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Super-resolution microscopy reveals the number and distribution of topoisomerase IIα and CENH3 molecules within barley metaphase chromosomes. Chromosoma 2023; 132:19-29. [PMID: 36719450 PMCID: PMC9981516 DOI: 10.1007/s00412-023-00785-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/25/2022] [Accepted: 12/13/2022] [Indexed: 02/01/2023]
Abstract
Topoisomerase IIα (Topo IIα) and the centromere-specific histone H3 variant CENH3 are key proteins involved in chromatin condensation and centromere determination, respectively. Consequently, they are required for proper chromosome segregation during cell divisions. We combined two super-resolution techniques, structured illumination microscopy (SIM) to co-localize Topo IIα and CENH3, and photoactivated localization microscopy (PALM) to determine their molecule numbers in barley metaphase chromosomes. We detected a dispersed Topo IIα distribution along chromosome arms but an accumulation at centromeres, telomeres, and nucleolus-organizing regions. With a precision of 10-50 nm, we counted ~ 20,000-40,000 Topo IIα molecules per chromosome, 28% of them within the (peri)centromere. With similar precision, we identified ~13,500 CENH3 molecules per centromere where Topo IIα proteins and CENH3-containing chromatin intermingle. In short, we demonstrate PALM as a useful method to count and localize single molecules with high precision within chromosomes. The ultrastructural distribution and the detected amount of Topo IIα and CENH3 are instrumental for a better understanding of their functions during chromatin condensation and centromere determination.
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2
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Sartsanga C, Phengchat R, Fukui K, Wako T, Ohmido N. Surface structures consisting of chromatin fibers in isolated barley (Hordeum vulgare) chromosomes revealed by helium ion microscopy. Chromosome Res 2021; 29:81-94. [PMID: 33615407 DOI: 10.1007/s10577-021-09649-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 01/19/2021] [Accepted: 01/27/2021] [Indexed: 11/24/2022]
Abstract
The chromosome compaction of chromatin fibers results in the formation of the nucleosome, which consists of a DNA unit coiled around a core of histone molecules associated with linker histone. The compaction of chromatin fibers has been a topic of controversy since the discovery of chromosomes in the 19th century. Although chromatin fibers were first identified using electron microscopy, the chromatin fibers on the surface of chromosome structures in plants remain unclear due to shrinking and breaking caused by prior chromosome isolation or preparation with alcohol and acid fixation, and critical point drying occurred into dehydration and denatured chromosomal proteins. This study aimed to develop a high-quality procedure for the isolation and preparation of plant chromosomes, maintaining the native chromosome structure, to elucidate the organization of chromatin fibers on the surface of plant chromosomes by electron microscopy. A simple technique to isolate intact barley (Hordeum vulgare) chromosomes with a high yield was developed, allowing chromosomes to be observed with a high-resolution scanning ion microscopy and helium ion microscopy (HIM) imaging technology, based on a scanning helium ion beam. HIM images from the surface chromatin fibers were analyzed to determine the size and alignment of the chromatin fibers. The unit size of the chromatin fibers was 11.6 ± 3.5 nm and was closely aligned to the chromatin network model. Our findings indicate that compacting the surface structure of barley via a chromatin network and observation via HIM are powerful tools for investigating the structure of chromatin.
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Affiliation(s)
- Channarong Sartsanga
- Graduate School of Human Development and Environment, Kobe University, Kobe, 657-8501, Japan
| | - Rinyaporn Phengchat
- Graduate School of Human Development and Environment, Kobe University, Kobe, 657-8501, Japan
| | - Kiichi Fukui
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Toshiyuki Wako
- Institute of Crop Sciences, National Agriculture and Food Research Organization, 2-1-1 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan
| | - Nobuko Ohmido
- Graduate School of Human Development and Environment, Kobe University, Kobe, 657-8501, Japan.
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3
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Steiner P, Luckner M, Kerschbaum H, Wanner G, Lütz-Meindl U. Ionic stress induces fusion of mitochondria to 3-D networks: An electron tomography study. J Struct Biol 2018; 204:52-63. [PMID: 29981486 DOI: 10.1016/j.jsb.2018.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 06/27/2018] [Accepted: 06/30/2018] [Indexed: 01/05/2023]
Abstract
Mitochondria are central organelles for energy supply of cells and play an important role in maintenance of ionic balance. Consequently mitochondria are highly sensitive to any kind of stress to which they mainly response by disturbance of respiration, ROS production and release of cytochrome c into the cytoplasm. Many of the physiological and molecular stress reactions of mitochondria are well known, yet there is a lack of information on corresponding stress induced structural changes. 3-D visualization of high-pressure frozen cells by FIB-SEM tomography and TEM tomography as used for the present investigation provide an excellent tool for studying structure related mitochondrial stress reactions. In the present study it is shown that mitochondria in the unicellular fresh-water algal model system Micrasterias as well as in the closely related aquatic higher plant Lemna fuse to local networks as a consequence of exposure to ionic stress induced by addition of KCl, NaCl and CoCl2. In dependence on concentration and duration of the treatment, fusion of mitochondria occurs either by formation of protuberances arising from the outer mitochondrial membrane, or by direct contact of the surface of elongated mitochondria. As our results show that respiration is maintained in both model systems during ionic stress and mitochondrial fusion, as well as formation of protuberances are reversible, we assume that mitochondrial fusion is a ubiquitous process that may help the cells to cope with stress. This may occur by interconnecting the respiratory chains of the individual mitochondria and by enhancing the buffer capacity against stress induced ionic imbalance.
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Affiliation(s)
- Philip Steiner
- Department of Biosciences, University of Salzburg, Hellbrunnerstraße 34, A-5020 Salzburg, Austria
| | - Manja Luckner
- Ultrastructural Research, Faculty of Biology, Ludwig-Maximilians-University, Munich, Großhadernerstr. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Hubert Kerschbaum
- Department of Biosciences, University of Salzburg, Hellbrunnerstraße 34, A-5020 Salzburg, Austria
| | - Gerhard Wanner
- Ultrastructural Research, Faculty of Biology, Ludwig-Maximilians-University, Munich, Großhadernerstr. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Ursula Lütz-Meindl
- Department of Biosciences, University of Salzburg, Hellbrunnerstraße 34, A-5020 Salzburg, Austria.
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Baroux C, Schubert V. Technical Review: Microscopy and Image Processing Tools to Analyze Plant Chromatin: Practical Considerations. Methods Mol Biol 2018; 1675:537-589. [PMID: 29052212 DOI: 10.1007/978-1-4939-7318-7_31] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
In situ nucleus and chromatin analyses rely on microscopy imaging that benefits from versatile, efficient fluorescent probes and proteins for static or live imaging. Yet the broad choice in imaging instruments offered to the user poses orientation problems. Which imaging instrument should be used for which purpose? What are the main caveats and what are the considerations to best exploit each instrument's ability to obtain informative and high-quality images? How to infer quantitative information on chromatin or nuclear organization from microscopy images? In this review, we present an overview of common, fluorescence-based microscopy systems and discuss recently developed super-resolution microscopy systems, which are able to bridge the resolution gap between common fluorescence microscopy and electron microscopy. We briefly present their basic principles and discuss their possible applications in the field, while providing experience-based recommendations to guide the user toward best-possible imaging. In addition to raw data acquisition methods, we discuss commercial and noncommercial processing tools required for optimal image presentation and signal evaluation in two and three dimensions.
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Affiliation(s)
- Célia Baroux
- Department of Plant and Microbial Biology, Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, 8008, Zürich, Switzerland.
| | - Veit Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, 06466, Seeland, Germany
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5
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Abstract
A portfolio is presented documenting economic, high-resolution correlative focused ion beam scanning electron microscopy (FIB/SEM) in routine, comprising: (i) the use of custom-labeled slides and coverslips, (ii) embedding of cells in thin, or ultra-thin resin layers for correlative light and electron microscopy (CLEM) and (iii) the claim to reach the highest resolution possible with FIB/SEM in xyz. Regions of interest (ROIs) defined in light microscope (LM), can be relocated quickly and precisely in SEM. As proof of principle, HeLa cells were investigated in 3D context at all stages of the cell cycle, documenting ultrastructural changes during mitosis: nuclear envelope breakdown and reassembly, Golgi degradation and reconstitution and the formation of the midzone and midbody.
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6
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Eot-Houllier G, Magnaghi-Jaulin L, Fulcrand G, Moyroud FX, Monier S, Jaulin C. Aurora A-dependent CENP-A phosphorylation at inner centromeres protects bioriented chromosomes against cohesion fatigue. Nat Commun 2018; 9:1888. [PMID: 29760389 PMCID: PMC5951908 DOI: 10.1038/s41467-018-04089-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 04/03/2018] [Indexed: 11/09/2022] Open
Abstract
Sustained spindle tension applied to sister centromeres during mitosis eventually leads to uncoordinated loss of sister chromatid cohesion, a phenomenon known as “cohesion fatigue.” We report that Aurora A-dependent phosphorylation of serine 7 of the centromere histone variant CENP-A (p-CENP-AS7) protects bioriented chromosomes against cohesion fatigue. Expression of a non-phosphorylatable version of CENP-A (CENP-AS7A) weakens sister chromatid cohesion only when sister centromeres are under tension, providing the first evidence of a regulated mechanism involved in protection against passive cohesion loss. Consistent with this observation, p-CENP-AS7 is detected at the inner centromere where it forms a discrete domain. The depletion or inhibition of Aurora A phenocopies the expression of CENP-AS7A and we show that Aurora A is recruited to centromeres in a Bub1-dependent manner. We propose that Aurora A-dependent phosphorylation of CENP-A at the inner centromere protects chromosomes against tension-induced cohesion fatigue until the last kinetochore is attached to spindle microtubules. Sustained spindle tension applied to sister centromeres during mitosis leads to loss of sister chromatid cohesion which is known as cohesion fatigue. Here the authors show that Aurora A-dependent phosphorylation of CENP-A at the inner centromeres protects bioriented chromosomes against cohesion fatigue.
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Affiliation(s)
- Grégory Eot-Houllier
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France.
| | - Laura Magnaghi-Jaulin
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France
| | - Géraldine Fulcrand
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France
| | - François-Xavier Moyroud
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France
| | - Solange Monier
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France
| | - Christian Jaulin
- Institut de Génétique et Développement de Rennes, Epigenetics and Cancer group, Université Rennes 1, UMR 6290 CNRS, 35043, Rennes cedex, France.
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Wanner G, Schroeder-Reiter E, Ma W, Houben A, Schubert V. The ultrastructure of mono- and holocentric plant centromeres: an immunological investigation by structured illumination microscopy and scanning electron microscopy. Chromosoma 2015; 124:503-17. [DOI: 10.1007/s00412-015-0521-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 05/12/2015] [Accepted: 05/18/2015] [Indexed: 11/29/2022]
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Ishii T, Karimi-Ashtiyani R, Banaei-Moghaddam AM, Schubert V, Fuchs J, Houben A. The differential loading of two barley CENH3 variants into distinct centromeric substructures is cell type- and development-specific. Chromosome Res 2015; 23:277-84. [PMID: 25688006 DOI: 10.1007/s10577-015-9466-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 01/14/2023]
Abstract
The organization of centromeric chromatin of diploid barley (Hordeum vulgare) encoding two (α and β) CENH3 variants was analysed by super-resolution microscopy. Antibody staining revealed that both CENH3 variants are organized in distinct but intermingled subdomains in interphase, mitotic and meiotic centromeres. Artificially extended chromatin fibres illustrate that these subdomains are formed by polynucleosome clusters. Thus, a CENH3 variant-specific loading followed by the arrangement into specific intermingling subdomains forming the centromere region appears. The CENH3 composition and transcription vary among different tissues. In young embryos, most interphase centromeres are composed of both CENH3 variants, while in meristematic root cells, a high number of nuclei contain βCENH3 mainly dispersed within the nucleoplasm. A similar distribution and no preferential arrangement of the two CENH3 variants in relationship to the spindle poles suggest that both homologs meet the same function in metaphase cells.
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Affiliation(s)
- Takayoshi Ishii
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Corrensstr. 3, 06466, Stadt Seeland, Germany
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9
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Hamano T, Dwiranti A, Kaneyoshi K, Fukuda S, Kometani R, Nakao M, Takata H, Uchiyama S, Ohmido N, Fukui K. Chromosome interior observation by focused ion beam/scanning electron microscopy (FIB/SEM) using ionic liquid technique. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:1340-7. [PMID: 25010743 DOI: 10.1017/s143192761401280x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Attempts to elucidate chromosome structure have long remained elusive. Electron microscopy is useful for chromosome structure research because of its high resolution and magnification. However, biological samples such as chromosomes need to be subjected to various preparation steps, including dehydration, drying, and metal/carbon coating, which may induce shrinkage and artifacts. The ionic liquid technique has recently been developed and it enables sample preparation without dehydration, drying, or coating, providing a sample that is closer to the native condition. Concurrently, focused ion beam/scanning electron microscopy (FIB/SEM) has been developed, allowing the investigation and direct analysis of chromosome interiors. In this study, we investigated chromosome interiors by FIB/SEM using plant and human chromosomes prepared by the ionic liquid technique. As a result, two types of chromosomes, with and without cavities, were visualized, both for barley and human chromosomes prepared by critical point drying. However, chromosome interiors were revealed only as a solid structure, lacking cavities, when prepared by the ionic liquid technique. Our results suggest that the existence and size of cavities depend on the preparation procedures. We conclude that combination of the ionic liquid technique and FIB/SEM is a powerful tool for chromosome study.
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Affiliation(s)
- Tohru Hamano
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Astari Dwiranti
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Kohei Kaneyoshi
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Shota Fukuda
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Reo Kometani
- 2Laboratory of Nano Mechanics,Department of Mechanical Engineering,Graduate School of Engineering,The University of Tokyo,Hongo,Bunkyo,Tokyo 113-8685,Japan
| | - Masayuki Nakao
- 3Department of Engineering Synthesis,Graduate School of Engineering,The University of Tokyo,Hongo,Bunkyo,Tokyo 113-8685,Japan
| | - Hideaki Takata
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Susumu Uchiyama
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
| | - Nobuko Ohmido
- 4Department of Human Environmental Science,Division of Living Environment,Graduate School of Human Development and Environment,Kobe University,Tsurukabuto,Nada,Kobe 657-8501,Japan
| | - Kiichi Fukui
- 1Laboratory of Dynamic Cell Biology,Department of Biotechnology,Graduate School of Engineering,Osaka University,Yamadaoka,Suita,Osaka 565-0871,Japan
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10
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Loginova DB, Silkova OG. Mitotic behavior of centromeres in meiosis as the fertility restoration mechanism in wheat-rye amphihaploids. RUSS J GENET+ 2014. [DOI: 10.1134/s1022795414070114] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Geiss CP, Keramisanou D, Sekulic N, Scheffer MP, Black BE, Frangakis AS. CENP-A arrays are more condensed than canonical arrays at low ionic strength. Biophys J 2014; 106:875-82. [PMID: 24559990 PMCID: PMC3944588 DOI: 10.1016/j.bpj.2014.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 01/02/2014] [Accepted: 01/07/2014] [Indexed: 10/25/2022] Open
Abstract
The centromeric histone H3 variant centromeric protein A (CENP-A), whose sequence is the least conserved among all histone variants, is responsible for specifying the location of the centromere. Here, we present a comprehensive study of CENP-A nucleosome arrays by cryo-electron tomography. We see that CENP-A arrays have different biophysical properties than canonical ones under low ionic conditions, as they are more condensed with a 20% smaller average nearest-neighbor distance and a 30% higher nucleosome density. We find that CENP-A nucleosomes have a predominantly crossed DNA entry/exit site that is narrowed on average by 8°, and they have a propensity to stack face to face. We therefore propose that CENP-A induces geometric constraints at the nucleosome DNA entry/exit site to bring neighboring nucleosomes into close proximity. This specific property of CENP-A may be responsible for generating a fundamental process that contributes to increased chromatin fiber compaction that is propagated under physiological conditions to form centromeric chromatin.
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Affiliation(s)
| | | | - Nikolina Sekulic
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Ben E Black
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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12
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Fišerová J, Goldberg MW. Imaging plant nuclei and membrane-associated cytoskeleton by field emission scanning electron microscopy. Methods Mol Biol 2014; 1080:171-81. [PMID: 24132428 DOI: 10.1007/978-1-62703-643-6_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Scanning electron microscopy (SEM) is a powerful technique that can image exposed surfaces in 3D. Modern scanning electron microscopes, with field emission electron sources and in-lens specimen chambers, achieve resolutions of better than 0.5 nm and thus offer views of ultrastructural details of subcellular structures or even macromolecular complexes. Obtaining a reliable image is, however, dependent on sample preparation methods that robustly but accurately preserve biological structures. In plants, exposing the object of interest may be difficult due to the existence of a cell wall. This protocol shows how to isolate plant nuclei for SEM imaging of the nuclear envelope and associated structures from both sides of the nuclear envelope in cultured cells as well as in leaf or root cells. Further, it provides a method for uncovering membrane-associated cytoskeletal structures.
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Affiliation(s)
- Jindřiška Fišerová
- Department of Experimental Plant Biology, Faculty of Science, Charles University and Institute of Molecular Genetics of the ASCR, Prague, Czech Republic
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13
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Wanner G, Schäfer T, Lütz-Meindl U. 3-D analysis of dictyosomes and multivesicular bodies in the green alga Micrasterias denticulata by FIB/SEM tomography. J Struct Biol 2013; 184:203-11. [PMID: 24135121 PMCID: PMC3899002 DOI: 10.1016/j.jsb.2013.10.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/30/2013] [Accepted: 10/02/2013] [Indexed: 12/24/2022]
Abstract
In the present study we employ FIB/SEM tomography for analyzing 3-D architecture of dictyosomes and formation of multivesicular bodies (MVB) in high pressure frozen and cryo-substituted interphase cells of the green algal model system Micrasterias denticulata. The ability of FIB/SEM of milling very thin ‘slices’ (5–10 nm), viewing the block face and of capturing cytoplasmic volumes of several hundred μm3 provides new insight into the close spatial connection of the ER–Golgi machinery in an algal cell particularly in z-direction, complementary to informations obtained by TEM serial sectioning or electron tomography. Our FIB/SEM series and 3-D reconstructions show that interphase dictyosomes of Micrasterias are not only closely associated to an ER system at their cis-side which is common in various plant cells, but are surrounded by a huge “trans-ER” sheath leading to an almost complete enwrapping of dictyosomes by the ER. This is particularly interesting as the presence of a trans-dictyosomal ER system is well known from mammalian secretory cells but not from cells of higher plants to which the alga Micrasterias is closely related. In contrast to findings in plant storage tissue indicating that MVBs originate from the trans-Golgi network or its derivatives our investigations show that MVBs in Micrasterias are in direct spatial contact with both, trans-Golgi cisternae and the trans-ER sheath which provides evidence that both endomembrane compartments are involved in their formation.
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Affiliation(s)
- Gerhard Wanner
- Ultrastructural Research, Faculty of Biology, Ludwig-Maximilians-University, Munich, Großhadernerstr. 2-4, D-82152 Planegg-Martinsried, Germany.
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14
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15
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Hübner B, Cremer T, Neumann J. Correlative microscopy of individual cells: sequential application of microscopic systems with increasing resolution to study the nuclear landscape. Methods Mol Biol 2013; 1042:299-336. [PMID: 23980016 DOI: 10.1007/978-1-62703-526-2_21] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The term correlative microscopy denotes the sequential visualization of one and the same cell using various microscopic techniques. Correlative microscopy provides a unique platform to combine the particular strength of each microscopic approach and compensate for its specific limitations. As an example, we report results of a correlative microscopic study exploring features of the nuclear landscape in HeLa cells. We present a detailed protocol to first investigate distinct structural features of a living cell in space and time (4D) using spinning disk laser scanning microscopy (SDLSM). Then, after fixation and staining of selected structures (e.g., by means of immunodetection), details of these structures are explored at increasingly higher resolution using three-dimensional (3D) confocal laser scanning microscopy (CLSM); super-resolution fluorescence microscopy, such as three-dimensional structured illumination microscopy (3D-SIM); and transmission electron microscopy (TEM). We discuss problems involved in the comparison of images of a given cell nucleus recorded with different microscopic approaches, which requires not only a compensation for different resolutions but also for various distortions.
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Affiliation(s)
- Barbara Hübner
- Department Biology II, Anthropology and Human Genetics, Biocenter, Ludwig-Maximilians-University (LMU), Martinsried, Germany
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16
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Quénet D, Dalal Y. The CENP-A nucleosome: a dynamic structure and role at the centromere. Chromosome Res 2012; 20:465-79. [PMID: 22825424 DOI: 10.1007/s10577-012-9301-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The centromere is a specialized locus that directs the formation of the kinetochore protein complex for correct chromosome segregation. The specific centromere histone H3 variant CENP-A has been described as the epigenetic mark of this chromatin region. Several laboratories have explored its properties, its partners, and its role in centromere formation. Specifically, two types of CENP-A nucleosomes have been described, suggesting there may be more complexity involved in centromere structure than previously thought. Recent work adds to this paradox by questioning the role of CENP-A as a unique centromeric mark and highlighting the assembly of a functional kinetochore in the absence of CENP-A. In this review, we discuss recent literature on the CENP-A nucleosomes and the debate on its role in kinetochore formation and centromere identity.
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Affiliation(s)
- Delphine Quénet
- Laboratory of Receptor Biology & Gene Expression-NCI-NIH, Building 41, Room B901, 41 Library Drive MSC 5055, Bethesda, MD 20892, USA
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17
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Neumann P, Navrátilová A, Schroeder-Reiter E, Koblížková A, Steinbauerová V, Chocholová E, Novák P, Wanner G, Macas J. Stretching the rules: monocentric chromosomes with multiple centromere domains. PLoS Genet 2012; 8:e1002777. [PMID: 22737088 PMCID: PMC3380829 DOI: 10.1371/journal.pgen.1002777] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 05/05/2012] [Indexed: 11/29/2022] Open
Abstract
The centromere is a functional chromosome domain that is essential for faithful chromosome segregation during cell division and that can be reliably identified by the presence of the centromere-specific histone H3 variant CenH3. In monocentric chromosomes, the centromere is characterized by a single CenH3-containing region within a morphologically distinct primary constriction. This region usually spans up to a few Mbp composed mainly of centromere-specific satellite DNA common to all chromosomes of a given species. In holocentric chromosomes, there is no primary constriction; the centromere is composed of many CenH3 loci distributed along the entire length of a chromosome. Using correlative fluorescence light microscopy and high-resolution electron microscopy, we show that pea (Pisum sativum) chromosomes exhibit remarkably long primary constrictions that contain 3-5 explicit CenH3-containing regions, a novelty in centromere organization. In addition, we estimate that the size of the chromosome segment delimited by two outermost domains varies between 69 Mbp and 107 Mbp, several factors larger than any known centromere length. These domains are almost entirely composed of repetitive DNA sequences belonging to 13 distinct families of satellite DNA and one family of centromeric retrotransposons, all of which are unevenly distributed among pea chromosomes. We present the centromeres of Pisum as novel "meta-polycentric" functional domains. Our results demonstrate that the organization and DNA composition of functional centromere domains can be far more complex than previously thought, do not require single repetitive elements, and do not require single centromere domains in order to segregate properly. Based on these findings, we propose Pisum as a useful model for investigation of centromere architecture and the still poorly understood role of repetitive DNA in centromere evolution, determination, and function.
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Affiliation(s)
- Pavel Neumann
- Biology Centre of the Academy of Sciences of the Czech Republic, Institute of Plant Molecular Biology, České Budějovice, Czech Republic.
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