1
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Presence of Intact Hepatitis B Virions in Exosomes. Cell Mol Gastroenterol Hepatol 2022; 15:237-259. [PMID: 36184032 PMCID: PMC9676402 DOI: 10.1016/j.jcmgh.2022.09.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 09/23/2022] [Accepted: 09/23/2022] [Indexed: 02/21/2023]
Abstract
BACKGROUND & AIMS Hepatitis B virus (HBV) was identified as an enveloped DNA virus with a diameter of 42 nm. Multivesicular bodies play a central role in HBV egress and exosome biogenesis. In light of this, it was studied whether intact virions wrapped in exosomes are released by HBV-producing cells. METHODS Robust methods for efficient separation of exosomes from virions were established. Exosomes were subjected to limited detergent treatment for release of viral particles. Electron microscopy of immunogold labeled ultrathin sections of purified exosomes was performed for characterization of exosomal HBV. Exosome formation/release was affected by inhibitors or Crispr/Cas-mediated gene silencing. Infectivity/uptake of exosomal HBV was investigated in susceptible and non-susceptible cells. RESULTS Exosomes could be isolated from supernatants of HBV-producing cells, which are characterized by the presence of exosomal and HBV markers. These exosomal fractions could be separated from the fractions containing free virions. Limited detergent treatment of exosomes causes stepwise release of intact HBV virions and naked capsids. Inhibition of exosome morphogenesis impairs the release of exosome-wrapped HBV. Electron microscopy confirmed the presence of intact virions in exosomes. Moreover, the presence of large hepatitis B virus surface antigen on the surface of exosomes derived from HBV expressing cells was observed, which conferred exosome-encapsulated HBV initiating infection in susceptible cells in a , large hepatitis B virus surface antigen/Na+-taurocholate co-transporting polypeptide-dependent manner. The uptake of exosomal HBV with low efficiency was also observed in non-permissive cells. CONCLUSION These data indicate that a fraction of intact HBV virions can be released as exosomes. This reveals a so far not described release pathway for HBV.
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2
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Avci U, Nakashima J. A Flat Embedding Method to Orient Gravistimulated Root Samples for Sectioning. Methods Mol Biol 2021; 2368:153-163. [PMID: 34647255 DOI: 10.1007/978-1-0716-1677-2_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
Microscopy is an important tool used for biological research and has played a crucial role toward understanding of cellular mechanisms and protein function. However, specific steps in processing of biological samples for microscopy warrant improvements to consistently generate data that can more reliably help in explaining mechanisms underlying complex biological phenomenon. Due to their small and fragile nature, some biological specimens such as Arabidopsis thaliana roots are vulnerable to damage during long sample preparation steps. Moreover, when specimens with a small diameter (typically less than 100 μm) are embedded in conventional silicone mold or capsule embedding, it is not only difficult to locate their orientation inside the capsule, but also a challenge to obtain good median longitudinal sections. Specimen orientation in particular is crucial because understanding certain plant biological processes such as gravitropism rely on precisely knowing spatial information of cells and tissues of the plant organ being studied. Here, we present a simple embedding technique to properly orient small plant organs such as roots so that the desired sectioning plane is achieved. This method is inexpensive and can be accomplished with minimal equipment and supplies.
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Affiliation(s)
- Utku Avci
- Faculty of Agriculture, Department of Agricultural Biotechnology, Eskisehir Osmangazi University, Eskisehir, Turkey
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3
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Dilsizoglu Senol A, Samarani M, Syan S, Guardia CM, Nonaka T, Liv N, Latour-Lambert P, Hasegawa M, Klumperman J, Bonifacino JS, Zurzolo C. α-Synuclein fibrils subvert lysosome structure and function for the propagation of protein misfolding between cells through tunneling nanotubes. PLoS Biol 2021; 19:e3001287. [PMID: 34283825 PMCID: PMC8291706 DOI: 10.1371/journal.pbio.3001287] [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: 09/24/2020] [Accepted: 05/13/2021] [Indexed: 01/06/2023] Open
Abstract
The accumulation of α-synuclein (α-syn) aggregates in specific brain regions is a hallmark of synucleinopathies including Parkinson disease (PD). α-Syn aggregates propagate in a "prion-like" manner and can be transferred inside lysosomes to recipient cells through tunneling nanotubes (TNTs). However, how lysosomes participate in the spreading of α-syn aggregates is unclear. Here, by using super-resolution (SR) and electron microscopy (EM), we find that α-syn fibrils affect the morphology of lysosomes and impair their function in neuronal cells. In addition, we demonstrate that α-syn fibrils induce peripheral redistribution of lysosomes, likely mediated by transcription factor EB (TFEB), increasing the efficiency of α-syn fibrils' transfer to neighboring cells. We also show that lysosomal membrane permeabilization (LMP) allows the seeding of soluble α-syn in cells that have taken up α-syn fibrils from the culture medium, and, more importantly, in healthy cells in coculture, following lysosome-mediated transfer of the fibrils. Moreover, we demonstrate that seeding occurs mainly at lysosomes in both donor and acceptor cells, after uptake of α-syn fibrils from the medium and following their transfer, respectively. Finally, by using a heterotypic coculture system, we determine the origin and nature of the lysosomes transferred between cells, and we show that donor cells bearing α-syn fibrils transfer damaged lysosomes to acceptor cells, while also receiving healthy lysosomes from them. These findings thus contribute to the elucidation of the mechanism by which α-syn fibrils spread through TNTs, while also revealing the crucial role of lysosomes, working as a Trojan horse for both seeding and propagation of disease pathology.
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Affiliation(s)
- Aysegul Dilsizoglu Senol
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et de l’Infection, Institut Pasteur, Paris, France
| | - Maura Samarani
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et de l’Infection, Institut Pasteur, Paris, France
| | - Sylvie Syan
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et de l’Infection, Institut Pasteur, Paris, France
| | - Carlos M. Guardia
- Neurosciences and Cellular and Structural Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Takashi Nonaka
- Dementia Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Patricia Latour-Lambert
- Dynamique des Interaction Hôte–Pathogène, Département de Biologie Cellulaire et de l’Infection, Institut Pasteur, Paris, France
| | - Masato Hasegawa
- Dementia Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Juan S. Bonifacino
- Neurosciences and Cellular and Structural Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Chiara Zurzolo
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et de l’Infection, Institut Pasteur, Paris, France
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4
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Okolo CA, Kounatidis I, Groen J, Nahas KL, Balint S, Fish TM, Koronfel MA, Cortajarena AL, Dobbie IM, Pereiro E, Harkiolaki M. Sample preparation strategies for efficient correlation of 3D SIM and soft X-ray tomography data at cryogenic temperatures. Nat Protoc 2021; 16:2851-2885. [PMID: 33990802 DOI: 10.1038/s41596-021-00522-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Accepted: 02/09/2021] [Indexed: 02/07/2023]
Abstract
3D correlative microscopy methods have revolutionized biomedical research, allowing the acquisition of multidimensional information to gain an in-depth understanding of biological systems. With the advent of relevant cryo-preservation methods, correlative imaging of cryogenically preserved samples has led to nanometer resolution imaging (2-50 nm) under harsh imaging regimes such as electron and soft X-ray tomography. These methods have now been combined with conventional and super-resolution fluorescence imaging at cryogenic temperatures to augment information content from a given sample, resulting in the immediate requirement for protocols that facilitate hassle-free, unambiguous cross-correlation between microscopes. We present here sample preparation strategies and a direct comparison of different working fiducialization regimes that facilitate 3D correlation of cryo-structured illumination microscopy and cryo-soft X-ray tomography. Our protocol has been tested at two synchrotron beamlines (B24 at Diamond Light Source in the UK and BL09 Mistral at ALBA in Spain) and has led to the development of a decision aid that facilitates experimental design with the strategic use of markers based on project requirements. This protocol takes between 1.5 h and 3.5 d to complete, depending on the cell populations used (adherent cells may require several days to grow on sample carriers).
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Affiliation(s)
- Chidinma A Okolo
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Ilias Kounatidis
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | | | - Kamal L Nahas
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK.,Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Stefan Balint
- Kennedy Institute of Rheumatology, University of Oxford, Oxford, UK
| | - Thomas M Fish
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Mohamed A Koronfel
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Aitziber L Cortajarena
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Donostia San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Ian M Dobbie
- Micron Advanced Imaging Consortium, Department of Biochemistry, University of Oxford, Oxford, UK
| | - Eva Pereiro
- Beamline 09-MISTRAL, ALBA Synchrotron, Barcelona, Spain
| | - Maria Harkiolaki
- Beamline B24, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK.
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5
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Jongsma ML, Bakker J, Cabukusta B, Liv N, van Elsland D, Fermie J, Akkermans JL, Kuijl C, van der Zanden SY, Janssen L, Hoogzaad D, van der Kant R, Wijdeven RH, Klumperman J, Berlin I, Neefjes J. SKIP-HOPS recruits TBC1D15 for a Rab7-to-Arl8b identity switch to control late endosome transport. EMBO J 2020; 39:e102301. [PMID: 32080880 PMCID: PMC7073467 DOI: 10.15252/embj.2019102301] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 01/10/2020] [Accepted: 01/17/2020] [Indexed: 02/06/2023] Open
Abstract
The endolysosomal system fulfils a myriad of cellular functions predicated on regulated membrane identity progressions, collectively termed maturation. Mature or “late” endosomes are designated by small membrane‐bound GTPases Rab7 and Arl8b, which can either operate independently or collaborate to form a joint compartment. Whether, and how, Rab7 and Arl8b resolve this hybrid identity compartment to regain functional autonomy is unknown. Here, we report that Arl8b employs its effector SKIP to instigate inactivation and removal of Rab7 from select membranes. We find that SKIP interacts with Rab7 and functions as its negative effector, delivering the cognate GAP, TBC1D15. Recruitment of TBC1D15 to SKIP occurs via the HOPS complex, whose assembly is facilitated by contacts between Rab7 and the KMI motif of SKIP. Consequently, SKIP mediates reinstatement of single identity Arl8b sub‐compartment through an ordered Rab7‐to‐Arl8b handover, and, together with Rab7's positive effector RILP, enforces spatial, temporal and morphological compartmentalization of endolysosomal organelles.
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Affiliation(s)
- Marlieke Lm Jongsma
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Jeroen Bakker
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Birol Cabukusta
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Daphne van Elsland
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Job Fermie
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jimmy Ll Akkermans
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Coenraad Kuijl
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands
| | - Sabina Y van der Zanden
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Lennert Janssen
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Denise Hoogzaad
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Rik van der Kant
- Center for Neurogenomics and Cognitive Research, Faculty of Sciences, VU Amsterdam, Amsterdam, The Netherlands
| | - Ruud H Wijdeven
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Ilana Berlin
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Jacques Neefjes
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.,Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
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6
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Yang J, Pan H, Mishina Y. Tissue Preparation and Immunostaining of Mouse Craniofacial Tissues and Undecalcified Bone. J Vis Exp 2019. [PMID: 31132049 DOI: 10.3791/59113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Tissue immunostaining provides highly specific and reliable detection of proteins of interest within a given tissue. Here we describe a complete and simple protocol to detect protein expression during craniofacial morphogenesis/pathogenesis using mouse craniofacial tissues as examples. The protocol consists of preparation and cryosectioning of tissues, indirect immunofluorescence, image acquisition, and quantification. In addition, a method for preparation and cryosectioning of undecalcified hard tissues for immunostaining is described, using craniofacial tissues and long bones as examples. Those methods are key to determine the protein expression and morphological/anatomical changes in various tissues during craniofacial morphogenesis/pathogenesis. They are also applicable to other tissues with appropriate modifications. Knowledge of the histology and high quality of sections are critical to draw scientific conclusions from experimental outcomes. Potential limitations of this methodology include but are not limited to specificity of antibodies and difficulties of quantification, which are also discussed here.
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Affiliation(s)
- Jingwen Yang
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory for Oral Biomedicine of Ministry of Education, School and Hospital of Stomatology, Wuhan University; Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan
| | - Haichun Pan
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan
| | - Yuji Mishina
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan;
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7
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Fokkema J, Fermie J, Liv N, van den Heuvel DJ, Konings TOM, Blab GA, Meijerink A, Klumperman J, Gerritsen HC. Fluorescently Labelled Silica Coated Gold Nanoparticles as Fiducial Markers for Correlative Light and Electron Microscopy. Sci Rep 2018; 8:13625. [PMID: 30206379 PMCID: PMC6133918 DOI: 10.1038/s41598-018-31836-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/22/2018] [Indexed: 11/09/2022] Open
Abstract
In this work, gold nanoparticles coated with a fluorescently labelled (rhodamine B) silica shell are presented as fiducial markers for correlative light and electron microscopy (CLEM). The synthesis of the particles is optimized to obtain homogeneous, spherical core-shell particles of arbitrary size. Next, particles labelled with different fluorophore densities are characterized to determine under which conditions bright and (photo)stable particles can be obtained. 2 and 3D CLEM examples are presented where optimized particles are used for correlation. In the 2D example, fiducials are added to a cryosection of cells whereas in the 3D example cells are imaged after endocytosis of the fiducials. Both examples demonstrate that the particles are clearly visible in both modalities and can be used for correlation. Additionally, the recognizable core-shell structure of the fiducials proves to be very powerful in electron microscopy: it makes it possible to irrefutably identify the particles and makes it easy to accurately determine the center of the fiducials.
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Affiliation(s)
- Jantina Fokkema
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Job Fermie
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Dave J van den Heuvel
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Tom O M Konings
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Gerhard A Blab
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Andries Meijerink
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Hans C Gerritsen
- Soft Condensed Matter and Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands.
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8
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Möbius W, Posthuma G. Sugar and ice: Immunoelectron microscopy using cryosections according to the Tokuyasu method. Tissue Cell 2018; 57:90-102. [PMID: 30201442 DOI: 10.1016/j.tice.2018.08.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 07/26/2018] [Accepted: 08/22/2018] [Indexed: 11/29/2022]
Abstract
Since the pioneering work of Kiyoteru Tokuyasu in the 70ths the use of thawed cryosections prepared according to the "Tokuyasu-method" for immunoelectron microscopy did not lose popularity. We owe this method a whole subcellular world described by discrete gold particles pointing at cargo, receptors and organelle markers on delicate images of the inner life of a cell. Here we explain the procedure of sample preparation, sectioning and immunolabeling in view of recent developments and the reasoning behind protocols including some historical perspective. Cryosections are prepared from chemically fixed and sucrose infiltrated samples and labeled with affinity probes and electron dense markers. These sections are ideal substrates for immunolabeling, since antigens are not exposed to organic solvent dehydration or masked by resin. Instead, the structures remain fully hydrated throughout the labeling procedure. Furthermore, target molecules inside dense intercellular structural elements, cells and organelles are accessible to antibodies from the section surface. For the validation of antibody specificity several approaches are recommended including knock-out tissue and reagent controls. Correlative light and electron microscopy strategies involving correlative probes are possible as well as correlation of live imaging with the underlying ultrastructure. By applying stereology, gold labeling can be quantified and evaluated for specificity.
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Affiliation(s)
- Wiebke Möbius
- Electron Microscopy Core Unit, Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany.
| | - George Posthuma
- Department of Cell Biology, Cell Microscopy Core, University Medical Center Utrecht, Utrecht University, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands.
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9
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Hess MW, Vogel GF, Yordanov TE, Witting B, Gutleben K, Ebner HL, de Araujo MEG, Filipek PA, Huber LA. Combining high-pressure freezing with pre-embedding immunogold electron microscopy and tomography. Traffic 2018; 19:639-649. [PMID: 29673018 DOI: 10.1111/tra.12575] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 04/13/2018] [Accepted: 04/13/2018] [Indexed: 12/11/2022]
Abstract
Immunogold labeling of permeabilized whole-mount cells or thin-sectioned material is widely used for the subcellular localization of biomolecules at the high spatial resolution of electron microscopy (EM). Those approaches are well compatible with either 3-dimensional (3D) reconstruction of organelle morphology and antigen distribution or with rapid cryofixation-but not easily with both at once. We describe here a specimen preparation and labeling protocol for animal cell cultures, which represents a novel blend of specifically adapted versions of established techniques. It combines the virtues of reliably preserved organelle ultrastructure, as trapped by rapid freezing within milliseconds followed by freeze-substitution and specimen rehydration, with the advantages of robust labeling of intracellular constituents in 3D through means of pre-embedding NANOGOLD-silver immunocytochemistry. So obtained thin and semi-thick epoxy resin sections are suitable for transmission EM imaging, as well as tomographic reconstruction and modeling of labeling patterns in the 3D cellular context.
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Affiliation(s)
- Michael W Hess
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Georg F Vogel
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.,Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.,Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria
| | - Teodor E Yordanov
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Barbara Witting
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Karin Gutleben
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hannes L Ebner
- Division of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Mariana E G de Araujo
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Przemyslaw A Filipek
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Lukas A Huber
- Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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10
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Kumar S, Filippi MD. An Alternative Approach for Sample Preparation with Low Cell Number for TEM Analysis. J Vis Exp 2016. [PMID: 27768053 DOI: 10.3791/54724] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, especially cells in suspension such as hematopoietic stem cells (HSCs), remains limited due to the requirement of a high cell number during sample preparation. There are a few cytospin or monolayer approaches for TEM analysis from scarce samples, but these approaches fail to get significant quantitative data from the limited number of cells. Here, an alternative and novel approach for sample preparation in TEM studies is described for rare cell populations that enables quantitative analysis. A relatively low cell number, i.e., 10,000 HSCs, was successfully used for TEM analysis compared to the millions of cells typically used for TEM studies. In particular, Evans blue staining was performed after paraformaldehyde-glutaraldehyde (PFA-GA) fixation to visualize the tiny cell pellet, which facilitated embedding in agarose. Clusters of numerous cells were observed in ultra-thin sections. The cells had a well preserved morphology, and the ultra-structural details of the Golgi complex and several mitochondria were visible. This efficient, easy and reproducible protocol allows sample preparation from a low cell number and can be used for qualitative and quantitative TEM analysis on rare cell populations from limited biological samples.
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Affiliation(s)
- Sachin Kumar
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation;
| | - Marie-Dominique Filippi
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation;
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11
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Avci U, Nakashima J. A flat embedding method to orient thin biological samples for sectioning. Methods Mol Biol 2015; 1309:13-22. [PMID: 25981764 DOI: 10.1007/978-1-4939-2697-8_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Microscopy is an important tool used for biological research and has played a crucial role toward understanding of cellular mechanisms and protein function. However, specific steps in processing of biological samples for microscopy warrant improvements to consistently generate data that can more reliably help in explaining mechanisms underlying complex biological phenomenon. Due to their small and fragile nature, some biological specimens such as Arabidopsis thaliana roots are vulnerable to damage during long sample preparation steps. Moreover, when specimens with a small diameter (typically less than 100 μm) are embedded in conventional silicone mold or capsule embedding, it is not only difficult to locate their orientation inside the capsule but also a challenge to obtain good median longitudinal sections. Specimen orientation in particular is crucial because understanding certain plant biological processes such as gravitropism rely on precisely knowing spatial information of cells and tissues of the plant organ being studied. Here we present a simple embedding technique to properly orient small plant organs so that the desired sectioning plane is achieved. This method is also inexpensive and can be accomplished with only minimal equipment and supplies.
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Affiliation(s)
- Utku Avci
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA,
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12
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Nicolle O, Burel A, Griffiths G, Michaux G, Kolotuev I. Adaptation of Cryo-Sectioning for IEM Labeling of Asymmetric Samples: A Study Using Caenorhabditis elegans. Traffic 2015; 16:893-905. [PMID: 25858477 DOI: 10.1111/tra.12289] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 04/07/2015] [Accepted: 04/08/2015] [Indexed: 01/17/2023]
Abstract
Cryo-sectioning procedures, initially developed by Tokuyasu, have been successfully improved for tissues and cultured cells, enabling efficient protein localization on the ultrastructural level. Without a standard procedure applicable to any sample, currently existing protocols must be individually modified for each model organism or asymmetric sample. Here, we describe our method that enables reproducible cryo-sectioning of Caenorhabditis elegans larvae/adults and embryos. We have established a chemical-fixation procedure in which flat embedding considerably simplifies manipulation and lateral orientation of larvae or adults. To bypass the limitations of chemical fixation, we have improved the hybrid cryo-immobilization-rehydration technique and reduced the overall time required to complete this procedure. Using our procedures, precise cryo-sectioning orientation can be combined with good ultrastructural preservation and efficient immuno-electron microscopy protein localization. Also, GFP fluorescence can be efficiently preserved, permitting a direct correlation of the fluorescent signal and its subcellular localization. Although developed for C. elegans samples, our method addresses the challenge of working with small asymmetric samples in general, and thus could be used to improve the efficiency of immuno-electron localization in other model organisms.
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Affiliation(s)
- Ophélie Nicolle
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France
| | - Agnès Burel
- Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
| | - Gareth Griffiths
- Department of Biosciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
| | - Grégoire Michaux
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France.,Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
| | - Irina Kolotuev
- Institut de Génétique et Développement de Rennes, Faculté de Médecine, CNRS, Université de Rennes 1, F-35043, Rennes, France.,Plateforme microscopie électronique MRic, Université de Rennes 1, UEB, SFR Biosit, UMS 'BIOSIT' CNRS 3480-INSERM 018, F-35043, Rennes, France
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13
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Accart N, Sergi F, Rooke R. Revisiting Fixation and Embedding Techniques for Optimal Detection of Dendritic Cell Subsets in Tissues. J Histochem Cytochem 2014; 62:661-71. [DOI: 10.1369/0022155414539963] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Organ-specific cell types are maintained by tissue homeostasis and may vary in nature and/or frequency in pathological situations. Moreover, within a cell lineage, some sub-populations, defined by combinations of cell-surface markers, may have specific functions. Dendritic cells are the epitome of such a population as they may be subdivided into discrete sub-groups with defined functions in specific compartments of various organs. Technically, to study the distribution of DC sub-populations, it involves performing multiparametric immunofluorescence on well-conserved organ structures. However, immunodetection may be impacted by protein cross-linking and antigenic epitope masking by the use of 10% neutral-buffered formalin. To circumvent this and to preserve a good morphological tissue structure, we evaluated alternative fixatives such as Periodate Lysine Paraformaldehyde or Tris Zinc fixatives in combination with other embedding techniques. The cryosection protocols were adapted for optimal antigen detection but offered a poor morphological preservation. We therefore developed a new methodology based on Tris Zinc fixative, gelatin-sucrose embedding and freezing. Using multiple DC markers, we demonstrate that this treatment is an optimal protocol for cell-surface marker detection on high-quality tissue sections.
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Affiliation(s)
- Nathalie Accart
- Transgene S.A., Illkirch Graffenstaden, France (NA, FS, RR)
- Novartis Institutes for Biomedical Research, Basel, Switzerland (NA)
- Fisher Scientific, Illkirch Graffenstaden., France (FS)
| | - Florinda Sergi
- Transgene S.A., Illkirch Graffenstaden, France (NA, FS, RR)
- Novartis Institutes for Biomedical Research, Basel, Switzerland (NA)
- Fisher Scientific, Illkirch Graffenstaden., France (FS)
| | - Ronald Rooke
- Transgene S.A., Illkirch Graffenstaden, France (NA, FS, RR)
- Novartis Institutes for Biomedical Research, Basel, Switzerland (NA)
- Fisher Scientific, Illkirch Graffenstaden., France (FS)
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14
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Peckys DB, de Jonge N. Liquid scanning transmission electron microscopy: imaging protein complexes in their native environment in whole eukaryotic cells. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:346-65. [PMID: 24548636 DOI: 10.1017/s1431927614000099] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Scanning transmission electron microscopy (STEM) of specimens in liquid, so-called Liquid STEM, is capable of imaging the individual subunits of macromolecular complexes in whole eukaryotic cells in liquid. This paper discusses this new microscopy modality within the context of state-of-the-art microscopy of cells. The principle of operation and equations for the resolution are described. The obtained images are different from those acquired with standard transmission electron microscopy showing the cellular ultrastructure. Instead, contrast is obtained on specific labels. Images can be recorded in two ways, either via STEM at 200 keV electron beam energy using a microfluidic chamber enclosing the cells, or via environmental scanning electron microscopy at 30 keV of cells in a wet environment. The first series of experiments involved the epidermal growth factor receptor labeled with gold nanoparticles. The labels were imaged in whole fixed cells with nanometer resolution. Since the cells can be kept alive in the microfluidic chamber, it is also feasible to detect the labels in unfixed, live cells. The rapid sample preparation and imaging allows studies of multiple whole cells.
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Affiliation(s)
- Diana B Peckys
- 1 Leibniz Institute for New Materials (INM), 66123 Saarbrücken, Germany
| | - Niels de Jonge
- 1 Leibniz Institute for New Materials (INM), 66123 Saarbrücken, Germany
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15
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Webster P, Webster A. Cryosectioning fixed and cryoprotected biological material for immunocytochemistry. Methods Mol Biol 2014; 1117:273-313. [PMID: 24357368 DOI: 10.1007/978-1-62703-776-1_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Immunocytochemistry for electron microscopy provides important information on the location and relative abundance of proteins inside cells. Gaining access to this information without extracting or disrupting the location of target proteins requires specialized preparation methods. Sectioning frozen blocks of chemically fixed and cryoprotected biological material is one method for obtaining immunocytochemical data. Once the cells or tissues are cut, the cryosections are thawed, mounted onto coated grids, and labeled with specific antibodies and colloidal gold probes. They are then embedded in a thin film of plastic containing a contrasting agent. Subcellular morphology can then be correlated with specific affinity labeling by examination in the transmission electron microscope (TEM). The major advantage of using thawed cryosections for immunolabeling is that the sections remain fully hydrated through the immunolabeling steps, reducing the possibility of dehydration-induced antigen modification. Modern technical advancements both in preparation protocols and equipment design make cryosectioning a routine and rapid approach for immunocytochemistry that may provide increased sensitivity for some antibodies.
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Affiliation(s)
- Paul Webster
- Center for Electron Microscopy and Microanalysis (CEMMA), University of Souther California, Los Angeles, CA, USA
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16
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Oorschot VMJ, Sztal TE, Bryson-Richardson RJ, Ramm G. Immuno correlative light and electron microscopy on Tokuyasu cryosections. Methods Cell Biol 2014; 124:241-58. [PMID: 25287844 DOI: 10.1016/b978-0-12-801075-4.00011-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Finding a rare structure by electron microscopy is the equivalent of finding a "needle in a haystack." Correlative light- and immunoelectron microscopy (CLEM) on Tokuyasu cryosections is a sophisticated technique to address this challenge. Hereby, fluorescently labeled structures of interest are identified in an overview image by light microscopy and subsequently traced in electron microscopy. While the direct transfer and imaging of the same sections from optical to electron microscopy enables straightforward correlation, the sample preparation is crucial and technically demanding. We provide a detailed guide outlining the critical steps for sample embedding, cryosectioning, immunolabeling, and imaging. In the example provided, we use CLEM to trace aggregates formed in a zebrafish myopathy model expressing enhanced green fluorescent protein (eGFP) tagged actin. In our case, only a few muscle fibers express eGFP-actin with a subset of fibers containing aggregates. By fluorescence microscopy, we are able to identify the aggregates in the zebrafish tissue, and we subsequently, use immunoelectron microscopy to image the same structures at high resolution. The CLEM method described here using Tokuyasu cryosections can be applied to a large range of samples including small organisms, tissue samples, and cells.
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Affiliation(s)
| | - Tamar E Sztal
- School of Biological Sciences, Faculty of Sciences, Monash University, Melbourne, Victoria, Australia
| | | | - Georg Ramm
- Monash Micro Imaging, Monash University, Melbourne, Victoria, Australia; Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
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17
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Abstract
In correlative microscopy, light microscopy provides the overview and orientation of the complex cells and tissue, while electron microscopy offers the detailed localization and correlation of subcellular structures. In this chapter we offer detailed high-quality electron microscopical preparation methods for optimum preservation of the cellular ultrastructure. From such preparations serial thin sections are collected and used for comparative histochemical, immunofluorescence, and immunogold staining.In light microscopy histological stains identify the orientation of the sample and immunofluorescence labeling facilitates to find the region of interest, namely, the labeled cells expressing the macromolecule under investigation. Sections, labeled with immunogold are analyzed by electron microscopy in order to identify the label within the cellular architecture at high resolution.
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Affiliation(s)
- Heinz Schwarz
- Max Planck Institute for Developmental Biology, Tübingen, Germany
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18
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Schmiedinger T, Vogel GF, Eiter O, Pfaller K, Kaufmann WA, Flörl A, Gutleben K, Schönherr S, Witting B, Lechleitner TW, Ebner HL, Seppi T, Hess MW. Cryo-immunoelectron microscopy of adherent cells improved by the use of electrospun cell culture substrates. Traffic 2013; 14:886-94. [PMID: 23631675 DOI: 10.1111/tra.12080] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 04/25/2013] [Accepted: 04/30/2013] [Indexed: 01/27/2023]
Abstract
Electrospun nanofibres are an excellent cell culture substrate, enabling the fast and non-disruptive harvest and transfer of adherent cells for microscopical and biochemical analyses. Metabolic activity and cellular structures are maintained during the only half a minute-long harvest and transfer process. We show here that such samples can be optimally processed by means of cryofixation combined either with freeze-substitution, sample rehydration and cryosection-immunolabelling or with freeze-fracture replica-immunolabelling. Moreover, electrospun fibre substrates are equally suitable for complementary approaches, such as biochemistry, fluorescence microscopy and cytochemistry.
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Affiliation(s)
- Thomas Schmiedinger
- Department of Therapeutic Radiology and Oncology, Innsbruck Medical University, Anichstrasse 35, A-6020, Innsbruck, Austria
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Polishchuk EV, Polishchuk RS, Luini A. Correlative light-electron microscopy as a tool to study in vivo dynamics and ultrastructure of intracellular structures. Methods Mol Biol 2013; 931:413-22. [PMID: 23027014 DOI: 10.1007/978-1-62703-056-4_20] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Correlative light-electron microscopy (CLEM) is a very effective technique that combines live-cell imaging and immuno-electron microscopy for ultrastructural morphological characterization of dynamic intracellular organelles. The use of green fluorescent protein (GFP)-tagged chimeras allows the user to follow the movements and/or behavior of intracellular structures in a live cell and to fix it at the moment of interest. The subsequent immuno-electron microscopy processing can then reveal the three-dimensional architecture of the same structure, together with precise recognition of the GFP-labeled protein. The process resembles the taking of a high-resolution snapshot of an interesting live scene. Considering that CLEM is a very useful but technically demanding and time-consuming technique, accurate protocols will be helpful to simplify the work of scientists who are willing to apply this method for their own purposes. Here, we present a detailed protocol that describes all of the "tricks" and know-hows involved in carrying out the crucial steps of a CLEM experiment.
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20
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Polishchuk EV, Polishchuk RS. Analysis of Golgi complex function using correlative light-electron microscopy. Methods Cell Biol 2013; 118:243-58. [PMID: 24295311 DOI: 10.1016/b978-0-12-417164-0.00015-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Though it has been studied for more than 100 years, the Golgi complex remains a fascinating organelle for cell biologists. This is because it is a unique intracellular structure with a list of well-known functions that continues to grow with the discovery of new genes and the development of novel advanced techniques. The Golgi apparatus has been carefully characterized in different organisms, tissues, and cell types both by light and by electron microscopy. However, the new quality step in Golgi research began with the development of correlative light-electron microscopy (CLEM). This innovative method allows visualizing the fate of the same organelle of interest at any moment of its life span first by video imaging in live cells and then by immunoelectron microscopy and 3D reconstruction. Here, we will present the historical overview of different Golgi-associated processes characterized by CLEM and describe the detailed protocol of this complex yet valuable technique.
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21
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Mechanical fixation techniques for processing and orienting delicate samples, such as the root of Arabidopsis thaliana, for light or electron microscopy. Nat Protoc 2012; 7:1113-24. [PMID: 22596224 DOI: 10.1038/nprot.2012.056] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Despite improvements in live imaging, fixation followed by embedding and sectioning for light or electron microscopy remains an indispensible approach in biology. During processing, small or delicate samples can be lost, damaged or poorly oriented. Here we present a protocol for overcoming these issues when, along with chemical fixation, the sample is fixed mechanically. The protocol features two alternatives for mechanical fixation: the sample is encased either in a rectangular block of agarose or between Formvar films suspended on a wire loop. We also provide methods for key steps all the way through to sectioning. We illustrate the method on the root of Arabidopsis thaliana, an object that is ∼0.15 mm in diameter and difficult to process conventionally. With this protocol, well-oriented sections can be obtained with excellent ultrastructural preservation. The protocol takes about 1 week.
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22
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Wilkens V, Kohl W, Busch K. Restricted diffusion of OXPHOS complexes in dynamic mitochondria delays their exchange between cristae and engenders a transitory mosaic distribution. J Cell Sci 2012; 126:103-16. [DOI: 10.1242/jcs.108852] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mitochondria are involved in cellular energy supply, signaling and apoptosis. Their ability to fuse and divide provides functional and morphological flexibility and is a key feature in mitochondrial quality maintenance. To study the impact of mitochondrial fusion/fission on the reorganization of inner membrane proteins, OXPHOS complexes in mitochondria of different HeLa cells were tagged with fluorescent proteins (GFP and RFP-HA, respectively), and cells were fused by PEG treatment. Redistribution of the tagged OXPHOS complexes was then followed by means of immuno electron microscopy, two color superresolution fluorescence microscopy and single molecule tracking. In contrast to outer membrane and matrix proteins, which mix fast and homogeneously upon mitochondrial fusion, the mixing of inner membrane proteins was decelerated. Our data suggest that in principle (i) with respect to their composition cristae are preserved during fusion of mitochondria and (ii) cristae with mixed OXPHOS complexes are only slowly and successively formed by restricted diffusion of inner membrane proteins into existing cristae. The resulting transitory mosaic appearance of the inner mitochondrial membrane in terms of composition illuminates mitochondrial heterogeneity and potentially is linked to local differences in function and membrane potential.
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23
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Polishchuk RS, Polishchuk EV, Luini A. Visualizing live dynamics and ultrastructure of intracellular organelles with preembedding correlative light-electron microscopy. Methods Cell Biol 2012; 111:21-35. [PMID: 22857921 DOI: 10.1016/b978-0-12-416026-2.00002-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
One of the very effective methods to perform correlative light-electron microscopy (CLEM) is to combine video imaging of live cells with immuno-electron microscopy. This technique can thus provide detailed, high-resolution characterization of dynamic intracellular organelles. The use of green fluorescent protein (GFP)-tagged chimeras allows the movements and/or behavior of intracellular structures in a live cell to be followed, which can then be fixed at the moment of interest. The subsequent immuno-electron microscopy analysis reveals the three-dimensional (3D) architecture of the same structure, together with the precise identification of the GFP-labeled protein pattern. The process resembles taking a high-resolution snapshot of an interesting and/or rare live event. Conceptually, it consists of a switch of wavelengths, from that of photons to that of electrons, with the associated huge gain in resolution. In this respect, CLEM can be considered as the first, and probably one of the most powerful, super-resolution microscopy techniques. This switch, however, requires complex manipulations of the sample. Considering that CLEM is a very valuable but technically challenging and time-consuming method, accurate protocols are needed to simplify the efforts of researchers who are willing to apply this method for their own purposes. Here, we present a detailed description of the preembedding CLEM procedures that explains the know-how and the "tricks of the trade" that are involved in carrying out the crucial steps of CLEM.
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24
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Rab35 GTPase and OCRL phosphatase remodel lipids and F-actin for successful cytokinesis. Nat Cell Biol 2011; 13:981-8. [DOI: 10.1038/ncb2279] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 05/09/2011] [Indexed: 12/17/2022]
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25
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Griffith J, Peñalva MA, Reggiori F. Adaptation of the Tokuyasu method for the ultrastructural study and immunogold labelling of filamentous fungi. JOURNAL OF ELECTRON MICROSCOPY 2011; 60:211-216. [PMID: 21527426 DOI: 10.1093/jmicro/dfr026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The study of filamentous fungi is fundamental not only to extend their biotechnological applications, but also to develop new drugs to fight pathological species. Morphological analyses are particularly relevant when investigating their development and differentiation. The need to maintain the orientation of hypahe and the presence of a cell wall, which hampers the sample infiltration with cryoprotectants and other reagents necessary to preserve the cell ultrastructure, creates difficulties with the use of electron microscopy (EM). Here, we present an immunoelectron microscopy (IEM) procedure that combines the Tokuyasu protocol adapted to yeast and the flat-embedding technique. While the first method leads to a fine resolution of the ultrastructure of Aspergillus nidulans because of both the cell wall permeabilization and the negative membrane coloration, the second permits us to preserve the spatial distribution of the hypahe of this fungus. The presented data demonstrate the advantages of this combination and the unprecedented potential of this relatively simple and rapid protocol in resolving the morphology of filamentous fungi and performing localization studies.
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Affiliation(s)
- Janice Griffith
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, The Netherlands
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26
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Abstract
Calcium-dependent secretion of neurotransmitters and hormones is essential for brain function and neuroendocrine-signaling. Prior to exocytosis, neurotransmitter-containing vesicles dock to the target membrane. In electron micrographs of neurons and neuroendocrine cells, like chromaffin cells many synaptic vesicles (SVs) and large dense-core vesicles (LDCVs) are docked. For many years the molecular identity of the morphologically docked state was unknown. Recently, we resolved the minimal docking machinery in adrenal medullary chromaffin cells using embryonic mouse model systems together with electron-microscopic analyses and also found that docking is controlled by the sub-membrane filamentous (F-)actin. Currently it is unclear if the same docking machinery operates in synapses. Here, I will review our docking assay that led to the identification of the LDCV docking machinery in chromaffin cells and also discuss whether identical docking proteins are required for SV docking in synapses.
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27
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van Weering JRT, Brown E, Sharp TH, Mantell J, Cullen PJ, Verkade P. Intracellular membrane traffic at high resolution. Methods Cell Biol 2010; 96:619-48. [PMID: 20869541 PMCID: PMC4067575 DOI: 10.1016/s0091-679x(10)96026-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Membrane traffic between organelles is essential for a multitude of processes that maintain cell homeostasis. Many steps in these tightly regulated trafficking pathways take place in microdomains on the membranes of organelles, which require analysis at nanometer resolution. Electron microscopy (EM) can visualize these processes in detail and is mainly responsible for our current view of morphology on the subcellular level. This review discusses how EM can be applied to solve many questions of intracellular membrane traffic, with a focus on the endosomal system. We describe the expansion of the technique from purely morphological analysis to cryo-immuno-EM, correlative light electron microscopy (CLEM), and 3D electron tomography. In this review we go into some technical details of these various techniques. Furthermore, we provide a full protocol for immunolabeling on Lowicryl sections of high-pressure frozen cells as well as a detailed description of a simple CLEM method that can be applied to answer many membrane trafficking questions. We believe that these EM-based techniques are important tools to expand our understanding of the molecular details of endosomal sorting and intracellular membrane traffic in general.
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Affiliation(s)
- Jan R T van Weering
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS81TD, United Kingdom
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28
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HEKKING L, LEBBINK M, DE WINTER D, SCHNEIJDENBERG C, BRAND C, HUMBEL B, VERKLEIJ A, POST J. Focused ion beam-scanning electron microscope: exploring large volumes of atherosclerotic tissue. J Microsc 2009; 235:336-47. [DOI: 10.1111/j.1365-2818.2009.03274.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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29
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Cortese K, Diaspro A, Tacchetti C. Advanced correlative light/electron microscopy: current methods and new developments using Tokuyasu cryosections. J Histochem Cytochem 2009; 57:1103-12. [PMID: 19654103 DOI: 10.1369/jhc.2009.954214] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microscopy is an essential tool for analysis of cellular structures and function. With the advent of new fluorescent probes and super-resolution light microscopy techniques, the study of dynamic processes in living cells has been greatly facilitated. Fluorescence light microscopy provides analytical, quantitative, and three-dimensional (3D) data with emphasis on analysis of live cells using fluorescent markers. Sample preparation is easy and relatively inexpensive, and the use of appropriate tags provides the ability to track specific proteins of interest. Of course, only electron microscopy (EM) achieves the highest definition in terms of ultrastructure and protein labeling. To fill the gap between light microscopy and EM, correlative light and electron microscopy (CLEM) strategies have been developed. In particular, hybrid techniques based upon immuno-EM provide sensitive protein detection combined with high-resolution information on cell structures and protein localization. By adding the third dimension to EM with electron tomography (ET) combined with rapid freezing, CLEM techniques now provide additional tools for quantitative 3D analysis. Here, we overview the major methods applied and highlight the latest advances in the field of CLEM. We then focus on two selected techniques that use cryosections as substrate for combined biomolecular imaging. Finally, we provide a perspective of future developments in the field.
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30
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Discovery of a new RNA-containing nuclear structure in UVC-induced apoptotic cells by integrated laser electron microscopy. Biol Cell 2009; 101:287-99. [PMID: 18823283 DOI: 10.1042/bc20080076] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION Treatment of cells with UVC radiation leads to the formation of DNA cross-links which, if not repaired, can lead to apoptosis. gamma-H2AX and cleaved caspase 3 are proteins formed during UVC-induced DNA damage and apoptosis respectively. The present study sets out to identify early morphological markers of apoptosis using a new method of correlative microscopy, ILEM (integrated laser electron microscopy). Cleaved caspase 3 and gamma-H2AX were immunofluorescently labelled to mark the cells of interest. These cells were subsequently searched in the fluorescence mode of the ILEM and further analysed at high resolution with TEM (transmission electron microscopy). RESULTS Following the treatment of HUVECs (human umbilical vein endothelial cells) with UVC radiation, in the majority of the cells gamma-H2AX was formed, whereas only in a subset of cells caspase 3 was activated. In severely damaged cells with high levels of gamma-H2AX a round, electron-dense nuclear structure was found, which was hitherto not identified in UV-stressed cells. This structure exists only in nuclei of cells containing cleaved caspase 3 and is present during all stages of the apoptotic process. Energy-loss imaging showed that the nuclear structure accumulates phosphorus, indicating that it is rich in nucleic acids. Because the nuclear structure did not label for DNA and was not affected by regressive EDTA treatment, it is suggested that the UV-induced nuclear structure contains a high amount of RNA. CONCLUSIONS Because the UV-induced nuclear structure was only found in cells labelled for cleaved caspase 3 it is proposed as an electron microscopic marker for all stages of apoptosis. Such a marker will especially facilitate the screening for early apoptotic cells, which lack the well-known hallmarks of apoptosis within a cell population. It also raises new questions on the mechanisms involved in the UV-induced apoptotic pathway.
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31
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Leitch B, Shevtsova O, Kerr JR. Selective reduction in synaptic proteins involved in vesicle docking and signalling at synapses in the ataxic mutant mouse stargazer. J Comp Neurol 2009; 512:52-73. [PMID: 18972569 DOI: 10.1002/cne.21890] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The spontaneous recessive mutant mouse stargazer has a specific and pronounced deficit in brain-derived neurotrophic factor (BDNF) mRNA expression in the cerebellum. Cerebellar granule cells, in particular, show a selective and near-total loss of BDNF. The mutation involves a defect in the calcium channel subunit Cacng2. This severely reduces expression of stargazin. A stargazin-induced failure in BDNF expression is thought to underlie the cerebellar ataxia with which the mutant presents. BDNF is known to regulate plasticity at cerebellar synapses. However, relatively little is known about the mechanism involved. We previously demonstrated that the stargazer mutation affects the phenotype of cerebellar glutamatergic neurons. Stargazer neurons have less glutamate and proportionally fewer docked vesicles at presynaptic sites than controls. In the current study, we investigate the mechanism underlying BDNF-induced synaptic changes by analyzing alterations in synaptic signalling proteins in the stargazer cerebellum. Expression levels of synaptic proteins were evaluated by measuring relative density of immunogold label over granule cell terminals in ultrathin sections from ataxic stargazer mutants compared with matched nonataxic littermates. We show that there is a selective and marked depletion in the levels of vesicle-associated proteins (synaptobrevin, synaptophysin, synaptotagmin, and Rab3a) but not of plasma membrane-associated protein (SNAP-25) in the terminals of the BDNF-deficient granule cells. Changes are restricted to the cerebellum; levels in the hippocampus are unaltered. These data suggest that the BDNF deficits in the cerebellum of stargazer affect synaptic vesicle docking by selectively altering synaptic-protein distribution and abundance.
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Affiliation(s)
- Beulah Leitch
- Department of Anatomy and Structural Biology, Otago School of Medical Sciences, University of Otago, Dunedin, 9054 New Zealand.
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van Rijnsoever C, Oorschot V, Klumperman J. Correlative light-electron microscopy (CLEM) combining live-cell imaging and immunolabeling of ultrathin cryosections. Nat Methods 2008; 5:973-80. [PMID: 18974735 DOI: 10.1038/nmeth.1263] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Carolien van Rijnsoever
- Cell Microscopy Center, Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
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Vicidomini G, Gagliani MC, Canfora M, Cortese K, Frosi F, Santangelo C, Di Fiore PP, Boccacci P, Diaspro A, Tacchetti C. High data output and automated 3D correlative light-electron microscopy method. Traffic 2008; 9:1828-38. [PMID: 18817522 PMCID: PMC2635477 DOI: 10.1111/j.1600-0854.2008.00815.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Correlative light/electron microscopy (CLEM) allows the simultaneous observation of a given subcellular structure by fluorescence light microscopy (FLM) and electron microscopy. The use of this approach is becoming increasingly frequent in cell biology. In this study, we report on a new high data output CLEM method based on the use of cryosections. We successfully applied the method to analyze the structure of rough and smooth Russell bodies used as model systems. The major advantages of our method are (i) the possibility to correlate several hundreds of events at the same time, (ii) the possibility to perform three-dimensional (3D) correlation, (iii) the possibility to immunolabel both endogenous and recombinantly expressed proteins at the same time and (iv) the possibility to combine the high data analysis capability of FLM with the high precision–accuracy of transmission electron microscopy in a CLEM hybrid morphometry analysis. We have identified and optimized critical steps in sample preparation, defined routines for sample analysis and retracing of regions of interest, developed software for semi/fully automatic 3D reconstruction and defined preliminary conditions for an hybrid light/electron microscopy morphometry approach.
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Yap CC, Wisco D, Kujala P, Lasiecka ZM, Cannon JT, Chang MC, Hirling H, Klumperman J, Winckler B. The somatodendritic endosomal regulator NEEP21 facilitates axonal targeting of L1/NgCAM. ACTA ACUST UNITED AC 2008; 180:827-42. [PMID: 18299352 PMCID: PMC2265569 DOI: 10.1083/jcb.200707143] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Correct targeting of proteins to axons and dendrites is crucial for neuronal function. We showed previously that axonal accumulation of the cell adhesion molecule L1/neuron-glia cell adhesion molecule (NgCAM) depends on endocytosis (Wisco, D., E.D. Anderson, M.C. Chang, C. Norden, T. Boiko, H. Folsch, and B. Winckler. 2003. J. Cell Biol. 162:1317–1328). Two endocytosis-dependent pathways to the axon have been proposed: transcytosis and selective retrieval/retention. We show here that axonal accumulation of L1/NgCAM occurs via nondegradative somatodendritic endosomes and subsequent anterograde axonal transport, which is consistent with transcytosis. Additionally, we identify the neuronal-specific endosomal protein NEEP21 (neuron-enriched endosomal protein of 21 kD) as a regulator of L1/NgCAM sorting in somatodendritic endosomes. Down-regulation of NEEP21 leads to missorting of L1/NgCAM to the somatodendritic surface as well as to lysosomes. Importantly, the axonal accumulation of endogenous L1 in young neurons is also sensitive to NEEP21 depletion. We propose that small endosomal carriers derived from somatodendritic recycling endosomes can serve to redistribute a distinct set of membrane proteins from dendrites to axons.
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Affiliation(s)
- Chan Choo Yap
- Department of Neuroscience, University of Virginia Medical School, Charlottesville, VA 22908, USA
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Abstract
In this protocol, we describe cryoimmunolabeling methods for the subcellular localization of proteins and certain lipids. The methods start with chemical fixation of cells and tissue in formaldehyde (FA) and/or glutaraldehyde (GA), sometimes supplemented with acrolein. Cell and tissue blocks are then immersed in 2.3 M sucrose before freezing in liquid nitrogen. Thin cryosections, cut in an ultracryotome, can be single- or multiple immunolabeled with differently sized gold particles, contrasted and viewed in an electron microscope. Semi-thin cryosections can be used for immunofluorescence microscopy. We describe the detailed procedures that have been developed and tested in practice in our laboratory during the past decades.
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Granata A, Watson R, Collinson LM, Schiavo G, Warner TT. The dystonia-associated protein torsinA modulates synaptic vesicle recycling. J Biol Chem 2007; 283:7568-79. [PMID: 18167355 DOI: 10.1074/jbc.m704097200] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The loss of a glutamic acid residue in the AAA-ATPase (ATPases associated with diverse cellular activities) torsinA is responsible for most cases of early onset autosomal dominant primary dystonia. In this study, we found that snapin, which binds SNAP-25 (synaptosome-associated protein of 25,000 Da) and enhances the association of the SNARE complex with synaptotagmin, is an interacting partner for both wild type and mutant torsinA. Snapin co-localized with endogenous torsinA on dense core granules in PC12 cells and was recruited to perinuclear inclusions containing mutant DeltaE-torsinA in neuroblastoma SH-SY5Y cells. In view of these observations, synaptic vesicle recycling was analyzed using the lipophilic dye FM1-43 and an antibody directed against an intravesicular epitope of synaptotagmin I. We found that overexpression of wild type torsinA negatively affects synaptic vesicle endocytosis. Conversely, overexpression of DeltaE-torsinA in neuroblastoma cells increases FM1-43 uptake. Knockdown of snapin and/or torsinA using small interfering RNAs had a similar inhibitory effect on the exo-endocytic process. In addition, down-regulation of torsinA causes the persistence of synaptotagmin I on the plasma membrane, which closely resembles the effect observed by the overexpression of the DeltaE-torsinA mutant. Altogether, these findings suggest that torsinA plays a role together with snapin in regulated exocytosis and that DeltaE-torsinA exerts its pathological effects through a loss of function mechanism. This may affect neuronal uptake of neurotransmitters, such as dopamine, playing a role in the development of dystonic movements.
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Affiliation(s)
- Alessandra Granata
- Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom
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Webster P, Webster A. Cryosectioning fixed and cryoprotected biological material for immunocytochemistry. Methods Mol Biol 2007; 369:257-89. [PMID: 17656755 DOI: 10.1007/978-1-59745-294-6_13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Immunocytochemistry for transmission electron microscopy provides important information on the location and relative abundance of proteins inside cells. Gaining access to this information without extracting or disrupting the location of target proteins requires specialized preparation methods. Sectioning frozen blocks of chemically fixed and cryoprotected biological material is one method for obtaining immunocytochemical data. Once the cells or tissues are cut, the thawed cryosections can be labeled with specific antibodies and colloidal gold probes. They are then embedded in a thin film of plastic containing a contrasting agent. Subcellular morphology can be correlated with specific affinity labeling by examination in the transmission electron microscope. Modern technical advancements both in preparation protocols and equipment design make cryosectioning a routine and rapid approach for immunocytochemistry that may provide increased sensitivity for some antibodies.
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Affiliation(s)
- Paul Webster
- Ahmanson Advanced Electron Microscopy and Imaging Center, House Ear Institute, Los Angeles, CA, USA
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Abstract
This chapter reviews the use of standard transmission electron microscopy (TEM) of plastic-embedded material, as well as protocols for the immunolabeling of cryosections, in the analysis of viral interactions with cells. It focuses particularly on the assembly of two types of enveloped viruses: (1) the beta herpesvirus—human cytomegalovirus (HCMV), and (2) the primate lentiviruses—the simian and human immunodeficiency viruses (SIV and HIV). The chapter discusses the ways EM is used to identify morphological features of the various stages in the assembly of virus particles, to distinguish immature and mature particles, or to analyze steps involved in the acquisition of lipid membranes by enveloped viruses. In addition, it demonstrates the way immunolabeling allows the quantification of viral components, even in individual virus particles, and comparisons between particles at different locations in the cell or at different stages in viral assembly. Together with the newly developed methods for electron tomography and correlative immunofluorescence studies and EM, huge potential exists to unravel more details about virus assembly in the near future.
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Affiliation(s)
- Annegret Pelchen-Matthews
- Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Biochemistry and Molecular Biology, University College London, London, United Kingdom
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Ishii M, Iwai K, Koike M, Ohshima S, Kudo-Tanaka E, Ishii T, Mima T, Katada Y, Miyatake K, Uchiyama Y, Saeki Y. RANKL-induced expression of tetraspanin CD9 in lipid raft membrane microdomain is essential for cell fusion during osteoclastogenesis. J Bone Miner Res 2006; 21:965-76. [PMID: 16753027 DOI: 10.1359/jbmr.060308] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
UNLABELLED We showed that CD9, a member of tetraspanin superfamily proteins, is expressed in a specific membrane microdomain, called "lipid raft," and is crucial for cell fusion during osteoclastogenesis after activation of the RANK/RANKL system. INTRODUCTION Osteoclasts are bone-resorbing multinuclear polykaryons that are essential for bone remodeling and are formed through cell fusion of mononuclear macrophage/monocyte lineage precursors. Although osteoclastogenesis has been shown to be critically regulated by the RANK/RANKL system, the mechanism how precursor cells fuse with each other remains unclear. We examined the function of CD9, a member of tetraspanin superfamily, which has previously been shown to form macromolecular membrane microdomains and to regulate cell-cell fusion in various cell types. MATERIALS AND METHODS We used RAW264.7, a macrophage/monocyte lineage cell line, which can differentiate into osteoclast-like polykaryons on the application of RANKL. Expression and distribution of CD9 was assessed by Western blotting, fluorescence-assorted cell sorting (FACS) and immunohistochemistry with light and electron microscopy. A specific neutralizing antibody and RNA interference were used to inhibit the function of CD9, and green fluorescent protein (GFP)-CD9 was exogenously expressed to enhance the effect of CD9. The distribution of CD9 in lipid microdomain was examined by biochemical (sucrose density gradient) isolation and imaging technique. RESULTS CD9 is expressed on cell surfaces of RAW264.7, which is enhanced by RANKL. Targeted inhibition of CD9 decreases the number of osteoclast-like cells. On the other hand, overexpression of CD9 promotes spontaneous cell fusion even in the absence of RANKL. CD9 is localized in detergent-insoluble "lipid raft" microdomain in RANKL stimulation, and disruption of lipid rafts markedly reduces the formation of osteoclast-like polykaryons. Immunohistochemical studies of bone tissues revealed the expression of CD9 in osteoclasts in vivo. CONCLUSIONS These data suggest that function of tetraspanin CD9 and its expression in lipid rafts are crucial for cell fusion during osteoclastogenesis.
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Affiliation(s)
- Masaru Ishii
- Department of Clinical Research, Osaka Minami Medical Center, Osaka, Japan.
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Brown DA, Chou YF, Beygui RE, Dunn JCY, Wu BM. Gelatin-embedded cell-polymer constructs for histological cryosectioning. J Biomed Mater Res B Appl Biomater 2005; 72:79-85. [PMID: 15389500 DOI: 10.1002/jbm.b.30116] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Many tissue-engineering strategies involve the delivery of cells via porous polymer scaffolds. Obtaining histological sections of the emerging tissue is often necessary to analyze numerous characteristics of the microscopic environment. However, difficulties arise upon applying standard histological techniques to cell-seeded polymer scaffolds. This report describes a simple and reliable method for cryosectioning cell-polymer constructs embedded in gelatin. Solvent-soluble (PLGA) and insoluble (PGA) scaffolds were cultured in vitro with preosteoblasts, followed by histological processing with paraffin, OCT, or gelatin. Although paraffin-embedded PGA scaffolds withstood standard sectioning and rinsing steps, paraffin-embedded PLGA scaffolds were partially dissolved during the clearing step. OCT-embedded scaffolds produced sections that did not adhere well to slides, and most of the sample was lost during rinsing steps. In contrast, gelatin-embedded scaffolds exhibited adequate structural integrity during cryosectioning, adhered well to the slides, retained the actual polymer morphology, and exhibited compatibility with common stains.
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Affiliation(s)
- David A Brown
- Department of Bioengineering, Henry L. Samueli School of Engineering, University of California, Los Angeles, California, USA
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Esselens C, Oorschot V, Baert V, Raemaekers T, Spittaels K, Serneels L, Zheng H, Saftig P, De Strooper B, Klumperman J, Annaert W. Presenilin 1 mediates the turnover of telencephalin in hippocampal neurons via an autophagic degradative pathway. ACTA ACUST UNITED AC 2004; 166:1041-54. [PMID: 15452145 PMCID: PMC2172014 DOI: 10.1083/jcb.200406060] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Presenilin 1 (PS1) interacts with telencephalin (TLN) and the amyloid precursor protein via their transmembrane domain (Annaert, W.G., C. Esselens, V. Baert, C. Boeve, G. Snellings, P. Cupers, K. Craessaerts, and B. De Strooper. 2001. Neuron. 32:579–589). Here, we demonstrate that TLN is not a substrate for γ-secretase cleavage, but displays a prolonged half-life in PS1−/− hippocampal neurons. TLN accumulates in intracellular structures bearing characteristics of autophagic vacuoles including the presence of Apg12p and LC3. Importantly, the TLN accumulations are suppressed by adenoviral expression of wild-type, FAD-linked and D257A mutant PS1, indicating that this phenotype is independent from γ-secretase activity. Cathepsin D deficiency also results in the localization of TLN to autophagic vacuoles. TLN mediates the uptake of microbeads concomitant with actin and PIP2 recruitment, indicating a phagocytic origin of TLN accumulations. Absence of endosomal/lysosomal proteins suggests that the TLN-positive vacuoles fail to fuse with endosomes/lysosomes, preventing their acidification and further degradation. Collectively, PS1 deficiency affects in a γ-secretase–independent fashion the turnover of TLN through autophagic vacuoles, most likely by an impaired capability to fuse with lysosomes.
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Affiliation(s)
- Cary Esselens
- Membrane Trafficking Laboratory, CME-VIB04, Gasthuisberg-KU Leuven, 3000 Leuven, Belgium
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Yang SJ, Liang HL, Ning G, Wong-Riley MTT. Ultrastructural study of depolarization-induced translocation of NRF-2 transcription factor in cultured rat visual cortical neurons. Eur J Neurosci 2004; 19:1153-62. [PMID: 15016074 DOI: 10.1111/j.1460-9568.2004.03250.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nuclear respiratory factor (NRF)-2 or GA-binding protein is a potential transcriptional, bigenomic coordinator of mitochondrial and nuclear-encoded subunits of cytochrome oxidase genes. It is composed of an alpha subunit that binds DNA and a beta subunit that has the transactivating domain. Previously, we found that the level of NRF-2 paralleled that of cytochrome oxidase under normal and functionally altered states. The goal of our present study was to increase the resolution to the ultrastructural level and to quantify changes before and after depolarizing stimulation. We used a pre-embedding immunogold-silver method for the two subunits of NRF-2 in cultured rat visual cortical neurons. NRF-2alpha and beta were normally located in both the nucleus and the cytoplasm. In the nucleus, both subunits were associated primarily with euchromatin rather than heterochromatin, consistent with active involvement in transcription. In the cytoplasm, they were associated mainly with free ribosomes and occasionally with the Golgi apparatus and the outer membrane of the nuclear envelope. Labelling was not found in the mitochondria, confirming the specificity of the antibodies. Neuronal depolarization by KCl for 5 h induced a six- to seven-fold increase in the nuclear-to-cytoplasmic ratio of both subunits (P < 0.001) without increases in total labelling densities. These results strongly indicate that both NRF-2alpha and NRF-2beta respond to increased neuronal activity by translocating from the cytoplasm to the nucleus, where they engage in transcriptional activation of target genes. Our results also indicate that the cytoplasmic to nuclear movement of transcription factors is a dynamic process induced by neuronal activity.
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Affiliation(s)
- Shou Jing Yang
- Department of Cell Biology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Fernandez MI, Prevost MC, Sansonetti PJ, Griffiths G. Applications of Cryo- and Transmission Electron Microscopy in the Study of Microbial Macromolecular Structure and Bacterial–Host Cell Interactions. METHODS IN MICROBIOLOGY 2004. [DOI: 10.1016/s0580-9517(04)34005-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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