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KENGAKU M. Cytoskeletal control of nuclear migration in neurons and non-neuronal cells. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2018; 94:337-349. [PMID: 30416174 PMCID: PMC6275330 DOI: 10.2183/pjab.94.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 09/10/2018] [Indexed: 06/09/2023]
Abstract
Cell migration is a complex molecular event that requires translocation of a large, stiff nucleus, oftentimes through interstitial pores of submicron size in tissues. Remarkable progress in the past decade has uncovered an ever-increasing array of diverse nuclear dynamics and underlying cytoskeletal control in various cell models. In many cases, the microtubule motors dynein and kinesin directly interact with the nucleus via the LINC complex and steer directional nuclear movement, while actomyosin contractility and its global flow exert forces to deform and move the nucleus. In this review, I focus on the synergistic interplay of the cytoskeletal motors and spatiotemporal sites of force transmission in various nuclear migration models, with a special focus on neuronal migration in the vertebrate brain.
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Affiliation(s)
- Mineko KENGAKU
- Kyoto University Institute for Advanced Study, Institute for Integrated Cell-Material Sciences (KUIAS-iCeMS), Kyoto University, Japan
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52
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Bernard F, Lepesant JA, Guichet A. Nucleus positioning within Drosophila egg chamber. Semin Cell Dev Biol 2017; 82:25-33. [PMID: 29056490 DOI: 10.1016/j.semcdb.2017.10.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/09/2017] [Accepted: 10/12/2017] [Indexed: 12/12/2022]
Abstract
Both types of Drosophila egg chamber germ cells, i.e. oocyte and nurse cells, have to control their nucleus positions in order to produce a viable gamete. Interestingly, while actin microfilaments are crucial to position the nuclei in nurse cells, these are the microtubules that are important for oocyte nucleus to migrate and adopt the correct position. In this review, we discuss the mechanisms underlying these positioning processes in the two cell types with respect to the organization and dynamics of the actin and microtubule skeleton. In the nurse cells it is essential to keep firmly the nuclei in a central position to prevent them from obstructing the ring canals when the cytoplasmic content of the cells is dumped into the oocyte cells toward the end of oogenesis. This is achieved by the assembly of thick filopodia-like actin cables anchored to the plasma membrane, which grow inwardly and eventually encase tightly the nuclei in a cage-like structure. In the oocyte, the migration at an early stage of oogenesis of the nucleus from a posterior location to an anchorage site at an asymmetric anterior position, is an essential step in the setting up of the dorsoventral polarity axis of the future embryo. This process is controlled by an interplay between MT networks that just start to be untangled. Although both mechanisms have evolved to fulfill cell-type specific cell processes in the context of fly oogenesis, interesting parallels can be drawn with other nuclear positioning mechanisms in the mouse oocyte and the developing muscle respectively.
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Affiliation(s)
- Fred Bernard
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
| | - Jean-Antoine Lepesant
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
| | - Antoine Guichet
- Institut Jacques Monod, CNRS UMR 7592, Université Paris-Diderot, Sorbonne Paris Cité, 75205, Paris Cedex, France.
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53
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Roman W, Martins JP, Carvalho FA, Voituriez R, Abella JV, Santos NC, Cadot B, Way M, Gomes ER. Myofibril contraction and crosslinking drive nuclear movement to the periphery of skeletal muscle. Nat Cell Biol 2017; 19:1189-1201. [PMID: 28892082 PMCID: PMC5675053 DOI: 10.1038/ncb3605] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 08/04/2017] [Indexed: 12/17/2022]
Abstract
Nuclear movements are important for multiple cellular functions, and are driven by polarized forces generated by motor proteins and the cytoskeleton. During skeletal myofibre formation or regeneration, nuclei move from the centre to the periphery of the myofibre for proper muscle function. Centrally located nuclei are also found in different muscle disorders. Using theoretical and experimental approaches, we demonstrate that nuclear movement to the periphery of myofibres is mediated by centripetal forces around the nucleus. These forces arise from myofibril contraction and crosslinking that 'zip' around the nucleus in combination with tight regulation of nuclear stiffness by lamin A/C. In addition, an Arp2/3 complex containing Arpc5L together with γ-actin is required to organize desmin to crosslink myofibrils for nuclear movement. Our work reveals that centripetal forces exerted by myofibrils squeeze the nucleus to the periphery of myofibres.
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Affiliation(s)
- William Roman
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France; Centre de Référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal
| | - Joao P. Martins
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal
| | - Filomena A. Carvalho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal
| | - Raphael Voituriez
- Laboratoire de Physique Théorique de la Matière Condensée; CNRS UMR 7600; Université Pierre et Marie Curie, Paris , France
- Laboratoire Jean Perrin; CNRS FRE 3231, Université Pierre et Marie Curie ; Paris, France
| | - Jasmine V.G. Abella
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK
| | - Nuno C. Santos
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal
| | - Bruno Cadot
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France; Centre de Référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Michael Way
- Cellular Signalling and Cytoskeletal Function, The Francis Crick Institute, 44 Lincoln’s Inn Fields, London, WC2A 3LY, UK
| | - Edgar R. Gomes
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, GH Pitié-Salpêtrière, 47 Boulevard de l'hôpital, 75013 Paris, France; Centre de Référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal
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54
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Voelzmann A, Liew YT, Qu Y, Hahn I, Melero C, Sánchez-Soriano N, Prokop A. Drosophila Short stop as a paradigm for the role and regulation of spectraplakins. Semin Cell Dev Biol 2017; 69:40-57. [DOI: 10.1016/j.semcdb.2017.05.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/22/2017] [Accepted: 05/29/2017] [Indexed: 02/07/2023]
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Abstract
Moving the nucleus to a specific position within the cell is an important event during many cell and developmental processes. Several different molecular mechanisms exist to position nuclei in various cell types. In this Commentary, we review the recent progress made in elucidating mechanisms of nuclear migration in a variety of important developmental models. Genetic approaches to identify mutations that disrupt nuclear migration in yeast, filamentous fungi, Caenorhabditis elegans, Drosophila melanogaster and plants led to the identification of microtubule motors, as well as Sad1p, UNC-84 (SUN) domain and Klarsicht, ANC-1, Syne homology (KASH) domain proteins (LINC complex) that function to connect nuclei to the cytoskeleton. We focus on how these proteins and various mechanisms move nuclei during vertebrate development, including processes related to wound healing of fibroblasts, fertilization, developing myotubes and the developing central nervous system. We also describe how nuclear migration is involved in cells that migrate through constricted spaces. On the basis of these findings, it is becoming increasingly clear that defects in nuclear positioning are associated with human diseases, syndromes and disorders.
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Affiliation(s)
- Courtney R Bone
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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56
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Vleugel M, Kok M, Dogterom M. Understanding force-generating microtubule systems through in vitro reconstitution. Cell Adh Migr 2017; 10:475-494. [PMID: 27715396 PMCID: PMC5079405 DOI: 10.1080/19336918.2016.1241923] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Microtubules switch between growing and shrinking states, a feature known as dynamic instability. The biochemical parameters underlying dynamic instability are modulated by a wide variety of microtubule-associated proteins that enable the strict control of microtubule dynamics in cells. The forces generated by controlled growth and shrinkage of microtubules drive a large range of processes, including organelle positioning, mitotic spindle assembly, and chromosome segregation. In the past decade, our understanding of microtubule dynamics and microtubule force generation has progressed significantly. Here, we review the microtubule-intrinsic process of dynamic instability, the effect of external factors on this process, and how the resulting forces act on various biological systems. Recently, reconstitution-based approaches have strongly benefited from extensive biochemical and biophysical characterization of individual components that are involved in regulating or transmitting microtubule-driven forces. We will focus on the current state of reconstituting increasingly complex biological systems and provide new directions for future developments.
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Affiliation(s)
- Mathijs Vleugel
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
| | - Maurits Kok
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
| | - Marileen Dogterom
- a Department of Bionanoscience , Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft Institute of Technology , Delft , The Netherlands
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57
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Elkouby YM, Mullins MC. Coordination of cellular differentiation, polarity, mitosis and meiosis - New findings from early vertebrate oogenesis. Dev Biol 2017; 430:275-287. [PMID: 28666956 DOI: 10.1016/j.ydbio.2017.06.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 06/23/2017] [Accepted: 06/26/2017] [Indexed: 12/21/2022]
Abstract
A mechanistic dissection of early oocyte differentiation in vertebrates is key to advancing our knowledge of germline development, reproductive biology, the regulation of meiosis, and all of their associated disorders. Recent advances in the field include breakthroughs in the identification of germline stem cells in Medaka, in the cellular architecture of the germline cyst in mice, in a mechanistic dissection of chromosomal pairing and bouquet formation in meiosis in mice, in tracing oocyte symmetry breaking to the chromosomal bouquet of meiosis in zebrafish, and in the biology of the Balbiani body, a universal oocyte granule. Many of the major events in early oogenesis are universally conserved, and some are co-opted for species-specific needs. The chromosomal events of meiosis are of tremendous consequence to gamete formation and have been extensively studied. New light is now being shed on other aspects of early oocyte differentiation, which were traditionally considered outside the scope of meiosis, and their coordination with meiotic events. The emerging theme is of meiosis as a common groundwork for coordinating multifaceted processes of oocyte differentiation. In an accompanying manuscript we describe methods that allowed for investigations in the zebrafish ovary to contribute to these breakthroughs. Here, we review these advances mostly from the zebrafish and mouse. We discuss oogenesis concepts across established model organisms, and construct an inclusive paradigm for early oocyte differentiation in vertebrates.
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Affiliation(s)
- Yaniv M Elkouby
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Mary C Mullins
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
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58
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Tariq Z, Zhang H, Chia-Liu A, Shen Y, Gete Y, Xiong ZM, Tocheny C, Campanello L, Wu D, Losert W, Cao K. Lamin A and microtubules collaborate to maintain nuclear morphology. Nucleus 2017; 8:433-446. [PMID: 28557611 DOI: 10.1080/19491034.2017.1320460] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Lamin A (LA) is a critical structural component of the nuclear lamina. Mutations within the LA gene (LMNA) lead to several human disorders, most striking of which is Hutchinson-Gilford Progeria Syndrome (HGPS), a premature aging disorder. HGPS cells are best characterized by an abnormal nuclear morphology known as nuclear blebbing, which arises due to the accumulation of progerin, a dominant mutant form of LA. The microtubule (MT) network is known to mediate changes in nuclear morphology in the context of specific events such as mitosis, cell polarization, nucleus positioning and cellular migration. What is less understood is the role of the microtubule network in determining nuclear morphology during interphase. In this study, we elucidate the role of the cytoskeleton in regulation and misregulation of nuclear morphology through perturbations of both the lamina and the microtubule network. We found that LA knockout cells exhibit a crescent shape morphology associated with the microtubule-organizing center. Furthermore, this crescent shape ameliorates upon treatment with MT drugs, Nocodazole or Taxol. Expression of progerin, in LA knockout cells also rescues the crescent shape, although the response to Nocodazole or Taxol treatment is altered in comparison to cells expressing LA. Together these results describe a collaborative effort between LA and the MT network to maintain nuclear morphology.
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Affiliation(s)
- Zeshan Tariq
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
| | - Haoyue Zhang
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
| | - Alexander Chia-Liu
- b Department of Physics , University of Maryland , College Park , MD , USA
| | - Yang Shen
- b Department of Physics , University of Maryland , College Park , MD , USA
| | - Yantenew Gete
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
| | - Zheng-Mei Xiong
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
| | - Claire Tocheny
- c Department of Biology , The College of William and Mary , Williamsburg , VA , USA
| | - Leonard Campanello
- b Department of Physics , University of Maryland , College Park , MD , USA
| | - Di Wu
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
| | - Wolfgang Losert
- b Department of Physics , University of Maryland , College Park , MD , USA
| | - Kan Cao
- a Department of Cell Biology and Molecular Genetics , University of Maryland , College Park , MD , USA
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59
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Distinct molecular cues ensure a robust microtubule-dependent nuclear positioning in the Drosophila oocyte. Nat Commun 2017; 8:15168. [PMID: 28447612 PMCID: PMC5414183 DOI: 10.1038/ncomms15168] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 03/02/2017] [Indexed: 11/08/2022] Open
Abstract
Controlling nucleus localization is crucial for a variety of cellular functions. In the Drosophila oocyte, nuclear asymmetric positioning is essential for the reorganization of the microtubule (MT) network that controls the polarized transport of axis determinants. A combination of quantitative three-dimensional live imaging and laser ablation-mediated force analysis reveal that nuclear positioning is ensured with an unexpected level of robustness. We show that the nucleus is pushed to the oocyte antero-dorsal cortex by MTs and that its migration can proceed through distinct tracks. Centrosome-associated MTs favour one migratory route. In addition, the MT-associated protein Mud/NuMA that is asymmetrically localized in an Asp-dependent manner at the nuclear envelope hemisphere where MT nucleation is higher promotes a separate route. Our results demonstrate that centrosomes do not provide an obligatory driving force for nuclear movement, but together with Mud, contribute to the mechanisms that ensure the robustness of asymmetric nuclear positioning. Asymmetric nuclear positioning in the fruit fly oocyte is essential for the correct localization of axis determinants. Here, the authors show that different microtubule-dependent mechanisms contribute to nuclear transport and ensure the robustness of nuclear positioning.
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60
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Spencer AK, Schaumberg AJ, Zallen JA. Scaling of cytoskeletal organization with cell size in Drosophila. Mol Biol Cell 2017; 28:1519-1529. [PMID: 28404752 PMCID: PMC5449150 DOI: 10.1091/mbc.e16-10-0691] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022] Open
Abstract
Actin-rich denticle precursors are regularly distributed in the Drosophila embryo. Cytoskeletal scaling occurs through changes in denticle number and spacing. Denticle spacing scales with cell length over a 10-fold range. Accurate denticle positioning requires the microtubule cytoskeleton. Spatially organized macromolecular complexes are essential for cell and tissue function, but the mechanisms that organize micron-scale structures within cells are not well understood. Microtubule-based structures such as mitotic spindles scale with cell size, but less is known about the scaling of actin structures within cells. Actin-rich denticle precursors cover the ventral surface of the Drosophila embryo and larva and provide templates for cuticular structures involved in larval locomotion. Using quantitative imaging and statistical modeling, we demonstrate that denticle number and spacing scale with cell length over a wide range of cell sizes in embryos and larvae. Denticle number and spacing are reduced under space-limited conditions, and both features robustly scale over a 10-fold increase in cell length during larval growth. We show that the relationship between cell length and denticle spacing can be recapitulated by specific mathematical equations in embryos and larvae and that accurate denticle spacing requires an intact microtubule network and the microtubule minus end–binding protein, Patronin. These results identify a novel mechanism of microtubule-dependent actin scaling that maintains precise patterns of actin organization during tissue growth.
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Affiliation(s)
- Alison K Spencer
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences.,Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Andrew J Schaumberg
- Weill Cornell Graduate School of Medical Sciences and the Tri-Institutional PhD Program in Computational Biology and Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Jennifer A Zallen
- Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
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61
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Kandel ME, Teng KW, Selvin PR, Popescu G. Label-Free Imaging of Single Microtubule Dynamics Using Spatial Light Interference Microscopy. ACS NANO 2017; 11:647-655. [PMID: 27997798 DOI: 10.1021/acsnano.6b06945] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Due to their diameter, of only 24 nm, single microtubules are extremely challenging to image without the use of extrinsic contrast agents. As a result, fluorescence tagging is the common method to visualize their motility. However, such investigation is limited by photobleaching and phototoxicity. We experimentally demonstrate the capability of combining label-free spatial light interference microscopy (SLIM) with numerical processing for imaging single microtubules in a gliding assay. SLIM combines four different intensity images to obtain the optical path length map associated with the sample. Because of the use of broadband fields, the sensitivity to path length is better than 1 nm without (temporal) averaging and better than 0.1 nm upon averaging. Our results indicate that SLIM can image the dynamics of microtubules in a full field of view, of 200 × 200 μm2, over many hours. Modeling the microtubule transport via the diffusion-advection equation, we found that the dispersion relation yields the standard deviation of the velocity distribution, without the need for tracking individual tubes. Interestingly, during a 2 h window, the microtubules begin to decelerate, at 100 pm/s2 over a 20 min period. Thus, SLIM is likely to serve as a useful tool for understanding molecular motor activity, especially over large time scales, where fluorescence methods are of limited utility.
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Affiliation(s)
- Mikhail E Kandel
- Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute of Advanced Science and Technology, ‡Center for the Physics of Living Cells, §Center for Biophysics and Quantitative Biology, ∥Department of Physics, and ⊥Department of Bioengineering, University of Illinois , Urbana, Illinois 61801, United States
| | - Kai Wen Teng
- Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute of Advanced Science and Technology, ‡Center for the Physics of Living Cells, §Center for Biophysics and Quantitative Biology, ∥Department of Physics, and ⊥Department of Bioengineering, University of Illinois , Urbana, Illinois 61801, United States
| | - Paul R Selvin
- Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute of Advanced Science and Technology, ‡Center for the Physics of Living Cells, §Center for Biophysics and Quantitative Biology, ∥Department of Physics, and ⊥Department of Bioengineering, University of Illinois , Urbana, Illinois 61801, United States
| | - Gabriel Popescu
- Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute of Advanced Science and Technology, ‡Center for the Physics of Living Cells, §Center for Biophysics and Quantitative Biology, ∥Department of Physics, and ⊥Department of Bioengineering, University of Illinois , Urbana, Illinois 61801, United States
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62
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Dehghani M, Lasko P. Multiple Functions of the DEAD-Box Helicase Vasa in Drosophila Oogenesis. Results Probl Cell Differ 2017; 63:127-147. [PMID: 28779316 DOI: 10.1007/978-3-319-60855-6_6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The DEAD-box helicase Vasa (Vas) has been most extensively studied in the fruit fly, Drosophila melanogaster, and numerous roles for it in germline development have been discovered. Here, we summarize the present state of knowledge about processes during oogenesis that involve Vas, as well as functions of Vas as a maternal determinant of embryonic spatial patterning and germ cell specification. We review literature that implicates Vas in Piwi-interacting RNA (piRNA) biogenesis in germline cells and in regulating mitosis in germline stem cells (GSCs). We describe the functions of Vas in translational activation of two mRNAs, gurken (grk) and mei-P26, which encode proteins that are important regulators of developmental processes, as Grk specifies both the dorsal-ventral and the anterior-posterior axis of the embryo and Mei-P26 promotes GSC differentiation. The role of Vas in assembly of polar granules, ribonucleoprotein particles that accumulate in the posterior pole plasm of the oocyte and are essential for germ cell specification and posterior embryonic patterning, is also described.
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Affiliation(s)
- Mehrnoush Dehghani
- Department of Biology, McGill University, 3649 Promenade Sir William Osler, Montréal, Québec, Canada, H3G 0B1
| | - Paul Lasko
- Department of Biology, McGill University, 3649 Promenade Sir William Osler, Montréal, Québec, Canada, H3G 0B1.
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63
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Nieuwburg R, Nashchekin D, Jakobs M, Carter AP, Khuc Trong P, Goldstein RE, St Johnston D. Localised dynactin protects growing microtubules to deliver oskar mRNA to the posterior cortex of the Drosophila oocyte. eLife 2017; 6:e27237. [PMID: 29035202 PMCID: PMC5643094 DOI: 10.7554/elife.27237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 09/19/2017] [Indexed: 11/13/2022] Open
Abstract
The localisation of oskar mRNA to the posterior of the Drosophila oocyte defines where the abdomen and germ cells form in the embryo. Kinesin 1 transports oskar mRNA to the oocyte posterior along a polarised microtubule cytoskeleton that grows from non-centrosomal microtubule organising centres (ncMTOCs) along the anterior/lateral cortex. Here, we show that the formation of this polarised microtubule network also requires the posterior regulation of microtubule growth. A missense mutation in the dynactin Arp1 subunit causes most oskar mRNA to localise in the posterior cytoplasm rather than cortically. oskar mRNA transport and anchoring are normal in this mutant, but the microtubules fail to reach the posterior pole. Thus, dynactin acts as an anti-catastrophe factor that extends microtubule growth posteriorly. Kinesin 1 transports dynactin to the oocyte posterior, creating a positive feedback loop that increases the length and persistence of the posterior microtubules that deliver oskar mRNA to the cortex.
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Affiliation(s)
- Ross Nieuwburg
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Dmitry Nashchekin
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Maximilian Jakobs
- The Department of Physiology, Development and NeuroscienceUniversity of CambridgeCambridgeUnited Kingdom
| | - Andrew P Carter
- Division of Structural StudiesMedical Research Council, Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Philipp Khuc Trong
- Department of Applied Mathematics and Theoretical PhysicsUniversity of Cambridge, Centre for Mathematical SciencesCambridgeUnited Kingdom
| | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical PhysicsUniversity of Cambridge, Centre for Mathematical SciencesCambridgeUnited Kingdom
| | - Daniel St Johnston
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
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64
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Chaigne A, Terret ME, Verlhac MH. Asymmetries and Symmetries in the Mouse Oocyte and Zygote. Results Probl Cell Differ 2017; 61:285-299. [PMID: 28409310 DOI: 10.1007/978-3-319-53150-2_13] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mammalian oocytes grow periodically after puberty thanks to the dialogue with their niche in the follicle. This communication between somatic and germ cells promotes the accumulation, inside the oocyte, of maternal RNAs, proteins and other molecules that will sustain the two gamete divisions and early embryo development up to its implantation. In order to preserve their stock of maternal products, oocytes from all species divide twice minimizing the volume of their daughter cells to their own benefit. For this, they undergo asymmetric divisions in size where one main objective is to locate the division spindle with its chromosomes off-centred. In this chapter, we will review how this main objective is reached with an emphasis on the role of actin microfilaments in this process in mouse oocytes, the most studied example in mammals. This chapter is subdivided into three parts: I-General features of asymmetric divisions in mouse oocytes, II-Mechanism of chromosome positioning by actin in mouse oocytes and III-Switch from asymmetric to symmetric division at the oocyte-to-embryo transition.
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Affiliation(s)
- Agathe Chaigne
- MRC Laboratory for Molecular Cell Biology, UCL, London, WC1E 6BT, UK.,Institute for the Physics of Living Systems, UCL, London, WC1E 6BT, UK
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65
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Abstract
Localized mRNA translation is a widespread mechanism for targeting protein synthesis, important for cell fate, motility and pathogenesis. In Drosophila, the spatiotemporal control of gurken/TGF-α mRNA translation is required for establishing the embryonic body axes. A number of recent studies have highlighted key aspects of the mechanism of gurken mRNA translational control at the dorsoanterior corner of the mid-stage oocyte. Orb/CPEB and Wispy/GLD-2 are required for polyadenylation of gurken mRNA, but unlocalized gurken mRNA in the oocyte is not fully polyadenylated. 1 At the dorsoanterior corner, Orb and gurken mRNA have been shown to be enriched at the edge of Processing bodies, where translation occurs. 2 Over-expression of Orb in the adjacent nurse cells, where gurken mRNA is transcribed, is sufficient to cause mis-expression of Gurken protein. 3 In orb mutant egg chambers, reducing the activity of CK2, a Serine/Threonine protein kinase, enhances the ventralized phenotype, consistent with perturbation of gurken translation. 4 Here we show that sites phosphorylated by CK2 overlap with active Orb and with Gurken protein expression. Together with our new findings we consolidate the literature into a working model for gurken mRNA translational control and review the role of kinases, cell cycle factors and polyadenylation machinery highlighting a multitude of conserved factors and mechanisms in the Drosophila egg chamber.
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Affiliation(s)
| | - Timothy T Weil
- a Department of Zoology , University of Cambridge , Cambridge , UK
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66
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Castelli-Gair Hombría J, González-Reyes A. Cell Signalling: Combining Pathways for Diversification and Reproducibility. Curr Biol 2016; 26:R1153-R1155. [PMID: 27825454 DOI: 10.1016/j.cub.2016.08.070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
How a given signalling pathway can generate diverse outcomes is an open question. A new study shows that EGFR signalling in combination with JAK/STAT or BMP pathways induces different cell fates. Antagonistic interactions between downstream targets further stabilizes epithelial patterning.
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Affiliation(s)
| | - Acaimo González-Reyes
- Centro Andaluz de Biología del Desarrollo, CSIC/JA/Universidad Pablo de Olavide, Seville, Spain
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67
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Bone CR, Chang YT, Cain NE, Murphy SP, Starr DA. Nuclei migrate through constricted spaces using microtubule motors and actin networks in C. elegans hypodermal cells. Development 2016; 143:4193-4202. [PMID: 27697906 DOI: 10.1242/dev.141192] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/20/2016] [Indexed: 12/22/2022]
Abstract
Cellular migrations through constricted spaces are a crucial aspect of many developmental and disease processes including hematopoiesis, inflammation and metastasis. A limiting factor in these events is nuclear deformation. Here, we establish an in vivo model in which nuclei can be visualized while moving through constrictions and use it to elucidate mechanisms for nuclear migration. C. elegans hypodermal P-cell larval nuclei traverse a narrow space that is about 5% their width. This constriction is blocked by fibrous organelles, structures that pass through P cells to connect the muscles to cuticle. Fibrous organelles are removed just prior to nuclear migration, when nuclei and lamins undergo extreme morphological changes to squeeze through the space. Both actin and microtubule networks are organized to mediate nuclear migration. The LINC complex, consisting of the SUN protein UNC-84 and the KASH protein UNC-83, recruits dynein and kinesin-1 to the nuclear surface. Both motors function in P-cell nuclear migration, but dynein, functioning through UNC-83, plays a more central role as nuclei migrate towards minus ends of polarized microtubule networks. Thus, the nucleoskeleton and cytoskeleton are coordinated to move nuclei through constricted spaces.
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Affiliation(s)
- Courtney R Bone
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Yu-Tai Chang
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Natalie E Cain
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Shaun P Murphy
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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68
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Cadot B, Gache V, Gomes ER. Moving and positioning the nucleus in skeletal muscle - one step at a time. Nucleus 2016; 6:373-81. [PMID: 26338260 DOI: 10.1080/19491034.2015.1090073] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Nuclear movement and positioning within cells has become an area of great interest in the past few years due to the identification of different molecular mechanisms and functions in distinct organisms and contexts. One extreme example occurs during skeletal muscle development and regeneration. Skeletal muscles are composed of individual multinucleated myofibers with nuclei positioned at their periphery. Myofibers are formed by fusion of mononucleated myoblasts and during their development, successive nuclear movements and positioning events have been described. The position of the nuclei in myofibers is important for muscle function. Interestingly, during muscle regeneration and in some muscular diseases, nuclei are positioned in the center of the myofiber. In this review, we discuss the multiple mechanisms of nuclear positioning that occur during myofiber formation and regeneration. We also discuss the role of nuclear positioning for skeletal muscle function.
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Affiliation(s)
- Bruno Cadot
- a Center of Research in Myology; INSERM UPMC UMR974; CNRS FRE3617 ; Paris , France
| | - Vincent Gache
- b Ecole Normale Superieure de Lyon; CNRS UMR5239 ; Lyon , France
| | - Edgar R Gomes
- a Center of Research in Myology; INSERM UPMC UMR974; CNRS FRE3617 ; Paris , France.,c Instituto de Medicina Molecular; Faculdade de Medicina; Universidade de Lisboa ; Lisbon, Portugal
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69
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Abstract
Objects are commonly moved within the cell by either passive diffusion or active directed transport. A third possibility is advection, in which objects within the cytoplasm are moved with the flow of the cytoplasm. Bulk movement of the cytoplasm, or streaming, as required for advection, is more common in large cells than in small cells. For example, streaming is observed in elongated plant cells and the oocytes of several species. In the Drosophila oocyte, two stages of streaming are observed: relatively slow streaming during mid-oogenesis and streaming that is approximately ten times faster during late oogenesis. These flows are implicated in two processes: polarity establishment and mixing. In this review, I discuss the underlying mechanism of streaming, how slow and fast streaming are differentiated, and what we know about the physiological roles of the two types of streaming.
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Affiliation(s)
- Margot E Quinlan
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, California 90095;
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70
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Tanimoto H, Kimura A, Minc N. Shape-motion relationships of centering microtubule asters. J Cell Biol 2016; 212:777-87. [PMID: 27022090 PMCID: PMC4810306 DOI: 10.1083/jcb.201510064] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/17/2016] [Indexed: 11/22/2022] Open
Abstract
Although mechanisms that contribute to microtubule (MT) aster positioning have been extensively studied, still little is known on how asters move inside cells to faithfully target a cellular location. Here, we study sperm aster centration in sea urchin eggs, as a stereotypical large-scale aster movement with extreme constraints on centering speed and precision. By tracking three-dimensional aster centration dynamics in eggs with manipulated shapes, we show that aster geometry resulting from MT growth and interaction with cell boundaries dictates aster instantaneous directionality, yielding cell shape-dependent centering trajectories. Aster laser surgery and modeling suggest that dynein-dependent MT cytoplasmic pulling forces that scale to MT length function to convert aster geometry into directionality. In contrast, aster speed remains largely independent of aster size, shape, or absolute dynein activity, which suggests it may be predominantly determined by aster growth rate rather than MT force amplitude. These studies begin to define the geometrical principles that control aster movements.
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Affiliation(s)
| | - Akatsuki Kimura
- Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima 411-8540, Japan National Institute of Genetics, Mishima 411-8540, Japan Institut Curie, Centre National de la Recherche Scientifique UMR 144, 75248 Paris, France
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71
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Lee J, Lee S, Chen C, Shim H, Kim-Ha J. shotregulates the microtubule reorganization required for localization of axis-determining mRNAs during oogenesis. FEBS Lett 2016; 590:431-44. [DOI: 10.1002/1873-3468.12086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 01/15/2016] [Accepted: 01/25/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Jiyeon Lee
- Department of Integrative Bioscience and Biotechnology; College of Life Sciences; Sejong University; Gwangjin-gu Seoul South Korea
| | - Sujung Lee
- Department of Integrative Bioscience and Biotechnology; College of Life Sciences; Sejong University; Gwangjin-gu Seoul South Korea
| | - Cheng Chen
- Department of Integrative Bioscience and Biotechnology; College of Life Sciences; Sejong University; Gwangjin-gu Seoul South Korea
| | - Hyeran Shim
- Department of Integrative Bioscience and Biotechnology; College of Life Sciences; Sejong University; Gwangjin-gu Seoul South Korea
| | - Jeongsil Kim-Ha
- Department of Integrative Bioscience and Biotechnology; College of Life Sciences; Sejong University; Gwangjin-gu Seoul South Korea
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72
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D'Alessandro M, Hnia K, Gache V, Koch C, Gavriilidis C, Rodriguez D, Nicot AS, Romero NB, Schwab Y, Gomes E, Labouesse M, Laporte J. Amphiphysin 2 Orchestrates Nucleus Positioning and Shape by Linking the Nuclear Envelope to the Actin and Microtubule Cytoskeleton. Dev Cell 2016; 35:186-98. [PMID: 26506308 DOI: 10.1016/j.devcel.2015.09.018] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 07/31/2015] [Accepted: 09/23/2015] [Indexed: 12/31/2022]
Abstract
Nucleus positioning is key for intracellular organization, cell differentiation, and organ development and is affected in many diseases, including myopathies due to alteration in amphiphysin-2 (BIN1). The actin and microtubule cytoskeletons are essential for nucleus positioning, but their crosstalk in this process is sparsely characterized. Here, we report that impairment of amphiphysin/BIN1 in Caenorhabditis elegans, mammalian cells, or muscles from patients with centronuclear myopathy alters nuclear position and shape. We show that AMPH-1/BIN1 binds to nesprin and actin, as well as to the microtubule-binding protein CLIP170 in both species. Expression of the microtubule-anchoring CAP-GLY domain of CLIP170 fused to the nuclear-envelope-anchoring KASH domain of nesprin rescues nuclear positioning defects of amph-1 mutants. Amphiphysins thus play a central role in linking the nuclear envelope with the actin and microtubule cytoskeletons. We propose that BIN1 has a direct and evolutionarily conserved role in nuclear positioning, altered in myopathies.
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Affiliation(s)
- Manuela D'Alessandro
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France; University Claude Bernard Lyon 1, CGphiMC UMR CNRS 5534, 69622 Villeurbanne, France.
| | - Karim Hnia
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France
| | - Vincent Gache
- Myology Group, UMR S 787 INSERM, Université Pierre et Marie Curie Paris 6, 75634 Paris, France; CNRS UMR5239, Laboratoire de Biologie Moléculaire de la Cellule (LBMC), Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
| | - Catherine Koch
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France
| | | | - David Rodriguez
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France
| | - Anne-Sophie Nicot
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France
| | - Norma B Romero
- Morphology Neuromuscular Unit of the Myology Institute, GHU Pitié-Salpêtrière, 75013 Paris, France
| | - Yannick Schwab
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France; Cell Biology and Biophysics Unit, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Edgar Gomes
- Myology Group, UMR S 787 INSERM, Université Pierre et Marie Curie Paris 6, 75634 Paris, France; Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Michel Labouesse
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France; UMR7622, IBPS, UPMC, 75252 Paris, France
| | - Jocelyn Laporte
- IGBMC, INSERM U964, CNRS UMR7104, Strasbourg University, 67404 Illkirch, France.
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73
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Jambor H, Mejstrik P, Tomancak P. Rapid Ovary Mass-Isolation (ROMi) to Obtain Large Quantities of Drosophila Egg Chambers for Fluorescent In Situ Hybridization. Methods Mol Biol 2016; 1478:253-262. [PMID: 27730587 DOI: 10.1007/978-1-4939-6371-3_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Isolation of large quantities of tissue from organisms is essential for many techniques such as genome-wide screens and biochemistry. However, obtaining large quantities of tissues or cells is often the rate-limiting step when working in vivo. Here, we present a rapid method that allows the isolation of intact, single egg chambers at various developmental stages from ovaries of adult female Drosophila flies. The isolated egg chambers are amenable for a variety of procedures such as fluorescent in situ hybridization, RNA isolation, extract preparation, or immunostaining. Isolation of egg chambers from adult flies can be completed in 5 min and results, depending on the input amount of flies, in several milliliters of material. The isolated egg chambers are then further processed depending on the exact requirements of the subsequent application. We describe high-throughput in situ hybridization in 96-well plates as example application for the mass-isolated egg chambers.
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Affiliation(s)
- Helena Jambor
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307, Dresden, Germany.
| | - Pavel Mejstrik
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307, Dresden, Germany
| | - Pavel Tomancak
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307, Dresden, Germany.
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74
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In Vitro Culturing and Live Imaging of Drosophila Egg Chambers: A History and Adaptable Method. Methods Mol Biol 2016; 1457:35-68. [PMID: 27557572 DOI: 10.1007/978-1-4939-3795-0_4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The development of the Drosophila egg chamber encompasses a myriad of diverse germline and somatic events, and as such, the egg chamber has become a widely used and influential developmental model. Advantages of this system include physical accessibility, genetic tractability, and amenability to microscopy and live culturing, the last of which is the focus of this chapter. To provide adequate context, we summarize the structure of the Drosophila ovary and egg chamber, the morphogenetic events of oogenesis, the history of egg-chamber live culturing, and many of the important discoveries that this culturing has afforded. Subsequently, we discuss various culturing methods that have facilitated analyses of different stages of egg-chamber development and different types of cells within the egg chamber, and we present an optimized protocol for live culturing Drosophila egg chambers.We designed this protocol for culturing late-stage Drosophila egg chambers and live imaging epithelial tube morphogenesis, but with appropriate modifications, it can be used to culture egg chambers of any stage. The protocol employs a liquid-permeable, weighted "blanket" to gently hold egg chambers against the coverslip in a glass-bottomed culture dish so the egg chambers can be imaged on an inverted microscope. This setup provides a more buffered, stable, culturing environment than previously published methods by using a larger volume of culture media, but the setup is also compatible with small volumes. This chapter should aid researchers in their efforts to culture and live-image Drosophila egg chambers, further augmenting the impressive power of this model system.
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75
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Christophorou N, Rubin T, Bonnet I, Piolot T, Arnaud M, Huynh JR. Microtubule-driven nuclear rotations promote meiotic chromosome dynamics. Nat Cell Biol 2015; 17:1388-400. [PMID: 26458247 DOI: 10.1038/ncb3249] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Accepted: 09/03/2015] [Indexed: 11/09/2022]
Abstract
At the onset of meiosis, each chromosome needs to find its homologue and pair to ensure proper segregation. In Drosophila, pairing occurs during the mitotic cycles preceding meiosis. Here we show that germ cell nuclei undergo marked movements during this developmental window. We demonstrate that microtubules and Dynein are driving nuclear rotations and are required for centromere pairing and clustering. We further found that Klaroid (SUN) and Klarsicht (KASH) co-localize with centromeres at the nuclear envelope and are required for proper chromosome motions and pairing. We identified Mud (NuMA in vertebrates) as co-localizing with centromeres, Klarsicht and Klaroid. Mud is also required to maintain the integrity of the nuclear envelope and for the correct assembly of the synaptonemal complex. Our findings reveal a mechanism for chromosome pairing in Drosophila, and indicate that microtubules, centrosomes and associated proteins play a crucial role in the dynamic organization of chromosomes inside the nucleus.
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Affiliation(s)
- Nicolas Christophorou
- Department of Genetics and Developmental Biology, Institut Curie, F-75248 Paris, France.,CNRS UMR3215, Inserm, U934 F-75248 Paris, France
| | - Thomas Rubin
- Department of Genetics and Developmental Biology, Institut Curie, F-75248 Paris, France.,CNRS UMR3215, Inserm, U934 F-75248 Paris, France
| | - Isabelle Bonnet
- Laboratoire Physico-Chimie, Institut Curie, F-75248 Paris, France.,CNRS UMR 168, UPMC, F-75248 Paris, France
| | - Tristan Piolot
- Department of Genetics and Developmental Biology, Institut Curie, F-75248 Paris, France.,CNRS UMR3215, Inserm, U934 F-75248 Paris, France
| | - Marion Arnaud
- Department of Genetics and Developmental Biology, Institut Curie, F-75248 Paris, France.,CNRS UMR3215, Inserm, U934 F-75248 Paris, France
| | - Jean-René Huynh
- Department of Genetics and Developmental Biology, Institut Curie, F-75248 Paris, France.,CNRS UMR3215, Inserm, U934 F-75248 Paris, France
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76
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Khuc Trong P, Doerflinger H, Dunkel J, St Johnston D, Goldstein RE. Cortical microtubule nucleation can organise the cytoskeleton of Drosophila oocytes to define the anteroposterior axis. eLife 2015; 4. [PMID: 26406117 PMCID: PMC4580948 DOI: 10.7554/elife.06088] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 08/14/2015] [Indexed: 02/02/2023] Open
Abstract
Many cells contain non-centrosomal arrays of microtubules (MTs), but the assembly, organisation and function of these arrays are poorly understood. We present the first theoretical model for the non-centrosomal MT cytoskeleton in Drosophila oocytes, in which bicoid and oskar mRNAs become localised to establish the anterior-posterior body axis. Constrained by experimental measurements, the model shows that a simple gradient of cortical MT nucleation is sufficient to reproduce the observed MT distribution, cytoplasmic flow patterns and localisation of oskar and naive bicoid mRNAs. Our simulations exclude a major role for cytoplasmic flows in localisation and reveal an organisation of the MT cytoskeleton that is more ordered than previously thought. Furthermore, modulating cortical MT nucleation induces a bifurcation in cytoskeletal organisation that accounts for the phenotypes of polarity mutants. Thus, our three-dimensional model explains many features of the MT network and highlights the importance of differential cortical MT nucleation for axis formation. DOI:http://dx.doi.org/10.7554/eLife.06088.001 Cells contain a network of filaments known as microtubules that serve as tracks along which proteins and other materials can be moved from one location to another. For example, molecules called messenger ribonucleic acids (or mRNAs for short) are made in the nucleus and are then moved to various locations around the cell. Each mRNA molecule encodes the instructions needed to make a particular protein and the network of microtubules allows these molecules to be directed to wherever these proteins are needed. In female fruit flies, an mRNA called bicoid is moved to one end (called the anterior end) of a developing egg cell, while another mRNA called oskar is moved to the opposite (posterior) end. These mRNAs determine which ends of the cell will give rise to the head and the abdomen if the egg is fertilized. The microtubules start to form at sites near the inner face of the membrane that surrounds the cell, known as the cortex. From there, the microtubules grow towards the interior of the egg cell. However, it is not clear how this allows bicoid, oskar and other mRNAs to be moved to the correct locations. Khuc Trong et al. used a combination of computational and experimental techniques to develop a model of how microtubules form in the egg cells of fruit flies. The model produces a very similar arrangement of microtubules as observed in living cells and can reproduce the patterns of bicoid and oskar RNA movements. This study suggests that microtubules are more highly organised than previously thought. Furthermore, Khuc Trong et al.'s findings indicate that the anchoring of microtubules in the cortex is sufficient to direct bicoid and oskar RNAs to the opposite ends of the cell. The next challenge will be to find out how the microtubules are linked to the cortex and how this is regulated. DOI:http://dx.doi.org/10.7554/eLife.06088.002
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Affiliation(s)
- Philipp Khuc Trong
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Hélène Doerflinger
- Wellcome Trust/Cancer Research UK Gurdon Institute, Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Jörn Dunkel
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Daniel St Johnston
- Wellcome Trust/Cancer Research UK Gurdon Institute, Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
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77
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Efficient Endocytic Uptake and Maturation in Drosophila Oocytes Requires Dynamitin/p50. Genetics 2015; 201:631-49. [PMID: 26265702 DOI: 10.1534/genetics.115.180018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 08/06/2015] [Indexed: 01/27/2023] Open
Abstract
Dynactin is a multi-subunit complex that functions as a regulator of the Dynein motor. A central component of this complex is Dynamitin/p50 (Dmn). Dmn is required for endosome motility in mammalian cell lines. However, the extent to which Dmn participates in the sorting of cargo via the endosomal system is unknown. In this study, we examined the endocytic role of Dmn using the Drosophila melanogaster oocyte as a model. Yolk proteins are internalized into the oocyte via clathrin-mediated endocytosis, trafficked through the endocytic pathway, and stored in condensed yolk granules. Oocytes that were depleted of Dmn contained fewer yolk granules than controls. In addition, these oocytes accumulated numerous endocytic intermediate structures. Particularly prominent were enlarged endosomes that were relatively devoid of Yolk proteins. Ultrastructural and genetic analyses indicate that the endocytic intermediates are produced downstream of Rab5. Similar phenotypes were observed upon depleting Dynein heavy chain (Dhc) or Lis1. Dhc is the motor subunit of the Dynein complex and Lis1 is a regulator of Dynein activity. We therefore propose that Dmn performs its function in endocytosis via the Dynein motor. Consistent with a role for Dynein in endocytosis, the motor colocalized with the endocytic machinery at the oocyte cortex in an endocytosis-dependent manner. Our results suggest a model whereby endocytic activity recruits Dynein to the oocyte cortex. The motor along with its regulators, Dynactin and Lis1, functions to ensure efficient endocytic uptake and maturation.
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78
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Kim DH, Li B, Si F, Phillip JM, Wirtz D, Sun SX. Volume regulation and shape bifurcation in the cell nucleus. J Cell Sci 2015; 128:3375-85. [PMID: 26243474 DOI: 10.1242/jcs.166330] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 07/27/2015] [Indexed: 12/26/2022] Open
Abstract
Alterations in nuclear morphology are closely associated with essential cell functions, such as cell motility and polarization, and correlate with a wide range of human diseases, including cancer, muscular dystrophy, dilated cardiomyopathy and progeria. However, the mechanics and forces that shape the nucleus are not well understood. Here, we demonstrate that when an adherent cell is detached from its substratum, the nucleus undergoes a large volumetric reduction accompanied by a morphological transition from an almost smooth to a heavily folded surface. We develop a mathematical model that systematically analyzes the evolution of nuclear shape and volume. The analysis suggests that the pressure difference across the nuclear envelope, which is influenced by changes in cell volume and regulated by microtubules and actin filaments, is a major factor determining nuclear morphology. Our results show that physical and chemical properties of the extracellular microenvironment directly influence nuclear morphology and suggest that there is a direct link between the environment and gene regulation.
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Affiliation(s)
- Dong-Hwee Kim
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA, 4KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Republic of Korea
| | - Bo Li
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Fangwei Si
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jude M Phillip
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Denis Wirtz
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sean X Sun
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD 21218, USA Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
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79
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Stewart RM, Zubek AE, Rosowski KA, Schreiner SM, Horsley V, King MC. Nuclear-cytoskeletal linkages facilitate cross talk between the nucleus and intercellular adhesions. ACTA ACUST UNITED AC 2015; 209:403-18. [PMID: 25963820 PMCID: PMC4427780 DOI: 10.1083/jcb.201502024] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The linker of nucleoskeleton and cytoskeleton (LINC) complex allows cells to actively control nuclear position by coupling the nucleus to the cytoplasmic cytoskeleton. Nuclear position responds to the formation of intercellular adhesions through coordination with the cytoskeleton, but it is not known whether this response impacts adhesion function. In this paper, we demonstrate that the LINC complex component SUN2 contributes to the mechanical integrity of intercellular adhesions between mammalian epidermal keratinocytes. Mice deficient for Sun2 exhibited irregular hair follicle intercellular adhesions, defective follicle structure, and alopecia. Primary mouse keratinocytes lacking Sun2 displayed aberrant nuclear position in response to adhesion formation, altered desmosome distribution, and mechanically defective adhesions. This dysfunction appeared rooted in a failure of Sun2-null cells to reorganize their microtubule network to support coordinated intercellular adhesion. Together, these results suggest that cross talk between the nucleus, cytoskeleton, and intercellular adhesions is important for epidermal tissue integrity.
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Affiliation(s)
- Rachel M Stewart
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
| | - Amanda E Zubek
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520 Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
| | - Kathryn A Rosowski
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
| | - Sarah M Schreiner
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
| | - Valerie Horsley
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520 Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
| | - Megan C King
- Department of Cell Biology and Department of Dermatology, Yale School of Medicine; and Department of Molecular, Cell and Developmental Biology; Yale University, New Haven, CT, 06520
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80
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Alam SG, Lovett D, Kim DI, Roux KJ, Dickinson RB, Lele TP. The nucleus is an intracellular propagator of tensile forces in NIH 3T3 fibroblasts. J Cell Sci 2015; 128:1901-11. [PMID: 25908852 DOI: 10.1242/jcs.161703] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 03/24/2015] [Indexed: 01/14/2023] Open
Abstract
Nuclear positioning is a crucial cell function, but how a migrating cell positions its nucleus is not understood. Using traction-force microscopy, we found that the position of the nucleus in migrating fibroblasts closely coincided with the center point of the traction-force balance, called the point of maximum tension (PMT). Positioning of the nucleus close to the PMT required nucleus-cytoskeleton connections through linker of nucleoskeleton-to-cytoskeleton (LINC) complexes. Although the nucleus briefly lagged behind the PMT following spontaneous detachment of the uropod during migration, the nucleus quickly repositioned to the PMT within a few minutes. Moreover, traction-generating spontaneous protrusions deformed the nearby nucleus surface to pull the nuclear centroid toward the new PMT, and subsequent retraction of these protrusions relaxed the nuclear deformation and restored the nucleus to its original position. We propose that the protruding or retracting cell boundary transmits a force to the surface of the nucleus through the intervening cytoskeletal network connected by the LINC complexes, and that these forces help to position the nucleus centrally and allow the nucleus to efficiently propagate traction forces across the length of the cell during migration.
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Affiliation(s)
- Samer G Alam
- Department of Chemical Engineering, University of Florida, Bldg. 723, Gainesville, FL 32611, USA
| | - David Lovett
- Department of Chemical Engineering, University of Florida, Bldg. 723, Gainesville, FL 32611, USA
| | - Dae In Kim
- Sanford Children's Health Research Center, University of South Dakota, Sioux Falls, SD 57104, USA
| | - Kyle J Roux
- Sanford Children's Health Research Center, University of South Dakota, Sioux Falls, SD 57104, USA
| | - Richard B Dickinson
- Department of Chemical Engineering, University of Florida, Bldg. 723, Gainesville, FL 32611, USA
| | - Tanmay P Lele
- Department of Chemical Engineering, University of Florida, Bldg. 723, Gainesville, FL 32611, USA
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81
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Revach OY, Weiner A, Rechav K, Sabanay I, Livne A, Geiger B. Mechanical interplay between invadopodia and the nucleus in cultured cancer cells. Sci Rep 2015; 5:9466. [PMID: 25820462 PMCID: PMC4377574 DOI: 10.1038/srep09466] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 03/02/2015] [Indexed: 01/11/2023] Open
Abstract
Invadopodia are actin-rich membrane protrusions through which cells adhere to the extracellular matrix and degrade it. In this study, we explored the mechanical interactions of invadopodia in melanoma cells, using a combination of correlative light and electron microscopy. We show here that the core actin bundle of most invadopodia interacts with integrin-containing matrix adhesions at its basal end, extends through a microtubule-rich cytoplasm, and at its apical end, interacts with the nuclear envelope and indents it. Abolishment of invadopodia by microtubules or src inhibitors leads to the disappearance of these nuclear indentations. Based on the indentation profile and the viscoelastic properties of the nucleus, the force applied by invadopodia is estimated to be in the nanoNewton range. We further show that knockdown of the LINC complex components nesprin 2 or SUN1 leads to a substantial increase in the prominence of the adhesion domains at the opposite end of the invadopodia. We discuss this unexpected, long-range mechanical interplay between the apical and basal domains of invadopodia, and its possible involvement in the penetration of invadopodia into the matrix.
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Affiliation(s)
- Or-Yam Revach
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Allon Weiner
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Katya Rechav
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ilana Sabanay
- 1] Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel [2] Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ariel Livne
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Benjamin Geiger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
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82
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Manning L, Starz-Gaiano M. Culturing Drosophila Egg Chambers and Investigating Developmental Processes Through Live Imaging. Methods Mol Biol 2015; 1328:73-88. [PMID: 26324430 DOI: 10.1007/978-1-4939-2851-4_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Drosophila oogenesis provides many examples of essential processes in development. A myriad of genetic tools combined with recent advances in culturing egg chambers ex vivo has revealed several surprising mechanisms that govern how this tissue develops, and which could not have been determined in fixed tissues. Here we describe a straightforward protocol for dissecting ovaries, culturing egg chambers, and observing egg development in real time by fluorescent microscopy. This technique is suitable for observation of early- or late-stage egg development, and can be adapted to study a variety of cellular, molecular, or developmental processes. Ongoing analysis of oogenesis in living egg chambers has tremendous potential for discovery of new developmental mechanisms.
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Affiliation(s)
- Lathiena Manning
- Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD, 21250, USA
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83
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Legent K, Tissot N, Guichet A. Visualizing Microtubule Networks During Drosophila Oogenesis Using Fixed and Live Imaging. Methods Mol Biol 2015; 1328:99-112. [PMID: 26324432 DOI: 10.1007/978-1-4939-2851-4_7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The microtubule cytoskeleton is a plastic network of polarized cables. These polymers of tubulin provide orientated routes for the dynamic transport of cytoplasmic molecules and organelles, through which cell polarity is established and maintained. The role of microtubule-mediated transport in the asymmetric localization of axis polarity determinants, in the Drosophila oocyte, has been the subject of extensive studies in the past years. However, imaging the distribution of microtubule fibers in a large cell, where vitellogenesis ensures the uptake of a thick and hazy yolk, presents a series of technical challenges. This chapter briefly reviews some of these aspects and describes two methods designed to circumvent these difficulties. We provide a detailed protocol for the visualization by immunohistochemistry of the three-dimensional organization of tubulin cables in the oocyte. Additionally, we detail the stepwise procedure for the live imaging of microtubule dynamics and network remodeling, using fluorescently labeled microtubule-associated proteins.
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Affiliation(s)
- Kevin Legent
- Institut Jacques Monod, UMR 7592 - CNRS, Université Paris Diderot, 15 rue Hélène Brion, Bât Buffon, 75205, Paris, France
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84
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Lowe N, Rees JS, Roote J, Ryder E, Armean IM, Johnson G, Drummond E, Spriggs H, Drummond J, Magbanua JP, Naylor H, Sanson B, Bastock R, Huelsmann S, Trovisco V, Landgraf M, Knowles-Barley S, Armstrong JD, White-Cooper H, Hansen C, Phillips RG, Lilley KS, Russell S, St Johnston D. Analysis of the expression patterns, subcellular localisations and interaction partners of Drosophila proteins using a pigP protein trap library. Development 2014; 141:3994-4005. [PMID: 25294943 PMCID: PMC4197710 DOI: 10.1242/dev.111054] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Although we now have a wealth of information on the transcription patterns of all the genes in the Drosophila genome, much less is known about the properties of the encoded proteins. To provide information on the expression patterns and subcellular localisations of many proteins in parallel, we have performed a large-scale protein trap screen using a hybrid piggyBac vector carrying an artificial exon encoding yellow fluorescent protein (YFP) and protein affinity tags. From screening 41 million embryos, we recovered 616 verified independent YFP-positive lines representing protein traps in 374 genes, two-thirds of which had not been tagged in previous P element protein trap screens. Over 20 different research groups then characterized the expression patterns of the tagged proteins in a variety of tissues and at several developmental stages. In parallel, we purified many of the tagged proteins from embryos using the affinity tags and identified co-purifying proteins by mass spectrometry. The fly stocks are publicly available through the Kyoto Drosophila Genetics Resource Center. All our data are available via an open access database (Flannotator), which provides comprehensive information on the expression patterns, subcellular localisations and in vivo interaction partners of the trapped proteins. Our resource substantially increases the number of available protein traps in Drosophila and identifies new markers for cellular organelles and structures.
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Affiliation(s)
- Nick Lowe
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Johanna S Rees
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK The Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - John Roote
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Ed Ryder
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Irina M Armean
- The Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Glynnis Johnson
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Emma Drummond
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Helen Spriggs
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Jenny Drummond
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Jose P Magbanua
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Huw Naylor
- The Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Bénédicte Sanson
- The Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Rebecca Bastock
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Sven Huelsmann
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Vitor Trovisco
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Matthias Landgraf
- The Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Seymour Knowles-Barley
- Institute for Adaptive and Neural Computation, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK
| | - J Douglas Armstrong
- Institute for Adaptive and Neural Computation, University of Edinburgh, 10 Crichton Street, Edinburgh EH8 9AB, UK
| | - Helen White-Cooper
- Cardiff School of Biosciences, The Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AX, UK
| | - Celia Hansen
- Department of Genetics, University of Leicester, Adrian Building, University Road, Leicester LE1 7RH, UK
| | - Roger G Phillips
- Centre for Advanced Microscopy, University of Sussex, School of Life Sciences, John Maynard Smith Building, Falmer, Brighton and Hove BN1 9QG, UK
| | | | - Kathryn S Lilley
- The Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Steven Russell
- The Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK
| | - Daniel St Johnston
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
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85
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Abstract
Localization and the associated translational control of mRNA is a well established mechanism for segregating cellular protein expression. Drosophila has been instrumental in deciphering the prevailing mechanisms of mRNA localization and regulation. This review will discuss the diverse roles of mRNA localization in the Drosophila germline, the cis-elements and cellular components regulating localization and the superimposition of translational regulatory mechanisms. Despite a history of discovery, there are still many fundamental questions regarding mRNA localization that remain unanswered. Take home messages, outstanding questions and future approaches that will likely lead to resolving these unknowns in the future are summarized at the end.
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Affiliation(s)
- Timothy T Weil
- a Department of Zoology ; University of Cambridge ; Cambridge , UK
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86
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Wu J, Kent IA, Shekhar N, Chancellor TJ, Mendonca A, Dickinson RB, Lele TP. Actomyosin pulls to advance the nucleus in a migrating tissue cell. Biophys J 2014; 106:7-15. [PMID: 24411232 DOI: 10.1016/j.bpj.2013.11.4489] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 10/29/2013] [Accepted: 11/19/2013] [Indexed: 01/14/2023] Open
Abstract
The cytoskeletal forces involved in translocating the nucleus in a migrating tissue cell remain unresolved. Previous studies have variously implicated actomyosin-generated pushing or pulling forces on the nucleus, as well as pulling by nucleus-bound microtubule motors. We found that the nucleus in an isolated migrating cell can move forward without any trailing-edge detachment. When a new lamellipodium was triggered with photoactivation of Rac1, the nucleus moved toward the new lamellipodium. This forward motion required both nuclear-cytoskeletal linkages and myosin activity. Apical or basal actomyosin bundles were found not to translate with the nucleus. Although microtubules dampen fluctuations in nuclear position, they are not required for forward translocation of the nucleus during cell migration. Trailing-edge detachment and pulling with a microneedle produced motion and deformation of the nucleus suggestive of a mechanical coupling between the nucleus and the trailing edge. Significantly, decoupling the nucleus from the cytoskeleton with KASH overexpression greatly decreased the frequency of trailing-edge detachment. Collectively, these results explain how the nucleus is moved in a crawling fibroblast and raise the possibility that forces could be transmitted from the front to the back of the cell through the nucleus.
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Affiliation(s)
- Jun Wu
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - Ian A Kent
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - Nandini Shekhar
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - T J Chancellor
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - Agnes Mendonca
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - Richard B Dickinson
- Department of Chemical Engineering, University of Florida, Gainesville, Florida
| | - Tanmay P Lele
- Department of Chemical Engineering, University of Florida, Gainesville, Florida.
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87
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Abstract
The nucleus is the defining feature of eukaryotic cells and often represents the largest organelle. Over the past decade, it has become apparent that the nucleus is tightly integrated into the structural network of the cell through so-called LINC (linker of the nucleoskeleton and cytoskeleton) complexes, which enable transmission of forces between the nucleus and cytoskeleton. This physical connection between the nucleus and the cytoskeleton is essential for a broad range of cellular functions, including intracellular nuclear movement and positioning, cytoskeletal organization, cell polarization, and cell migration. Recent reports further indicate that forces transmitted from the extracellular matrix to the nucleus via the cytoskeleton may also directly contribute to the cell's ability to probe its mechanical environment by triggering force-induced changes in nuclear structures. In addition, it is now emerging that the physical properties of the nucleus play a crucial role during cell migration in three-dimensional (3D) environments, where cells often have to transit through narrow constrictions that are smaller than the nuclear diameter, e.g., during development, wound healing, or cancer metastasis. In this review, we provide a brief overview of how LINC complex proteins and lamins facilitate nucleo-cytoskeletal coupling, highlight recent findings regarding the role of the nucleus in cellular mechanotransduction and cell motility in 3D environments, and discuss how mutations and/or changes in the expression of these nuclear envelope proteins can result in a broad range of human diseases, including muscular dystrophy, dilated cardiomyopathy, and premature aging.
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88
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A genetic screen based on in vivo RNA imaging reveals centrosome-independent mechanisms for localizing gurken transcripts in Drosophila. G3-GENES GENOMES GENETICS 2014; 4:749-60. [PMID: 24531791 PMCID: PMC4059244 DOI: 10.1534/g3.114.010462] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have screened chromosome arm 3L for ethyl methanesulfonate−induced mutations that disrupt localization of fluorescently labeled gurken (grk) messenger (m)RNA, whose transport along microtubules establishes both major body axes of the developing Drosophila oocyte. Rapid identification of causative mutations by single-nucleotide polymorphism recombinational mapping and whole-genomic sequencing allowed us to define nine complementation groups affecting grk mRNA localization and other aspects of oogenesis, including alleles of elg1, scaf6, quemao, nudE, Tsc2/gigas, rasp, and Chd5/Wrb, and several null alleles of the armitage Piwi-pathway gene. Analysis of a newly induced kinesin light chain allele shows that kinesin motor activity is required for both efficient grk mRNA localization and oocyte centrosome integrity. We also show that initiation of the dorsoanterior localization of grk mRNA precedes centrosome localization, suggesting that microtubule self-organization contributes to breaking axial symmetry to generate a unique dorsoventral axis.
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89
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Jambor H, Mueller S, Bullock SL, Ephrussi A. A stem-loop structure directs oskar mRNA to microtubule minus ends. RNA (NEW YORK, N.Y.) 2014; 20:429-39. [PMID: 24572808 PMCID: PMC3964905 DOI: 10.1261/rna.041566.113] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 01/06/2014] [Indexed: 05/22/2023]
Abstract
mRNA transport coupled with translational control underlies the intracellular localization of many proteins in eukaryotic cells. This is exemplified in Drosophila, where oskar mRNA transport and translation at the posterior pole of the oocyte direct posterior patterning of the embryo. oskar localization is a multistep process. Within the oocyte, a spliced oskar localization element (SOLE) targets oskar mRNA for plus end-directed transport by kinesin-1 to the posterior pole. However, the signals mediating the initial minus end-directed, dynein-dependent transport of the mRNA from nurse cells into the oocyte have remained unknown. Here, we show that a 67-nt stem-loop in the oskar 3' UTR promotes oskar mRNA delivery to the developing oocyte and that it shares functional features with the fs(1)K10 oocyte localization signal. Thus, two independent cis-acting signals, the oocyte entry signal (OES) and the SOLE, mediate sequential dynein- and kinesin-dependent phases of oskar mRNA transport during oogenesis. The OES also promotes apical localization of injected RNAs in blastoderm stage embryos, another dynein-mediated process. Similarly, when ectopically expressed in polarized cells of the follicular epithelium or salivary glands, reporter RNAs bearing the oskar OES are apically enriched, demonstrating that this element promotes mRNA localization independently of cell type. Our work sheds new light on how oskar mRNA is trafficked during oogenesis and the RNA features that mediate minus end-directed transport.
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Affiliation(s)
- Helena Jambor
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Mueller
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Simon L. Bullock
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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90
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Sitaram P, Merkle JA, Lee E, Lee LA. asunder is required for dynein localization and dorsal fate determination during Drosophila oogenesis. Dev Biol 2013; 386:42-52. [PMID: 24333177 DOI: 10.1016/j.ydbio.2013.12.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 11/19/2013] [Accepted: 12/04/2013] [Indexed: 10/25/2022]
Abstract
We previously showed that asunder (asun) is a critical regulator of dynein localization during Drosophila spermatogenesis. Because the expression of asun is much higher in Drosophila ovaries and early embryos than in testes, we herein sought to determine whether ASUN plays roles in oogenesis and/or embryogenesis. We characterized the female germline phenotypes of flies homozygous for a null allele of asun (asun(d93)). We find that asun(d93) females lay very few eggs and contain smaller ovaries with a highly disorganized arrangement of ovarioles in comparison to wild-type females. asun(d93) ovaries also contain a significant number of egg chambers with structural defects. A majority of the eggs laid by asun(d93) females are ventralized to varying degrees, from mild to severe; this ventralization phenotype may be secondary to defective localization of gurken transcripts, a dynein-regulated step, within asun(d93) oocytes. We find that dynein localization is aberrant in asun(d93) oocytes, indicating that ASUN is required for this process in both male and female germ cells. In addition to the loss of gurken mRNA localization, asun(d93) ovaries exhibit defects in other dynein-mediated processes such as migration of nurse cell centrosomes into the oocyte during the early mitotic divisions, maintenance of the oocyte nucleus in the anterior-dorsal region of the oocyte in late-stage egg chambers, and coupling between the oocyte nucleus and centrosomes. Taken together, our data indicate that asun is a critical regulator of dynein localization and dynein-mediated processes during Drosophila oogenesis.
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Affiliation(s)
- Poojitha Sitaram
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, U-4225 Medical Research Building III, 465 21st Avenue South, Nashville, TN 37232-8240, USA
| | - Julie A Merkle
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, U-4225 Medical Research Building III, 465 21st Avenue South, Nashville, TN 37232-8240, USA
| | - Ethan Lee
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, U-4225 Medical Research Building III, 465 21st Avenue South, Nashville, TN 37232-8240, USA
| | - Laura A Lee
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, U-4225 Medical Research Building III, 465 21st Avenue South, Nashville, TN 37232-8240, USA.
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91
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Huelsmann S, Ylänne J, Brown NH. Filopodia-like actin cables position nuclei in association with perinuclear actin in Drosophila nurse cells. Dev Cell 2013; 26:604-15. [PMID: 24091012 PMCID: PMC3791400 DOI: 10.1016/j.devcel.2013.08.014] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 06/18/2013] [Accepted: 08/17/2013] [Indexed: 11/21/2022]
Abstract
Controlling the position of the nucleus is vital for a number of cellular processes from yeast to humans. In Drosophila nurse cells, nuclear positioning is crucial during dumping, when nurse cells contract and expel their contents into the oocyte. We provide evidence that in nurse cells, continuous filopodia-like actin cables, growing from the plasma membrane and extending to the nucleus, achieve nuclear positioning. These actin cables move nuclei away from ring canals. When nurse cells contract, actin cables associate laterally with the nuclei, in some cases inducing nuclear turning so that actin cables become partially wound around the nuclei. Our data suggest that a perinuclear actin meshwork connects actin cables to nuclei via actin-crosslinking proteins such as the filamin Cheerio. We provide a revised model for how actin structures position nuclei in nurse cells, employing evolutionary conserved machinery. Actin cables in Drosophila nurse cells are unsegmented filopodia-like structures E-cadherin is required for the orientation of actin cables toward the nucleus Nuclear positioning is achieved by continuous elongation of actin cables Actin cables associate with perinuclear actin-containing crosslinkers like filamin
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Affiliation(s)
- Sven Huelsmann
- Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
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92
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Avidor-Reiss T, Gopalakrishnan J. Cell Cycle Regulation of the Centrosome and Cilium. ACTA ACUST UNITED AC 2013; 10:e119-e124. [PMID: 24982683 DOI: 10.1016/j.ddmec.2013.03.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Centrosomes and cilia are conserved microtubule-based organelles whose structure and function depend on cell cycle stages. In dividing cells, centrosomes organize mitotic spindle poles, while in differentiating cells, centrosomes template ciliogenesis. Classically, this functional dichotomy has been attributed to regulation by cell cycle-dependent post-translational modifications, and recently PLK1, Nek2, Aurora A, and tubulin deacetylase were implicated in regulating the transition from cilia to centrosome. However, other recent studies suggest that tubulin dimers, the core structural components of centrosomes and cilia, also have a regulatory role. These regulatory mechanisms can be a target for chemotherapeutic intervention.
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Affiliation(s)
- Tomer Avidor-Reiss
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606, USA
| | - Jayachandran Gopalakrishnan
- Center for Molecular Medicine, University of Cologne, Germany ; Institute of Biochemistry I, University of Cologne, Germany
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93
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Williams LS, Ganguly S, Loiseau P, Ng BF, Palacios IM. The auto-inhibitory domain and ATP-independent microtubule-binding region of Kinesin heavy chain are major functional domains for transport in the Drosophila germline. Development 2013; 141:176-86. [PMID: 24257625 PMCID: PMC3865757 DOI: 10.1242/dev.097592] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The major motor Kinesin-1 provides a key pathway for cell polarization through intracellular transport. Little is known about how Kinesin works in complex cellular surroundings. Several cargos associate with Kinesin via Kinesin light chain (KLC). However, KLC is not required for all Kinesin transport. A putative cargo-binding domain was identified in the C-terminal tail of fungal Kinesin heavy chain (KHC). The tail is conserved in animal KHCs and might therefore represent an alternative KLC-independent cargo-interacting region. By comprehensive functional analysis of the tail during Drosophila oogenesis we have gained an understanding of how KHC achieves specificity in its transport and how it is regulated. This is, to our knowledge, the first in vivo structural/functional analysis of the tail in animal Kinesins. We show that the tail is essential for all functions of KHC except Dynein transport, which is KLC dependent. These tail-dependent KHC activities can be functionally separated from one another by further characterizing domains within the tail. In particular, our data show the following. First, KHC is temporally regulated during oogenesis. Second, the IAK domain has an essential role distinct from its auto-inhibitory function. Third, lack of auto-inhibition in itself is not necessarily detrimental to KHC function. Finally, the ATP-independent microtubule-binding motif is required for cargo localization. These results stress that two unexpected highly conserved domains, namely the auto-inhibitory IAK and the auxiliary microtubule-binding motifs, are crucial for transport by Kinesin-1 and that, although not all cargos are conserved, their transport involves the most conserved domains of animal KHCs.
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Affiliation(s)
- Lucy S Williams
- University of Cambridge, Zoology Department, Downing Street, Cambridge CB2 3EJ, UK
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94
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Sanghavi P, Laxani S, Li X, Bullock SL, Gonsalvez GB. Dynein associates with oskar mRNPs and is required for their efficient net plus-end localization in Drosophila oocytes. PLoS One 2013; 8:e80605. [PMID: 24244700 PMCID: PMC3823658 DOI: 10.1371/journal.pone.0080605] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 10/04/2013] [Indexed: 11/18/2022] Open
Abstract
In order for eukaryotic cells to function properly, they must establish polarity. The Drosophila oocyte uses mRNA localization to establish polarity and hence provides a genetically tractable model in which to study this process. The spatial restriction of oskar mRNA and its subsequent protein product is necessary for embryonic patterning. The localization of oskar mRNA requires microtubules and microtubule-based motor proteins. Null mutants in Kinesin heavy chain (Khc), the motor subunit of the plus end-directed Kinesin-1, result in oskar mRNA delocalization. Although the majority of oskar particles are non-motile in khc nulls, a small fraction of particles display active motility. Thus, a motor other than Kinesin-1 could conceivably also participate in oskar mRNA localization. Here we show that Dynein heavy chain (Dhc), the motor subunit of the minus end-directed Dynein complex, extensively co-localizes with Khc and oskar mRNA. In addition, immunoprecipitation of the Dynein complex specifically co-precipitated oskar mRNA and Khc. Lastly, germline-specific depletion of Dhc resulted in oskar mRNA and Khc delocalization. Our results therefore suggest that efficient posterior localization of oskar mRNA requires the concerted activities of both Dynein and Kinesin-1.
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Affiliation(s)
- Paulomi Sanghavi
- Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States of America
| | - Shobha Laxani
- Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States of America
| | - Xuan Li
- Division of Cell Biology, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Simon L. Bullock
- Division of Cell Biology, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Graydon B. Gonsalvez
- Cellular Biology and Anatomy, Georgia Regents University, Augusta, Georgia, United States of America
- * E-mail:
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95
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Abstract
Asymmetric cell division (ACD), a mechanism for cell-type diversification in both prokaryotes and eukaryotes, is accomplished through highly coordinated cell-fate segregation, genome partitioning, and cell division. Whereas important paradigms have arisen from the study of animal embryonic divisions, the strategies for choreographing the dynamic subprocesses are, in fact, highly varied. This review examines divergent mechanisms of ACD across different kingdoms. Examples discussed show that there is no obligatory hierarchy among the dynamic events and that asymmetry can emerge from each event, but cell polarization more often occurs as the initial instructive process for patterning ACD especially in the multicellular context.
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Affiliation(s)
- Rong Li
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
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96
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Rebuilding MTOCs upon centriole loss during mouse oogenesis. Dev Biol 2013; 382:48-56. [PMID: 23954884 DOI: 10.1016/j.ydbio.2013.07.029] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 07/25/2013] [Accepted: 07/30/2013] [Indexed: 11/21/2022]
Abstract
The vast majority of animal cells contain canonical centrosomes as a main microtubule-organizing center defined by a central pair of centrioles. As a rare and striking exception to this rule, vertebrate oocytes loose their centrioles at an early step of oogenesis. At the end of oogenesis, centrosomes are eventually replaced by numerous acentriolar microtubule-organizing centers (MTOCs) that shape the spindle poles during meiotic divisions. The mechanisms involved in centrosome and acentriolar MTOCs metabolism in oocytes have not been elucidated yet. In addition, little is known about microtubule organization and its impact on intracellular architecture during the oocyte growth phase following centrosome disassembly. We have investigated this question in the mouse by coupling immunofluorescence and live-imaging approaches. We show that growing oocytes contain dispersed pericentriolar material, responsible for microtubule assembly and distribution all over the cell. The gradual enlargement of PCM foci eventually leads in competent oocytes to the formation of big perinuclear MTOCs and to the assembly of large microtubule asters emanating from the close vicinity of the nucleus. Upon meiosis resumption, perinuclear MTOCs spread around the nuclear envelope, which in parallel is remodelled before breaking-down, via a MT- and dynein-dependent mechanism. Only fully competent oocytes are able to perform this dramatic reorganization at NEBD. Therefore, the MTOC-MT reorganization that we describe is one of key feature of mouse oocyte competency.
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97
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Niehl A, Peña EJ, Amari K, Heinlein M. Microtubules in viral replication and transport. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:290-308. [PMID: 23379770 DOI: 10.1111/tpj.12134] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/29/2013] [Accepted: 01/31/2013] [Indexed: 05/05/2023]
Abstract
Viruses use and subvert host cell mechanisms to support their replication and spread between cells, tissues and organisms. Microtubules and associated motor proteins play important roles in these processes in animal systems, and may also play a role in plants. Although transport processes in plants are mostly actin based, studies, in particular with Tobacco mosaic virus (TMV) and its movement protein (MP), indicate direct or indirect roles of microtubules in the cell-to-cell spread of infection. Detailed observations suggest that microtubules participate in the cortical anchorage of viral replication complexes, in guiding their trafficking along the endoplasmic reticulum (ER)/actin network, and also in developing the complexes into virus factories. Microtubules also play a role in the plant-to-plant transmission of Cauliflower mosaic virus (CaMV) by assisting in the development of specific virus-induced inclusions that facilitate viral uptake by aphids. The involvement of microtubules in the formation of virus factories and of other virus-induced inclusions suggests the existence of aggresomal pathways by which plant cells recruit membranes and proteins into localized macromolecular assemblies. Although studies related to the involvement of microtubules in the interaction of viruses with plants focus on specific virus models, a number of observations with other virus species suggest that microtubules may have a widespread role in viral pathogenesis.
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Affiliation(s)
- Annette Niehl
- Zürich-Basel Plant Science Center, Botany, Department of Environmental Sciences, University of Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland
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98
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Abstract
The nucleus is the largest organelle and is commonly depicted in the center of the cell. Yet during cell division, migration, and differentiation, it frequently moves to an asymmetric position aligned with cell function. We consider the toolbox of proteins that move and anchor the nucleus within the cell and how forces generated by the cytoskeleton are coupled to the nucleus to move it. The significance of proper nuclear positioning is underscored by numerous diseases resulting from genetic alterations in the toolbox proteins. Finally, we discuss how nuclear position may influence cellular organization and signaling pathways.
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Affiliation(s)
- Gregg G Gundersen
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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99
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100
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Vreede BM, Lynch JA, Roth S, Sucena E. Co-option of a coordinate system defined by the EGFr and Dpp pathways in the evolution of a morphological novelty. EvoDevo 2013; 4:7. [PMID: 23448685 PMCID: PMC3621409 DOI: 10.1186/2041-9139-4-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 12/06/2012] [Indexed: 12/01/2022] Open
Abstract
Background Morphological innovation is an elusive and fascinating concept in evolutionary biology. A novel structure may open up an array of possibilities for adaptation, and thus is fundamental to the evolution of complex multicellular life. We use the respiratory appendages on the dorsal-anterior side of the Drosophila eggshell as a model system for morphological novelty. To study the co-option of genetic pathways in the evolution of this novelty we have compared oogenesis and eggshell patterning in Drosophila melanogaster with Ceratitis capitata, a dipteran whose eggs do not bear dorsal appendages. Results During the final stages of oogenesis, the appendages are formed by specific groups of cells in the follicular epithelium of the egg chamber. These cells are defined via signaling activity of the Dpp and EGFr pathways, and we find that both pathways are active in C. capitata oogenesis. The transcription factor gene mirror is expressed downstream of EGFr activation in a dorsolateral domain in the D. melanogaster egg chamber, but could not be detected during C. capitata oogenesis. In D. melanogaster, mirror regulates the expression of two important genes: broad, which defines the appendage primordia, and pipe, involved in embryonic dorsoventral polarity. In C. capitata, broad remains expressed ubiquitously throughout the follicular epithelium, and is not restricted to the appendage primordia. Interestingly pipe expression did not differ between the two species. Conclusions Our analysis identifies both broad and mirror as important nodes that have been redeployed in the Drosophila egg chamber patterning network in the evolution of a morphologically novel feature. Further, our results show how pre-existing signals can provide an epithelium with a spatial coordinate system, which can be co-opted for novel patterns.
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Affiliation(s)
- Barbara Mi Vreede
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras, Portugal.
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