1
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Stevens-Sostre WA, Hoon M. Cellular and Molecular Mechanisms Regulating Retinal Synapse Development. Annu Rev Vis Sci 2024; 10:377-402. [PMID: 39292551 DOI: 10.1146/annurev-vision-102122-105721] [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] [Indexed: 09/20/2024]
Abstract
Synapse formation within the retinal circuit ensures that distinct neuronal types can communicate efficiently to process visual signals. Synapses thus form the core of the visual computations performed by the retinal circuit. Retinal synapses are diverse but can be broadly categorized into multipartner ribbon synapses and 1:1 conventional synapses. In this article, we review our current understanding of the cellular and molecular mechanisms that regulate the functional establishment of mammalian retinal synapses, including the role of adhesion proteins, synaptic proteins, extracellular matrix and cytoskeletal-associated proteins, and activity-dependent cues. We outline future directions and areas of research that will expand our knowledge of these mechanisms. Understanding the regulators moderating synapse formation and function not only reveals the integrated developmental processes that establish retinal circuits, but also divulges the identity of mechanisms that could be engaged during disease and degeneration.
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Affiliation(s)
- Whitney A Stevens-Sostre
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA;
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA;
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin, USA
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2
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Hellevik AM, Mardoum P, Hahn J, Kölsch Y, D'Orazi FD, Suzuki SC, Godinho L, Lawrence O, Rieke F, Shekhar K, Sanes JR, Baier H, Baden T, Wong RO, Yoshimatsu T. Ancient origin of the rod bipolar cell pathway in the vertebrate retina. Nat Ecol Evol 2024; 8:1165-1179. [PMID: 38627529 DOI: 10.1038/s41559-024-02404-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/20/2024] [Indexed: 04/30/2024]
Abstract
Vertebrates rely on rod photoreceptors for vision in low-light conditions. The specialized downstream circuit for rod signalling, called the primary rod pathway, is well characterized in mammals, but circuitry for rod signalling in non-mammals is largely unknown. Here we demonstrate that the mammalian primary rod pathway is conserved in zebrafish, which diverged from extant mammals ~400 million years ago. Using single-cell RNA sequencing, we identified two bipolar cell types in zebrafish that are related to mammalian rod bipolar cell (RBCs), the only bipolar type that directly carries rod signals from the outer to the inner retina in the primary rod pathway. By combining electrophysiology, histology and ultrastructural reconstruction of the zebrafish RBCs, we found that, similar to mammalian RBCs, both zebrafish RBC types connect with all rods in their dendritic territory and provide output largely onto amacrine cells. The wiring pattern of the amacrine cells postsynaptic to one RBC type is strikingly similar to that of mammalian RBCs and their amacrine partners, suggesting that the cell types and circuit design of the primary rod pathway emerged before the divergence of teleost fish and mammals. The second RBC type, which forms separate pathways, was either lost in mammals or emerged in fish.
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Affiliation(s)
- Ayana M Hellevik
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Philip Mardoum
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Joshua Hahn
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA, USA
| | - Yvonne Kölsch
- Department Genes - Circuits - Behavior, Max Planck Institute for Biological Intelligence, Martinsried, Germany
| | - Florence D D'Orazi
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Sachihiro C Suzuki
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Leanne Godinho
- Institute of Neuronal Cell Biology, Technische Universität München, Munich, Germany
| | - Owen Lawrence
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA
- Vision Science Center, University of Washington, Seattle, WA, USA
| | - Karthik Shekhar
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology, and Center for Brain Science, Harvard University, Cambridge, MA, USA
| | - Herwig Baier
- Department Genes - Circuits - Behavior, Max Planck Institute for Biological Intelligence, Martinsried, Germany
| | - Tom Baden
- School of Life Sciences, University of Sussex, Brighton, UK
- Institute of Ophthalmic Research, University of Tübingen, Tübingen, Germany
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Takeshi Yoshimatsu
- Department of Ophthalmology and Visual Sciences, Washington University in St Louis School of Medicine, St Louis, MO, USA.
- BioRTC, Yobe State University, Damatsuru, Yobe, Nigeria.
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Carrier Y, Rio LQ, Formicola N, de Sousa-Xavier V, Tabet M, Chen YCD, Wislez M, Orts L, Pinto-Teixeira F. Biased cell adhesion organizes a circuit for visual motion integration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.11.571076. [PMID: 38168373 PMCID: PMC10760042 DOI: 10.1101/2023.12.11.571076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Layer specific computations in the brain rely on neuronal processes establishing synaptic connections with specific partners in distinct laminae. In the Drosophila lobula plate neuropile, the axons of the four subtypes of T4 and T5 visual motion direction-selective neurons segregate into four layers, based on their directional preference, and form synapses with distinct subsets of postsynaptic neurons. Four bi-stratified inhibitory lobula plate intrinsic cells exhibit a consistent synaptic pattern, receiving excitatory T4/T5 inputs in one layer, and conveying inhibitory signals to an adjacent layer. This layered arrangement establishes motion opponency. Here, we identify layer-specific expression of different receptor-ligand pairs belonging to the Beat and Side families of Cell Adhesion Molecules (CAMs) between T4/T5 neurons and their postsynaptic partners. Genetic analysis reveals that Beat/Side mediated interactions are required to restrict T4/T5 axonal innervation to a single layer. We propose that Beat/Side contribute to synaptic specificity by biasing adhesion between synaptic partners before synaptogenesis.
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Affiliation(s)
- Yannick Carrier
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Laura Quintana Rio
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Nadia Formicola
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Vicente de Sousa-Xavier
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Maha Tabet
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | | | - Maëva Wislez
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Lisa Orts
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
| | - Filipe Pinto-Teixeira
- MCD, Centre de Biologie Intégrative (CBI), CNRS, Université de Toulouse, UT3, Toulouse, France
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4
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Keeley PW, Trod S, Gamboa BN, Coffey PJ, Reese BE. Nfia Is Critical for AII Amacrine Cell Production: Selective Bipolar Cell Dependencies and Diminished ERG. J Neurosci 2023; 43:8367-8384. [PMID: 37775301 PMCID: PMC10711738 DOI: 10.1523/jneurosci.1099-23.2023] [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: 06/13/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/01/2023] Open
Abstract
The nuclear factor one (NFI) transcription factor genes Nfia, Nfib, and Nfix are all enriched in late-stage retinal progenitor cells, and their loss has been shown to retain these progenitors at the expense of later-generated retinal cell types. Whether they play any role in the specification of those later-generated fates is unknown, but the expression of one of these, Nfia, in a specific amacrine cell type may intimate such a role. Here, Nfia conditional knockout (Nfia-CKO) mice (both sexes) were assessed, finding a massive and largely selective absence of AII amacrine cells. There was, however, a partial reduction in type 2 cone bipolar cells (CBCs), being richly interconnected to AII cells. Counts of dying cells showed a significant increase in Nfia-CKO retinas at postnatal day (P)7, after AII cell numbers were already reduced but in advance of the loss of type 2 CBCs detected by P10. Those results suggest a role for Nfia in the specification of the AII amacrine cell fate and a dependency of the type 2 CBCs on them. Delaying the conditional loss of Nfia to the first postnatal week did not alter AII cell number nor differentiation, further suggesting that its role in AII cells is solely associated with their production. The physiological consequences of their loss were assessed using the ERG, finding the oscillatory potentials to be profoundly diminished. A slight reduction in the b-wave was also detected, attributed to an altered distribution of the terminals of rod bipolar cells, implicating a role of the AII amacrine cells in constraining their stratification.SIGNIFICANCE STATEMENT The transcription factor NFIA is shown to play a critical role in the specification of a single type of retinal amacrine cell, the AII cell. Using an Nfia-conditional knockout mouse to eliminate this population of retinal neurons, we demonstrate two selective bipolar cell dependencies on the AII cells; the terminals of rod bipolar cells become mis-stratified in the inner plexiform layer, and one type of cone bipolar cell undergoes enhanced cell death. The physiological consequence of this loss of the AII cells was also assessed, finding the cells to be a major contributor to the oscillatory potentials in the electroretinogram.
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Affiliation(s)
- Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Stephanie Trod
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Bruno N Gamboa
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Pete J Coffey
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, California 93106-5060
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5
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Saha A, Zuniga J, Mian K, Zhai H, Derr PJ, Hoon M, Sinha R. Regional variation in the organization and connectivity of the first synapse in the primate night vision pathway. iScience 2023; 26:108113. [PMID: 37915604 PMCID: PMC10616377 DOI: 10.1016/j.isci.2023.108113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 08/25/2023] [Accepted: 09/29/2023] [Indexed: 11/03/2023] Open
Abstract
Sensitivity of primate daylight vision varies across the visual field. This is attributed to regional variations in cone photoreceptor density and synaptic connectivity of the underlying circuitry. In contrast, we have limited understanding of how synapse organization of the primate night vision pathway changes across space. Using serial electron microscopy, we reconstructed the first synapse of the night vision pathway between rod photoreceptors and second-order neurons, at multiple locations from the central part of the primate retina, fovea, to the periphery. We find that most facets of the rod synapse connectivity vary across retinal regions. However, rod synaptic divergence and convergence patterns do not change in the same manner across locations. Moreover, patterns of rod synapse organization are tightly correlated with photoreceptor density. Such regional heterogeneities revise the connectivity diagram of the primate rod synapse which will shape synapse function and sensitivity of the night vision pathway across visual space.
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Affiliation(s)
- Aindrila Saha
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI, USA
| | - Juan Zuniga
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
| | - Kainat Mian
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
| | - Haoshen Zhai
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
| | - Paul J. Derr
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
| | - Mrinalini Hoon
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI, USA
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI, USA
| | - Raunak Sinha
- Department of Neuroscience, University of Wisconsin, Madison, WI, USA
- McPherson Eye Research Institute, University of Wisconsin, Madison, WI, USA
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI, USA
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6
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Hellevik AM, Mardoum P, Hahn J, Kölsch Y, D’Orazi FD, Suzuki SC, Godinho L, Lawrence O, Rieke F, Shekhar K, Sanes JR, Baier H, Baden T, Wong RO, Yoshimatsu T. Ancient origin of the rod bipolar cell pathway in the vertebrate retina. RESEARCH SQUARE 2023:rs.3.rs-3411693. [PMID: 37886445 PMCID: PMC10602083 DOI: 10.21203/rs.3.rs-3411693/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
Vertebrates rely on rod photoreceptors for vision in low-light conditions. Mammals have a specialized downstream circuit for rod signaling called the primary rod pathway, which comprises specific cell types and wiring patterns that are thought to be unique to this lineage. Thus, it has been long assumed that the primary rod pathway evolved in mammals. Here, we challenge this view by demonstrating that the mammalian primary rod pathway is conserved in zebrafish, which diverged from extant mammals ~400 million years ago. Using single-cell RNA-sequencing, we identified two bipolar cell (BC) types in zebrafish that are related to mammalian rod BCs (RBCs) of the primary rod pathway. By combining electrophysiology, histology, and ultrastructural reconstruction of the zebrafish RBCs, we found that, like mammalian RBCs, both zebrafish RBC types connect with all rods in their dendritic territory, and provide output largely onto amacrine cells. The wiring pattern of the amacrine cells post-synaptic to one RBC type is strikingly similar to that of mammalian RBCs, suggesting that the cell types and circuit design of the primary rod pathway have emerged before the divergence of teleost fish and amniotes. The second RBC type, which forms separate pathways, is either lost in mammals or emerged in fish.
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Affiliation(s)
- Ayana M Hellevik
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Philip Mardoum
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Joshua Hahn
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA 94720, USA
| | - Yvonne Kölsch
- Department of Molecular & Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
- Max Planck Institute for Biological Intelligence, Department Genes – Circuits – Behavior, 82152 Martinsried, Germany
| | - Florence D D’Orazi
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Sachihiro C. Suzuki
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Leanne Godinho
- Institute of Neuronal Cell Biology, Technische Universität München, 80802 Munich, Germany
| | - Owen Lawrence
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
- Vision Science Center, University of Washington, Seattle, WA 98195, USA
| | - Karthik Shekhar
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA 94720, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Joshua R Sanes
- Department of Molecular & Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Herwig Baier
- Max Planck Institute for Biological Intelligence, Department Genes – Circuits – Behavior, 82152 Martinsried, Germany
| | - Tom Baden
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, UK
- Institute of Ophthalmic Research, University of Tübingen, Tübingen, 72076, Germany
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Takeshi Yoshimatsu
- Department of Ophthalmology & Visual Sciences, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
- BioRTC, Yobe State University, Damatsuru, Yobe 620101, Nigeria
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7
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Hellevik AM, Mardoum P, Hahn J, Kölsch Y, D’Orazi FD, Suzuki SC, Godinho L, Lawrence O, Rieke F, Shekhar K, Sanes JR, Baier H, Baden T, Wong RO, Yoshimatsu T. Ancient origin of the rod bipolar cell pathway in the vertebrate retina. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.12.557433. [PMID: 37771914 PMCID: PMC10525478 DOI: 10.1101/2023.09.12.557433] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Vertebrates rely on rod photoreceptors for vision in low-light conditions1. Mammals have a specialized downstream circuit for rod signaling called the primary rod pathway, which comprises specific cell types and wiring patterns that are thought to be unique to this lineage2-6. Thus, it has been long assumed that the primary rod pathway evolved in mammals3,5-7. Here, we challenge this view by demonstrating that the mammalian primary rod pathway is conserved in zebrafish, which diverged from extant mammals ~400 million years ago. Using single-cell RNA-sequencing, we identified two bipolar cell (BC) types in zebrafish that are related to mammalian rod BCs (RBCs) of the primary rod pathway. By combining electrophysiology, histology, and ultrastructural reconstruction of the zebrafish RBCs, we found that, like mammalian RBCs8, both zebrafish RBC types connect with all rods and red-cones in their dendritic territory, and provide output largely onto amacrine cells. The wiring pattern of the amacrine cells post-synaptic to one RBC type is strikingly similar to that of mammalian RBCs. This suggests that the cell types and circuit design of the primary rod pathway may have emerged before the divergence of teleost fish and amniotes (mammals, bird, reptiles). The second RBC type in zebrafish, which forms separate pathways from the first RBC type, is either lost in mammals or emerged in fish to serve yet unknown roles.
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Affiliation(s)
- Ayana M Hellevik
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Philip Mardoum
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Joshua Hahn
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA 94720, USA
| | - Yvonne Kölsch
- Department of Molecular & Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
- Max Planck Institute for Biological Intelligence, Department Genes – Circuits – Behavior, 82152 Martinsried, Germany
| | - Florence D D’Orazi
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Sachihiro C. Suzuki
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Leanne Godinho
- Institute of Neuronal Cell Biology, Technische Universität München, 80802 Munich, Germany
| | - Owen Lawrence
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
- Vision Science Center, University of Washington, Seattle, WA 98195, USA
| | - Karthik Shekhar
- Department of Chemical and Biomolecular Engineering; Helen Wills Neuroscience Institute; Vision Sciences Graduate Program; California Institute of Quantitative Biosciences (QB3), University of California Berkley, Berkeley, CA 94720, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Joshua R Sanes
- Department of Molecular & Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Herwig Baier
- Max Planck Institute for Biological Intelligence, Department Genes – Circuits – Behavior, 82152 Martinsried, Germany
| | - Tom Baden
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, UK
- Institute of Ophthalmic Research, University of Tübingen, Tübingen, 72076, Germany
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Takeshi Yoshimatsu
- Department of Ophthalmology & Visual Sciences, Washington University in St Louis School of Medicine, St Louis, MO 63110, USA
- BioRTC, Yobe State University, Damatsuru, Yobe 620101, Nigeria
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8
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Sawant A, Saha A, Khoussine J, Sinha R, Hoon M. New insights into retinal circuits through EM connectomics: what we have learnt and what remains to be learned. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1168548. [PMID: 38983069 PMCID: PMC11182165 DOI: 10.3389/fopht.2023.1168548] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 04/05/2023] [Indexed: 07/11/2024]
Abstract
The retinal neural circuit is intricately wired for efficient processing of visual signals. This is well-supported by the specialized connections between retinal neurons at both the functional and ultrastructural levels. Through 3D electron microscopic (EM) reconstructions of retinal neurons and circuits we have learnt much about the specificities of connections within the retinal layers including new insights into how retinal neurons establish connections and perform sophisticated visual computations. This mini-review will summarize the retinal circuitry and provide details about the novel insights EM connectomics has brought into our understanding of the retinal circuitry. We will also discuss unresolved questions about the retinal circuitry that can be addressed by EM connectomics in the future.
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Affiliation(s)
- Abhilash Sawant
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, United States
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, United States
- Cellular and Molecular Biology Program, University of Wisconsin-Madison, Madison, WI, United States
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, United States
| | - Aindrila Saha
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, United States
- Cellular and Molecular Biology Program, University of Wisconsin-Madison, Madison, WI, United States
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, United States
| | - Jacob Khoussine
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, United States
- Cellular and Molecular Biology Program, University of Wisconsin-Madison, Madison, WI, United States
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, United States
- Medical Scientist Training Program, University of Wisconsin-Madison, Madison, WI, United States
| | - Raunak Sinha
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, United States
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, United States
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, United States
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, United States
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, United States
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, United States
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9
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Sladek AL, Thoreson WB. Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1146785. [PMID: 37426783 PMCID: PMC10327572 DOI: 10.3389/fopht.2023.1146785] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Introduction Light responses of rod photoreceptor cells traverse the retina through three pathways. The primary pathway involves synapses from rods to ON-type rod bipolar cells with OFF signals reaching retinal ganglion cells (RGCs) via sign-inverting glycinergic synapses. Secondly, rod signals can enter cones through gap junctions. Finally, rods can synapse directly onto cone OFF bipolar cells. Methods To analyze these pathways, we obtained whole cell recordings from OFF-type α RGCs in mouse retinas while expressing channelrhodopsin-2 in rods and/or cones. Results Optogenetic stimulation of rods or cones evoked large fast currents in OFF RGCs. Blocking the primary rod pathway with L-AP4 and/or strychnine reduced rod-driven optogenetic currents in OFF RGCs by ~1/3. Blocking kainate receptors of OFF cone bipolar cells suppressed both rod- and cone-driven optogenetic currents in OFF RGCs. Inhibiting gap junctions between rods and cones with mecloflenamic acid or quinpirole reduced rod-driven responses in OFF RGCs. Eliminating the exocytotic Ca2+ sensor, synaptotagmin 1 (Syt1), from cones abolished cone-driven optogenetic responses in RGCs. Rod-driven currents were not significantly reduced after isolating the secondary pathway by eliminating Syt1 and synaptotagmin 7 (Syt7) to block synaptic release from rods. Eliminating Syt1 from both rods and cones abolished responses to optogenetic stimulation. In Cx36 KO retinas lacking rod-cone gap junctions, optogenetic activation of rods evoked small and slow responses in most OFF RGCs suggesting rod signals reached them through an indirect pathway. Two OFF cells showed faster responses consistent with more direct input from cone OFF bipolar cells. Discussion These data show that the secondary rod pathway supports robust inputs into OFF α RGCs and suggests the tertiary pathway recruits both direct and indirect inputs.
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Affiliation(s)
- Asia L. Sladek
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE, United States
| | - Wallace B. Thoreson
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE, United States
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, United States
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