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Chekulaeva M. Mechanistic insights into the basis of widespread RNA localization. Nat Cell Biol 2024; 26:1037-1046. [PMID: 38956277 DOI: 10.1038/s41556-024-01444-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 05/20/2024] [Indexed: 07/04/2024]
Abstract
The importance of subcellular mRNA localization is well established, but the underlying mechanisms mostly remain an enigma. Early studies suggested that specific mRNA sequences recruit RNA-binding proteins (RBPs) to regulate mRNA localization. However, despite the observation of thousands of localized mRNAs, only a handful of these sequences and RBPs have been identified. This suggests the existence of alternative, and possibly predominant, mechanisms for mRNA localization. Here I re-examine currently described mRNA localization mechanisms and explore alternative models that could account for its widespread occurrence.
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Affiliation(s)
- Marina Chekulaeva
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
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2
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Lu W, Gelfand VI. Go with the flow - bulk transport by molecular motors. J Cell Sci 2023; 136:jcs260300. [PMID: 36250267 PMCID: PMC10755412 DOI: 10.1242/jcs.260300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells are the smallest building blocks of all living eukaryotic organisms, usually ranging from a couple of micrometers (for example, platelets) to hundreds of micrometers (for example, neurons and oocytes) in size. In eukaryotic cells that are more than 100 µm in diameter, very often a self-organized large-scale movement of cytoplasmic contents, known as cytoplasmic streaming, occurs to compensate for the physical constraints of large cells. In this Review, we discuss cytoplasmic streaming in multiple cell types and the mechanisms driving this event. We particularly focus on the molecular motors responsible for cytoplasmic movements and the biological roles of cytoplasmic streaming in cells. Finally, we describe bulk intercellular flow that transports cytoplasmic materials to the oocyte from its sister germline cells to drive rapid oocyte growth.
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Affiliation(s)
- Wen Lu
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611-3008, USA
| | - Vladimir I. Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611-3008, USA
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3
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Shamipour S, Caballero-Mancebo S, Heisenberg CP. Cytoplasm's Got Moves. Dev Cell 2021; 56:213-226. [PMID: 33321104 DOI: 10.1016/j.devcel.2020.12.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/22/2020] [Accepted: 11/30/2020] [Indexed: 01/01/2023]
Abstract
Cytoplasm is a gel-like crowded environment composed of various macromolecules, organelles, cytoskeletal networks, and cytosol. The structure of the cytoplasm is highly organized and heterogeneous due to the crowding of its constituents and their effective compartmentalization. In such an environment, the diffusive dynamics of the molecules are restricted, an effect that is further amplified by clustering and anchoring of molecules. Despite the crowded nature of the cytoplasm at the microscopic scale, large-scale reorganization of the cytoplasm is essential for important cellular functions, such as cell division and polarization. How such mesoscale reorganization of the cytoplasm is achieved, especially for large cells such as oocytes or syncytial tissues that can span hundreds of micrometers in size, is only beginning to be understood. In this review, we will discuss recent advances in elucidating the molecular, cellular, and biophysical mechanisms by which the cytoskeleton drives cytoplasmic reorganization across different scales, structures, and species.
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Affiliation(s)
- Shayan Shamipour
- Institute of Science and Technology Austria, Klosterneuburg, Austria
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4
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Antel M, Baena V, Terasaki M, Inaba M. Ultrastructural Analysis of Cell-Cell Interactions in Drosophila Ovary. Methods Mol Biol 2021; 2346:79-90. [PMID: 33460026 DOI: 10.1007/7651_2020_342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The Drosophila ovary is an exceptional model for studying cell-cell interactions in vivo. Cells communicate with each other in a highly coordinated manner. Accurate spatiotemporal regulation of cell-cell interaction is critical for the development of eggs. Ultrastructural analysis using electron microscopy (EM) permits the visualization of both cells and subcellular signaling structures with high resolution. Here we describe a method for the processing of intact fly ovaries by scanning electron microscopy (SEM).
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Affiliation(s)
- Matthew Antel
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Valentina Baena
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Mark Terasaki
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Mayu Inaba
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA.
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5
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Schotthöfer SK, Bohrmann J. Bioelectrical and cytoskeletal patterns correlate with altered axial polarity in the follicular epithelium of the Drosophila mutant gurken. BMC DEVELOPMENTAL BIOLOGY 2020; 20:5. [PMID: 32169045 PMCID: PMC7071586 DOI: 10.1186/s12861-020-00210-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/26/2020] [Indexed: 01/08/2023]
Abstract
Background Bioelectrical signals are known to be involved in the generation of cell and tissue polarity as well as in cytoskeletal dynamics. The epithelium of Drosophila ovarian follicles is a suitable model system for studying connections between electrochemical gradients, patterns of cytoskeletal elements and axial polarity. By interactions between soma and germline cells, the transforming growth factor-α homolog Gurken (Grk) establishes both the anteroposterior and the dorsoventral axis during oogenesis. Results In the follicular epithelium of the wild-type (wt) and the polarity mutant grk, we analysed stage-specific gradients of membrane potentials (Vmem) and intracellular pH (pHi) using the potentiometric dye DiBAC4(3) and the fluorescent pH-indicator 5-CFDA,AM, respectively. In addition, we compared the cytoskeletal organisation in the follicular epithelium of wt and grk using fluorescent phalloidin and an antibody against acetylated α-tubulin. Corresponding to impaired polarity in grk, the slope of the anteroposterior Vmem-gradient in stage S9 is significantly reduced compared to wt. Even more striking differences in Vmem- and pHi-patterns become obvious during stage S10B, when the respective dorsoventral gradients are established in wt but not in grk. Concurrent with bioelectrical differences, wt and grk exhibit differences concerning cytoskeletal patterns in the follicular epithelium. During all vitellogenic stages, basal microfilaments in grk are characterised by transversal alignment, while wt-typical condensations in centripetal follicle cells (S9) and in dorsal centripetal follicle cells (S10B) are absent. Moreover, in grk, longitudinal alignment of microtubules occurs throughout vitellogenesis in all follicle cells, whereas in wt, microtubules in mainbody and posterior follicle cells exhibit a more cell-autonomous organisation. Therefore, in contrast to wt, the follicular epithelium in grk is characterised by missing or shallower electrochemical gradients and by more coordinated transcellular cytoskeletal patterns. Conclusions Our results show that bioelectrical polarity and cytoskeletal polarity are closely linked to axial polarity in both wt and grk. When primary polarity signals are altered, both bioelectrical and cytoskeletal patterns in the follicular epithelium change. We propose that not only cell-specific levels of Vmem and pHi, or the polarities of transcellular electrochemical gradients, but also the slopes of these gradients are crucial for cytoskeletal modifications and, thus, for proper development of epithelial polarity.
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Affiliation(s)
- Susanne Katharina Schotthöfer
- RWTH Aachen University, Institut für Biologie II, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany
| | - Johannes Bohrmann
- RWTH Aachen University, Institut für Biologie II, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany.
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6
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Modulation of Cell-Cell Interactions in Drosophila Oocyte Development. Cells 2020; 9:cells9020274. [PMID: 31979180 PMCID: PMC7072342 DOI: 10.3390/cells9020274] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 01/17/2020] [Accepted: 01/21/2020] [Indexed: 02/07/2023] Open
Abstract
The Drosophila ovary offers a suitable model system to study the mechanisms that orchestrate diverse cellular processes. Oogenesis starts from asymmetric stem cell division, proper differentiation and the production of fully patterned oocytes equipped with all the maternal information required for embryogenesis. Spatial and temporal regulation of cell-cell interaction is particularly important to fulfill accurate biological outcomes at each step of oocyte development. Progress has been made in understanding diverse cell physiological regulation of signaling. Here we review the roles of specialized cellular machinery in cell-cell communication in different stages of oogenesis.
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7
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Ravichandran A, Duman Ö, Hoore M, Saggiorato G, Vliegenthart GA, Auth T, Gompper G. Chronology of motor-mediated microtubule streaming. eLife 2019; 8:e39694. [PMID: 30601119 PMCID: PMC6338466 DOI: 10.7554/elife.39694] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 12/28/2018] [Indexed: 12/19/2022] Open
Abstract
We introduce a filament-based simulation model for coarse-grained, effective motor-mediated interaction between microtubule pairs to study the time-scales that compose cytoplasmic streaming. We characterise microtubule dynamics in two-dimensional systems by chronologically arranging five distinct processes of varying duration that make up streaming, from microtubule pairs to collective dynamics. The structures found were polarity sorted due to the propulsion of antialigned microtubules. This also gave rise to the formation of large polar-aligned domains, and streaming at the domain boundaries. Correlation functions, mean squared displacements, and velocity distributions reveal a cascade of processes ultimately leading to microtubule streaming and advection, spanning multiple microtubule lengths. The characteristic times for the processes extend over three orders of magnitude from fast single-microtubule processes to slow collective processes. Our approach can be used to directly test the importance of molecular components, such as motors and crosslinking proteins between microtubules, on the collective dynamics at cellular scale.
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Affiliation(s)
- Arvind Ravichandran
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Özer Duman
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Masoud Hoore
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Guglielmo Saggiorato
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Gerard A Vliegenthart
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Thorsten Auth
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced SimulationForschungszentrum JülichJülichGermany
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8
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Ravichandran A, Vliegenthart GA, Saggiorato G, Auth T, Gompper G. Enhanced Dynamics of Confined Cytoskeletal Filaments Driven by Asymmetric Motors. Biophys J 2017; 113:1121-1132. [PMID: 28877494 DOI: 10.1016/j.bpj.2017.07.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/10/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022] Open
Abstract
Cytoskeletal filaments and molecular motors facilitate the micron-scale force generation necessary for the distribution of organelles and the restructuring of the cytoskeleton within eukaryotic cells. Although the mesoscopic structure and the dynamics of such filaments have been studied in vitro and in vivo, their connection with filament polarity-dependent motor-mediated force generation is not well understood. Using 2D Brownian dynamics simulations, we study a dense, confined mixture of rigid microtubules (MTs) and active springs that have arms that cross-link neighboring MT pairs and move unidirectionally on the attached MT. We simulate depletion interactions between MTs using an attractive potential. We show that dimeric motors, with a motile arm on only one of the two MTs, produce large polarity-sorted MT clusters, whereas tetrameric motors, with motile arms on both microtubules, produce bundles. Furthermore, dimeric motors induce, on average, higher velocities between antialigned MTs than tetrameric motors. Our results, where MTs move faster near the confining wall, are consistent with experimental observations in Drosophila oocytes where enhanced microtubule activity is found close to the confining plasma membrane.
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Affiliation(s)
- Arvind Ravichandran
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany
| | - Gerrit A Vliegenthart
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany
| | - Guglielmo Saggiorato
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany; LPTMS, CNRS, University Paris-Sud, Université Paris-Saclay, Orsay, France
| | - Thorsten Auth
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany.
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany
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9
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Bilinski SM, Jaglarz MK, Tworzydlo W. The Pole (Germ) Plasm in Insect Oocytes. Results Probl Cell Differ 2017; 63:103-126. [PMID: 28779315 DOI: 10.1007/978-3-319-60855-6_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Animal germline cells are specified either through zygotic induction or cytoplasmic inheritance. Zygotic induction takes place in mid- or late embryogenesis and requires cell-to-cell signaling leading to the acquisition of germline fate de novo. In contrast, cytoplasmic inheritance involves formation of a specific, asymmetrically localized oocyte region, termed the germ (pole) plasm. This region contains maternally provided germline determinants (mRNAs, proteins) that are capable of inducing germline fate in a subset of embryonic cells. Recent data indicate that among insects, the zygotic induction represents an ancestral condition, while the cytoplasmic inheritance evolved at the base of Holometabola or in the last common ancestor of Holometabola and its sister taxon, Paraneoptera.In this chapter, we first describe subsequent stages of morphogenesis of the pole plasm and polar granules in the model organism, Drosophila melanogaster. Then, we present an overview of morphology and cytoarchitecture of the pole plasm in various holometabolan and paraneopteran insect species. Finally, we focus on phylogenetic hypotheses explaining the known distribution of two different strategies of germline specification among insects.
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Affiliation(s)
- Szczepan M Bilinski
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland.
| | - Mariusz K Jaglarz
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
| | - Waclaw Tworzydlo
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
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10
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Myachina F, Bosshardt F, Bischof J, Kirschmann M, Lehner CF. Drosophila beta-tubulin 97EF is upregulated at low temperature and stabilizes microtubules. Development 2017; 144:4573-4587. [DOI: 10.1242/dev.156109] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/20/2017] [Indexed: 12/22/2022]
Abstract
Cells in ectotherms function normally within an often wide temperature range. As temperature dependence is not uniform across all the distinct biological processes, acclimation presumably requires complex regulation. The molecular mechanisms coping with the disruptive effects of temperature variation are still poorly understood. Interestingly, one of five different beta-tubulin paralogs, betaTub97EF, was among the genes up-regulated at low temperature in cultured Drosophila cells. As microtubules are known to be cold-sensitive, we analyzed whether betaTub97EF protects microtubules at low temperatures. During development at the optimal temperature (25°C), betaTub97EF was expressed in a tissue-specific pattern primarily in the gut. There, as well as in hemocytes, expression was increased at low temperature (14°C). While betaTub97EF mutants were viable and fertile at 25°C, their sensitivity within the well-tolerated range was slightly enhanced during embryogenesis specifically at low temperatures. Changing beta-tubulin isoform ratios in hemocytes demonstrated that beta-Tubulin 97EF has a pronounced microtubule stabilizing effect. Moreover, betaTub97EF is required for normal microtubule stability in the gut. These results suggest that betaTub97EF up-regulation at low temperature contributes to acclimation by stabilizing microtubules.
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Affiliation(s)
- Faina Myachina
- Institute of Molecular Life Sciences (IMLS), University of Zurich, 8057 Zurich, Switzerland
| | - Fritz Bosshardt
- Institute of Molecular Life Sciences (IMLS), University of Zurich, 8057 Zurich, Switzerland
| | - Johannes Bischof
- Institute of Molecular Life Sciences (IMLS), University of Zurich, 8057 Zurich, Switzerland
| | - Moritz Kirschmann
- Center for Microscopy and Image Analysis, University of Zurich, 8057 Zurich, Switzerland
| | - Christian F. Lehner
- Institute of Molecular Life Sciences (IMLS), University of Zurich, 8057 Zurich, Switzerland
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11
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Microtubule-microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes. Proc Natl Acad Sci U S A 2016; 113:E4995-5004. [PMID: 27512034 DOI: 10.1073/pnas.1522424113] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cytoplasmic streaming in Drosophila oocytes is a microtubule-based bulk cytoplasmic movement. Streaming efficiently circulates and localizes mRNAs and proteins deposited by the nurse cells across the oocyte. This movement is driven by kinesin-1, a major microtubule motor. Recently, we have shown that kinesin-1 heavy chain (KHC) can transport one microtubule on another microtubule, thus driving microtubule-microtubule sliding in multiple cell types. To study the role of microtubule sliding in oocyte cytoplasmic streaming, we used a Khc mutant that is deficient in microtubule sliding but able to transport a majority of cargoes. We demonstrated that streaming is reduced by genomic replacement of wild-type Khc with this sliding-deficient mutant. Streaming can be fully rescued by wild-type KHC and partially rescued by a chimeric motor that cannot move organelles but is active in microtubule sliding. Consistent with these data, we identified two populations of microtubules in fast-streaming oocytes: a network of stable microtubules anchored to the actin cortex and free cytoplasmic microtubules that moved in the ooplasm. We further demonstrated that the reduced streaming in sliding-deficient oocytes resulted in posterior determination defects. Together, we propose that kinesin-1 slides free cytoplasmic microtubules against cortically immobilized microtubules, generating forces that contribute to cytoplasmic streaming and are essential for the refinement of posterior determinants.
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12
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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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13
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Welte MA. As the fat flies: The dynamic lipid droplets of Drosophila embryos. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1156-85. [PMID: 25882628 DOI: 10.1016/j.bbalip.2015.04.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/31/2015] [Accepted: 04/06/2015] [Indexed: 01/09/2023]
Abstract
Research into lipid droplets is rapidly expanding, and new cellular and organismal roles for these lipid-storage organelles are continually being discovered. The early Drosophila embryo is particularly well suited for addressing certain questions in lipid-droplet biology and combines technical advantages with unique biological phenomena. This review summarizes key features of this experimental system and the techniques available to study it, in order to make it accessible to researchers outside this field. It then describes the two topics most heavily studied in this system, lipid-droplet motility and protein sequestration on droplets, discusses what is known about the molecular players involved, points to open questions, and compares the results from Drosophila embryo studies to what it is known about lipid droplets in other systems.
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Affiliation(s)
- Michael A Welte
- Department of Biology University of Rochester, RC Box 270211, 317 Hutchison Hall, Rochester, NY 14627, USA.
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14
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Bor B, Bois JS, Quinlan ME. Regulation of the formin Cappuccino is critical for polarity of Drosophila oocytes. Cytoskeleton (Hoboken) 2015; 72:1-15. [PMID: 25557988 DOI: 10.1002/cm.21205] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 12/19/2014] [Indexed: 11/06/2022]
Abstract
The Drosophila formin Cappuccino (Capu) creates an actin mesh-like structure that traverses the oocyte during midoogenesis. This mesh is thought to prevent premature onset of fast cytoplasmic streaming which normally happens during late-oogenesis. Proper cytoskeletal organization and cytoplasmic streaming are crucial for localization of polarity determinants such as osk, grk, bcd, and nanos mRNAs. Capu mutants disrupt these events, leading to female sterility. Capu is regulated by another nucleator, Spire, as well as by autoinhibition in vitro. Studies in vivo confirm that Spire modulates Capu's function in oocytes; however, how autoinhibition contributes is still unclear. To study the role of autoinhibition in flies, we expressed a Capu construct that is missing the Capu Inhibitory Domain, CapuΔN. Consistent with a gain of activity due to loss of autoinhibition, the actin mesh was denser in CapuΔN oocytes. Further, cytoplasmic streaming was delayed and fertility levels decreased. Localization of osk mRNA in early stages, and bcd and nanos in late stages, were disrupted in CapuΔN-expressing oocytes. Finally, evidence that these phenotypes were due to a loss of autoinhibition comes from coexpression of the N-terminal half of Capu with CapuΔN, which suppressed the defects in actin, cytoplasmic streaming and fertility. From these results, we conclude that Capu can be autoinhibited during Drosophila oocyte development.
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Affiliation(s)
- Batbileg Bor
- Molecular Biology Interdepartmental PhD Program, University of California, Los Angeles, California, 90095-1570
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15
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Riparbelli MG, Gigliotti S, Callaini G. The Drosophila nucleoporin gene nup154 is required for correct microfilament dynamics and cell death during oogenesis. ACTA ACUST UNITED AC 2007; 64:590-604. [PMID: 17410542 DOI: 10.1002/cm.20206] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The Drosophila nucleoporin gene nup154 is required in both male and female germline for successful gametogenesis. Mutant flies lack differentiated sperm and lay abnormal eggs. We demonstrated that the egg phenotype was associated with specific alterations of the actin cytoskeleton at different stages of oogenesis. Actually, mutant egg chambers displayed an abnormal organization of both subcortical microfilaments and cytoplasmic actin bundles, that led to defective nurse cell dumping. TUNEL analysis also showed that the dumpless phenotype was associated with delayed apoptosis. The nup154 gene product was localized by conventional immunofluorescence microscopy to the nuclear envelope in a distinct punctuate pattern, characteristic of nuclear pore complex components. TEM analysis revealed that the protein was mainly distributed along filamentous structures that extended radially on the nuclear side of the pore, suggesting that Nup154 could be an integral component of the basket filaments associated with the nuclear pore complexes. We propose that Nup154 is necessary for correct nuclear pore complex functions and that the proper regulation of the actin cytoskeleton dynamics strongly relies upon nuclear pore integrity.
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16
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Weil TT, Forrest KM, Gavis ER. Localization of bicoid mRNA in late oocytes is maintained by continual active transport. Dev Cell 2006; 11:251-62. [PMID: 16890164 DOI: 10.1016/j.devcel.2006.06.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 05/22/2006] [Accepted: 06/20/2006] [Indexed: 10/24/2022]
Abstract
Localization of bicoid mRNA to the anterior of the Drosophila oocyte is essential to produce the Bicoid protein gradient that patterns the anterior-posterior axis of the embryo. Previous studies have characterized a microtubule-dependent pathway for bicoid mRNA localization during midoogenesis, when bicoid first accumulates at the anterior. We show that the majority of bicoid is actually localized later in oogenesis, when the only known mechanism for mRNA localization is based on passive trapping. Through live imaging of fluorescently tagged endogenous bicoid mRNA, we identify a temporally distinct pathway for bicoid localization in late oocytes that utilizes a specialized subpopulation of anterior microtubules and dynein. The directional movement of bicoid RNA particles within the oocyte observed here is consistent with dynein-mediated transport. Furthermore, our results indicate that association of bicoid with the anterior oocyte cortex is dynamic and support a model for maintenance of bicoid localization by continual active transport on microtubules.
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Affiliation(s)
- Timothy T Weil
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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17
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Ganot P, Kallesøe T, Thompson EM. The cytoskeleton organizes germ nuclei with divergent fates and asynchronous cycles in a common cytoplasm during oogenesis in the chordate Oikopleura. Dev Biol 2006; 302:577-90. [PMID: 17123503 DOI: 10.1016/j.ydbio.2006.10.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 09/25/2006] [Accepted: 10/14/2006] [Indexed: 11/15/2022]
Abstract
Germline cysts are conserved structures in which cells initiating meiosis are interconnected by ring canals. In many species, the cyst phase is of limited duration, but the chordate, Oikopleura, maintains it throughout prophase I as a unique cell, the coenocyst. We show that despite sharing one common cytoplasm with meiotic and nurse nuclei evenly distributed in a 1:1 ratio, both entry into meiosis and subsequent endocycles of nurse nuclei were asynchronous. Coenocyst cytoskeletal elements played central roles as oogenesis progressed from a syncytial state of indistinguishable germ nuclei, to a final arrangement where the common cytoplasm had been equally partitioned into resolved, mature oocytes. During chromosomal bouquet formation in zygotene, nuclear pore complexes clustered and anchored meiotic nuclei to the coenocyst F-actin network opposite ring canals, polarizing oocytes early in prophase I. F-actin synthesis was required for oocyte growth but movement of cytoplasmic organelles into oocytes did not require cargo transport along colchicine-sensitive microtubules. Instead, microtubules maintained nurse nuclei on the F-actin scaffold and prevented their entry into growing oocytes. Finally, it was possible to both decouple meiotic progression from cellular mechanisms governing oocyte growth, and to advance the timing of oocyte growth in response to external cues.
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Affiliation(s)
- Philippe Ganot
- Sars Centre for Marine Molecular Biology, Bergen High Technology Centre, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway
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Serbus LR, Cha BJ, Theurkauf WE, Saxton WM. Dynein and the actin cytoskeleton control kinesin-driven cytoplasmic streaming in Drosophila oocytes. Development 2005; 132:3743-52. [PMID: 16077093 PMCID: PMC1534125 DOI: 10.1242/dev.01956] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mass movements of cytoplasm, known as cytoplasmic streaming, occur in some large eukaryotic cells. In Drosophila oocytes there are two forms of microtubule-based streaming. Slow, poorly ordered streaming occurs during stages 8-10A, while pattern formation determinants such as oskar mRNA are being localized and anchored at specific sites on the cortex. Then fast well-ordered streaming begins during stage 10B, just before nurse cell cytoplasm is dumped into the oocyte. We report that the plus-end-directed microtubule motor kinesin-1 is required for all streaming and is constitutively capable of driving fast streaming. Khc mutations that reduce the velocity of kinesin-1 transport in vitro blocked streaming yet still supported posterior localization of oskar mRNA, suggesting that streaming is not essential for the oskar localization mechanism. Inhibitory antibodies indicated that the minus-end-directed motor dynein is required to prevent premature fast streaming, suggesting that slow streaming is the product of a novel dynein-kinesin competition. As F-actin and some associated proteins are also required to prevent premature fast streaming, our observations support a model in which the actin cytoskeleton triggers the shift from slow to fast streaming by inhibiting dynein. This allows a cooperative self-amplifying loop of plus-end-directed organelle motion and parallel microtubule orientation that drives vigorous streaming currents and thorough mixing of oocyte and nurse-cell cytoplasm.
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Affiliation(s)
- Laura R Serbus
- Department of Biology, Indiana University, Bloomington, 1001 East 3rd Street, IN 47405, USA
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19
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Tavosanis G, Gonzalez C. gamma-Tubulin function during female germ-cell development and oogenesis in Drosophila. Proc Natl Acad Sci U S A 2003; 100:10263-8. [PMID: 12915734 PMCID: PMC193549 DOI: 10.1073/pnas.1731925100] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2003] [Indexed: 11/18/2022] Open
Abstract
A series of unconventional microtubule organizing centers play a fundamental role during egg chamber development in Drosophila. To gain a better understanding of their molecular nature, we have studied the centrosomal component gamma-tubulin during Drosophila oogenesis. We find that although single mutations in either of the two gamma-tubulin genes identified in Drosophila do not affect oogenesis progression the simultaneous depletion of both protein products has severe consequences. The combination of loss-of-function mutant alleles for the two gamma-tubulin genes leads to mitotic defects in female germ cells, resulting in agametic ovaries. A combination of weaker mutant alleles instead allows female germ-cell development to proceed, although the resulting egg chambers display pleiotropic abnormalities, most frequently affecting the number of nurse cells and oocytes per egg chamber. Thus, gamma-tubulin is required for several processes at different stages of germ-cell development and oogenesis, including oocyte determination and differentiation. Our data provide a functional link between a component of the peri-centriolar material, such as gamma-tubulin, and microtubule organization during Drosophila oogenesis. In addition, our results show that gamma-tubulin is required for female germ-cell proliferation and that the two gamma-tubulins present in Drosophila are functionally equivalent during female germ-cell development and oogenesis.
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Affiliation(s)
- Gaia Tavosanis
- Cell Biology Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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20
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Forrest KM, Gavis ER. Live imaging of endogenous RNA reveals a diffusion and entrapment mechanism for nanos mRNA localization in Drosophila. Curr Biol 2003; 13:1159-68. [PMID: 12867026 DOI: 10.1016/s0960-9822(03)00451-2] [Citation(s) in RCA: 302] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Localization of nanos mRNA to the posterior pole of the Drosophila embryo directs local synthesis of Nanos protein that is essential for patterning of the anterior-posterior body axis and germ cell function. While nanos RNA is synthesized by the ovarian nurse cells and appears at the posterior pole of the ooctye late in oogenesis, the mechanism by which this RNA is translocated to and anchored at the oocyte posterior is unknown. RESULTS By labeling endogenous nanos RNA with GFP, we have been able to follow the dynamic pathway of nanos localization in living oocytes. We demonstrate that nanos localization initiates immediately upon nurse cell dumping, whereby diffusion, enhanced by microtubule-dependent cytoplasmic movements, translocates nanos RNA from the nurse cells to the ooctye posterior. At the posterior, nanos is trapped by association, in particles, with the posteriorly localized germ plasm. Actin-dependent anchoring of nanos RNA complexed to the germ plasm at the posterior maintains localization in the face of rapid cytoplasmic movements. CONCLUSIONS These results reveal a diffusion-based, late-acting posterior localization mechanism for long-range transport of nanos mRNA. This mechanism differs from directed transport-based localization mechanisms in its reliance on bulk movement of RNA.
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Affiliation(s)
- Kevin M Forrest
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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21
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Palacios IM, St Johnston D. Kinesin light chain-independent function of the Kinesin heavy chain in cytoplasmic streaming and posterior localisation in the Drosophila oocyte. Development 2002; 129:5473-85. [PMID: 12403717 DOI: 10.1242/dev.00119] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Microtubules and the Kinesin heavy chain, the force-generating component of the plus end-directed microtubule motor Kinesin I are required for the localisation of oskar mRNA to the posterior pole of the Drosophila oocyte, an essential step in the determination of the anteroposterior axis. We show that the Kinesin heavy chain is also required for the posterior localisation of Dynein, and for all cytoplasmic movements within the oocyte. Furthermore, the KHC localises transiently to the posterior pole in an oskar mRNA-independent manner. Surprisingly, cytoplasmic streaming still occurs in kinesin light chain null mutants, and both oskar mRNA and Dynein localise to the posterior pole. Thus, the Kinesin heavy chain can function independently of the light chain in the oocyte, indicating that it associates with its cargoes by a novel mechanism.
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Affiliation(s)
- Isabel M Palacios
- Wellcome Trust/Cancer Research UK Institute and Department of Genetics, University of Cambridge, Tennis Court Road, UK
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22
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Schnorrer F, Luschnig S, Koch I, Nüsslein-Volhard C. Gamma-tubulin37C and gamma-tubulin ring complex protein 75 are essential for bicoid RNA localization during drosophila oogenesis. Dev Cell 2002; 3:685-96. [PMID: 12431375 DOI: 10.1016/s1534-5807(02)00301-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
bicoid (bcd) RNA localization requires the activity of exuperantia and swallow at sequential steps of oogenesis and is microtubule dependent. In a genetic screen, we identified two novel genes essential for bcd RNA localization. They encode maternal gamma-Tubulin37C (gammaTub37C) and gamma-tubulin ring complex protein 75 (Dgrip75), both of which are gamma-tubulin ring complex components. Mutations in these genes specifically affect bcd RNA localization, whereas other microtubule-dependent processes during oogenesis are not impaired. This provides direct evidence that a subset of microtubules organized by the gamma-tubulin ring complex is essential for localization of bcd RNA. At stage 10b, we find gammaTub37C and Dgrip75 anteriorly concentrated and propose the formation of a microtubule-organizing center at the anterior pole of the oocyte.
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Affiliation(s)
- Frank Schnorrer
- Max-Planck-Institut für Entwicklungsbiologie, Abteilung Genetik, Spemannstr. 35, 72076, Tübingen, Germany.
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23
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Dequier E, Souid S, Pál M, Maróy P, Lepesant JA, Yanicostas C. Top-DER- and Dpp-dependent requirements for the Drosophila fos/kayak gene in follicular epithelium morphogenesis. Mech Dev 2001; 106:47-60. [PMID: 11472834 DOI: 10.1016/s0925-4773(01)00418-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The Drosophila fos (Dfos)/kayak gene has been previously identified as a key regulator of epithelial cell morphogenesis during dorsal closure of the embryo and fusion of the adult thorax. We show here that it is also required for two morphogenetic movements of the follicular epithelium during oogenesis. Firstly, it is necessary for the proper posteriorward migration of main body follicle cells during stage 9. Secondly, it controls, from stage 11 onwards, the morphogenetic reorganization of the follicle cells that are committed to secrete the respiratory appendages. We demonstrate that DER pathway activation and a critical level of Dpp/TGFbeta signalling are required to pattern a high level of transcription of Dfos at the anterior and dorsal edges of the two groups of cells that will give rise to the respiratory appendages. In addition, we provide evidence that, within the dorsal-anterior territory, the level of paracrine Dpp/TGFbeta signalling controls the commitment of follicle cells towards either an operculum or an appendage secretion fate. Finally, we show that Dfos is required in follicle cells for the dumping of the nurse cell cytoplasm into the oocyte and the subsequent apoptosis of nurse cells. This suggests that in somatic follicle cells, Dfos controls the expression of one or several factors that are necessary for these processes in underlying germinal nurse cells.
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Affiliation(s)
- E Dequier
- Department of Developmental Biology, Institut Jacques Monod, UMR 7592, CNRS, Université Paris 7 Denis-Diderot and Université Paris 6 Pierre et Marie Curie, 2, Place Jussieu, F-75251 Cedex 05, Paris, France
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24
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Abstract
The Drosophila ovary provides a favorable model system in which to study cellular morphogenesis. The development of a mature egg involves a syncytium of 16 germline cells and over 1000 somatically derived follicle cells. Intercellular transport, stable intercellular bridges, cell migrations, cell shape changes, and specific subcellular localization of many embryonic patterning determinants contribute to egg development and require a dynamic cytoskeleton. We discuss many of the recent genetic and cell biological studies that have led to insights into how the actin cytoskeleton is assembled and regulated during the morphogenesis of the Drosophila egg.
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Affiliation(s)
- D N Robinson
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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25
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BRADLEY JAMEST, ESTRIDGE BARBARAH. Vitellogenin uptake and vitellin localization in insect follicles examined using monoclonal antibodies and confocal scanning microscopy. INVERTEBR REPROD DEV 1997. [DOI: 10.1080/07924259.1997.9672630] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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26
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Glotzer JB, Saffrich R, Glotzer M, Ephrussi A. Cytoplasmic flows localize injected oskar RNA in Drosophila oocytes. Curr Biol 1997; 7:326-37. [PMID: 9115398 DOI: 10.1016/s0960-9822(06)00156-4] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The oskar (osk) gene encodes a determinant of posterior identity in Drosophila, and the localization of osk RNA to the pole plasm at the posterior pole of the oocyte is essential for development of the embryo. The mechanisms by which osk RNA is localized are unknown. RESULTS To study the mechanisms underlying localization of osk RNA, we have injected fluorescently labelled RNA into oocytes at stages 9, 10 and 11. Injected osk RNA localizes to the pole plasm, reproducing localization of the endogenous RNA. In oocytes at stages 10 and 11, the long-range movement of injected osk RNA is promoted by a vigorous, microtubule-dependent cytoplasmic flow, or ooplasmic streaming. Treatment with colchicine, a microtubule-destabilizing drug, inhibits ooplasmic streaming and prevents localization of the RNA from an injection site distal to the posterior pole. If the RNA is injected close to the posterior pole, however, it localizes even in the presence of colchicine. Similarly, in small oocytes, such as stage 9 oocytes, localization of injected osk RNA is insensitive to colchicine. CONCLUSIONS These results reveal that microtubule-dependent cytoplasmic flows could contribute to the long-range transport of osk RNA, whereas microtubule-independent processes could mediate short-range transport. These results also highlight the role of the osk RNA anchor in the localization process.
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Affiliation(s)
- J B Glotzer
- Programme in Developmental Biology, European Molecular Biology Laboratory, Meyerhofstrasse 1, Heidelberg, D-69117, Germany
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27
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Ray RP, Schüpbach T. Intercellular signaling and the polarization of body axes during Drosophila oogenesis. Genes Dev 1996; 10:1711-23. [PMID: 8698232 DOI: 10.1101/gad.10.14.1711] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- R P Ray
- Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, New Jersey 08544, USA
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28
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Emmons S, Phan H, Calley J, Chen W, James B, Manseau L. Cappuccino, a Drosophila maternal effect gene required for polarity of the egg and embryo, is related to the vertebrate limb deformity locus. Genes Dev 1995; 9:2482-94. [PMID: 7590229 DOI: 10.1101/gad.9.20.2482] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We report the molecular isolation of cappuccino (capu), a gene required for localization of molecular determinants within the developing Drosophila oocyte. The carboxy-terminal half of the capu protein is closely related to that of the vertebrate limb deformity locus, which is known to function in polarity determination in the developing vertebrate limb. In addition, capu shares both a proline-rich region and a 70-amino-acid domain with a number of other genes, two of which also function in pattern formation, the Saccharomyes cerevisiae BNI1 gene and the Aspergillus FigA gene. We also show that capu mutant oocytes have abnormal microtubule distributions and premature microtubule-based cytoplasmic streaming within the oocyte, but that neither the speed nor the timing of the cytoplasmic streaming correlates with the strength of the mutant allele. This suggests that the premature cytoplasmic streaming in capu mutant oocytes does not suffice to explain the patterning defects. By inducing cytoplasmic streaming in wild-type oocytes during mid-oogenesis, we show that premature cytoplasmic streaming can displace staufen protein from the posterior pole, but not gurken mRNA from around the oocyte nucleus.
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Affiliation(s)
- S Emmons
- Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721, USA
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29
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Erdélyi M, Michon AM, Guichet A, Glotzer JB, Ephrussi A. Requirement for Drosophila cytoplasmic tropomyosin in oskar mRNA localization. Nature 1995; 377:524-7. [PMID: 7566149 DOI: 10.1038/377524a0] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The localization of oskar (osk) RNA to the posterior pole of the developing fruit fly (Drosophila) oocyte induces the assembly of pole plasm, causing development of the abdomen and germ line. Failure to localize oskar RNA results in embryos that lack abdomen and germ cells. Conversely, mis-targeting of oskar RNA to the anterior of the oocyte causes formation of ectopic abdomen and germ cells at the anterior pole. Maternal mutants that have reduced pole plasm activity produce sterile adults with normal abdominal development, suggesting that germ cells are more sensitive than abdomen to defects in pole plasm assembly. Thus mutations in genes that reduce oskar RNA localization or activity can be recovered as viable sterile adults. In a screen for mutants defective in germ cell formation, we isolated nine alleles of the tropomyosin II gene. Here we show that mutations in tropomyosin II (TmII) virtually abolish oskar RNA localization to the posterior pole, suggesting an involvement of the actin network in oskar RNA localization.
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Affiliation(s)
- M Erdélyi
- European Molecular Biology Laboratory, Heidelberg, Germany
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30
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Biliński SM, Klag J, Kubrakiewicz J. Subcortical microtubule network separates the periplasm from the endoplasm and is responsible for maintaining the position of accessory nuclei in hymenopteran oocytes. ACTA ACUST UNITED AC 1995; 205:54-61. [DOI: 10.1007/bf00188843] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/1995] [Accepted: 05/18/1995] [Indexed: 11/29/2022]
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31
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Abstract
As I hope this review has made clear, mRNA localization plays an important role in directing specific proteins to their correct position within a cell. Although the study of this process is still in its infancy, it is already apparent that there are several ways that mRNAs can be targeted to particular subcellular sites. However, the molecular mechanisms responsible for these different localization pathways are still largely obscure, and their elucidation must await the identification of the specific factors that mediate the interactions between the localized mRNAs and more general components such as the cytoskeleton. Most examples of localized mRNAs are likely to share several common features. First, the site of localization will be determined by the preexisting polarity of the cell, and this will most often depend on the organization of the cytoskeleton, either directly, in the case of active transport, or indirectly, when localization is mediated by localized anchoring sites or stability factors. Second, mRNA localization is likely to be tightly coupled to translational control. If it is important for a cell to synthesize a protein in a particular place, then the translation of the mRNA must be repressed until it is localized. Indeed, there are already several examples where the direct linkage between translational control and localization has been demonstrated, and these are discussed in the accompanying review by Curtis et al. (1995).
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Affiliation(s)
- D St Johnston
- Wellcome Trust/Cancer Research Campaign Institute, University of Cambridge, England
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32
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Mutations in supernova, indicate that this gene is required for the division of germ line cells in Drosophila. Dev Genes Evol 1995; 204:250-258. [PMID: 28306120 DOI: 10.1007/bf00208492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/1994] [Accepted: 08/24/1994] [Indexed: 10/26/2022]
Abstract
Mutations in supernova, previously shown to uncouple chromosome replication from segregation during cleavage in Drosophila embryos, also sanctions extra divisions of cystoblasts and spermatoblasts. This leads either to the formation of egg chambers which contain more than fifteen nurse cells or testes which have an excess of spermatocytes. In maturing egg chambers two potential oocytes may be specified in which case they are often ectopically located and connected with surrounding nurse cells by four ring canals. However, a typical oocyte nucleus is not always present and these chambers usually become necrotic and degenerate. The nurse cells are of variable size, but are still interconnected by a system of ring canals. They all possess a polyploid nucleus. Sequestering of maternal mRNA's from the nurse cells into the potential oocyte(s) takes place but there is no localization of this maternal information within the oocyte probably because of defective microtubule assembly. Many spermatocytes fail to complete meiosis so that bundles of spermatids are reduced in size and the males have reduced fertility. It is proposed that this gene is indirectly involved in regulating the timing of mitotic divisions in both cystoblasts and spermatoblasts through its interference with microtubule assembly which is consistent with its role during embryogenesis.
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33
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Abstract
We have characterized the requirements for the Protein Kinase A (PKA) catalytic subunit, DC0, in Drosophila oogenesis. Intercellular bridges in egg chambers from PKA deficient females are unstable, leading to the formation of multinucleate nurse cells by fusions of adjacent cells. Germline clones of cells homozygous for null mutations of DC0 indicate that PKA acts autonomously in the germline. Highest levels of PKA catalytic subunit protein are associated with germ cell membranes, suggesting that targets of PKA are associated with the membrane or membrane skeleton and contribute to the stabilization of intercellular bridges. The migration of a subset of follicle cells, the border cells, is also disrupted by germline PKA mutations, implying that nurse cell junctions provide an essential path for border cell migrations.
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Affiliation(s)
- M E Lane
- Department of Biological Sciences, Columbia University, New York, NY 1002, USA
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34
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Riparbelli MG, Callaini G. Cytoskeleton of the Drosophila egg chamber: new observations on microfilament distribution during oocyte growth. CELL MOTILITY AND THE CYTOSKELETON 1995; 31:298-306. [PMID: 7553916 DOI: 10.1002/cm.970310406] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The distribution of microfilaments in Drosophila egg chambers stained with rhodamine (Rh)-conjugated phalloidin was studied by laser scanning confocal microscopy and transmission electron microscopy. These techniques revealed new details in the pattern of microfilament localization. We observed in stage 1-3 egg chambers accumulation of filamentous actin in the oocyte cytoplasm between the ring canals connecting the oocyte with adjacent nurse cells. Starting from stages 6-7 short microfilament bundles arranged in basket-like structures were associated with the side of the ring canals facing the nurse cell cytoplasm. We also observed a dramatic decrease in the actin network associated with the cortex of the oocyte in stage 10. During stage 10B the nurse cell cytoplasm was crossed by radial actin bundles that showed a sarcomeric-like cross striation after Rh-phalloidin staining. The ring canals also did not uniformly stain but showed a punctate labeling. The implications of the actin cytoskeleton during oocyte growth are discussed.
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Affiliation(s)
- M G Riparbelli
- Department of Evolutionary Biology, University of Siena, Italy
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35
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Abstract
Organismal morphogenesis is driven by a complex series of developmentally coordinated changes in cell shape, size, and number. These changes in cell morphology are in turn dependent on alterations in basic cytoarchitecture. Elucidating the mechanisms of development thus requires an understanding of the cytoskeletal elements that organize the cytoplasm of differentiating cells. Drosophila oogenesis has emerged as a versatile system for the study of cytoskeletal function during development. A series of highly coordinated changes in cytoskeletal organization are required to produce a mature Drosophila oocyte, and these cytoskeletal transformations are amenable to a variety of experimental approaches. Genetic, molecular, and cytological studies have shed light on the specific functions of the cytoskeleton during oogenesis. The results of these studies are reviewed here, and their mechanistic implications are considered.
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Affiliation(s)
- L Cooley
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510
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36
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Abstract
The Drosophila egg chamber is emerging as a uniquely versatile system for studying cytoskeletal rearrangements during development. Initial determination of the oocyte fate and subsequent growth of the oocyte depend on a series of highly coordinated changes in cell architecture. Homologs or relatives of many known cytoskeletal proteins play key roles in these events.
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Affiliation(s)
- B A Knowles
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06510
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37
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Wang S, Hazelrigg T. Implications for bcd mRNA localization from spatial distribution of exu protein in Drosophila oogenesis. Nature 1994; 369:400-03. [PMID: 7910952 DOI: 10.1038/369400a0] [Citation(s) in RCA: 383] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Subcellular RNA localization in different cell types leads to asymmetric distribution of proteins in these cells. The localization of bicoid (bcd) messenger RNA to the anterior pole of the developing Drosophila oocyte gives rise in embryogenesis to a steep concentration gradient of the bcd protein, a transcription factor that activates expression of zygotic genes needed for anterior development. The exuperantia (exu) gene is necessary for this localization of bcd mRNA. Here we express a chimaeric gene encoding a fusion between the Acquorea victoria green fluorescent protein (GFP) and the exu protein (Exu) in female germ cells, and find that the fusion protein fluoresces strongly in both live and fixed cells during Drosophila oogenesis. The fusion protein rescues an exu null allele, restoring full fertility to females, and is expressed and localized in a temporal and spatial pattern similar to native Exu. The high sensitivity of the GFP tag provides important new details on the subcellular localization of Exu. The fusion protein is found in particles concentrated at ring canals, where transport occurs between nurse cells and the oocyte. Drugs such as colchicine and taxol that affect microtubule stability alter localization of the particles. We propose that the particles are ribonucleoprotein complexes or vesicles which transport bcd mRNA along microtubules and target it to the anterior oocyte cortex.
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Affiliation(s)
- S Wang
- Department of Biological Sciences, Columbia University, New York, New York 10027
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38
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Ruohola-Baker H, Grell E, Chou TB, Baker D, Jan LY, Jan YN. Spatially localized rhomboid is required for establishment of the dorsal-ventral axis in Drosophila oogenesis. Cell 1993; 73:953-65. [PMID: 8500182 DOI: 10.1016/0092-8674(93)90273-s] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The establishment of dorsal-ventral asymmetry of the Drosophila embryo requires a group of genes that act maternally. None of the previously identified dorsal-ventral axis genes are known to produce asymmetrically localized gene products during oogenesis. We show that rhomboid (rho), a novel member of this group, encodes a protein that is localized on the apical surface of the dorsal-anterior follicle cells surrounding the oocyte. Loss of rho function causes ventralization of the eggshell and the embryo, whereas ectopic expression leads to dorsalization of both structures. Thus, spatially restricted rho is necessary and sufficient for dorsal-ventral axis formation. We propose, based on these observations and double mutant experiments, that the spatially restricted rho protein leads to selective activation of the epidermal growth factor receptor in the dorsal follicle cells and subsequently the specification of the dorsal follicle cells.
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Affiliation(s)
- H Ruohola-Baker
- Howard Hughes Medical Institute, University of California, San Francisco 94143-0724
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39
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Szklarzewicz T, Szlendak E, Boczek J, Biliński S. Oogenesis in the lesser grain borer, Rhizopertha dominica(Fabricius) (Coleoptera : Bostrichidae). ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0020-7322(92)90005-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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40
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Affiliation(s)
- E C Stephenson
- Department of Biology, University of Rochester, New York 14627
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41
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Zhang Y, Joseph G. K. Program of F-actin in the follicular epithelium during oogenesis of the german cockroach, Blattella germanica. Tissue Cell 1992. [DOI: 10.1016/0040-8166(92)90025-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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42
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Comparative developmental physiology and molecular cytology of the polytrophic ovarian follicles of the blowfly Sarcophaga bullata and the fruitfly Drosophila melanogaster. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1990; 96:309-21. [PMID: 1976473 DOI: 10.1016/0300-9629(90)90698-r] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. The ovarian follicles of Sarcophaga and Drosophila consist of one oocyte and 15 nurse cells, the whole being surrounded by follicle cells. Although oocyte and nurse cells are genetically identical sibling cells, and although they are interconnected by cytoplasmic bridges, their physiology is very different. 2. The DNA content of the oocyte nucleus (germinal vesicle) never exceeds 4C, while values of polyploidisation up to 1024C have been measured in the nurse cells, this being dependent on their position within a follicle. 3. The nurse cell nuclei very actively synthesize RNA, while the germinal vesicle is almost completely inactive in this respect. 4. It has been possible to visualise the major cytoskeletal elements in the different ovarian cell types. Cellular markers of polarity and dorsoventral asymmetry have been described. 5. Electrophysiological measurements have been performed to find out whether or not the self-electrophoresis principle may be involved in polarised transport between nurse cells and oocyte. 6. Most of the vitellogenin is synthesized by the fat body but some follicle cells also synthesize small amounts. 7. The role of 20-OH ecdysone in the induction of vitellogenin synthesis in the fat body, as well as the presence of met-enkephalin like immunoreactivity in the gonads is well established in both species. Not so clear is the exact role of juvenile hormones and the nature of brain factors controlling ovarian development. 8. Drosophila has the advantage of its well documented genetics while the larger species Sarcophaga is preferable for the study of (electro-) physiological and cell biological mechanisms.
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Matthews KA, Miller DF, Kaufman TC. Developmental distribution of RNA and protein products of the Drosophila alpha-tubulin gene family. Dev Biol 1989; 132:45-61. [PMID: 2492961 DOI: 10.1016/0012-1606(89)90203-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The developmental pattern of gene expression of the Drosophila melanogaster alpha-tubulin family has been examined in detail at both the mRNA and protein levels. Northern data from 16 stages of development have been quantified to produce estimates of pool sizes of each of the alpha-tubulin transcripts through development. The in situ pattern of alpha 67C RNA localization in developing oocytes and early embryos has also been determined. At the protein level, two of the three previously unidentified products of alpha-tubulin genes (alpha 67C and alpha 85E) have been identified. Evidence that protein from the fourth gene comigrates with the ubiquitously expressed alpha 84B is presented. In addition to the primary translational products of the alpha-tubulin genes, an elaborate series of post-translationally modified alpha-tubulins has been resolved. The developmental profiles of both synthesis and accumulation of these alpha-tubulin proteins are described.
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Affiliation(s)
- K A Matthews
- Department of Biology, Indiana University, Bloomington 47405
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MEER JITSEMVANDER. THE ROLE OF METABOLISM AND CALCIUM IN THE CONTROL OF MITOSIS AND OOPLASMIC MOVEMENTS IN INSECT EGGS: A WORKING HYPOTHESIS. Biol Rev Camb Philos Soc 1988. [DOI: 10.1111/j.1469-185x.1988.tb00628.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cellular and molecular markers of anteroposterior and dorsoventral organisation in the vitellogenic follicles of adult Sarcophaga bullata (Diptera) and dorsoventral orientation of follicles in the ovary. ACTA ACUST UNITED AC 1988; 197:101-109. [DOI: 10.1007/bf00375932] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/1987] [Accepted: 11/02/1987] [Indexed: 10/26/2022]
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