1
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Galaz-Montoya JG. The advent of preventive high-resolution structural histopathology by artificial-intelligence-powered cryogenic electron tomography. Front Mol Biosci 2024; 11:1390858. [PMID: 38868297 PMCID: PMC11167099 DOI: 10.3389/fmolb.2024.1390858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Accepted: 05/08/2024] [Indexed: 06/14/2024] Open
Abstract
Advances in cryogenic electron microscopy (cryoEM) single particle analysis have revolutionized structural biology by facilitating the in vitro determination of atomic- and near-atomic-resolution structures for fully hydrated macromolecular complexes exhibiting compositional and conformational heterogeneity across a wide range of sizes. Cryogenic electron tomography (cryoET) and subtomogram averaging are rapidly progressing toward delivering similar insights for macromolecular complexes in situ, without requiring tags or harsh biochemical purification. Furthermore, cryoET enables the visualization of cellular and tissue phenotypes directly at molecular, nanometric resolution without chemical fixation or staining artifacts. This forward-looking review covers recent developments in cryoEM/ET and related technologies such as cryogenic focused ion beam milling scanning electron microscopy and correlative light microscopy, increasingly enhanced and supported by artificial intelligence algorithms. Their potential application to emerging concepts is discussed, primarily the prospect of complementing medical histopathology analysis. Machine learning solutions are poised to address current challenges posed by "big data" in cryoET of tissues, cells, and macromolecules, offering the promise of enabling novel, quantitative insights into disease processes, which may translate into the clinic and lead to improved diagnostics and targeted therapeutics.
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Affiliation(s)
- Jesús G. Galaz-Montoya
- Department of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA, United States
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2
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Perez D, Dowlatshahi DP, Azaldegui CA, Dahlberg PD, Moerner WE. Exploring transient states of PAmKate to enable improved cryogenic single-molecule imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.24.590965. [PMID: 38712218 PMCID: PMC11071506 DOI: 10.1101/2024.04.24.590965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Super-resolved cryogenic correlative light and electron microscopy is a powerful approach which combines the single-molecule specificity and sensitivity of fluorescence imaging with the nano-scale resolution of cryogenic electron tomography. Key to this method is active control over the emissive state of fluorescent labels to ensure sufficient sparsity to localize individual emitters. Recent work has identified fluorescent proteins (FPs) which photoactivate or photoswitch efficiently at cryogenic temperatures, but long on-times due to reduced quantum yield of photobleaching remains a challenge for imaging structures with a high density of localizations. In this work, we explore the photophysical properties of the red photoactivatable FP PAmKate and identify a 2-color process leading to enhanced turn-off of active emitters, improving localization rate. Specifically, after excitation of ground state molecules, we find a transient state forms with a lifetime of ~2 ms which can be bleached by exposure to a second wavelength. We measure the response of the transient state to different wavelengths, demonstrate how this mechanism can be used to improve imaging, and provide a blueprint for study of other FPs at cryogenic temperatures.
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Affiliation(s)
- Davis Perez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dara P Dowlatshahi
- Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Structural Biology, Stanford University, Stanford, California 94305, United States
| | - Christopher A Azaldegui
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Peter D Dahlberg
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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3
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COPELAND CRAIGR, PINTAR ADAML, DIXSON RONALDG, CHANANA ASHISH, SRINIVASAN KARTIK, WESTLY DARONA, ROBERT ILIC B, DAVANCO MARCELOI, STAVIS SAMUELM. Traceable localization enables accurate integration of quantum emitters and photonic structures with high yield. OPTICA QUANTUM 2024; 2:72-84. [PMID: 38741706 PMCID: PMC11089896 DOI: 10.1364/opticaq.502464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 01/02/2024] [Indexed: 05/16/2024]
Abstract
In a popular integration process for quantum information technologies, localization microscopy of quantum emitters guides lithographic placement of photonic structures. However, a complex coupling of microscopy and lithography errors degrades registration accuracy, severely limiting device performance and process yield. We introduce a methodology to solve this widespread but poorly understood problem. A new foundation of traceable localization enables rapid characterization of lithographic standards and comprehensive calibration of cryogenic microscopes, revealing and correcting latent systematic effects. Of particular concern, we discover that scale factor deviation and complex optical distortion couple to dominate registration errors. These novel results parameterize a process model for integrating quantum dots and bullseye resonators, predicting higher yield by orders of magnitude, depending on the Purcell factor threshold as a quantum performance metric. Our foundational methodology is a key enabler of the lab-to-fab transition of quantum information technologies and has broader implications to cryogenic and correlative microscopy.
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Affiliation(s)
- CRAIG R. COPELAND
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - ADAM L. PINTAR
- Statistical Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - RONALD G. DIXSON
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - ASHISH CHANANA
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - KARTIK SRINIVASAN
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Joint Quantum Institute, NIST/University of Maryland, College Park, Maryland 20742, USA
| | - DARON A. WESTLY
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - B. ROBERT ILIC
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- CNST NanoFab, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - MARCELO I. DAVANCO
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - SAMUEL M. STAVIS
- Microsystems and Nanotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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4
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Keck C, Enninga J, Swistak L. Caught in the act: In situ visualization of bacterial secretion systems by cryo-electron tomography. Mol Microbiol 2024; 121:636-645. [PMID: 37975530 DOI: 10.1111/mmi.15186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/09/2023] [Accepted: 10/15/2023] [Indexed: 11/19/2023]
Abstract
Bacterial secretion systems, such as the type 3, 4, and 6 are multiprotein nanomachines expressed at the surface of pathogens with Gram-negative like envelopes. They are known to be crucial for virulence and to translocate bacteria-encoded effector proteins into host cells to manipulate cellular functions. This facilitates either pathogen attachment or invasion of the targeted cell. Effector proteins also promote evasion of host immune recognition. Imaging by cryo-electron microscopy in combination with structure determination has become a powerful approach to understand how these nanomachines work. Still, questions on their assembly, the precise secretion mechanisms, and their direct involvement in pathogenicity remain unsolved. Here, we present an overview of the recent developments in in situ cryo-electron microscopy. We discuss its potential for the investigation of the role of bacterial secretion systems during the host-bacterial crosstalk at the molecular level. These in situ studies open new perspectives for our understanding of secretion system structure and function.
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Affiliation(s)
- Camille Keck
- Dynamics of Host-Pathogen Interactions, Institut Pasteur, Université de Paris Cité, CNRS UMR3691, Paris, France
| | - Jost Enninga
- Dynamics of Host-Pathogen Interactions, Institut Pasteur, Université de Paris Cité, CNRS UMR3691, Paris, France
| | - Léa Swistak
- Dynamics of Host-Pathogen Interactions, Institut Pasteur, Université de Paris Cité, CNRS UMR3691, Paris, France
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5
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Pepe A, Groen J, Zurzolo C, Sartori-Rupp A. Correlative cryo-microscopy pipelines for in situ cellular studies. Methods Cell Biol 2024; 187:175-203. [PMID: 38705624 DOI: 10.1016/bs.mcb.2024.02.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Correlative cryo-microscopy pipelines combining light and electron microscopy and tomography in cryogenic conditions (cryoCLEM) on the same sample are powerful methods for investigating the structure of specific cellular targets identified by a fluorescent tag within their unperturbed cellular environment. CryoCLEM approaches circumvent one of the inherent limitations of cryo EM, and specifically cryo electron tomography (cryoET), of identifying the imaged structures in the crowded 3D environment of cells. Whereas several cryoCLEM approaches are based on thinning the sample by cryo FIB milling, here we present detailed protocols of two alternative cryoCLEM approaches for in situ studies of adherent cells at the single-cell level without the need for such cryo-thinning. The first approach is a complete cryogenic pipeline in which both fluorescence and electronic imaging are performed on frozen-hydrated samples, the second is a hybrid cryoCLEM approach in which fluorescence imaging is performed at room temperature, followed by rapid freezing and subsequent cryoEM imaging. We provide a detailed description of the two methods we have employed for imaging fluorescently labeled cellular structures with thickness below 350-500nm, such as cell protrusions and organelles located in the peripheral areas of the cells.
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Affiliation(s)
- Anna Pepe
- Membrane Traffic and Pathogenesis, Institut Pasteur, Paris, France
| | - Johannes Groen
- NanoImaging Core Facility, Institut Pasteur, Paris, France; Dynamics of Host-Pathogen Interactions, Institut Pasteur, Paris, France
| | - Chiara Zurzolo
- Membrane Traffic and Pathogenesis, Institut Pasteur, Paris, France
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6
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Zanetti-Domingues LC, Hirsch M, Wang L, Eastwood TA, Baker K, Mulvihill DP, Radford S, Horne J, White P, Bateman B. Toward quantitative super-resolution methods for cryo-CLEM. Methods Cell Biol 2024; 187:249-292. [PMID: 38705627 DOI: 10.1016/bs.mcb.2024.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Cryogenic ultrastructural imaging techniques such as cryo-electron tomography have produced a revolution in how the structure of biological systems is investigated by enabling the determination of structures of protein complexes immersed in a complex biological matrix within vitrified cell and model organisms. However, so far, the portfolio of successes has been mostly limited to highly abundant complexes or to structures that are relatively unambiguous and easy to identify through electron microscopy. In order to realize the full potential of this revolution, researchers would have to be able to pinpoint lower abundance species and obtain functional annotations on the state of objects of interest which would then be correlated to ultrastructural information to build a complete picture of the structure-function relationships underpinning biological processes. Fluorescence imaging at cryogenic conditions has the potential to be able to meet these demands. However, wide-field images acquired at low numeric aperture (NA) using air immersion objective have a low resolving power and cannot provide accurate enough three-dimensional (3D) localization to enable the assignment of functional annotations to individual objects of interest or target sample debulking to ensure the preservation of the structures of interest. It is therefore necessary to develop super-resolved cryo-fluorescence workflows capable of fulfilling this role and enabling new biological discoveries. In this chapter, we present the current state of development of two super-resolution cryogenic fluorescence techniques, superSIL-STORM and astigmatism-based 3D STORM, show their application to a variety of biological systems and discuss their advantages and limitations. We further discuss the future applicability to cryo-CLEM workflows though examples of practical application to the study of membrane protein complexes both in mammalian cells and in Escherichia coli.
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Affiliation(s)
- Laura C Zanetti-Domingues
- CLF Octopus Facility, UKRI-Science and Technology Facilities Council, R92, Rutherford Appleton Laboratory, Didcot, United Kingdom.
| | - Michael Hirsch
- CLF Octopus Facility, UKRI-Science and Technology Facilities Council, R92, Rutherford Appleton Laboratory, Didcot, United Kingdom
| | - Lin Wang
- CLF Octopus Facility, UKRI-Science and Technology Facilities Council, R92, Rutherford Appleton Laboratory, Didcot, United Kingdom
| | - Tara A Eastwood
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Karen Baker
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | | | - Sheena Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Science, University of Leeds, Leeds, United Kingdom
| | - Jim Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Science, University of Leeds, Leeds, United Kingdom
| | - Paul White
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Science, University of Leeds, Leeds, United Kingdom
| | - Benji Bateman
- CLF Octopus Facility, UKRI-Science and Technology Facilities Council, R92, Rutherford Appleton Laboratory, Didcot, United Kingdom
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7
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Palao L, Murakami K, Chang YW. Combining per-particle cryo-ET and cryo-EM single particle analysis to elucidate heterogeneous DNA-protein organization. Curr Opin Struct Biol 2024; 84:102765. [PMID: 38181688 PMCID: PMC10922635 DOI: 10.1016/j.sbi.2023.102765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 12/06/2023] [Accepted: 12/11/2023] [Indexed: 01/07/2024]
Abstract
Cryo-electron microscopy single particle analysis (cryo-EM SPA) and cryo-electron tomography (cryo-ET) have historically been employed as distinct approaches for investigating molecular structures of disparate sample types, focusing on highly purified biological macromolecules and in situ cellular contexts, respectively. However, these techniques offer inherently complementary structural insights that, when combined, provide a more comprehensive understanding of complex biological systems. For example, if both techniques are applied to the same purified biological macromolecules, cryo-ET has the ability to resolve highly flexible yet strong signal features on an individual target molecule which will not be preserved in the high-resolution cryo-EM SPA results. In this review, we highlight recent achievements utilizing such applications to unveil new insights into the chromatin assembly and activities of DNA-protein assemblies. This convergence of cryo-EM SPA and cryo-ET holds great promise for elucidating new structural aspects of these essential molecular processes.
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Affiliation(s)
- Leon Palao
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Kenji Murakami
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA; Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, PA, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, PA, USA; Institute of Structural Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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8
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Mazal H, Wieser FF, Sandoghdar V. Insights into protein structure using cryogenic light microscopy. Biochem Soc Trans 2023; 51:2041-2059. [PMID: 38015555 PMCID: PMC10754291 DOI: 10.1042/bst20221246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/29/2023]
Abstract
Fluorescence microscopy has witnessed many clever innovations in the last two decades, leading to new methods such as structured illumination and super-resolution microscopies. The attainable resolution in biological samples is, however, ultimately limited by residual motion within the sample or in the microscope setup. Thus, such experiments are typically performed on chemically fixed samples. Cryogenic light microscopy (Cryo-LM) has been investigated as an alternative, drawing on various preservation techniques developed for cryogenic electron microscopy (Cryo-EM). Moreover, this approach offers a powerful platform for correlative microscopy. Another key advantage of Cryo-LM is the strong reduction in photobleaching at low temperatures, facilitating the collection of orders of magnitude more photons from a single fluorophore. This results in much higher localization precision, leading to Angstrom resolution. In this review, we discuss the general development and progress of Cryo-LM with an emphasis on its application in harnessing structural information on proteins and protein complexes.
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Affiliation(s)
- Hisham Mazal
- Max Planck Institute for the Science of Light, 91058 Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058 Erlangen, Germany
| | - Franz-Ferdinand Wieser
- Max Planck Institute for the Science of Light, 91058 Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058 Erlangen, Germany
- Friedrich-Alexander University of Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Vahid Sandoghdar
- Max Planck Institute for the Science of Light, 91058 Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058 Erlangen, Germany
- Friedrich-Alexander University of Erlangen-Nürnberg, 91058 Erlangen, Germany
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9
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Ochner H, Bharat TAM. Charting the molecular landscape of the cell. Structure 2023; 31:1297-1305. [PMID: 37699393 PMCID: PMC7615466 DOI: 10.1016/j.str.2023.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 08/15/2023] [Accepted: 08/17/2023] [Indexed: 09/14/2023]
Abstract
Biological function of macromolecules is closely tied to their cellular location, as well as to interactions with other molecules within the native environment of the cell. Therefore, to obtain detailed mechanistic insights into macromolecular functionality, one of the outstanding targets for structural biology is to produce an atomic-level understanding of the cell. One structural biology technique that has already been used to directly derive atomic models of macromolecules from cells, without any additional external information, is electron cryotomography (cryoET). In this perspective article, we discuss possible routes to chart the molecular landscape of the cell by advancing cryoET imaging as well as by embedding cryoET into correlative imaging workflows.
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Affiliation(s)
- Hannah Ochner
- Structural Studies Division, MRC Laboratory of Molecular Biology, CB2 0QH Cambridge, UK
| | - Tanmay A M Bharat
- Structural Studies Division, MRC Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.
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10
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Kirchweger P, Mullick D, Swain PP, Wolf SG, Elbaum M. Correlating cryo-super resolution radial fluctuations and dual-axis cryo-scanning transmission electron tomography to bridge the light-electron resolution gap. J Struct Biol 2023; 215:107982. [PMID: 37268154 DOI: 10.1016/j.jsb.2023.107982] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 05/05/2023] [Accepted: 05/24/2023] [Indexed: 06/04/2023]
Abstract
Visualization of organelles and their interactions with other features in the native cell remains a challenge in modern biology. We have introduced cryo-scanning transmission electron tomography (CSTET), which can access 3D volumes on the scale of 1 micron with a resolution of nanometers, making it ideal for this task. Here we introduce two relevant advances: (a) we demonstrate the utility of multi-color super-resolution radial fluctuation light microscopy under cryogenic conditions (cryo-SRRF), and (b) we extend the use of deconvolution processing for dual-axis CSTET data. We show that cryo-SRRF nanoscopy is able to reach resolutions in the range of 100 nm, using commonly available fluorophores and a conventional widefield microscope for cryo-correlative light-electron microscopy. Such resolution aids in precisely identifying regions of interest before tomographic acquisition and enhances precision in localizing features of interest within the 3D reconstruction. Dual-axis CSTET tilt series data and application of entropy regularized deconvolution during post-processing results in close-to-isotropic resolution in the reconstruction without averaging. The integration of cryo-SRRF with deconvolved dual-axis CSTET provides a versatile workflow for studying unique objects in a cell.
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Affiliation(s)
- Peter Kirchweger
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel; Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Debakshi Mullick
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Prabhu Prasad Swain
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel; School of Physical Sciences, UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400098, India
| | - Sharon G Wolf
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Michael Elbaum
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel.
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11
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Lin C, Zhang L, Zhang Z, Jiang Y, Li X. Locating cellular contents during cryoFIB milling using cellular secondary-electron imaging. J Struct Biol 2023; 215:108005. [PMID: 37495195 DOI: 10.1016/j.jsb.2023.108005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 07/19/2023] [Accepted: 07/23/2023] [Indexed: 07/28/2023]
Abstract
Cryo-electron tomography (cryoET) is a powerful technology that allows in-situ observation of the molecular structure of tissues and cells. Cryo-focused ion beam (cryoFIB) milling plays an important role in the preparation of high-quality thin lamellar samples for cryoET studies, thus, promoting the rapid development of cryoET in recent years. However, locating the regions of interest in a large cell or tissue during cryoFIB milling remains a major challenge limiting cryoET applications on arbitrary biological samples. Here, we report an on-the-fly localization method based on cellular secondary electron imaging (CSEI), which is derived from a basic imaging function of the cryoFIB instruments and enables high-contrast imaging of the cellular contents of frozen-hydrated biological samples. Moreover, CSEI does not require fluorescent labels and additional devices. The present study discusses the imaging principles and settings for optimizing CSEI. Tests on several commercially available cryoFIB instruments demonstrated that CSEI was feasible on mainstream instruments to observe all types of cellular contents and reliable under different milling conditions. We established a simple milling-localization workflow and tested it using the basal body of Chlamydomonas reinhardtii.
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Affiliation(s)
- Chao Lin
- Key Laboratory for Protein Sciences of Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, China; Beijing Frontier Research Center for Biological Structure, Beijing 100084, China; Advanced Innovation Center for Structural Biology, Beijing 100084, China
| | - Li Zhang
- Key Laboratory for Protein Sciences of Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, China; Beijing Frontier Research Center for Biological Structure, Beijing 100084, China; Advanced Innovation Center for Structural Biology, Beijing 100084, China
| | - Ziying Zhang
- Key Laboratory for Protein Sciences of Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, China; Beijing Frontier Research Center for Biological Structure, Beijing 100084, China; Advanced Innovation Center for Structural Biology, Beijing 100084, China
| | - Yifeng Jiang
- ZEISS Microscopy Customer Center, Beijing laboratory, Beijing 100088, China
| | - Xueming Li
- Key Laboratory for Protein Sciences of Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, China; Beijing Frontier Research Center for Biological Structure, Beijing 100084, China; Advanced Innovation Center for Structural Biology, Beijing 100084, China.
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12
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Perez D, Dahlberg PD, Moerner WE. Advanced Cryogenic Light Microscopy Stage to Enable 3D Super-resolved Cryogenic Correlative Light and Electron Microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1941. [PMID: 37612900 DOI: 10.1093/micmic/ozad067.1005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Davis Perez
- Department of Chemistry, Stanford University, Stanford, CA, United States
| | - Peter D Dahlberg
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, United States
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, CA, United States
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13
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Sanders S, Jensen Y, Reimer R, Bosse JB. From the beginnings to multidimensional light and electron microscopy of virus morphogenesis. Adv Virus Res 2023; 116:45-88. [PMID: 37524482 DOI: 10.1016/bs.aivir.2023.05.001] [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: 08/02/2023]
Abstract
Individual functional viral morphogenesis events are often dynamic, short, and infrequent and might be obscured by other pathways and dead-end products. Volumetric live cell imaging has become an essential tool for studying viral morphogenesis events. It allows following entire dynamic processes while providing functional evidence that the imaged process is involved in viral production. Moreover, it allows to capture many individual events and allows quantitative analysis. Finally, the correlation of volumetric live-cell data with volumetric electron microscopy (EM) can provide crucial insights into the ultrastructure and mechanisms of viral morphogenesis events. Here, we provide an overview and discussion of suitable imaging methods for volumetric correlative imaging of viral morphogenesis and frame them in a historical summary of their development.
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Affiliation(s)
- Saskia Sanders
- Department of Virology, Hannover Medical School, Hannover, Germany; Leibniz Institute of Virology (LIV), Hamburg, Germany; Centre for Structural Systems Biology, Hamburg, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
| | - Yannick Jensen
- Department of Virology, Hannover Medical School, Hannover, Germany; Leibniz Institute of Virology (LIV), Hamburg, Germany; Centre for Structural Systems Biology, Hamburg, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
| | | | - Jens B Bosse
- Department of Virology, Hannover Medical School, Hannover, Germany; Leibniz Institute of Virology (LIV), Hamburg, Germany; Centre for Structural Systems Biology, Hamburg, Germany; Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany.
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14
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Last MGF, Tuijtel MW, Voortman LM, Sharp TH. Selecting optimal support grids for super-resolution cryogenic correlated light and electron microscopy. Sci Rep 2023; 13:8270. [PMID: 37217690 DOI: 10.1038/s41598-023-35590-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 05/20/2023] [Indexed: 05/24/2023] Open
Abstract
Cryogenic transmission electron microscopy (cryo-TEM) and super-resolution fluorescence microscopy are two popular and ever improving methods for high-resolution imaging of biological samples. In recent years, the combination of these two techniques into one correlated workflow has gained attention as a promising route towards contextualizing and enriching cryo-TEM imagery. A problem that is often encountered in the combination of these methods is that of light-induced damage to the sample during fluorescence imaging that renders the sample structure unsuitable for TEM imaging. In this paper, we describe how absorption of light by TEM sample support grids leads to sample damage, and we systematically explore the importance of parameters of grid design. We explain how, by changing the grid geometry and materials, one can increase the maximum illumination power density in fluorescence microscopy by up to an order of magnitude. Finally, we demonstrate the significant improvements in super-resolution image quality that are enabled by the selection of support grids that are optimally suited for correlated cryo-microscopy.
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Affiliation(s)
- Mart G F Last
- Department of Cell and Chemical Biology, Leiden University Medical Centre, 2300 RC, Leiden, The Netherlands
| | - Maarten W Tuijtel
- Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438, Frankfurt Am Main, Germany
| | - Lenard M Voortman
- Department of Cell and Chemical Biology, Leiden University Medical Centre, 2300 RC, Leiden, The Netherlands
| | - Thomas H Sharp
- Department of Cell and Chemical Biology, Leiden University Medical Centre, 2300 RC, Leiden, The Netherlands.
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15
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de Beer M, Daviran D, Roverts R, Rutten L, Macías-Sánchez E, Metz JR, Sommerdijk N, Akiva A. Precise targeting for 3D cryo-correlative light and electron microscopy volume imaging of tissues using a FinderTOP. Commun Biol 2023; 6:510. [PMID: 37169904 PMCID: PMC10175257 DOI: 10.1038/s42003-023-04887-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 04/28/2023] [Indexed: 05/13/2023] Open
Abstract
Cryo-correlative light and electron microscopy (cryoCLEM) is a powerful strategy to high resolution imaging in the unperturbed hydrated state. In this approach fluorescence microscopy aids localizing the area of interest, and cryogenic focused ion beam/scanning electron microscopy (cryoFIB/SEM) allows preparation of thin cryo-lamellae for cryoET. However, the current method cannot be accurately applied on bulky (3D) samples such as tissues and organoids. 3D cryo-correlative imaging of large volumes is needed to close the resolution gap between cryo-light microscopy and cryoET, placing sub-nanometer observations in a larger biological context. Currently technological hurdles render 3D cryoCLEM an unexplored approach. Here we demonstrate a cryoCLEM workflow for tissues, correlating cryo-Airyscan confocal microscopy with 3D cryoFIB/SEM volume imaging. Accurate correlation is achieved by imprinting a FinderTOP pattern in the sample surface during high pressure freezing, and allows precise targeting for cryoFIB/SEM volume imaging.
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Affiliation(s)
- Marit de Beer
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Deniz Daviran
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rona Roverts
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Luco Rutten
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Elena Macías-Sánchez
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Stratigraphy and Paleontology, University of Granada, Granada, Spain
| | - Juriaan R Metz
- Department of Animal Ecology and Physiology, Radboud Institute for Biological and Environmental Sciences, Faculty of Science, Radboud University, Nijmegen, The Netherlands
| | - Nico Sommerdijk
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands.
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - Anat Akiva
- Electron Microscopy Center, Radboud Technology Center Microscopy, Radboud University Medical Center, Nijmegen, The Netherlands.
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands.
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16
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Berger C, Premaraj N, Ravelli RBG, Knoops K, López-Iglesias C, Peters PJ. Cryo-electron tomography on focused ion beam lamellae transforms structural cell biology. Nat Methods 2023; 20:499-511. [PMID: 36914814 DOI: 10.1038/s41592-023-01783-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 01/20/2023] [Indexed: 03/16/2023]
Abstract
Cryogenic electron microscopy and data processing enable the determination of structures of isolated macromolecules to near-atomic resolution. However, these data do not provide structural information in the cellular environment where macromolecules perform their native functions, and vital molecular interactions can be lost during the isolation process. Cryogenic focused ion beam (FIB) fabrication generates thin lamellae of cellular samples and tissues, enabling structural studies on the near-native cellular interior and its surroundings by cryogenic electron tomography (cryo-ET). Cellular cryo-ET benefits from the technological developments in electron microscopes, detectors and data processing, and more in situ structures are being obtained and at increasingly higher resolution. In this Review, we discuss recent studies employing cryo-ET on FIB-generated lamellae and the technological developments in ultrarapid sample freezing, FIB fabrication of lamellae, tomography, data processing and correlative light and electron microscopy that have enabled these studies. Finally, we explore the future of cryo-ET in terms of both methods development and biological application.
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Affiliation(s)
- Casper Berger
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
- Structural Biology, The Rosalind Franklin Institute, Didcot, UK
| | - Navya Premaraj
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Raimond B G Ravelli
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Kèvin Knoops
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Carmen López-Iglesias
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Peter J Peters
- Division of Nanoscopy, Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands.
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17
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Sartor A, Dahlberg PD, Perez D, Moerner WE. Characterization of mApple as a Red Fluorescent Protein for Cryogenic Single-Molecule Imaging with Turn-Off and Turn-On Active Control Mechanisms. J Phys Chem B 2023; 127:2690-2700. [PMID: 36943356 PMCID: PMC10069424 DOI: 10.1021/acs.jpcb.2c08995] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 03/01/2023] [Indexed: 03/23/2023]
Abstract
Single-molecule superresolution microscopy is a powerful tool for the study of biological structures on size scales smaller than the optical diffraction limit. Imaging samples at cryogenic temperatures (77 K) reduces the quantum yield of photobleaching for many fluorescent labels, yielding localization precisions below 10 nm. Cryogenic imaging further enables correlation with cryogenic electron tomography. A key limitation in applying methods such as PALM and STORM to samples maintained at 77 K is the limited number of fluorophores known to undergo efficient turn-on and turn-off mechanisms necessary to control the sparsity of active emitters. We find that mApple, a red-emitting fluorescent protein, undergoes a novel turn-off mechanism in response to simultaneous illumination with two colors of light. This turn-off mechanism enables localization of many individual molecules in initially bright samples, but the final density of localizable emitters is limited by relatively inefficient turn-on (photoactivation). Bulk excitation and emission spectroscopy shows that mApple has access to two distinct emissive states as well as dark states accessible optically or through changes in pH. The bright and stable emission of mApple enables widefield collection of single-molecule emission spectra, which highlight the complex nature and environmental sensitivity of states observed in red fluorescent proteins.
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Affiliation(s)
- Annina
M. Sartor
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Peter D. Dahlberg
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Division
of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Davis Perez
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - W. E. Moerner
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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18
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Gong J, Jin Z, Chen H, He J, Zhang Y, Yang X. Super-resolution fluorescence microscopic imaging in pathogenesis and drug treatment of neurological disease. Adv Drug Deliv Rev 2023; 196:114791. [PMID: 37004939 DOI: 10.1016/j.addr.2023.114791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 03/16/2023] [Accepted: 03/19/2023] [Indexed: 04/03/2023]
Abstract
Since super-resolution fluorescence microscopic technology breaks the diffraction limit that has existed for a long time in optical imaging, it can observe the process of synapses formed between nerve cells and the protein aggregation related to neurological disease. Thus, super-resolution fluorescence microscopic imaging has significantly impacted several industries, including drug development and pathogenesis research, and it is anticipated that it will significantly alter the future of life science research. Here, we focus on several typical super-resolution fluorescence microscopic technologies, introducing their benefits and drawbacks, as well as applications in several common neurological diseases, in the hope that their services will be expanded and improved in the pathogenesis and drug treatment of neurological diseases.
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19
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Lai L, Cheung YW, Martinez M, Kixmoeller K, Palao L, Steimle S, Ho MC, Black BE, Lai EM, Chang YW. In Situ Structure Determination of Bacterial Surface Nanomachines Using Cryo-Electron Tomography. Methods Mol Biol 2023; 2646:211-248. [PMID: 36842118 DOI: 10.1007/978-1-0716-3060-0_18] [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: 04/13/2023]
Abstract
Bacterial surface nanomachines are often refractory to structural determination in their intact form due to their extensive association with the cell envelope preventing them from being properly purified for traditional structural biology methods. Cryo-electron tomography (cryo-ET) is an emerging branch of cryo-electron microscopy that can visualize supramolecular complexes directly inside frozen-hydrated cells in 3D at nanometer resolution, therefore posing a unique capability to study the intact structures of bacterial surface nanomachines in situ and reveal their molecular association with other cellular components. Furthermore, the resolution of cryo-ET is continually improving alongside methodological advancement. Here, using the type IV pilus machine in Myxococcus xanthus as an example, we describe a step-by-step workflow for in situ structure determination including sample preparation and screening, microscope and camera tuning, tilt series acquisition, data processing and tomogram reconstruction, subtomogram averaging, and structural analysis.
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Affiliation(s)
- Longsheng Lai
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Yee-Wai Cheung
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Matthew Martinez
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kathryn Kixmoeller
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Leon Palao
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Stefan Steimle
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Meng-Chiao Ho
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Ben E Black
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Erh-Min Lai
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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20
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Integrated multimodality microscope for accurate and efficient target-guided cryo-lamellae preparation. Nat Methods 2023; 20:268-275. [PMID: 36646896 PMCID: PMC9911353 DOI: 10.1038/s41592-022-01749-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 12/06/2022] [Indexed: 01/18/2023]
Abstract
Cryo-electron tomography (cryo-ET) is a revolutionary technique for resolving the structure of subcellular organelles and macromolecular complexes in their cellular context. However, the application of the cryo-ET is hampered by the sample preparation step. Performing cryo-focused ion beam milling at an arbitrary position on the sample is inefficient, and the target of interest is not guaranteed to be preserved when thinning the cell from several micrometers to less than 300 nm thick. Here, we report a cryogenic correlated light, ion and electron microscopy (cryo-CLIEM) technique that is capable of preparing cryo-lamellae under the guidance of three-dimensional confocal imaging. Moreover, we demonstrate a workflow to preselect and preserve nanoscale target regions inside the finished cryo-lamellae. By successfully preparing cryo-lamellae that contain a single centriole or contact sites between subcellular organelles, we show that this approach is generally applicable, and shall help in innovating more applications of cryo-ET.
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21
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Golmohammadzadeh M, Sexton DL, Parmar S, Tocheva EI. Advanced imaging techniques: Microscopy. ADVANCES IN APPLIED MICROBIOLOGY 2023; 122:1-25. [PMID: 37085191 DOI: 10.1016/bs.aambs.2023.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
For decades, bacteria were thought of as "bags" of enzymes, lacking organelles and significant subcellular structures. This stood in sharp contrast with eukaryotes, where intracellular compartmentalization and the role of large-scale order had been known for a long time. However, the emerging field of Bacterial Cell Biology has established that bacteria are in fact highly organized, with most macromolecular components having specific subcellular locations that can change depending on the cell's physiological state (Barry & Gitai, 2011; Lenz & Søgaard-Andersen, 2011; Thanbichler & Shapiro, 2008). For example, we now know that many processes in bacteria are orchestrated by cytoskeletal proteins, which polymerize into surprisingly diverse superstructures, such as rings, sheets, and tread-milling rods (Pilhofer & Jensen, 2013). These superstructures connect individual proteins, macromolecular assemblies, and even two neighboring cells, to affect essential higher-order processes including cell division, DNA segregation, and motility. Understanding these processes requires resolving the in vivo dynamics and ultrastructure at different functional stages of the cell, at macromolecular resolution and in 3-dimensions (3D). Fluorescence light microscopy (fLM) of tagged proteins is highly valuable for investigating protein localization and dynamics, and the resolution power of transmission electron microscopy (TEM) is required to elucidate the structure of macromolecular complexes in vivo and in vitro. This chapter summarizes the most recent advances in LM and TEM approaches that have revolutionized our knowledge and understanding of the microbial world.
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Affiliation(s)
- Mona Golmohammadzadeh
- Department of Microbiology and Immunology, Life Sciences Institute, Health Sciences Mall, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Danielle L Sexton
- Department of Microbiology and Immunology, Life Sciences Institute, Health Sciences Mall, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Shweta Parmar
- Department of Microbiology and Immunology, Life Sciences Institute, Health Sciences Mall, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Elitza I Tocheva
- Department of Microbiology and Immunology, Life Sciences Institute, Health Sciences Mall, The University of British Columbia, Vancouver, British Columbia, Canada.
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22
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Wang C, Wojtynek M, Medalia O. Structural investigation of eukaryotic cells: From the periphery to the interior by cryo-electron tomography. Adv Biol Regul 2023; 87:100923. [PMID: 36280452 DOI: 10.1016/j.jbior.2022.100923] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/05/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
Abstract
Cryo-electron tomography (cryo-ET) combines a close-to-life preservation of the cell with high-resolution three-dimensional (3D) imaging. This allows to study the molecular architecture of the cellular landscape and provides unprecedented views on biological processes and structures. In this review we mainly focus on the application of cryo-ET to visualize and structurally characterize eukaryotic cells - from the periphery to the cellular interior. We discuss strategies that can be employed to investigate the structure of challenging targets in their cellular environment as well as the application of complimentary approaches in conjunction with cryo-ET.
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Affiliation(s)
- Chunyang Wang
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Matthias Wojtynek
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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23
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Dahlberg PD, Perez D, Hecksel CW, Chiu W, Moerner WE. Metallic support films reduce optical heating in cryogenic correlative light and electron tomography. J Struct Biol 2022; 214:107901. [PMID: 36191745 PMCID: PMC9729463 DOI: 10.1016/j.jsb.2022.107901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 08/28/2022] [Accepted: 09/26/2022] [Indexed: 12/30/2022]
Abstract
Super-resolved cryogenic correlative light and electron tomography is an emerging method that provides both the single-molecule sensitivity and specificity of fluorescence imaging, and the molecular scale resolution and detailed cellular context of tomography, all in vitrified cells preserved in their native hydrated state. Technical hurdles that limit these correlative experiments need to be overcome for the full potential of this approach to be realized. Chief among these is sample heating due to optical excitation which leads to devitrification, a phase transition from amorphous to crystalline ice. Here we show that much of this heating is due to the material properties of the support film of the electron microscopy grid, specifically the absorptivity and thermal conductivity. We demonstrate through experiment and simulation that the properties of the standard holey carbon electron microscopy grid lead to substantial heating under optical excitation. In order to avoid devitrification, optical excitation intensities must be kept orders of magnitude lower than the intensities commonly employed in room temperature super-resolution experiments. We further show that the use of metallic films, either holey gold grids, or custom made holey silver grids, alleviate much of this heating. For example, the holey silver grids permit 20× the optical intensities used on the standard holey carbon grids. Super-resolution correlative experiments conducted on holey silver grids under these increased optical excitation intensities have a corresponding increase in the rate of single-molecule fluorescence localizations. This results in an increased density of localizations and improved correlative imaging without deleterious effects from sample heating.
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Affiliation(s)
- Peter D Dahlberg
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
| | - Davis Perez
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Corey W Hecksel
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Wah Chiu
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA; Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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24
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Digitalizing neuronal synapses with cryo-electron tomography and correlative microscopy. Curr Opin Neurobiol 2022; 76:102595. [DOI: 10.1016/j.conb.2022.102595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/22/2022] [Accepted: 05/24/2022] [Indexed: 11/22/2022]
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25
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Perez D, Dahlberg PD, Wang J, Sartor AM, Borden JS, Shapiro L, Moerner WE. Identification and demonstration of roGFP2 as an environmental sensor for cryogenic correlative light and electron microscopy. J Struct Biol 2022; 214:107881. [PMID: 35811036 PMCID: PMC9452478 DOI: 10.1016/j.jsb.2022.107881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 06/29/2022] [Accepted: 07/04/2022] [Indexed: 10/17/2022]
Abstract
Cryogenic correlative light and electron microscopy (cryo-CLEM) seeks to leverage orthogonal information present in two powerful imaging modalities. While recent advances in cryogenic electron microscopy (cryo-EM) allow for the visualization and identification of structures within cells at the nanometer scale, information regarding the cellular environment, such as pH, membrane potential, ionic strength, etc., which influences the observed structures remains absent. Fluorescence microscopy can potentially be used to reveal this information when specific labels, known as fluorescent biosensors, are used, but there has been minimal use of such biosensors in cryo-CLEM to date. Here we demonstrate the applicability of one such biosensor, the fluorescent protein roGFP2, for cryo-CLEM experiments. At room temperature, the ratio of roGFP2 emission brightness when excited at 425 nm or 488 nm is known to report on the local redox potential. When samples containing roGFP2 are rapidly cooled to 77 K in a manner compatible with cryo-EM, the ratio of excitation peaks remains a faithful indicator of the redox potential at the time of freezing. Using purified protein in different oxidizing/reducing environments, we generate a calibration curve which can be used to analyze in situ measurements. As a proof-of-principle demonstration, we investigate the oxidation/reduction state within vitrified Caulobacter crescentus cells. The polar organizing protein Z (PopZ) localizes to the polar regions of C. crescentus where it is known to form a distinct microdomain. By expressing an inducible roGFP2-PopZ fusion we visualize individual microdomains in the context of their redox environment.
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Affiliation(s)
- Davis Perez
- Department of Chemistry, Stanford University, United States
| | - Peter D Dahlberg
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, United States
| | - Jiarui Wang
- Department of Chemistry, Stanford University, United States; Department of Developmental Biology, Stanford University, United States
| | | | - Julia S Borden
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University, United States
| | - W E Moerner
- Department of Chemistry, Stanford University, United States
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26
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Gold nanomaterials and their potential use as cryo-electron tomography labels. J Struct Biol 2022; 214:107880. [PMID: 35809758 DOI: 10.1016/j.jsb.2022.107880] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 06/30/2022] [Accepted: 07/04/2022] [Indexed: 12/14/2022]
Abstract
Rapid advances in cryo-electron tomography (cryo-ET) are driving a revolution in cellular structural biology. However, unambiguous identification of specific biomolecules within cellular tomograms remains challenging. Overcoming this obstacle and reliably identifying targets in the crowded cellular environment is of major importance for the understanding of cellular function and is a pre-requisite for high-resolution structural analysis. The use of highly-specific, readily visualised and adjustable labels would help mitigate this issue, improving both data quality and sample throughput. While progress has been made in cryo-CLEM and in the development of cloneable high-density tags, technical issues persist and a robust 'cryo-GFP' remains elusive. Readily-synthesized gold nanomaterials conjugated to small 'affinity modules' may represent a solution. The synthesis of materials including gold nanoclusters (AuNCs) and gold nanoparticles (AuNPs) is increasingly well understood and is now within the capabilities of non-specialist laboratories. The remarkable chemical and photophysical properties of <3nm diameter nanomaterials and their emergence as tools with widespread biomedical application presents significant opportunities to the cryo-microscopy community. In this review, we will outline developments in the synthesis, functionalisation and labelling uses of both AuNPs and AuNCs in cryo-ET, while discussing their potential as multi-modal probes for cryo-CLEM.
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27
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Nienhaus K, Nienhaus GU. Genetically encodable fluorescent protein markers in advanced optical imaging. Methods Appl Fluoresc 2022; 10. [PMID: 35767981 DOI: 10.1088/2050-6120/ac7d3f] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 06/29/2022] [Indexed: 11/12/2022]
Abstract
Optical fluorescence microscopy plays a pivotal role in the exploration of biological structure and dynamics, especially on live specimens. Progress in the field relies, on the one hand, on technical advances in imaging and data processing and, on the other hand, on progress in fluorescent marker technologies. Among these, genetically encodable fluorescent proteins (FPs) are invaluable tools, as they allow facile labeling of live cells, tissues or organisms, as these produce the FP markers all by themselves after introduction of a suitable gene. Here we cover FP markers from the GFP family of proteins as well as tetrapyrrole-binding proteins, which further complement the FP toolbox in important ways. A broad range of FP variants have been endowed, by using protein engineering, with photophysical properties that are essential for specific fluorescence microscopy techniques, notably those offering nanoscale image resolution. We briefly introduce various advanced imaging methods and show how they utilize the distinct properties of the FP markers in exciting imaging applications, with the aim to guide researchers toward the design of powerful imaging experiments that are optimally suited to address their biological questions.
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Affiliation(s)
- Karin Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology, Wolfgang Gaede Str. 1, Karlsruhe, 76131, GERMANY
| | - Gerd Ulrich Nienhaus
- Karlsruhe Institute of Technology, Wolfgang Gaede Str. 1, Karlsruhe, 76131, GERMANY
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28
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van den Dries K, Fransen J, Cambi A. Fluorescence CLEM in biology: historic developments and current super-resolution applications. FEBS Lett 2022; 596:2486-2496. [PMID: 35674424 DOI: 10.1002/1873-3468.14421] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/12/2022]
Abstract
Correlative light and electron microscopy (CLEM) is a powerful imaging approach that allows the direct correlation of information obtained on a light and an electron microscope. There is a growing interest in the application of CLEM in biology, mainly attributable to technical advances in field of fluorescence microscopy in the past two decades. In this review, we summarize the important developments in CLEM for biological applications, focusing on the combination of fluorescence microscopy and electron microscopy. We first provide a brief overview of the early days of fluorescence CLEM usage starting with the initial rise in the late 1970s and the subsequent optimization of CLEM workflows during the following two decades. Next, we describe how the engineering of fluorescent proteins and the development of super-resolution fluorescence microscopy have significantly renewed the interest in CLEM resulting in the present application of fluorescence CLEM in many different areas of cellular and molecular biology. Lastly, we present the promises and challenges for the future of fluorescence CLEM discussing novel workflows, probe development and quantification possibilities.
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Affiliation(s)
- Koen van den Dries
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboudumc, Nijmegen, The Netherlands
| | - Jack Fransen
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboudumc, Nijmegen, The Netherlands.,Microscopic Imaging Center, Radboud Institute for Molecular Life Sciences, Radboudumc, Nijmegen, The Netherlands
| | - Alessandra Cambi
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboudumc, Nijmegen, The Netherlands
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Automated vitrification of cryo-EM samples with controllable sample thickness using suction and real-time optical inspection. Nat Commun 2022; 13:2985. [PMID: 35624105 PMCID: PMC9142589 DOI: 10.1038/s41467-022-30562-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 04/26/2022] [Indexed: 12/13/2022] Open
Abstract
The speed and efficiency of data collection and image processing in cryo-electron microscopy have increased over the last decade. However, cryo specimen preparation techniques have lagged and faster, more reproducible specimen preparation devices are needed. Here, we present a vitrification device with highly automated sample handling, requiring only limited user interaction. Moreover, the device allows inspection of thin films using light microscopy, since the excess liquid is removed through suction by tubes, not blotting paper. In combination with dew-point control, this enables thin film preparation in a controlled and reproducible manner. The advantage is that the quality of the prepared cryo specimen is characterized before electron microscopy data acquisition. The practicality and performance of the device are illustrated with experimental results obtained by vitrification of protein suspensions, lipid vesicles, bacterial and human cells, followed by imaged using single particle analysis, cryo-electron tomography, and cryo correlated light and electron microscopy. Faster cryo specimen preparation can advance cryo electron microscopy (cryoEM). Here, the authors present a vitrification device with automated sample handling for cryoEM of proteins, suspensions and cells, enabling blot-free sample thinning, dew-point control and characterization of cryo grids prior to data acquisition.
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30
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Mazal H, Wieser FF, Sandoghdar V. Deciphering a hexameric protein complex with Angstrom optical resolution. eLife 2022; 11:76308. [PMID: 35616526 PMCID: PMC9142145 DOI: 10.7554/elife.76308] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 05/12/2022] [Indexed: 12/24/2022] Open
Abstract
Cryogenic optical localization in three dimensions (COLD) was recently shown to resolve up to four binding sites on a single protein. However, because COLD relies on intensity fluctuations that result from the blinking behavior of fluorophores, it is limited to cases where individual emitters show different brightness. This significantly lowers the measurement yield. To extend the number of resolved sites as well as the measurement yield, we employ partial labeling and combine it with polarization encoding in order to identify single fluorophores during their stochastic blinking. We then use a particle classification scheme to identify and resolve heterogenous subsets and combine them to reconstruct the three-dimensional arrangement of large molecular complexes. We showcase this method (polarCOLD) by resolving the trimer arrangement of proliferating cell nuclear antigen (PCNA) and six different sites of the hexamer protein Caseinolytic Peptidase B (ClpB) of Thermus thermophilus in its quaternary structure, both with Angstrom resolution. The combination of polarCOLD and single-particle cryogenic electron microscopy (cryoEM) promises to provide crucial insight into intrinsic heterogeneities of biomolecular structures. Furthermore, our approach is fully compatible with fluorescent protein labeling and can, thus, be used in a wide range of studies in cell and membrane biology.
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Affiliation(s)
- Hisham Mazal
- Max Planck Institute for the Science of Light, Erlangen, Germany.,Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany
| | - Franz-Ferdinand Wieser
- Max Planck Institute for the Science of Light, Erlangen, Germany.,Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany.,Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany
| | - Vahid Sandoghdar
- Max Planck Institute for the Science of Light, Erlangen, Germany.,Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany.,Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany
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31
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Understanding immune signaling using advanced imaging techniques. Biochem Soc Trans 2022; 50:853-866. [PMID: 35343569 PMCID: PMC9162467 DOI: 10.1042/bst20210479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 12/13/2022]
Abstract
Advanced imaging is key for visualizing the spatiotemporal regulation of immune signaling which is a complex process involving multiple players tightly regulated in space and time. Imaging techniques vary in their spatial resolution, spanning from nanometers to micrometers, and in their temporal resolution, ranging from microseconds to hours. In this review, we summarize state-of-the-art imaging methodologies and provide recent examples on how they helped to unravel the mysteries of immune signaling. Finally, we discuss the limitations of current technologies and share our insights on how to overcome these limitations to visualize immune signaling with unprecedented fidelity.
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Liedtke J, Depelteau JS, Briegel A. How advances in cryo-electron tomography have contributed to our current view of bacterial cell biology. J Struct Biol X 2022; 6:100065. [PMID: 35252838 PMCID: PMC8894267 DOI: 10.1016/j.yjsbx.2022.100065] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 02/17/2022] [Accepted: 02/23/2022] [Indexed: 12/13/2022] Open
Abstract
Advancements in the field of cryo-electron tomography have greatly contributed to our current understanding of prokaryotic cell organization and revealed intracellular structures with remarkable architecture. In this review, we present some of the prominent advancements in cryo-electron tomography, illustrated by a subset of structural examples to demonstrate the power of the technique. More specifically, we focus on technical advances in automation of data collection and processing, sample thinning approaches, correlative cryo-light and electron microscopy, and sub-tomogram averaging methods. In turn, each of these advances enabled new insights into bacterial cell architecture, cell cycle progression, and the structure and function of molecular machines. Taken together, these significant advances within the cryo-electron tomography workflow have led to a greater understanding of prokaryotic biology. The advances made the technique available to a wider audience and more biological questions and provide the basis for continued advances in the near future.
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Affiliation(s)
- Janine Liedtke
- Department of Microbial Sciences, Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands.,Centre for Microbial Cell Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Jamie S Depelteau
- Department of Microbial Sciences, Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands.,Centre for Microbial Cell Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Ariane Briegel
- Department of Microbial Sciences, Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands.,Centre for Microbial Cell Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
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33
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Mazaheri L, Jelken J, Avilés MO, Legge S, Lagugné-Labarthet F. Investigating the Performances of Wide-Field Raman Microscopy with Stochastic Optical Reconstruction Post-Processing. APPLIED SPECTROSCOPY 2022; 76:340-351. [PMID: 35128956 PMCID: PMC8915227 DOI: 10.1177/00037028211056975] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 10/07/2021] [Indexed: 05/25/2023]
Abstract
Super-resolution fluorescence microscopy based on localization algorithms has tremendously impacted the field of imaging by improving the spatial resolution of optical measurements with specific blinking fluorophores and concomitant reduction of acquisition time. In vibrational spectroscopy and imaging, various methods have been developed to surpass the diffraction limit including near-field scattering methods, such as in tip-enhanced Raman and infrared spectroscopies. Although these scanning-probe techniques can provide exquisite spatial resolution, they often require long acquisition times and tedious fabrication of nano-scale scanning probes. Herein, stochastic optical reconstruction microscopy (STORM) protocol is applied on Raman measurements acquired using a wide-field home-built microscopy setup. We explore how the fluctuations of the Raman signal acquired over a series of time-lapse images at specific spectral ranges can be exploited with STORM processing, possibly revealing details with improved spatial resolution, under lower irradiance and with faster acquisition speed that cannot be achieved in point scanning mode over the same field of view. Samples studied here include patterned silicon, polystyrene microspheres on a silicon wafer, and graphene on a silicon/silicon dioxide substrate. The outcome presents an effective way to collect Raman images at selected spectral ranges with spatial resolutions of ∼200 nm over a large field of view under 532 nm excitation together with an acquisition speed improved by two orders of magnitude and under a significantly reduced irradiance compared to confocal laser scanning acquisition.
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Affiliation(s)
| | | | | | | | - François Lagugné-Labarthet
- François Lagugné-Labarthet, Department of Chemistry, The Centre for Advanced Materials and Biomaterials Research (CAMBR), The University of Western Ontario (Western University), 1151 Richmond St., London, ON N6A 5B7, Canada.
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34
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Kwon J, Elgawish MS, Shim S. Bleaching-Resistant Super-Resolution Fluorescence Microscopy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2101817. [PMID: 35088584 PMCID: PMC8948665 DOI: 10.1002/advs.202101817] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 01/07/2022] [Indexed: 05/08/2023]
Abstract
Photobleaching is the permanent loss of fluorescence after extended exposure to light and is a major limiting factor in super-resolution microscopy (SRM) that restricts spatiotemporal resolution and observation time. Strategies for preventing or overcoming photobleaching in SRM are reviewed developing new probes and chemical environments. Photostabilization strategies are introduced first, which are borrowed from conventional fluorescence microscopy, that are employed in SRM. SRM-specific strategies are then highlighted that exploit the on-off transitions of fluorescence, which is the key mechanism for achieving super-resolution, which are becoming new routes to address photobleaching in SRM. Off states can serve as a shelter from excitation by light or an exit to release a damaged probe and replace it with a fresh one. Such efforts in overcoming the photobleaching limits are anticipated to enhance resolution to molecular scales and to extend the observation time to physiological lifespans.
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Affiliation(s)
- Jiwoong Kwon
- Department of Biophysics and Biophysical ChemistryJohns Hopkins UniversityBaltimoreMD21205USA
| | - Mohamed Saleh Elgawish
- Department of ChemistryKorea UniversitySeoul02841Republic of Korea
- Medicinal Chemistry DepartmentFaculty of PharmacySuez Canal UniversityIsmailia41522Egypt
| | - Sang‐Hee Shim
- Department of ChemistryKorea UniversitySeoul02841Republic of Korea
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35
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Weiner E, Pinskey JM, Nicastro D, Otegui MS. Electron microscopy for imaging organelles in plants and algae. PLANT PHYSIOLOGY 2022; 188:713-725. [PMID: 35235662 PMCID: PMC8825266 DOI: 10.1093/plphys/kiab449] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 08/23/2021] [Indexed: 05/31/2023]
Abstract
Recent developments in both instrumentation and image analysis algorithms have allowed three-dimensional electron microscopy (3D-EM) to increase automated image collections through large tissue volumes using serial block-face scanning EM (SEM) and to achieve near-atomic resolution of macromolecular complexes using cryo-electron tomography (cryo-ET) and sub-tomogram averaging. In this review, we discuss applications of cryo-ET to cell biology research on plant and algal systems and the special opportunities they offer for understanding the organization of eukaryotic organelles with unprecedently resolution. However, one of the most challenging aspects for cryo-ET is sample preparation, especially for multicellular organisms. We also discuss correlative light and electron microscopy (CLEM) approaches that have been developed for ET at both room and cryogenic temperatures.
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Affiliation(s)
- Ethan Weiner
- Department of Botany, University of Wisconsin, Madison 53706, Wisconsin
- Center for Quantitative Cell Imaging, University of Wisconsin, Madison 53706, Wisconsin
| | - Justine M Pinskey
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas 75390, Texas
| | - Daniela Nicastro
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas 75390, Texas
| | - Marisa S Otegui
- Department of Botany, University of Wisconsin, Madison 53706, Wisconsin
- Center for Quantitative Cell Imaging, University of Wisconsin, Madison 53706, Wisconsin
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36
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Parasitology meets cryo-electron tomography – exciting prospects await. Trends Parasitol 2022; 38:365-378. [DOI: 10.1016/j.pt.2022.01.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 12/27/2022]
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37
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Jeong D, Kim D. Recent Developments in Correlative Super-Resolution Fluorescence Microscopy and Electron Microscopy. Mol Cells 2022; 45:41-50. [PMID: 35114646 PMCID: PMC8819494 DOI: 10.14348/molcells.2021.5011] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/31/2021] [Accepted: 12/31/2021] [Indexed: 11/27/2022] Open
Abstract
The recently developed correlative super-resolution fluorescence microscopy (SRM) and electron microscopy (EM) is a hybrid technique that simultaneously obtains the spatial locations of specific molecules with SRM and the context of the cellular ultrastructure by EM. Although the combination of SRM and EM remains challenging owing to the incompatibility of samples prepared for these techniques, the increasing research attention on these methods has led to drastic improvements in their performances and resulted in wide applications. Here, we review the development of correlative SRM and EM (sCLEM) with a focus on the correlation of EM with different SRM techniques. We discuss the limitations of the integration of these two microscopy techniques and how these challenges can be addressed to improve the quality of correlative images. Finally, we address possible future improvements and advances in the continued development and wide application of sCLEM approaches.
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Affiliation(s)
- Dokyung Jeong
- Department of Chemistry, Hanyang University, Seoul 04763, Korea
| | - Doory Kim
- Department of Chemistry, Hanyang University, Seoul 04763, Korea
- Research Institute for Convergence of Basic Sciences, Hanyang University, Seoul 04763, Korea
- Institute of Nano Science and Technology, Hanyang University, Seoul 04763, Korea
- Research Institute for Natural Sciences, Hanyang University, Seoul 04763, Korea
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38
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Bond C, Santiago-Ruiz AN, Tang Q, Lakadamyali M. Technological advances in super-resolution microscopy to study cellular processes. Mol Cell 2022; 82:315-332. [PMID: 35063099 PMCID: PMC8852216 DOI: 10.1016/j.molcel.2021.12.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 01/22/2023]
Abstract
Since its initial demonstration in 2000, far-field super-resolution light microscopy has undergone tremendous technological developments. In parallel, these developments have opened a new window into visualizing the inner life of cells at unprecedented levels of detail. Here, we review the technical details behind the most common implementations of super-resolution microscopy and highlight some of the recent, promising advances in this field.
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Affiliation(s)
- Charles Bond
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Adriana N. Santiago-Ruiz
- Department of Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Qing Tang
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Melike Lakadamyali
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA,Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA,Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA,Correspondence should be sent to M.L.:
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39
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Sexton DL, Burgold S, Schertel A, Tocheva EI. Super-resolution confocal cryo-CLEM with cryo-FIB milling for in situ imaging of Deinococcus radiodurans. Curr Res Struct Biol 2022; 4:1-9. [PMID: 34977598 PMCID: PMC8688812 DOI: 10.1016/j.crstbi.2021.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 11/17/2021] [Accepted: 12/02/2021] [Indexed: 12/14/2022] Open
Abstract
Studying bacterial cell envelope architecture with electron microscopy is challenging due to the poor preservation of microbial ultrastructure with traditional methods. Here, we established and validated a super-resolution cryo-correlative light and electron microscopy (cryo-CLEM) method, and combined it with cryo-focused ion beam (cryo-FIB) milling and scanning electron microscopy (SEM) volume imaging to structurally characterize the bacterium Deinococcus radiodurans. Subsequent cryo-electron tomography (cryo-ET) revealed an unusual diderm cell envelope architecture with a thick layer of peptidoglycan (PG) between the inner and outer membranes, an additional periplasmic layer, and a proteinaceous surface S-layer. Cells grew in tetrads, and division septa were formed by invagination of the inner membrane (IM), followed by a thick layer of PG. Cytoskeletal filaments, FtsA and FtsZ, were observed at the leading edges of constricting septa. Numerous macromolecular complexes were found associated with the cytoplasmic side of the IM. Altogether, our study revealed several unique ultrastructural features of D. radiodurans cells, opening new lines of investigation into the physiology and evolution of the bacterium. User-friendly, commercially available method for correlative cryo-super resolution light microscopy (LM) and cryo-FIB-milling. Cryo-super resolution LM, cryo-FIB milling, cryo-SEM volume imaging, and cryo-electron tomography (cryo-ET) to study Deinococcus radiodurans. Unique D. radiodurans cell envelope is composed of two membranes, thick peptidoglycan, an additional layer, and an S-layer. Cytoskeletal filaments FtsA and FtsZ were observed at the leading edges of division septa.
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Affiliation(s)
- Danielle L Sexton
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | | | | | - Elitza I Tocheva
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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40
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Tian B, Xu X, Xue Y, Ji W, Xu T. Cryogenic superresolution correlative light and electron microscopy on the frontier of subcellular imaging. Biophys Rev 2021; 13:1163-1171. [DOI: 10.1007/s12551-021-00851-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 10/03/2021] [Indexed: 12/22/2022] Open
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41
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Zeng X, Howe G, Xu M. End-to-end robust joint unsupervised image alignment and clustering. PROCEEDINGS. IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION 2021; 2021:3834-3846. [PMID: 35392630 PMCID: PMC8986091 DOI: 10.1109/iccv48922.2021.00383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Computing dense pixel-to-pixel image correspondences is a fundamental task of computer vision. Often, the objective is to align image pairs from the same semantic category for manipulation or segmentation purposes. Despite achieving superior performance, existing deep learning alignment methods cannot cluster images; consequently, clustering and pairing images needed to be a separate laborious and expensive step. Given a dataset with diverse semantic categories, we propose a multi-task model, Jim-Net, that can directly learn to cluster and align images without any pixel-level or image-level annotations. We design a pair-matching alignment unsupervised training algorithm that selectively matches and aligns image pairs from the clustering branch. Our unsupervised Jim-Net achieves comparable accuracy with state-of-the-art supervised methods on benchmark 2D image alignment dataset PF-PASCAL. Specifically, we apply Jim-Net to cryo-electron tomography, a revolutionary 3D microscopy imaging technique of native subcellular structures. After extensive evaluation on seven datasets, we demonstrate that Jim-Net enables systematic discovery and recovery of representative macromolecular structures in situ, which is essential for revealing molecular mechanisms underlying cellular functions. To our knowledge, Jim-Net is the first end-to-end model that can simultaneously align and cluster images, which significantly improves the performance as compared to performing each task alone.
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42
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Abstract
Cryo-electron tomography has stepped fully into the spotlight. Enthusiasm is high. Fortunately for us, this is an exciting time to be a cryotomographer, but there is still a way to go before declaring victory. Despite its potential, cryo-electron tomography possesses many inherent challenges. How do we image through thick cell samples, and possibly even tissue? How do we identify a protein of interest amidst the noisy, crowded environment of the cytoplasm? How do we target specific moments of a dynamic cellular process for tomographic imaging? In this review, we cover the history of cryo-electron tomography and how it came to be, roughly speaking, as well as the many approaches that have been developed to overcome its intrinsic limitations.
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Affiliation(s)
- Ryan K. Hylton
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Matthew T. Swulius
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA
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43
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Bäuerlein FJB, Baumeister W. Towards Visual Proteomics at High Resolution. J Mol Biol 2021; 433:167187. [PMID: 34384780 DOI: 10.1016/j.jmb.2021.167187] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/02/2021] [Accepted: 08/02/2021] [Indexed: 11/24/2022]
Abstract
Traditionally, structural biologists approach the complexity of cellular proteomes in a reductionist manner. Proteomes are fractionated, their molecular components purified and studied one-by-one using the experimental methods for structure determination at their disposal. Visual proteomics aims at obtaining a holistic picture of cellular proteomes by studying them in situ, ideally in unperturbed cellular environments. The method that enables doing this at highest resolution is cryo-electron tomography. It allows to visualize cellular landscapes with molecular resolution generating maps or atlases revealing the interaction networks which underlie cellular functions in health and in disease states. Current implementations of cryo ET do not yet realize the full potential of the method in terms of resolution and interpretability. To this end, further improvements in technology and methodology are needed. This review describes the state of the art as well as measures which we expect will help overcoming current limitations.
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Affiliation(s)
- Felix J B Bäuerlein
- Max-Planck-Institute of Biochemistry, Department for Molecular Structural Biology, Am Klopferspitz 18, 82152 Planegg, Germany; Georg-August-University, Institute for Neuropathology, Robert-Koch-Strasse 40, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Germany.
| | - Wolfgang Baumeister
- Max-Planck-Institute of Biochemistry, Department for Molecular Structural Biology, Am Klopferspitz 18, 82152 Planegg, Germany.
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Abstract
The application of cryo-correlative light and cryo-electron microscopy (cryo-CLEM) gives us a way to locate structures of interest in the electron microscope. In brief, the structures of interest are fluorescently tagged, and images from the cryo-fluorescent microscope (cryo-FM) maps are superimposed on those from the cryo-electron microscope (cryo-EM). By enhancing cryo-FM to include single-molecule localization microscopy (SMLM), we can achieve much better localization. The introduction of cryo-SMLM increased the yield of photons from fluorophores, which can benefit localization efforts. Dahlberg and Moerner (2021, Annual Review of Physical Chemistry, 72, 253-278) have a recent broad and elegant review of super-resolution cryo-CLEM. This paper focuses on cryo(F)PALM/STORM for the cryo-electron tomography community. I explore the current challenges to increase the accuracy of localization by SMLM and the mapping of those positions onto cryo-EM images and maps. There is much to consider: we need to know if the excitation of fluorophores damages the structures we seek to visualize. We need to determine if higher numerical aperture (NA) objectives, which add complexity to image analysis but increase resolution and the efficiency of photon collection, are better than lower NA objectives, which pose fewer problems. We need to figure out the best way to determine the axial position of fluorophores. We need to have better ways of aligning maps determined by FM with those determined by EM. We need to improve the instrumentation to be easier to use, more accurate, and ice-contamination free. The bottom line is that we have more work to do.
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45
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Dahlberg PD, Moerner WE. Cryogenic Super-Resolution Fluorescence and Electron Microscopy Correlated at the Nanoscale. Annu Rev Phys Chem 2021; 72:253-278. [PMID: 33441030 PMCID: PMC8877847 DOI: 10.1146/annurev-physchem-090319-051546] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
We review the emerging method of super-resolved cryogenic correlative light and electron microscopy (srCryoCLEM). Super-resolution (SR) fluorescence microscopy and cryogenic electron tomography (CET) are both powerful techniques for observing subcellular organization, but each approach has unique limitations. The combination of the two brings the single-molecule sensitivity and specificity of SR to the detailed cellular context and molecular scale resolution of CET. The resulting correlative data is more informative than the sum of its parts. The correlative images can be used to pinpoint the positions of fluorescently labeled proteins in the high-resolution context of CET with nanometer-scale precision and/or to identify proteins in electron-dense structures. The execution of srCryoCLEM is challenging and the approach is best described as a method that is still in its infancy with numerous technical challenges. In this review, we describe state-of-the-art srCryoCLEM experiments, discuss the most pressing challenges, and give a brief outlook on future applications.
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Affiliation(s)
- Peter D Dahlberg
- Department of Chemistry, Stanford University, Stanford, California 94305, USA;
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, California 94305, USA;
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Two PAAR Proteins with Different C-Terminal Extended Domains Have Distinct Ecological Functions in Myxococcus xanthus. Appl Environ Microbiol 2021; 87:AEM.00080-21. [PMID: 33608292 DOI: 10.1128/aem.00080-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 02/11/2021] [Indexed: 11/20/2022] Open
Abstract
Bacterial proline-alanine-alanine-arginine (PAAR) proteins are located at the top of the type VI secretion system (T6SS) nanomachine and carry and deliver effectors into neighboring cells. Many PAAR proteins are fused with a variable C-terminal extended domain (CTD). Here, we report that two paar-ctd genes (MXAN_RS08765 and MXAN_RS36995) located in two homologous operons are involved in different ecological functions of Myxococcus xanthus MXAN_RS08765 inhibited the growth of plant-pathogenic fungi, while MXAN_RS36995 was associated with the colony-merger incompatibility of M. xanthus cells. These two PAAR-CTD proteins were both toxic to Escherichia coli cells, while MXAN_RS08765, but not MXAN_RS36995, was also toxic to Saccharomyces cerevisiae cells. Their downstream adjacent genes, i.e., MXAN_RS08760 and MXAN_RS24590, protected against the toxicities. The MXAN_RS36995 protein was demonstrated to have nuclease activity, and the activity was inhibited by the presence of MXAN_RS24590. Our results highlight that the PAAR proteins diversify the CTDs to play divergent roles in M. xanthus IMPORTANCE The type VI secretion system (T6SS) is a bacterial cell contact-dependent weapon capable of delivering protein effectors into neighboring cells. The PAAR protein is located at the top of the nanomachine and carries an effector for delivery. Many PAAR proteins are extended with a diverse C-terminal sequence with an unknown structure and function. Here, we report two paar-ctd genes located in two homologous operons involved in different ecological functions of Myxococcus xanthus; one has antifungal activity, and the other is associated with the kin discrimination phenotype. The PAAR-CTD proteins and the proteins encoded by their downstream genes form two toxin-immunity protein pairs. We demonstrated that the C-terminal diversification of the PAAR-CTD proteins enriches the ecological functions of bacterial cells.
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Find your coat: Using correlative light and electron microscopy to study intracellular protein coats. Curr Opin Cell Biol 2021; 71:21-28. [PMID: 33684808 DOI: 10.1016/j.ceb.2021.01.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/27/2021] [Accepted: 01/30/2021] [Indexed: 12/14/2022]
Abstract
Protein coats, important for vesicular trafficking in eukaryotic cells, help shape membranes and package cargo. But their dynamic construction cannot be fully understood until the distinct steps of their assembly in their native intracellular context at molecular resolution can be visualized. For this, correlative light and electron microscopy (CLEM) is an essential tool. Here, we discuss how emerging CLEM techniques have been used to study the assembly of protein coats inside cells. We review how current and developing CLEM technologies are poised to answer fundamental questions of protein coat architecture at the nanoscale.
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Yang JE, Larson MR, Sibert BS, Shrum S, Wright ER. CorRelator: Interactive software for real-time high precision cryo-correlative light and electron microscopy. J Struct Biol 2021; 213:107709. [PMID: 33610654 PMCID: PMC8601405 DOI: 10.1016/j.jsb.2021.107709] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 01/06/2021] [Accepted: 02/11/2021] [Indexed: 12/31/2022]
Abstract
Cryo-correlative light and electron microscopy (CLEM) is a technique that uses the spatiotemporal cues from fluorescence light microscopy (FLM) to investigate the high-resolution ultrastructure of biological samples by cryo-electron microscopy (cryo-EM). Cryo-CLEM provides advantages for identifying and distinguishing fluorescently labeled proteins, macromolecular complexes, and organelles from the cellular environment. Challenges remain on how correlation workflows and software tools are implemented on different microscope platforms to support automated cryo-EM data acquisition. Here, we present CorRelator: an open-source desktop application that bridges between cryo-FLM and real-time cryo-EM/ET automated data collection. CorRelator implements a pixel-coordinate-to-stage-position transformation for flexible, high accuracy on-the-fly and post-acquisition correlation. CorRelator can be integrated into cryo-CLEM workflows and easily adapted to standard fluorescence and transmission electron microscope (TEM) system configurations. CorRelator was benchmarked under live-cell and cryogenic conditions using several FLM and TEM instruments, demonstrating that CorRelator reliably supports real-time, automated correlative cryo-EM/ET acquisition, through a combination of software-aided and interactive alignment. CorRelator is a cross-platform software package featuring an intuitive Graphical User Interface (GUI) that guides the user through the correlation process. CorRelator source code is available at: https://github.com/wright-cemrc-projects/corr.
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Affiliation(s)
- Jie E Yang
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Matthew R Larson
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Bryan S Sibert
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Samantha Shrum
- Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States
| | - Elizabeth R Wright
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States; Morgridge Institute for Research, Madison, WI, 53715, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States.
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Lam V, Villa E. Practical Approaches for Cryo-FIB Milling and Applications for Cellular Cryo-Electron Tomography. Methods Mol Biol 2021; 2215:49-82. [PMID: 33367999 DOI: 10.1007/978-1-0716-0966-8_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cryo-electron tomography (cryo-ET) is a powerful technique to examine cellular structures as they exist in situ. However, direct imaging by TEM for cryo-ET is limited to specimens up to ∼400 nm in thickness, narrowing its applicability to areas such as cellular projections or small bacteria and viruses. Cryo-focused ion beam (cryo-FIB) milling has emerged in recent years as a method to generate thin specimens from cellular samples in preparation for cryo-ET. In this technique, specimens are thinned with a beam of gallium ions to gradually ablate cellular material in order to leave a thin, electron-transparent section (a lamella) through the bulk material. The lamella can be used for high-resolution cryo-ET to visualize cells in 3D in a near-native state. This approach has proved to be robust and relatively simple for new users and exhibits minimal sectioning artifacts. In this chapter, we describe a general approach to cryo-FIB milling for users with prior cryo-EM experience, with extensive notes on operation and troubleshooting.
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Affiliation(s)
- Vinson Lam
- University of California, San Diego, La Jolla, CA, USA
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Correlative super-resolution fluorescence and electron cryo-microscopy based on cryo-SOFI. Methods Cell Biol 2020; 162:253-271. [PMID: 33707015 DOI: 10.1016/bs.mcb.2020.10.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The combination of super-resolution fluorescence microscopy and electron microscopy at ambient temperatures has become an established technique and a broad variety of modalities are now available to the cell biology community. In contrast, correlative cryogenic super-resolution fluorescence and electron microscopy (super-resolution cryo-CLEM) is just emerging. Aside from technical challenges, one of the major issues is the risk of devitrification of the specimen caused by the laser intensities required for super-resolution imaging. Cryo-SOFI (cryogenic super-resolution optical fluctuation imaging) allows the reconstruction of super-resolution images at particularly low laser intensities. It is fully compatible with the standard sample preparation for cryogenic electron microscopy (cryo-EM) and fairly easy to implement in any standard cryogenic fluorescence microscope.
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