontal cells in the primate retina. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1173706. [PMID: 38983052 PMCID: PMC11182241 DOI: 10.3389/fopht.2023.1173706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 10/03/2023] [Indexed: 07/11/2024]
Abstract
In the monkey retina, there are two distinct types of axon-bearing horizontal cells, known as H1 and H2 horizontal cells (HCs). In this study, cell bodies were prelabled using 4',6-diamidino-2-phenylindole (DAPI), and both H1 and H2 horizontal cells were filled with Neurobiotin™ to reveal their coupling, cellular details, and photoreceptor contacts. The confocal analysis of H1 and H2 HCs was used to assess the colocalization of terminal dendrites with glutamate receptors at cone pedicles. After filling H1 somas, a large coupled mosaic of H1 cells was labeled. The dendritic terminals of H1 cells contacted red/green cone pedicles, with the occasional sparse contact with blue cone pedicles observed. The H2 cells were also dye-coupled. They had larger dendritic fields and lower densities. The dendritic terminals of H2 cells preferentially contacted blue cone pedicles, but additional contacts with nearly all cones within the dendritic field were still observed. The red/green cones constitute 99% of the input to H1 HCs, whereas H2 HCs receive a more balanced input, which is composed of 58% red/green cones and 42% blue cones. These observations confirm those made in earlier studies on primate horizontal cells by Dacey and Goodchild in 1996. Both H1 and H2 HCs were axon-bearing. H1 axon terminals (H1 ATs) were independently coupled and contacted rod spherules exclusively. In contrast, the H2 axon terminals contacted cones, with some preference for blue cone pedicles, as reported by Chan and Grünert in 1998. The primate retina contains three independently coupled HC networks in the outer plexiform layer (OPL), identified as H1 and H2 somatic dendrites, and H1 ATs. At each cone pedicle, the colocalization of both H1 and H2 dendritic tips with GluA4 subunits close to the cone synaptic ribbons indicates that glutamate signaling from the cones to H1 and H2 horizontal cells is mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors.
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Affiliation(s)
- Feng Pan
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR, China
- Centre for Eye and Vision Research (CEVR), Hong Kong, Hong Kong SAR, China
- Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR, China
| | - Stephen C. Massey
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, TX, United States
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Thoreson WB, Chhunchha B. EAAT5 glutamate transporter rapidly binds glutamate with micromolar affinity in mouse rods. J Gen Physiol 2023; 155:e202313349. [PMID: 37477643 PMCID: PMC10359920 DOI: 10.1085/jgp.202313349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/17/2023] [Accepted: 07/05/2023] [Indexed: 07/22/2023] Open
Abstract
Light responses of rod photoreceptor cells in the retina are encoded by changes in synaptic glutamate release that is in turn shaped by reuptake involving EAAT5 plasma membrane glutamate transporters. Heterologously expressed EAAT5 activates too slowly upon glutamate binding to support significant uptake. We tested EAAT5 activation in mouse rods in vivo by stimulating glutamate transporter anion currents (IA(glu)) with UV flash photolysis of MNI-glutamate, varying flash intensity to vary glutamate levels. Responses to uncaging rose rapidly with time constants of 2-3 ms, similar to IA(glu) events arising from spontaneous release. Spontaneous release events and IA(glu) evoked by weak flashes also declined with similar time constants of 40-50 ms. Stronger flashes evoked responses that decayed more slowly. Time constants were twofold faster at 35°C, suggesting that they reflect transporter kinetics, not diffusion. Selective EAAT1 and EAAT2 inhibitors had no significant effect, suggesting IA(glu) in rods arises solely from EAAT5. We calibrated glutamate levels attained during flash photolysis by expressing a fluorescent glutamate sensor iGluSnFr in cultured epithelial cells. We compared fluorescence at different glutamate concentrations to fluorescence evoked by photolytic uncaging of MNI-glutamate. The relationship between flash intensity and glutamate yielded EC50 values for EAAT5 amplitude, decay time, and rise time of ∼10 μM. Micromolar affinity and rapid activation of EAAT5 in rods show it can rapidly bind synaptic glutamate. However, we also found that EAAT5 currents are saturated by the synchronous release of only a few vesicles, suggesting limited capacity and a role for glial uptake at higher release rates.
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Affiliation(s)
- Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Bhavana Chhunchha
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
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