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Thomas CI, Ryan MA, McNabb MC, Kamasawa N, Scholl B. Astrocyte coverage of excitatory synapses correlates to measures of synapse structure and function in ferret primary visual cortex. Glia 2024; 72:1785-1800. [PMID: 38856149 PMCID: PMC11324397 DOI: 10.1002/glia.24582] [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: 12/08/2023] [Revised: 05/25/2024] [Accepted: 06/02/2024] [Indexed: 06/11/2024]
Abstract
Most excitatory synapses in the mammalian brain are contacted or ensheathed by astrocyte processes, forming tripartite synapses. Astrocytes are thought to be critical regulators of the structural and functional dynamics of synapses. While the degree of synaptic coverage by astrocytes is known to vary across brain regions and animal species, the reason for and implications of this variability remains unknown. Further, how astrocyte coverage of synapses relates to in vivo functional properties of individual synapses has not been investigated. Here, we characterized astrocyte coverage of synapses of pyramidal neurons in the ferret visual cortex and, using correlative light and electron microscopy, examined their relationship to synaptic strength and sensory-evoked Ca2+ activity. Nearly, all synapses were contacted by astrocytes, and most were contacted along the axon-spine interface. Structurally, we found that the degree of synaptic astrocyte coverage directly scaled with synapse size and postsynaptic density complexity. Functionally, we found that the amount of astrocyte coverage scaled with how selectively a synapse responds to a particular visual stimulus and, at least for the largest synapses, scaled with the reliability of visual stimuli to evoke postsynaptic Ca2+ events. Our study shows astrocyte coverage is highly correlated with structural metrics of synaptic strength of excitatory synapses in the visual cortex and demonstrates a previously unknown relationship between astrocyte coverage and reliable sensory activation.
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Affiliation(s)
- Connon I Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, USA
| | - Melissa A Ryan
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, USA
| | - Micaiah C McNabb
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, Florida, USA
| | - Benjamin Scholl
- Department of Physiology and Biophysics, University of Colorado Denver, Aurora, Colorado, USA
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2
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Thomas CI, Ryan MA, Kamasawa N, Scholl B. Postsynaptic mitochondria are positioned to support functional diversity of dendritic spines. eLife 2023; 12:RP89682. [PMID: 38059805 PMCID: PMC10703439 DOI: 10.7554/elife.89682] [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: 12/08/2023] Open
Abstract
Postsynaptic mitochondria are critical for the development, plasticity, and maintenance of synaptic inputs. However, their relationship to synaptic structure and functional activity is unknown. We examined a correlative dataset from ferret visual cortex with in vivo two-photon calcium imaging of dendritic spines during visual stimulation and electron microscopy reconstructions of spine ultrastructure, investigating mitochondrial abundance near functionally and structurally characterized spines. Surprisingly, we found no correlation to structural measures of synaptic strength. Instead, we found that mitochondria are positioned near spines with orientation preferences that are dissimilar to the somatic preference. Additionally, we found that mitochondria are positioned near groups of spines with heterogeneous orientation preferences. For a subset of spines with a mitochondrion in the head or neck, synapses were larger and exhibited greater selectivity to visual stimuli than those without a mitochondrion. Our data suggest mitochondria are not necessarily positioned to support the energy needs of strong spines, but rather support the structurally and functionally diverse inputs innervating the basal dendrites of cortical neurons.
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Affiliation(s)
- Connon I Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Max Planck WayJupiterUnited States
| | - Melissa A Ryan
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Max Planck WayJupiterUnited States
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Max Planck WayJupiterUnited States
| | - Benjamin Scholl
- Department of Neuroscience, Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaUnited States
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3
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Thomas CI, Ryan MA, McNabb MC, Kamasawa N, Scholl B. Astrocyte coverage of excitatory synapses correlates to measures of synapse structure and function in primary visual cortex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.01.569664. [PMID: 38106030 PMCID: PMC10723302 DOI: 10.1101/2023.12.01.569664] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Most excitatory synapses in the mammalian brain are contacted by astrocytes, forming the tripartite synapse. This interface is thought to be critical for glutamate turnover and structural or functional dynamics of synapses. While the degree of synaptic contact of astrocytes is known to vary across brain regions and animal species, the implications of this variability remain unknown. Furthermore, precisely how astrocyte coverage of synapses relates to in vivo functional properties of individual dendritic spines has yet to be investigated. Here, we characterized perisynaptic astrocyte processes (PAPs) contacting synapses of pyramidal neurons of the ferret visual cortex and, using correlative light and electron microscopy, examined their relationship to synaptic strength and to sensory-evoked Ca2+ activity. Nearly all synapses were contacted by PAPs, and most were contacted along the axon-spine interface (ASI). Structurally, we found that the degree of PAP coverage scaled with synapse size and complexity. Functionally, we found that PAP coverage scaled with the selectivity of Ca2+ responses of individual synapses to visual stimuli and, at least for the largest synapses, scaled with the reliability of visual stimuli to evoke postsynaptic Ca2+ events. Our study shows astrocyte coverage is highly correlated with structural properties of excitatory synapses in the visual cortex and implicates astrocytes as a contributor to reliable sensory activation.
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Affiliation(s)
- Connon I Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Melissa A Ryan
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
- Department of Neuroscience, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Micaiah C McNabb
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
- Department of Neuroscience, The Ohio State University, 460 Medical Center Drive, Columbus, OH 43210, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Benjamin Scholl
- Department of Physiology and Biophysics, University of Colorado Denver, 12800 East 19th Ave, Aurora, CO 80045, USA
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Thomas CI, Ryan MA, Kamasawa N, Scholl B. Postsynaptic mitochondria are positioned to support functional diversity of dendritic spines. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.14.549063. [PMID: 37502969 PMCID: PMC10370038 DOI: 10.1101/2023.07.14.549063] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Postsynaptic mitochondria are critical to the development, plasticity, and maintenance of synaptic inputs. However, their relationship to synaptic structure and functional activity is unknown. We examined a correlative dataset from ferret visual cortex with in vivo two-photon calcium imaging of dendritic spines during visual stimulation and electron microscopy (EM) reconstructions of spine ultrastructure, investigating mitochondrial abundance near functionally- and structurally-characterized spines. Surprisingly, we found no correlation to structural measures of synaptic strength. Instead, we found that mitochondria are positioned near spines with orientation preferences that are dissimilar to the somatic preference. Additionally, we found that mitochondria are positioned near groups of spines with heterogeneous orientation preferences. For a subset of spines with mitochondrion in the head or neck, synapses were larger and exhibited greater selectivity to visual stimuli than those without a mitochondrion. Our data suggest mitochondria are not necessarily positioned to support the energy needs of strong spines, but rather support the structurally and functionally diverse inputs innervating the basal dendrites of cortical neurons.
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Affiliation(s)
- Connon I. Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Melissa A. Ryan
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
- Present Address: Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Benjamin Scholl
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, 415 Curie Blvd, Philadelphia, PA, 19104, USA
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5
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Hayashi S, Ohno N, Knott G, Molnár Z. Correlative light and volume electron microscopy to study brain development. Microscopy (Oxf) 2023; 72:279-286. [PMID: 36620906 DOI: 10.1093/jmicro/dfad002] [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: 11/30/2022] [Accepted: 01/06/2023] [Indexed: 01/10/2023] Open
Abstract
Recent advances in volume electron microscopy (EM) have been driving our thorough understanding of the brain architecture. Volume EM becomes increasingly powerful when cells and their subcellular structures that are imaged in light microscopy are correlated to those in ultramicrographs obtained with EM. This correlative approach, called correlative light and volume electron microscopy (vCLEM), is used to link three-dimensional ultrastructural information with physiological data such as intracellular Ca2+ dynamics. Genetic tools to express fluorescent proteins and/or an engineered form of a soybean ascorbate peroxidase allow us to perform vCLEM using natural landmarks including blood vessels without immunohistochemical staining. This immunostaining-free vCLEM has been successfully employed in two-photon Ca2+ imaging in vivo as well as in studying complex synaptic connections in thalamic neurons that receive a variety of specialized inputs from the cerebral cortex. In this mini-review, we overview how volume EM and vCLEM have contributed to studying the developmental processes of the brain. We also discuss potential applications of genetic manipulation of target cells using clustered regularly interspaced short palindromic repeats-associated protein 9 and subsequent volume EM to the analysis of protein localization as well as to loss-of-function studies of genes regulating brain development. We give examples for the combinatorial usage of genetic tools with vCLEM that will further enhance our understanding of regulatory mechanisms underlying brain development.
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Affiliation(s)
- Shuichi Hayashi
- Department of Anatomy, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
- Division of Ultrastructural Research, National Institute for Physiological Sciences, 5-1 Higashiyama Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Graham Knott
- Biological Electron Microscopy Facility, Faculty of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Route Cantonale, Lausanne CH-1015, Switzerland
| | - Zoltán Molnár
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
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6
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Marshall AG, Neikirk K, Stephens DC, Vang L, Vue Z, Beasley HK, Crabtree A, Scudese E, Lopez EG, Shao B, Krystofiak E, Rutledge S, Davis J, Murray SA, Damo SM, Katti P, Hinton A. Serial Block Face-Scanning Electron Microscopy as a Burgeoning Technology. Adv Biol (Weinh) 2023; 7:e2300139. [PMID: 37246236 PMCID: PMC10950369 DOI: 10.1002/adbi.202300139] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Revised: 05/09/2023] [Indexed: 05/30/2023]
Abstract
Serial block face scanning electron microscopy (SBF-SEM), also referred to as serial block-face electron microscopy, is an advanced ultrastructural imaging technique that enables three-dimensional visualization that provides largerx- and y-axis ranges than other volumetric EM techniques. While SEM is first introduced in the 1930s, SBF-SEM is developed as a novel method to resolve the 3D architecture of neuronal networks across large volumes with nanometer resolution by Denk and Horstmann in 2004. Here, the authors provide an accessible overview of the advantages and challenges associated with SBF-SEM. Beyond this, the applications of SBF-SEM in biochemical domains as well as potential future clinical applications are briefly reviewed. Finally, the alternative forms of artificial intelligence-based segmentation which may contribute to devising a feasible workflow involving SBF-SEM, are also considered.
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Affiliation(s)
- Andrea G Marshall
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Kit Neikirk
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Dominique C Stephens
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Larry Vang
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Zer Vue
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Heather K Beasley
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Amber Crabtree
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Estevão Scudese
- Laboratory of Biosciences of Human Motricity (LABIMH) of the Federal University of State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
- Sport Sciences and Exercise Laboratory (LaCEE), Catholic University of Petrópolis (UCP), Catholic, 25685-100, Brazil
| | - Edgar Garza Lopez
- Department of Internal Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Bryanna Shao
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
| | - Evan Krystofiak
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, 37232, USA
| | - Sharifa Rutledge
- Department of Chemistry, University of Alabama in Huntsville, Huntsville, AL, 35899, USA
| | - Jaimaine Davis
- Department of Biochemistry, Cancer Biology, Neuroscience, Pharmacology, Meharry Medical College, Nashville, TN, 37232, USA
| | - Sandra A Murray
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Steven M Damo
- Department of Life and Physical Sciences, Fisk University, Nashville, TN, 37208, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN, 37232, USA
| | - Prasanna Katti
- National Heart, Lung and Blood Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Antentor Hinton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA
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Stempinski ES, Pagano L, Riesterer JL, Adamou SK, Thibault G, Song X, Chang YH, López CS. Automated large volume sample preparation for vEM. Methods Cell Biol 2023; 177:1-32. [PMID: 37451763 DOI: 10.1016/bs.mcb.2023.01.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
New developments in electron microscopy technology, improved efficiency of detectors, and artificial intelligence applications for data analysis over the past decade have increased the use of volume electron microscopy (vEM) in the life sciences field. Moreover, sample preparation methods are continuously being modified by investigators to improve final sample quality, increase electron density, combine imaging technologies, and minimize the introduction of artifacts into specimens under study. There are a variety of conventional bench protocols that a researcher can utilize, though most of these protocols require several days. In this work, we describe the utilization of an automated specimen processor, the mPrep™ ASP-2000™, to prepare samples for vEM that are compatible with focused ion beam scanning electron microscopy (FIB-SEM), serial block face scanning electron microscopy (SBF-SEM), and array tomography (AT). The protocols described here aimed for methods that are completed in a much shorter period of time while minimizing the exposure of the operator to hazardous and toxic chemicals and improving the reproducibility of the specimens' heavy metal staining, all without compromising the quality of the data acquired using backscattered electrons during SEM imaging. As a control, we have included a widely used sample bench protocol and have utilized it as a comparator for image quality analysis, both qualitatively and using image quality analysis metrics.
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Affiliation(s)
- Erin S Stempinski
- Multiscale Microscopy Core, Oregon Health & Science University, Portland, OR, United States
| | - Lucas Pagano
- Knight Cancer Institute-CEDAR, Oregan Health & Science University, Portland, OR, United States
| | - Jessica L Riesterer
- Multiscale Microscopy Core, Oregon Health & Science University, Portland, OR, United States; Knight Cancer Institute-CEDAR, Oregan Health & Science University, Portland, OR, United States
| | - Steven K Adamou
- Multiscale Microscopy Core, Oregon Health & Science University, Portland, OR, United States
| | - Guillaume Thibault
- Knight Cancer Institute-CEDAR, Oregan Health & Science University, Portland, OR, United States; Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, United States
| | - Xubo Song
- Knight Cancer Institute-CEDAR, Oregan Health & Science University, Portland, OR, United States
| | - Young Hwan Chang
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, United States
| | - Claudia S López
- Multiscale Microscopy Core, Oregon Health & Science University, Portland, OR, United States; Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, United States; Pacific Northwest Center for Cryo-EM, Oregon Health & Science University, Portland, OR, United States.
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8
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Peddie CJ, Genoud C, Kreshuk A, Meechan K, Micheva KD, Narayan K, Pape C, Parton RG, Schieber NL, Schwab Y, Titze B, Verkade P, Aubrey A, Collinson LM. Volume electron microscopy. NATURE REVIEWS. METHODS PRIMERS 2022; 2:51. [PMID: 37409324 PMCID: PMC7614724 DOI: 10.1038/s43586-022-00131-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/10/2022] [Indexed: 07/07/2023]
Abstract
Life exists in three dimensions, but until the turn of the century most electron microscopy methods provided only 2D image data. Recently, electron microscopy techniques capable of delving deep into the structure of cells and tissues have emerged, collectively called volume electron microscopy (vEM). Developments in vEM have been dubbed a quiet revolution as the field evolved from established transmission and scanning electron microscopy techniques, so early publications largely focused on the bioscience applications rather than the underlying technological breakthroughs. However, with an explosion in the uptake of vEM across the biosciences and fast-paced advances in volume, resolution, throughput and ease of use, it is timely to introduce the field to new audiences. In this Primer, we introduce the different vEM imaging modalities, the specialized sample processing and image analysis pipelines that accompany each modality and the types of information revealed in the data. We showcase key applications in the biosciences where vEM has helped make breakthrough discoveries and consider limitations and future directions. We aim to show new users how vEM can support discovery science in their own research fields and inspire broader uptake of the technology, finally allowing its full adoption into mainstream biological imaging.
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Affiliation(s)
- Christopher J. Peddie
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, London, UK
| | - Christel Genoud
- Electron Microscopy Facility, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Anna Kreshuk
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Kimberly Meechan
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Present address: Faculty of Biosciences, Heidelberg University, Heidelberg, Germany
| | - Kristina D. Micheva
- Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA, USA
| | - Kedar Narayan
- Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
- Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Constantin Pape
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Robert G. Parton
- The Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
- Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland, Australia
| | - Nicole L. Schieber
- Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland, Australia
| | - Yannick Schwab
- Cell Biology and Biophysics Unit/ Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
| | | | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, UK
| | - Aubrey Aubrey
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Lucy M. Collinson
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, London, UK
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9
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Tazerart S, Blanchard MG, Miranda-Rottmann S, Mitchell DE, Navea Pina B, Thomas CI, Kamasawa N, Araya R. Selective activation of BK channels in small-headed dendritic spines suppresses excitatory postsynaptic potentials. J Physiol 2022; 600:2165-2187. [PMID: 35194785 DOI: 10.1113/jp282303] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 02/14/2022] [Indexed: 12/22/2022] Open
Abstract
Dendritic spines are the main receptacles of excitatory information in the brain. Their particular morphology, with a small head connected to the dendrite by a slender neck, has inspired theoretical and experimental work to understand how these structural features affect the processing, storage and integration of synaptic inputs in pyramidal neurons (PNs). The activation of glutamate receptors in spines triggers a large voltage change as well as calcium signals at the spine head. Thus, voltage-gated and calcium-activated potassium channels located in the spine head likely play a key role in synaptic transmission. Here we study the presence and function of large conductance calcium-activated potassium (BK) channels in spines from layer 5 PNs. We found that BK channels are localized to dendrites and spines regardless of their size, but their activity can only be detected in spines with small head volumes (≤0.09 μm3 ), which reduces the amplitude of two-photon uncaging excitatory postsynaptic potentials recorded at the soma. In addition, we found that calcium signals in spines with small head volumes are significantly larger than those observed in spines with larger head volumes. In accordance with our experimental data, numerical simulations predict that synaptic inputs impinging onto spines with small head volumes generate voltage responses and calcium signals within the spine head itself that are significantly larger than those observed in spines with larger head volumes, which are sufficient to activate spine BK channels. These results show that BK channels are selectively activated in small-headed spines, suggesting a new level of dendritic spine-mediated regulation of synaptic processing, integration and plasticity in cortical PNs. KEY POINTS: BK channels are expressed in the visual cortex and layer 5 pyramidal neuron somata, dendrites and spines regardless of their size. BK channels are selectively activated in small-headed spines (≤0.09 μm3 ), which reduces the amplitude of two-photon (2P) uncaging excitatory postsynaptic potentials (EPSPs) recorded at the soma. Two-photon imaging revealed that intracellular calcium responses in the head of 2P-activated spines are significantly larger in small-headed spines (≤0.09 μm3 ) than in spines with larger head volumes. In accordance with our experimental data, numerical simulations showed that synaptic inputs impinging onto spines with small head volumes (≤0.09 μm3 ) generate voltage responses and calcium signals within the spine head itself that are significantly larger than those observed in spines with larger head volumes, sufficient to activate spine BK channels and suppress EPSPs.
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Affiliation(s)
- Sabrina Tazerart
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
| | - Maxime G Blanchard
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
| | - Soledad Miranda-Rottmann
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
| | - Diana E Mitchell
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
| | - Bruno Navea Pina
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
| | - Connon I Thomas
- The Imaging Center and Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
| | - Naomi Kamasawa
- The Imaging Center and Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
| | - Roberto Araya
- Département de Neurosciences, Université de Montréal, Montréal, Canada.,The CHU Sainte-Justine Research Center, Montréal, Canada
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10
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Scholl B, Tepohl C, Ryan MA, Thomas CI, Kamasawa N, Fitzpatrick D. A binocular synaptic network supports interocular response alignment in visual cortical neurons. Neuron 2022; 110:1573-1584.e4. [PMID: 35123654 PMCID: PMC9081247 DOI: 10.1016/j.neuron.2022.01.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 10/13/2021] [Accepted: 01/19/2022] [Indexed: 10/19/2022]
Abstract
In visual cortex, signals from the two eyes merge to form a coherent binocular representation. Here we investigate the synaptic interactions underlying the binocular representation of stimulus orientation in ferret visual cortex with in vivo calcium imaging of layer 2/3 neurons and their dendritic spines. Individual neurons with aligned somatic responses received a mixture of monocular and binocular synaptic inputs. Surprisingly, monocular pathways alone could not account for somatic alignment because ipsilateral monocular inputs poorly matched somatic preference. Binocular inputs exhibited different degrees of interocular alignment, and those with a high degree of alignment (congruent) had greater selectivity and somatic specificity. While congruent inputs were similar to others in measures of strength, simulations show that the number of active congruent inputs predicts aligned somatic output. Our study suggests that coherent binocular responses derive from connectivity biases that support functional amplification of aligned signals within a heterogeneous binocular intracortical network.
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11
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Johkura K, Usuda N, Tanaka Y, Fukasawa M, Murata K, Noda T, Ohno N. OUP accepted manuscript. Microscopy (Oxf) 2022; 71:262-270. [PMID: 35535544 PMCID: PMC9535788 DOI: 10.1093/jmicro/dfac024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 04/25/2022] [Accepted: 06/06/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kohei Johkura
- Department of Histology and Embryology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan
| | - Nobuteru Usuda
- *To whom correspondence should be addressed. E-mail: (N.U.); (N.O.)
| | - Yoshihiro Tanaka
- Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Motoaki Fukasawa
- Department of Biomedical Molecular Sciences (Anatomy II), Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Kazuyoshi Murata
- National Institute for Physiological Sciences, National Institutes of Natural Sciences, 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - Toru Noda
- Department of Occupational Therapy (Anatomy), Biwako Professional University of Rehabilitation, 967 Kitasakacho, Higashiomi, Shiga 527-0145, Japan
- Department of Cell Biology and Anatomy, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
| | - Nobuhiko Ohno
- *To whom correspondence should be addressed. E-mail: (N.U.); (N.O.)
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12
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Parlanti P, Cappello V. Microscopes, tools, probes, and protocols: A guide in the route of correlative microscopy for biomedical investigation. Micron 2021; 152:103182. [PMID: 34801960 DOI: 10.1016/j.micron.2021.103182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 11/12/2021] [Accepted: 11/14/2021] [Indexed: 12/11/2022]
Abstract
In the last decades, the advancements of microscopes technology, together with the development of new imaging approaches, are trying to address some biological questions that have been unresolved in the past: the need to combine in the same analysis temporal, functional and morphological information on the biological sample has become pressing. For this reason, the use of correlative microscopy, in which two or more imaging techniques are combined in the same analysis, is getting increasingly widespread. In fact, correlative microscopy can overcome limitations of a single imaging method, giving access to a larger amount of information from the same specimen. However, correlative microscopy can be challenging, and appropriate protocols for sample preparation and imaging methods must be selected. Here we review the state of the art of correlating electron microscopy with different imaging methods, focusing on sample preparation, tools, and labeling methods, with the aim to provide a comprehensive guide for those scientists who are approaching the field of correlative methods.
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Affiliation(s)
- Paola Parlanti
- Istituto Italiano di Tecnologia, Center for Materials Interfaces, Electron Crystallography, Viale Rinaldo Piaggio 34, I-56025, Pontedera (PI), Italy.
| | - Valentina Cappello
- Istituto Italiano di Tecnologia, Center for Materials Interfaces, Electron Crystallography, Viale Rinaldo Piaggio 34, I-56025, Pontedera (PI), Italy.
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Talapka P, Kocsis Z, Marsi LD, Szarvas VE, Kisvárday ZF. Application of the Mirror Technique for Three-Dimensional Electron Microscopy of Neurochemically Identified GABA-ergic Dendrites. Front Neuroanat 2021; 15:652422. [PMID: 33958990 PMCID: PMC8093522 DOI: 10.3389/fnana.2021.652422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 03/25/2021] [Indexed: 11/15/2022] Open
Abstract
In the nervous system synaptic input arrives chiefly on dendrites and their type and distribution have been assumed pivotal in signal integration. We have developed an immunohistochemistry (IH)-correlated electron microscopy (EM) method – the “mirror” technique – by which synaptic input to entire dendrites of neurochemically identified interneurons (INs) can be mapped due preserving high-fidelity tissue ultrastructure. Hence, this approach allows quantitative assessment of morphometric parameters of synaptic inputs along the whole length of dendrites originating from the parent soma. The method exploits the fact that adjoining sections have truncated or cut cell bodies which appear on the common surfaces in a mirror fashion. In one of the sections the histochemical marker of the GABAergic subtype, calbindin was revealed in cell bodies whereas in the other section the remaining part of the very same cell bodies were subjected to serial section EM to trace and reconstruct the synaptology of entire dendrites. Here, we provide exemplary data on the synaptic coverage of two dendrites belonging to the same calbindin-D28K immunopositive IN and determine the spatial distribution of asymmetric and symmetric synapses, surface area and volume of the presynaptic boutons, morphometric parameters of synaptic vesicles, and area extent of the active zones.
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Affiliation(s)
- Petra Talapka
- MTA-DE Neuroscience Research Group, University of Debrecen, Debrecen, Hungary.,Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsolt Kocsis
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Lívia Diána Marsi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Vera Etelka Szarvas
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltán F Kisvárday
- MTA-DE Neuroscience Research Group, University of Debrecen, Debrecen, Hungary.,Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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14
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Scholl B, Thomas CI, Ryan MA, Kamasawa N, Fitzpatrick D. Cortical response selectivity derives from strength in numbers of synapses. Nature 2021; 590:111-114. [PMID: 33328635 PMCID: PMC7872059 DOI: 10.1038/s41586-020-03044-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 10/26/2020] [Indexed: 11/23/2022]
Abstract
Single neocortical neurons are driven by populations of excitatory inputs, which form the basis of neuronal selectivity to features of sensory input. Excitatory connections are thought to mature during development through activity-dependent Hebbian plasticity1, whereby similarity between presynaptic and postsynaptic activity selectively strengthens some synapses and weakens others2. Evidence in support of this process includes measurements of synaptic ultrastructure and in vitro and in vivo physiology and imaging studies3-8. These corroborating lines of evidence lead to the prediction that a small number of strong synaptic inputs drive neuronal selectivity, whereas weak synaptic inputs are less correlated with the somatic output and modulate activity overall6,7. Supporting evidence from cortical circuits, however, has been limited to measurements of neighbouring, connected cell pairs, raising the question of whether this prediction holds for a broad range of synapses converging onto cortical neurons. Here we measure the strengths of functionally characterized excitatory inputs contacting single pyramidal neurons in ferret primary visual cortex (V1) by combining in vivo two-photon synaptic imaging and post hoc electron microscopy. Using electron microscopy reconstruction of individual synapses as a metric of strength, we find no evidence that strong synapses have a predominant role in the selectivity of cortical neuron responses to visual stimuli. Instead, selectivity appears to arise from the total number of synapses activated by different stimuli. Moreover, spatial clustering of co-active inputs appears to be reserved for weaker synapses, enhancing the contribution of weak synapses to somatic responses. Our results challenge the role of Hebbian mechanisms in shaping neuronal selectivity in cortical circuits, and suggest that selectivity reflects the co-activation of large populations of presynaptic neurons with similar properties and a mixture of strengths.
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Affiliation(s)
- Benjamin Scholl
- Functional Architecture and Development of Cerebral Cortex, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA.
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
| | - Connon I Thomas
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
| | - Melissa A Ryan
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
| | - David Fitzpatrick
- Functional Architecture and Development of Cerebral Cortex, Max Planck Florida Institute for Neuroscience, Jupiter, FL, USA
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