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Ruehle MD, Li S, Agard DA, Pearson CG. Poc1 bridges basal body inner junctions to promote triplet microtubule integrity and connections. J Cell Biol 2024; 223:e202311104. [PMID: 38743010 PMCID: PMC11094743 DOI: 10.1083/jcb.202311104] [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: 11/27/2023] [Revised: 03/15/2024] [Accepted: 04/09/2024] [Indexed: 05/16/2024] Open
Abstract
Basal bodies (BBs) are conserved eukaryotic structures that organize cilia. They are comprised of nine, cylindrically arranged, triplet microtubules (TMTs) connected to each other by inter-TMT linkages which stabilize the structure. Poc1 is a conserved protein important for BB structural integrity in the face of ciliary forces transmitted to BBs. To understand how Poc1 confers BB stability, we identified the precise position of Poc1 in the Tetrahymena BB and the effect of Poc1 loss on BB structure. Poc1 binds at the TMT inner junctions, stabilizing TMTs directly. From this location, Poc1 also stabilizes inter-TMT linkages throughout the BB, including the cartwheel pinhead and the inner scaffold. The full localization of the inner scaffold protein Fam161A requires Poc1. As ciliary forces are increased, Fam161A is reduced, indicative of a force-dependent molecular remodeling of the inner scaffold. Thus, while not essential for BB assembly, Poc1 promotes BB interconnections that establish an architecture competent to resist ciliary forces.
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Affiliation(s)
- Marisa D. Ruehle
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Sam Li
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - David A. Agard
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Chan Zuckerberg Institute for Advanced Biological Imaging, Redwood Shores, CA, USA
| | - Chad G. Pearson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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Ruehle MD, Li S, Agard DA, Pearson CG. Poc1 is a basal body inner junction protein that promotes triplet microtubule integrity and interconnections. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.17.567593. [PMID: 38014135 PMCID: PMC10680851 DOI: 10.1101/2023.11.17.567593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Basal bodies (BBs) are conserved eukaryotic structures that organize motile and primary cilia. The BB is comprised of nine, cylindrically arranged, triplet microtubules (TMTs) that are connected to each other by inter-TMT linkages which maintain BB structure. During ciliary beating, forces transmitted to the BB must be resisted to prevent BB disassembly. Poc1 is a conserved BB protein important for BBs to resist ciliary forces. To understand how Poc1 confers BB stability, we identified the precise position of Poc1 binding in the Tetrahymena BB and the effect of Poc1 loss on BB structure. Poc1 binds at the TMT inner junctions, stabilizing TMTs directly. From this location, Poc1 also stabilizes inter-TMT linkages throughout the BB, including the cartwheel pinhead and the inner scaffold. Moreover, we identify a molecular response to ciliary forces via a molecular remodeling of the inner scaffold, as determined by differences in Fam161A localization. Thus, while not essential for BB assembly, Poc1 promotes BB interconnections that establish an architecture competent to resist ciliary forces.
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Affiliation(s)
- Marisa D. Ruehle
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Sam Li
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - David A. Agard
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Chan Zuckerberg Institute for Advanced Biological Imaging, 3400 Bridge Parkway, Redwood Shores, CA, USA
| | - Chad G. Pearson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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Junker AD, Woodhams LG, Soh AWJ, O’Toole ET, Bayly PV, Pearson CG. Basal bodies bend in response to ciliary forces. Mol Biol Cell 2022; 33:ar146. [PMID: 36287828 PMCID: PMC9727800 DOI: 10.1091/mbc.e22-10-0468-t] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Motile cilia beat with an asymmetric waveform consisting of a power stroke that generates a propulsive force and a recovery stroke that returns the cilium back to the start. Cilia are anchored to the cell cortex by basal bodies (BBs) that are directly coupled to the ciliary doublet microtubules (MTs). We find that, consistent with ciliary forces imposing on BBs, bending patterns in BB triplet MTs are responsive to ciliary beating. BB bending varies as environmental conditions change the ciliary waveform. Bending occurs where striated fibers (SFs) attach to BBs and mutants with short SFs that fail to connect to adjacent BBs exhibit abnormal BB bending, supporting a model in which SFs couple ciliary forces between BBs. Finally, loss of the BB stability protein Poc1, which helps interconnect BB triplet MTs, prevents the normal distributed BB and ciliary bending patterns. Collectively, BBs experience ciliary forces and manage mechanical coupling of these forces to their surrounding cellular architecture for normal ciliary beating.
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Affiliation(s)
- Anthony D. Junker
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Louis G. Woodhams
- Department of Mechanical Engineering and Material Science, Washington University in St. Louis, St. Louis, MO 63130
| | - Adam W. J. Soh
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Eileen T. O’Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80302
| | - Philip V. Bayly
- Department of Mechanical Engineering and Material Science, Washington University in St. Louis, St. Louis, MO 63130
| | - Chad G. Pearson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045,*Address correspondence to: Chad G. Pearson ()
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4
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Soh AWJ, Woodhams LG, Junker AD, Enloe CM, Noren BE, Harned A, Westlake CJ, Narayan K, Oakey JS, Bayly PV, Pearson CG. Intracellular connections between basal bodies promote the coordinated behavior of motile cilia. Mol Biol Cell 2022; 33:br18. [PMID: 35767367 DOI: 10.1091/mbc.e22-05-0150] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Hydrodynamic flow produced by multiciliated cells is critical for fluid circulation and cell motility. Hundreds of cilia beat with metachronal synchrony for fluid flow. Cilia-driven fluid flow produces extracellular hydrodynamic forces that cause neighboring cilia to beat in a synchronized manner. However, hydrodynamic coupling between neighboring cilia is not the sole mechanism that drives cilia synchrony. Cilia are nucleated by basal bodies (BBs) that link to each other and to the cell's cortex via BB-associated appendages. The intracellular BB and cortical network is hypothesized to synchronize ciliary beating by transmitting cilia coordination cues. The extent of intracellular ciliary connections and the nature of these stimuli remain unclear. Moreover, how BB connections influence the dynamics of individual cilia has not been established. We show by focused ion beam scanning electron microscopy imaging that cilia are coupled both longitudinally and laterally in the ciliate Tetrahymena thermophila by the underlying BB and cortical cytoskeletal network. To visualize the behavior of individual cilia in live, immobilized Tetrahymena cells, we developed Delivered Iron Particle Ubiety Live Light (DIPULL) microscopy. Quantitative and computer analyses of ciliary dynamics reveal that BB connections control ciliary waveform and coordinate ciliary beating. Loss of BB connections reduces cilia-dependent fluid flow forces.
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Affiliation(s)
- Adam W J Soh
- Department of Cell and Developmental Biology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045
| | - Louis G Woodhams
- Department of Mechanical Engineering and Material Science, Washington University in St. Louis, St. Louis, MO 63130
| | - Anthony D Junker
- Department of Cell and Developmental Biology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045
| | - Cassidy M Enloe
- Department of Chemical Engineering, College of Engineering and Applied Science, University of Wyoming, Laramie, WY 82071
| | - Benjamin E Noren
- Department of Chemical Engineering, College of Engineering and Applied Science, University of Wyoming, Laramie, WY 82071
| | - Adam Harned
- Center for Molecular Microscopy and Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, and
| | - Christopher J Westlake
- Laboratory of Cell and Developmental Signaling, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702
| | - Kedar Narayan
- Center for Molecular Microscopy and Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.,Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, and
| | - John S Oakey
- Department of Chemical Engineering, College of Engineering and Applied Science, University of Wyoming, Laramie, WY 82071
| | - Philip V Bayly
- Department of Mechanical Engineering and Material Science, Washington University in St. Louis, St. Louis, MO 63130
| | - Chad G Pearson
- Department of Cell and Developmental Biology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045
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5
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Chang IY, Rahman M, Harned A, Cohen-Fix O, Narayan K. Cryo-fluorescence microscopy of high-pressure frozen C. elegans enables correlative FIB-SEM imaging of targeted embryonic stages in the intact worm. Methods Cell Biol 2020; 162:223-252. [PMID: 33707014 PMCID: PMC9472676 DOI: 10.1016/bs.mcb.2020.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Rapidly changing features in an intact biological sample are challenging to efficiently trap and image by conventional electron microscopy (EM). For example, the model organism C. elegans is widely used to study embryonic development and differentiation, yet the fast kinetics of cell division makes the targeting of specific developmental stages for ultrastructural study difficult. We set out to image the condensed metaphase chromosomes of an early embryo in the intact worm in 3-D. To achieve this, one must capture this transient structure, then locate and subsequently image the corresponding volume by EM in the appropriate context of the organism, all while minimizing a variety of artifacts. In this methodological advance, we report on the high-pressure freezing of spatially constrained whole C. elegans hermaphrodites in a combination of cryoprotectants to identify embryonic cells in metaphase by in situ cryo-fluorescence microscopy. The screened worms were then freeze substituted, resin embedded and further prepared such that the targeted cells were successfully located and imaged by focused ion beam scanning electron microscopy (FIB-SEM). We reconstructed the targeted metaphase structure and also correlated an intriguing punctate fluorescence signal to a H2B-enriched putative polar body autophagosome in an adjacent cell undergoing telophase. By enabling cryo-fluorescence microscopy of thick samples, our workflow can thus be used to trap and image transient structures in C. elegans or similar organisms in a near-native state, and then reconstruct their corresponding cellular architectures at high resolution and in 3-D by correlative volume EM.
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Affiliation(s)
- Irene Y Chang
- Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, United States; Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, United States
| | - Mohammad Rahman
- The Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Adam Harned
- Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, United States; Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, United States
| | - Orna Cohen-Fix
- The Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Kedar Narayan
- Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, United States; Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, United States.
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6
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Soh AWJ, van Dam TJP, Stemm-Wolf AJ, Pham AT, Morgan GP, O'Toole ET, Pearson CG. Ciliary force-responsive striated fibers promote basal body connections and cortical interactions. J Cell Biol 2020; 219:jcb.201904091. [PMID: 31740506 PMCID: PMC7039215 DOI: 10.1083/jcb.201904091] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 07/15/2019] [Accepted: 10/02/2019] [Indexed: 12/28/2022] Open
Abstract
Multi-ciliary arrays promote fluid flow and cellular motility using the polarized and coordinated beating of hundreds of motile cilia. Tetrahymena basal bodies (BBs) nucleate and position cilia, whereby BB-associated striated fibers (SFs) promote BB anchorage and orientation into ciliary rows. Mutants that shorten SFs cause disoriented BBs. In contrast to the cytotaxis model, we show that disoriented BBs with short SFs can regain normal orientation if SF length is restored. In addition, SFs adopt unique lengths by their shrinkage and growth to establish and maintain BB connections and cortical interactions in a ciliary force-dependent mechanism. Tetrahymena SFs comprise at least eight uniquely localizing proteins belonging to the SF-assemblin family. Loss of different proteins that localize to the SF base disrupts either SF steady-state length or ciliary force-induced SF elongation. Thus, the dynamic regulation of SFs promotes BB connections and cortical interactions to organize ciliary arrays.
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Affiliation(s)
- Adam W J Soh
- Anschutz Medical Campus, Department of Cell and Developmental Biology, University of Colorado, Aurora, CO
| | - Teunis J P van Dam
- Theoretical Biology and Bioinformatics, Department of Biology, Science Faculty, Utrecht University, Utrecht, Netherlands
| | - Alexander J Stemm-Wolf
- Anschutz Medical Campus, Department of Cell and Developmental Biology, University of Colorado, Aurora, CO
| | - Andrew T Pham
- Anschutz Medical Campus, Department of Cell and Developmental Biology, University of Colorado, Aurora, CO
| | - Garry P Morgan
- Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, CO
| | - Eileen T O'Toole
- Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, CO
| | - Chad G Pearson
- Anschutz Medical Campus, Department of Cell and Developmental Biology, University of Colorado, Aurora, CO
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7
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Heydeck W, Bayless BA, Stemm-Wolf AJ, O'Toole ET, Fabritius AS, Ozzello C, Nguyen M, Winey M. Tetrahymena Poc5 is a transient basal body component that is important for basal body maturation. J Cell Sci 2020; 133:jcs.240838. [PMID: 32350068 DOI: 10.1242/jcs.240838] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 04/06/2020] [Indexed: 01/26/2023] Open
Abstract
Basal bodies (BBs) are microtubule-based organelles that act as a template for and stabilize cilia at the cell surface. Centrins ubiquitously associate with BBs and function in BB assembly, maturation and stability. Human POC5 (hPOC5) is a highly conserved centrin-binding protein that binds centrins through Sfi1p-like repeats and is required for building full-length, mature centrioles. Here, we use the BB-rich cytoskeleton of Tetrahymena thermophila to characterize Poc5 BB functions. Tetrahymena Poc5 (TtPoc5) uniquely incorporates into assembling BBs and is then removed from mature BBs prior to ciliogenesis. Complete genomic knockout of TtPOC5 leads to a significantly increased production of BBs, yet a markedly reduced ciliary density, both of which are rescued by reintroduction of TtPoc5. A second Tetrahymena POC5-like gene, SFR1, is similarly implicated in modulating BB production. When TtPOC5 and SFR1 are co-deleted, cell viability is compromised and BB overproduction is exacerbated. Overproduced BBs display defective transition zone formation and a diminished capacity for ciliogenesis. This study uncovers a requirement for Poc5 in building mature BBs, providing a possible functional link between hPOC5 mutations and impaired cilia.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Westley Heydeck
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Brian A Bayless
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Alexander J Stemm-Wolf
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Eileen T O'Toole
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Amy S Fabritius
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Courtney Ozzello
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Marina Nguyen
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Mark Winey
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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8
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Junker AD, Soh AWJ, O'Toole ET, Meehl JB, Guha M, Winey M, Honts JE, Gaertig J, Pearson CG. Microtubule glycylation promotes attachment of basal bodies to the cell cortex. J Cell Sci 2019; 132:jcs.233726. [PMID: 31243050 DOI: 10.1242/jcs.233726] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 06/18/2019] [Indexed: 12/13/2022] Open
Abstract
Motile cilia generate directed hydrodynamic flow that is important for the motility of cells and extracellular fluids. To optimize directed hydrodynamic flow, motile cilia are organized and oriented into a polarized array. Basal bodies (BBs) nucleate and position motile cilia at the cell cortex. Cytoplasmic BB-associated microtubules are conserved structures that extend from BBs. By using the ciliate, Tetrahymena thermophila, combined with EM-tomography and light microscopy, we show that BB-appendage microtubules assemble coincidently with new BB assembly and that they are attached to the cell cortex. These BB-appendage microtubules are specifically marked by post translational modifications of tubulin, including glycylation. Mutations that prevent glycylation shorten BB-appendage microtubules and disrupt BB positioning and cortical attachment. Consistent with the attachment of BB-appendage microtubules to the cell cortex to position BBs, mutations that disrupt the cellular cortical cytoskeleton disrupt the cortical attachment and positioning of BBs. In summary, BB-appendage microtubules promote the organization of ciliary arrays through attachment to the cell cortex.
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Affiliation(s)
- Anthony D Junker
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Adam W J Soh
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Eileen T O'Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80302, USA
| | - Janet B Meehl
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80302, USA
| | - Mayukh Guha
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Mark Winey
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Jerry E Honts
- Department of Biology, Drake University, 2507 University Avenue, Des Moines, IA 50311, USA
| | - Jacek Gaertig
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Chad G Pearson
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
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9
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Cole ES, Dmytrenko O, Chmelik CJ, Li M, Christensen TA, Macon EP, Nilsson HJ, Blower RJ, Reuter TG, Beckman JP, Remmers BC, Smith CL, O'Toole E, Ozzello C, Morgan G, Giddings T. Restoration of cellular integrity following "ballistic" pronuclear exchange during Tetrahymena conjugation. Dev Biol 2018; 444:33-40. [PMID: 30268714 DOI: 10.1016/j.ydbio.2018.09.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 09/22/2018] [Accepted: 09/25/2018] [Indexed: 11/15/2022]
Abstract
During sexual reproduction or conjugation, ciliates form a specialized cell adhesion zone for the purpose of exchanging gametic pronuclei. Hundreds of individual membrane fusion events transform the adhesion zone into a perforated membrane curtain, the mating junction. Pronuclei from each mating partner are propelled through this fenestrated membrane junction by a web of short, cris-crossing microtubules. Pronuclear passage results in the formation of two breaches in the membrane junction. Following pronuclear exchange and karyogamy (fertilization), cells seal these twin membrane breaches thereby re-establishing cellular independence. This would seem like a straightforward problem: simply grow membrane in from the edges of each breach in a fashion similar to how animal cells "grow" their cytokinetic furrows or how plant cells construct a cell wall during mitosis. Serial section electron microscopy and 3-D electron tomography reveal that the actual mechanism is less straightforward. Each of the two membrane breaches transforms into a bowed membrane assembly platform. The resulting membrane protrusions continue to grow into the cytoplasm of the mating partner, traverse the cytoplasm in anti-parallel directions and make contact with the plasma membrane that flanks the mating junction. This investigation reveals the details of a novel, developmentally-induced mechanism of membrane disruption and restoration associated with pronuclear exchange and fertilization in the ciliate, Tetrahymena thermophila.
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Affiliation(s)
- Eric S Cole
- Biology Department, St. Olaf College, Northfield, MN, USA.
| | | | - Carl J Chmelik
- Biology Department, St. Olaf College, Northfield, MN, USA
| | - Mark Li
- Biology Department, St. Olaf College, Northfield, MN, USA
| | | | - Elaine P Macon
- Biology Department, St. Olaf College, Northfield, MN, USA
| | | | - Ruth J Blower
- Biology Department, St. Olaf College, Northfield, MN, USA
| | | | - John P Beckman
- Biology Department, St. Olaf College, Northfield, MN, USA
| | | | - Claire L Smith
- Biology Department, St. Olaf College, Northfield, MN, USA
| | - Eileen O'Toole
- The Boulder Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Courtney Ozzello
- The Boulder Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Garry Morgan
- The Boulder Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Thomas Giddings
- The Boulder Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
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10
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Sfr1, a Tetrahymena thermophila Sfi1 Repeat Protein, Modulates the Production of Cortical Row Basal Bodies. mSphere 2016; 1:mSphere00257-16. [PMID: 27904881 PMCID: PMC5112337 DOI: 10.1128/msphere.00257-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 10/14/2016] [Indexed: 01/08/2023] Open
Abstract
Basal bodies and centrioles are structurally similar and, when rendered dysfunctional as a result of improper assembly or maintenance, are associated with human diseases. Centrins are conserved and abundant components of both structures whose basal body and centriolar functions remain incompletely understood. Despite the extensive study of centrins in Tetrahymena thermophila, little is known about how centrin-binding proteins contribute to centrin’s roles in basal body assembly, stability, and orientation. The sole previous study of the large centrin-binding protein family in Tetrahymena revealed a role for Sfr13 in the stabilization and separation of basal bodies. In this study, we found that Sfr1 localizes to all Tetrahymena basal bodies and complete genetic deletion of SFR1 leads to overproduction of basal bodies. The uncovered inhibitory role of Sfr1 in basal body production suggests that centrin-binding proteins, as well as centrins, may influence basal body number both positively and negatively. Basal bodies are essential microtubule-based structures that template, anchor, and orient cilia at the cell surface. Cilia act primarily in the generation of directional fluid flow and sensory reception, both of which are utilized for a broad spectrum of cellular processes. Although basal bodies contribute to vital cell functions, the molecular contributors of their assembly and maintenance are poorly understood. Previous studies of the ciliate Tetrahymena thermophila revealed important roles for two centrin family members in basal body assembly, separation of new basal bodies, and stability. Here, we characterize the basal body function of a centrin-binding protein, Sfr1, in Tetrahymena. Sfr1 is part of a large family of 13 proteins in Tetrahymena that contain Sfi1 repeats (SFRs), a motif originally identified in Saccharomyces cerevisiae Sfi1 that binds centrin. Sfr1 is the only SFR protein in Tetrahymena that localizes to all cortical row and oral apparatus basal bodies. In addition, Sfr1 resides predominantly at the microtubule scaffold from the proximal cartwheel to the distal transition zone. Complete genomic knockout of SFR1 (sfr1Δ) causes a significant increase in both cortical row basal body density and the number of cortical rows, contributing to an overall overproduction of basal bodies. Reintroduction of Sfr1 into sfr1Δ mutant cells leads to a marked reduction of cortical row basal body density and the total number of cortical row basal bodies. Therefore, Sfr1 directly modulates cortical row basal body production. This study reveals an inhibitory role for Sfr1, and potentially centrins, in Tetrahymena basal body production. IMPORTANCE Basal bodies and centrioles are structurally similar and, when rendered dysfunctional as a result of improper assembly or maintenance, are associated with human diseases. Centrins are conserved and abundant components of both structures whose basal body and centriolar functions remain incompletely understood. Despite the extensive study of centrins in Tetrahymena thermophila, little is known about how centrin-binding proteins contribute to centrin’s roles in basal body assembly, stability, and orientation. The sole previous study of the large centrin-binding protein family in Tetrahymena revealed a role for Sfr13 in the stabilization and separation of basal bodies. In this study, we found that Sfr1 localizes to all Tetrahymena basal bodies and complete genetic deletion of SFR1 leads to overproduction of basal bodies. The uncovered inhibitory role of Sfr1 in basal body production suggests that centrin-binding proteins, as well as centrins, may influence basal body number both positively and negatively.
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11
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Waclawek E, Joachimiak E, Hall MH, Fabczak H, Wloga D. Regulation of katanin activity in the ciliate Tetrahymena thermophila. Mol Microbiol 2016; 103:134-150. [PMID: 27726198 DOI: 10.1111/mmi.13547] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2016] [Indexed: 01/10/2023]
Abstract
Katanin is a microtubule severing protein that functions as a heterodimer composed of an AAA domain catalytic subunit, p60, and a regulatory subunit, a WD40 repeat protein, p80. Katanin-dependent severing of microtubules is important for proper execution of key cellular activities including cell division, migration, and differentiation. Published data obtained in Caenorhabditis elegans, Xenopus and mammals indicate that katanin is regulated at multiple levels including transcription, posttranslational modifications (of both katanin and microtubules) and degradation. Little is known about how katanin is regulated in unicellular organisms. Here we show that in the ciliated protist Tetrahymena thermophila, as in Metazoa, the localization and activity of katanin requires specific domains of both p60 and p80, and that the localization of p60, but not p80, is sensitive to the levels of microtubule glutamylation. A prolonged overexpression of either a full length, or a fragment of p80 containing WD40 repeats, partly phenocopies a knockout of p60, indicating that in addition to its activating role, p80 could also contribute to the inhibition of p60. We also show that the level of p80 depends on the 26S proteasome activity.
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Affiliation(s)
- Ewa Waclawek
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str, Warsaw, 02-093, Poland
| | - Ewa Joachimiak
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str, Warsaw, 02-093, Poland
| | - Malgorzata Hanna Hall
- Laboratory of Molecular and Systemic Neuromorphology, Department of Neurophysiology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str, Warsaw, 02-093, Poland
| | - Hanna Fabczak
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str, Warsaw, 02-093, Poland
| | - Dorota Wloga
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str, Warsaw, 02-093, Poland
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12
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Membrane dynamics at the nuclear exchange junction during early mating (one to four hours) in the ciliate Tetrahymena thermophila. EUKARYOTIC CELL 2014; 14:116-27. [PMID: 25107923 DOI: 10.1128/ec.00164-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Using serial-section transmission electron microscopy and three-dimensional (3D) electron tomography, we characterized membrane dynamics that accompany the construction of a nuclear exchange junction between mating cells in the ciliate Tetrahymena thermophila. Our methods revealed a number of previously unknown features. (i) Membrane fusion is initiated by the extension of hundreds of 50-nm-diameter protrusions from the plasma membrane. These protrusions extend from both mating cells across the intercellular space to fuse with membrane of the mating partner. (ii) During this process, small membrane-bound vesicles or tubules are shed from the plasma membrane and into the extracellular space within the junction. The resultant vesicle-filled pockets within the extracellular space are referred to as junction lumens. (iii) As junction lumens fill with extracellular microvesicles and swell, the plasma membrane limiting these swellings undergoes another deformation, pinching off vesicle-filled vacuoles into the cytoplasm (reclamation). (iv) These structures (resembling multivesicular bodies) seem to associate with autophagosomes abundant near the exchange junction. We propose a model characterizing the membrane-remodeling events that establish cytoplasmic continuity between mating Tetrahymena cells. We also discuss the possible role of nonvesicular lipid transport in conditioning the exchange junction lipid environment. Finally, we raise the possibility of an intercellular signaling mechanism involving microvesicle shedding and uptake.
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13
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Abstract
In this chapter we discuss the latest developments in the field of high-pressure freezing (HPF). The Leica HPF machine EM HPM100 is discussed in detail due to significant changes compared to its predecessor model. Its centerpiece is a multipart polymer cartridge which holds the specimen carrier sandwich and guides it automatically through the freezing process until immersed in liquid nitrogen. The cartridge can be adapted to the specimen and carrier geometry to optimize the flow of liquid nitrogen and hence rapid cooling. Dedicated cartridges are available for a variety of different carriers, including carriers for samples of up to 5 mm in diameter. Cartridge-specific handling and carrier assemblies are described extensively for freezing samples in aluminum specimen carriers, cell cultures grown on Sapphire discs, suspensions for freeze-fracturing, and specimens for cryo-sectioning. Additionally, we include an advanced technique to freeze monolayer cell cultures on Sapphire discs with the Leica EM PACT2 HPF machine using a composite carrier.
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Affiliation(s)
- Andres Kaech
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
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14
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Ross I, Clarissa C, Giddings TH, Winey M. ε-tubulin is essential in Tetrahymena thermophila for the assembly and stability of basal bodies. J Cell Sci 2013; 126:3441-51. [PMID: 23704354 DOI: 10.1242/jcs.128694] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Basal bodies and centrioles are conserved microtubule-based organelles the improper assembly of which leads to a number of diseases, including ciliopathies and cancer. Tubulin family members are conserved components of these structures that are integral to their proper formation and function. We have identified the ε-tubulin gene in Tetrahymena thermophila and detected the protein, through fluorescence of a tagged allele, to basal bodies. Immunoelectron microscopy has shown that ε-tubulin localizes primarily to the core microtubule scaffold. A complete genomic knockout of ε-tubulin has revealed that it is an essential gene required for the assembly and maintenance of the triplet microtubule blades of basal bodies. We have conducted site-directed mutagenesis of the ε-tubulin gene and shown that residues within the nucleotide-binding domain, longitudinal interacting domains, and C-terminal tail are required for proper function. A single amino acid change of Thr150, a conserved residue in the nucleotide-binding domain, to Val is a conditional mutation that results in defects in the spatial and temporal assembly of basal bodies as well as their stability. We have genetically separated functions for the domains of ε-tubulin and identified a novel role for the nucleotide-binding domain in the regulation of basal body assembly and stability.
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Affiliation(s)
- Ian Ross
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado-Boulder, Boulder, CO 80309, USA
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15
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Stemm-Wolf AJ, Meehl JB, Winey M. Sfr13, a member of a large family of asymmetrically localized Sfi1-repeat proteins, is important for basal body separation and stability in Tetrahymena thermophila. J Cell Sci 2013; 126:1659-71. [PMID: 23426847 DOI: 10.1242/jcs.120238] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Directed fluid flow, which is achieved by the coordinated beating of motile cilia, is required for processes as diverse as cellular swimming, developmental patterning and mucus clearance. Cilia are nucleated, anchored and aligned at the plasma membrane by basal bodies, which are cylindrical microtubule-based structures with ninefold radial symmetry. In the unicellular ciliate Tetrahymena thermophila, two centrin family members associated with the basal body are important for both basal body organization and stabilization. We have identified a family of 13 proteins in Tetrahymena that contain centrin-binding repeats related to those identified in the Saccharomyces cerevisiae Sfi1 protein. We have named these proteins Sfr1-Sfr13 (for Sfi1-repeat). Nine of the Sfr proteins localize in unique polarized patterns surrounding the basal body, suggesting non-identical roles in basal body organization and association with basal body accessory structures. Furthermore, the Sfr proteins are found in distinct basal body populations in Tetrahymena cells, indicating that they are responsive to particular developmental programs. A complete genetic deletion of one of the family members, Sfr13, causes unstable basal bodies and defects in daughter basal body separation from the mother, phenotypes also observed with centrin disruption. It is likely that the other Sfr family members are involved in distinct centrin functions, providing specificity to the tasks that centrins perform at basal bodies.
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Affiliation(s)
- Alexander J Stemm-Wolf
- Department of Molecular, Cellular and Developmental Biology, University of Colorado - Boulder, Boulder, CO 80309, USA
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16
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Vonderfecht T, Cookson MW, Giddings TH, Clarissa C, Winey M. The two human centrin homologues have similar but distinct functions at Tetrahymena basal bodies. Mol Biol Cell 2012; 23:4766-77. [PMID: 23087207 PMCID: PMC3521684 DOI: 10.1091/mbc.e12-06-0454] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Centrins are a ubiquitous family of small Ca(2+)-binding proteins found at basal bodies that are placed into two groups based on sequence similarity to the human centrins 2 and 3. Analyses of basal body composition in different species suggest that they contain a centrin isoform from each group. We used the ciliate protist Tetrahymena thermophila to gain a better understanding of the functions of the two centrin groups and to determine their potential redundancy. We have previously shown that the Tetrahymena centrin 1 (Cen1), a human centrin 2 homologue, is required for proper basal body function. In this paper, we show that the Tetrahymena centrin 2 (Cen2), a human centrin 3 homologue, has functions similar to Cen1 in basal body orientation, maintenance, and separation. The two are, however, not redundant. A further examination of human centrin 3 homologues shows that they function in a manner distinct from human centrin 2 homologues. Our data suggest that basal bodies require a centrin from both groups in order to function correctly.
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Affiliation(s)
- Tyson Vonderfecht
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado-Boulder, Boulder, CO 80309, USA
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17
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Kurth T, Wiedmer S, Entzeroth R. Improvement of Ultrastructural Preservation of Eimeria Oocysts by Microwave-assisted Chemical Fixation or by High Pressure Freezing and Freeze Substitution. Protist 2012; 163:296-305. [DOI: 10.1016/j.protis.2011.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 05/14/2011] [Indexed: 11/24/2022]
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18
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Fisch C, Dupuis-Williams P. [The rebirth of the ultrastructure of cilia and flagella]. Biol Aujourdhui 2012; 205:245-67. [PMID: 22251859 DOI: 10.1051/jbio/2011023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Indexed: 11/14/2022]
Abstract
The sensory and motility functions of eukaryotic cilia and flagella are essential for cell survival in protozoans and for cell differentiation and homoeostasis in metazoans. Ciliary biology has benefited early on from the input of electron microscopy. Over the last decade, the visualization of cellular structures has greatly progressed, thus it becomes timely to review the ultrastructure of cilia and flagella. Briefly touching upon the typical features of a 9+2 axoneme, we dwell extensively on the transition zone, the singlet zone, the ciliary necklace, cap and crown. The relation of the singlet zone to sensory and/or motile function, the link of the ciliary cap to microtubule dynamics and to ciliary beat, the involvement of the ciliary crown in ovocyte and mucosal propulsion, and the role of the transition zone/the ciliary necklace in axonemal stabilization, autotomy and as a diffusion barrier will all be discussed.
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Affiliation(s)
- Cathy Fisch
- ATIGE Centriole et Pathologies Associées, INSERM/UEVE U829, 91000 Évry, France.
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19
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Winey M, Stemm-Wolf AJ, Giddings TH, Pearson CG. Cytological analysis of Tetrahymena thermophila. Methods Cell Biol 2012; 109:357-78. [PMID: 22444152 DOI: 10.1016/b978-0-12-385967-9.00013-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Since their first detection in pond water, large ciliates such as Tetrahymena thermophila, have captivated school children and scientists alike with the elegance of their swimming and the beauty of their cortical organization. Indeed, cytology - simply looking at cells - is an important component of most areas of study in cell biology and is particularly intriguing in the large, complex Tetrahymena cell. Cytological analysis of Tetrahymena is critical for the study of the microtubule cytoskeleton, membrane trafficking, complex nuclear movements and interactions, and the cellular remodeling during conjugation, to name a few topics. We briefly review previously reported cytological techniques for both light and electron microscopy, and point the reader to resources to learn about those protocols. We go on to present new and emerging technologies for the study of these marvelous cells. These include the use of fluorescent-protein tagging to localize cellular components in live cells, as well as for tracking the dynamic behavior of proteins using pulse labeling and fluorescence recovery after photobleaching. For electron microscopy, cellular and antigenic preservation has been improved with the use of cryofixation and freeze-substitution. The technologies described here advance Tetrahymena cell biology to the cutting-edge of cytological analysis.
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Affiliation(s)
- Mark Winey
- MCD Biology, University of Colorado at Boulder, 347 UCB, Boulder, Colorado 80309-0347, USA
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20
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Wloga D, Frankel J. From Molecules to Morphology: Cellular Organization of Tetrahymena thermophila. Methods Cell Biol 2012; 109:83-140. [DOI: 10.1016/b978-0-12-385967-9.00005-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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21
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Bouchet-Marquis C, Pagratis M, Kirmse R, Hoenger A. Metallothionein as a clonable high-density marker for cryo-electron microscopy. J Struct Biol 2012; 177:119-27. [PMID: 22068155 PMCID: PMC3261350 DOI: 10.1016/j.jsb.2011.10.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 11/24/2022]
Abstract
Cryo-electron microscopy is expanding its scope from macromolecules towards much larger and more complex cellular specimens such as organelles, cells and entire tissues. While isolated macromolecular specimens are typically composed of only very few different components that may be recognized by their shape, size or state of polymerization, cellular specimens combine large numbers of proteinaceous structures as well as nucleic acids and lipid arrays. Consequently, an unambiguous identification of these structures within the context of a whole cell may create a very difficult challenge. On plastic-embedded specimens, or Tokuyasu sections (Tokuyasu, 1980), epitopes that are exposed at the surface can be tagged by antibodies. However, vitrified sections have to be kept at strict cryo-conditions (below -140 °C) and therefore do not allow any post-sectioning treatment of the specimens other than data acquisition in the microscope. Hence, the labels have to be placed into the specimen before freezing. Here we report on the application of a small metal-clustering protein, metallothionein (MTH), as a clonable label capable of clustering metal atoms into a high-density particle with high spatial resolution. We tested MTH as a label for kinesin-decorated microtubules (MTs) as well as the building blocks of desmin intermediate filaments (IFs).
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Affiliation(s)
| | | | | | - Andreas Hoenger
- Dept. of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder CO, 80309-0347, USA
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22
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Li S, Fernandez JJ, Marshall WF, Agard DA. Three-dimensional structure of basal body triplet revealed by electron cryo-tomography. EMBO J 2011; 31:552-62. [PMID: 22157822 PMCID: PMC3273388 DOI: 10.1038/emboj.2011.460] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Accepted: 11/15/2011] [Indexed: 12/03/2022] Open
Abstract
The basal body, derived from the centriole, is a microtubule-organizing organelle that nucleates the cilium in non-dividing cells. Cryo-electron tomography reveals the overall structure of this organelle, and provides insights its biogenesis and function. Basal bodies and centrioles play central roles in microtubule (MT)-organizing centres within many eukaryotes. They share a barrel-shaped cylindrical structure composed of nine MT triplet blades. Here, we report the structure of the basal body triplet at 33 Å resolution obtained by electron cryo-tomography and 3D subtomogram averaging. By fitting the atomic structure of tubulin into the EM density, we built a pseudo-atomic model of the tubulin protofilaments at the core of the triplet. The 3D density map reveals additional densities that represent non-tubulin proteins attached to the triplet, including a large inner circular structure in the basal body lumen, which functions as a scaffold to stabilize the entire basal body barrel. We found clear longitudinal structural variations along the basal body, suggesting a sequential and coordinated assembly mechanism. We propose a model in which δ-tubulin and other components participate in the assembly of the basal body.
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Affiliation(s)
- Sam Li
- The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158-2517, USA
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23
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Abstract
Eukaryotic cilia and flagella perform motility and sensory functions which are essential for cell survival in protozoans, and to organism development and homoeostasis in metazoans. Their ultrastructure has been studied from the early beginnings of electron microscopy, and these studies continue to contribute to much of our understanding about ciliary biology. In the light of the progress made in the visualization of cellular structures over the last decade, we revisit the ultrastructure of cilia and flagella. We briefly describe the typical features of a 9+2 axoneme before focusing extensively on the transition zone, the ciliary necklace, the singlet zone, the ciliary cap and the ciliary crown. We discuss how the singlet zone is linked to sensory and/or motile function, the contribution of the ciliary crown to ovocyte and mucosal propulsion, and the relationship between the ciliary cap and microtubule growth and shortening, and its relation to ciliary beat. We further examine the involvement of the transition zone/the ciliary necklace in axonemal stabilization, autotomy and as a diffusion barrier.
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24
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Vonderfecht T, Stemm-Wolf AJ, Hendershott M, Giddings TH, Meehl JB, Winey M. The two domains of centrin have distinct basal body functions in Tetrahymena. Mol Biol Cell 2011; 22:2221-34. [PMID: 21562224 PMCID: PMC3128525 DOI: 10.1091/mbc.e11-02-0151] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 04/15/2011] [Accepted: 04/29/2011] [Indexed: 11/11/2022] Open
Abstract
The basal body is a microtubule-organizing center responsible for organizing the cilium, a structure important for cell locomotion and sensing of the surrounding environment. A widely conserved basal body component is the Ca(2+)-binding protein centrin. Analyses of centrin function suggest a role in basal body assembly and stability; however, its molecular mechanisms remain unclear. Here we describe a mutagenic strategy to study the function and essential nature of the various structural features of Cen1 in the ciliate Tetrahymena. We find that the two domains of Cen1 are both essential, and examination of strains containing mutant CEN1 alleles indicates that there are two predominant basal body phenotypes: misorientation of newly assembled basal bodies and stability defects. The results also show that the two domains of Cen1 are able to bind Ca(2+) and that perturbation of Ca(2+) binding affects Cen1 function. In all, the data suggest that the two domains of Cen1 have distinct functions.
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Affiliation(s)
- Tyson Vonderfecht
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado–Boulder, Boulder, CO 80309
| | - Alexander J. Stemm-Wolf
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado–Boulder, Boulder, CO 80309
| | | | - Thomas H. Giddings
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado–Boulder, Boulder, CO 80309
| | - Janet B. Meehl
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado–Boulder, Boulder, CO 80309
| | - Mark Winey
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado–Boulder, Boulder, CO 80309
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