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Kuburich NA, den Hollander P, Pietz JT, Mani SA. Vimentin and cytokeratin: Good alone, bad together. Semin Cancer Biol 2022; 86:816-826. [PMID: 34953942 PMCID: PMC9213573 DOI: 10.1016/j.semcancer.2021.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/26/2021] [Accepted: 12/14/2021] [Indexed: 01/27/2023]
Abstract
The cytoskeleton plays an integral role in maintaining the integrity of epithelial cells. Epithelial cells primarily employ cytokeratin in their cytoskeleton, whereas mesenchymal cells use vimentin. During the epithelial-mesenchymal transition (EMT), cytokeratin-positive epithelial cells begin to express vimentin. EMT induces stem cell properties and drives metastasis, chemoresistance, and tumor relapse. Most studies of the functions of cytokeratin and vimentin have relied on the use of either epithelial or mesenchymal cell types. However, it is important to understand how these two cytoskeleton intermediate filaments function when co-expressed in cells undergoing EMT. Here, we discuss the individual and shared functions of cytokeratin and vimentin that coalesce during EMT and how alterations in intermediate filament expression influence carcinoma progression.
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Affiliation(s)
- Nick A Kuburich
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States
| | - Petra den Hollander
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States
| | - Jordan T Pietz
- Department of Creative Services, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States
| | - Sendurai A Mani
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, United States.
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2
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Martinovic V, Vukusic Pusic T, Restovic I, Bocina I, Filipovic N, Saraga-Babic M, Vukojevic K. Expression of Epithelial and Mesenchymal Differentiation Markers in the Early Human Gonadal Development. Anat Rec (Hoboken) 2017; 300:1315-1326. [PMID: 27981799 DOI: 10.1002/ar.23531] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Revised: 07/23/2016] [Accepted: 08/01/2016] [Indexed: 12/14/2022]
Abstract
Expressions of cytokeratin 8 (CK8), vimentin, nestin, and alpha-smooth-muscle-actin (alpha-SMA) were analyzed in the developing gonads of 12, 5-9 week old (W) human conceptuses by immunohistochemistry and immunofluorescence. During the investigated period, the number of CK8 positive cells increased from 56% to 92% in the gonadal surface epithelium, from 50% to 60% in the stroma, and from 23% to 42% in the medulla. In the early fetal period, the cell expression of CK8 increased in all gonadal parts, whereas primordial germ cells (PGC) remained negative. The expression of vimentin increased in the gonad stroma (gs) from 73% to 88%, and in the surface epithelium from 18% to 97% until ninth W. The medulla had the highest expression of vimentin in the seventh to eighth W (93%). Vimentin and CK8 colocalized in the somatic cells, while some PGCs showed vimentin expression only. Initially, nestin was positive in the gonad surface epithelium (8%) and stroma (52%), however during further development it decreased to 1% and 33%, respectively. In the early fetal period, the nestin positive cells decreased from 44% to 31% in the gonad medulla. Alpha-SMA was positive only in the blood vessels and mesonephros. The described pattern of expression of intermediate filaments (IF) in developing human gonads suggests their role in the control of PGC apoptosis, early differentiation of gs cells and cell migration. Both epithelial and mesenchymal origins of follicular cells and possible epithelial-to-mesenchymal transition of somatic cells is proposed. Lastly, IF intensity expression varies depending on the cell type and developmental period analyzed. Anat Rec, 300:1315-1326, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Vlatka Martinovic
- Department of Pediatric Surgery, University Hospital Mostar, Bosnia and Herzegovina
| | | | | | - Ivana Bocina
- Faculty of Science, University of Split, Croatia
| | - Natalija Filipovic
- Laboratory for Neurocardiology, Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, Croatia.,Laboratory for Early Human Development, Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, Croatia
| | - Mirna Saraga-Babic
- Laboratory for Early Human Development, Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, Croatia
| | - Katarina Vukojevic
- Laboratory for Early Human Development, Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, Croatia.,Department of Histology and Embryology, School of Medicine, University of Mostar, Bosnia and Herzegovina
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3
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Mohanty BK, Gupta BL. A marked animal-vegetal polarity in the localization of Na(+),K(+) -ATPase activity and its down-regulation following progesterone-induced maturation. Mol Reprod Dev 2011; 79:138-60. [PMID: 22213374 DOI: 10.1002/mrd.22012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 11/22/2011] [Indexed: 01/01/2023]
Abstract
The stage-VI Xenopus oocyte has a very distinct animal-vegetal polarity with structural and functional asymmetry. In this study, we show the expression and distribution pattern of Na(+),K(+) -ATPase in stage-VI oocytes, and its changes following progesterone-induced maturation. Using enzyme-specific electron microscopy phosphatase histochemistry, [(3) H]-ouabain autoradiography, and immunofluorescence cytochemistry at light microscopic level, we find that Na(+),K(+) -ATPase activity is mainly confined to the animal hemisphere. Electron microscopy histochemical results also suggest that polarized distribution of Na(+),K(+) -ATPase activity persists following progesterone-induced maturation, and it becomes gradually more polarized towards the animal pole. The time course following progesterone-induced maturation suggests that there is an initial up-regulation and then gradual down-regulation of Na(+),K(+) -ATPase activity leading to germinal vesicle breakdown (GVBD). By GVBD, the Na(+),K(+) -ATPase activity is completely down-regulated due to endocytotic removal of pump molecules from the plasma membrane into the sub-cortical region of the oocyte. This study provides the first direct evidence for a marked asymmetric localization of Na(+),K(+) -ATPase activity in any vertebrate oocyte. Here, we propose that such asymmetry in Na(+),K(+) -ATPase activity in stage-VI oocytes, and their down-regulation following progesterone-induced maturation, is likely to have a role in the active state of the germinal vesicle in stage-VI oocytes and chromosomal condensation after GVBD.
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4
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Abstract
Xenopus oocytes contain a complex cytoskeleton composed of three filament systems: (1) microtubules, composed of tubulin and at least three different microtubule-associated proteins (XMAPs); (2) microfilaments composed of actin and associated proteins; and (3) intermediate filaments, composed of keratins. For the past several years, we have used confocal immunofluorescence microscopy to characterize the organization of the oocyte cytoskeleton throughout the course of oogenesis. Together with computer-assisted reconstruction of the oocyte in three dimensions, confocal microscopy gives an unprecedented view of the assembly and reorganization of the cytoskeleton during oocyte growth and differentiation. Results of these studies, combined with the effects of cytoskeletal inhibitors, suggest that organization of the cytoskeleton in Xenopus oocytes is dependent upon a hierarchy of interactions between microtubules, microfilaments, and keratin filaments. This article presents a gallery of confocal images and 3-D reconstructions depicting the assembly and organization of the oocyte cytoskeleton during stages 0-VI of oogenesis, a discussion of the mechanisms that might regulate cytoskeletal organization during oogenesis, and speculates on the potential roles of the oocyte cytoskeleton during oogenesis and axis formation.
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Affiliation(s)
- D L Gard
- Department of Biology, University of Utah, Salt Lake City 84112-0840, USA.
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5
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Mencarelli C, Cotelli F. Intermediate filament proteins immunologically related to cytokeratins in the oocyte of the fish Cyprinus carpio. ZYGOTE 1997; 5:207-12. [PMID: 9460904 DOI: 10.1017/s0967199400003634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We have used monoclonal antibodies specific for different sets of human cytokeratins and the anti-IFA (Intermediate Filament Antigen) antibody to investigate the expression of intermediate filament proteins in the mature oocyte of the teleost Cyprinus carpio. Several polypeptides have been identified, showing molecular weights ranging from 43 to 65 kDa. Two-dimensional analysis of the immunoreactive species revealed the presence of at least six major protein spots and a series of minor components, grouped in quite a narrow pI range from 5.52 to 6.28. The general complexity of the carp oocyte cytokeratin-related cytoskeleton appears to be higher than those described for oocytes of other vertebrate species.
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Affiliation(s)
- C Mencarelli
- Department of Evolutionary Biology, University of Siena, Italy.
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Affiliation(s)
- C A Larabell
- Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA
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7
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Gard DL, Cha BJ, Roeder AD. F-actin is required for spindle anchoring and rotation in Xenopus oocytes: a re-examination of the effects of cytochalasin B on oocyte maturation. ZYGOTE 1995; 3:17-26. [PMID: 7613871 DOI: 10.1017/s0967199400002331] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We used confocal immunofluorescence microscopy to examine spindle migration, morphology and orientation during the maturation of Xenopus oocytes, in the presence or absence of cytochalasin B (CB), an inhibitor of actin assembly. Treatment with CB during maturation (10-50 micrograms/ml beginning 0-3 h prior to addition of progesterone) disrupted the normal organisation of the novel MTOC and transient microtubule array (MTOC-TMA complex) that serves as the immediate precursor of the first meiotic spindle, suggesting that F-actin plays an important role in the assembly or maintenance of this complex. However, CB treatment did not block translocation of the MTOC-TMA complex to the oocyte cortex, suggesting that MTOC-TMA translocation is not dependent on an actin-based mechanism. Bipolar spindles were observed in CB-treated oocytes fixed during both M1 and M2. However, rotation of the M1 and M2 spindles into an orientation orthogonal to the oocyte surface was inhibited by CB. Rhodamine-phalloidin revealed a concentration of F-actin at the site of M1 spindle attachment, further suggesting that cortical actin is required for anchoring and rotation of the meiotic spindles. Finally, the incidence of M1 monasters was significantly increased in CB-treated oocytes, suggesting that interactions between the nascent M1 spindle and cortex are dependent on F-actin.
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Affiliation(s)
- D L Gard
- Department of Biology, University of Utah, Salt Lake City 84112, USA
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8
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Card DL. 7 Axis Formation during Amphibian Oogenesis: Reevaluating the Role of the Cytoskeleton. Curr Top Dev Biol 1995. [DOI: 10.1016/s0070-2153(08)60568-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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9
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Ryabova LV, Vassetzky SG, Capco DG. Development of cortical contractility in the Xenopus laevis oocyte mediated by reorganisation of the cortical cytoskeleton: a model. ZYGOTE 1994; 2:263-71. [PMID: 8785685 DOI: 10.1017/s0967199400002069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
As the amphibian oocyte becomes the fertilisation-competent egg an actin-myosin network assembles in the cortex which provides for the cortical contraction that accompanies fertilisation. A number of recent investigations provide data for development of a model detailing the structural changes which should accompany the development of this contractile network as well as the signalling mechanisms which regular assembly and contraction.
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Affiliation(s)
- L V Ryabova
- Institute of Developmental Biology, Russian Academy of Sciences, Russia
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10
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van de Klundert FA, Raats JM, Bloemendal H. Intermediate filaments: regulation of gene expression and assembly. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 214:351-66. [PMID: 8513786 DOI: 10.1111/j.1432-1033.1993.tb17931.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- F A van de Klundert
- Department of Biochemistry, Faculty of Science, University of Nijmegen, The Netherlands
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11
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Possible mechanisms in the rearrangement of non-yolk cytoplasmic materials during maturation of theXenopus laevis oocyte. ACTA ACUST UNITED AC 1993; 202:240-245. [DOI: 10.1007/bf02427885] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/1992] [Accepted: 10/15/1992] [Indexed: 10/24/2022]
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12
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Lessman CA, Kessel RG. Effects of acrylamide on germinal vesicle migration and dissolution in oocytes of the frog, Rana pipiens. Exp Cell Res 1992; 202:151-60. [PMID: 1511729 DOI: 10.1016/0014-4827(92)90414-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have demonstrated that when Rana oocytes are treated with 10 mM acrylamide, germinal vesicle migration (GVM) is promoted while meiosis reinitiation by progesterone is inhibited. A number of other specific alterations result from the acrylamide treatment: (i) A dense band of fibrillar material appears adjacent to the oolemma in acrylamide-treated oocytes. Furthermore, (ii) the fibrillar material reacts with an intermediate filament antibody using immunogold techniques applied to transmission electron microscopy. Moreover, (iii) acrylamide inhibits progestogen-induced annulate lamellae breakdown. In addition, (iv) the cortical mitochondria-rich layer appears to be thickened by acrylamide, which also (v) affects oocyte microvillar retraction and organization. Finally, (vi) electrophysiological measurement of membrane voltage indicates that acrylamide does not significantly affect cell viability during the incubation period used in this study. In summary, acrylamide exerts profound effects on the physiological event of GVM, and these are consistent with the hypothesis that changes in the cytoskeleton are a contributing factor in meiosis reinitiation.
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Affiliation(s)
- C A Lessman
- Department of Biology, Memphis State University, Tennessee 38152
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13
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Abstract
Oocytes, eggs, and embryos from a diverse array of species have evolved cytoskeletal specializations which allow them to meet the needs of early embryogenesis. While each species studied possesses one or more specializations which are unique, several cytoskeletal features are widely conserved across different animal phyla. These features include highly-developed cortical cytoskeletal domains associated with developmental information, microtubule-mediated pronuclear transport, and rapid intracellular signal-regulated control of cytoskeletal organization.
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Affiliation(s)
- W M Bement
- Department of Zoology, Arizona State University, Tempe 85287-1501
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14
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Abstract
Intermediate filaments are ubiquitous in eukaryotic cells, but their functions are poorly understood. The Xenopus oocyte contains both messenger RNA and protein products of cytokeratin and vimentin genes in non-overlapping arrays. The cytokeratin filaments contain dimers of the type I (acidic) subunit XLK3a(19), and the type II (basic) subunit XCK1(8), polymerized to form a cortical network. These are homologues of the human simple epithelial keratins 19 and 8, respectively. After the first few cell cycles following fertilization these filaments become restricted to the superficial cells of the blastula. We have depleted the oocyte's store of the type II cytokeratin mRNA by injecting antisense oligodeoxynucleotides (oligos) and studied the effect on embryonic development. As zygotic transcription does not commence until the late blastula stage, there are at least 9 hours in which to see the effect of loss of function of this mRNA. We report here that the cytokeratin filaments become depleted in the cortical cells of the embryo. As a result, there is a loss of the 'compacted' epithelial surface of the blastula, an inability to close a wounded surface and defective gastrulation.
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Affiliation(s)
- N Torpey
- Wellcome/Cancer Research Campaign Institute of Cancer, Cambridge, UK
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15
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Raats JM, Bloemendal H. The role of protein domains in the assembly process of intermediate filaments. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1992; 43:67-86. [PMID: 1410448 DOI: 10.1016/s0079-6603(08)61044-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J M Raats
- Department of Biochemistry, University of Nijmegen, The Netherlands
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16
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Suzuki AS, Manabe J, Hirakawa A. Dynamic distribution of region-specific maternal protein during oogenesis and early embryogenesis of Xenopus laevis. ACTA ACUST UNITED AC 1991; 200:213-222. [DOI: 10.1007/bf00361340] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/1991] [Accepted: 05/17/1991] [Indexed: 11/28/2022]
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17
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Heasman J, Holwill S, Wylie CC. Fertilization of cultured Xenopus oocytes and use in studies of maternally inherited molecules. Methods Cell Biol 1991; 36:213-30. [PMID: 1811135 DOI: 10.1016/s0091-679x(08)60279-4] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The methods described here of fertilizing stage VI oocytes are lengthy and quite difficult techniques. They would become more attractive if the success rate (i.e., the number of fertilizations compared to the numbers of matured oocytes) could be improved. An important step toward this for the host transfer technique would be to monitor carefully the status of mature Xenopus females ovaries in relation to cyclical HCG stimulation, so that we could predict more accurately whether stage VI oocytes are fertilizable. The in vitro technique would obviously be improved if oocytes could be fertilized without removing their membranes, perhaps by using oviduct extracts. So far, this approach has had only limited success. It seems that the rewards of using these techniques could be great, in terms of understanding the maternal contribution to development. Although our experiments have not yet shown that oocyte injection of DNA has any advantage over egg injection, it is clear that it is possible to make "mRNA-minus mutants" by this approach. In the message depletion experiments mentioned here, we targeted the cleavage of an mRNA which is of low abundance in the full grown oocyte, but preliminary experiments have shown that we can deplete more abundant messages and produce specific phenotypes. Of course such experiments need to be controlled to show that the effect is specific, and the best proof that this is the case is to rescue the effect with injection of the appropriate mRNA. Finally, it seems likely that the method can be used to study the function of both localized molecules, such as the putative primordial germ cell (PGC) or dorsal determinants, and more ubiquitous molecules such as cytoskeletal elements.
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Affiliation(s)
- J Heasman
- Department of Zoology, Cambridge University, England
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18
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Abstract
In this review, the types of mRNAs found in oocytes and eggs of several animal species, particularly Drosophila, marine invertebrates, frogs, and mice, are described. The roles that proteins derived from these mRNAs play in early development are discussed, and connections between maternally inherited information and embryonic pattern are sought. Comparisons between genetically identified maternally expressed genes in Drosophila and maternal mRNAs biochemically characterized in other species are made when possible. Regulation of the meiotic and early embryonic cell cycles is reviewed, and translational control of maternal mRNA following maturation and/or fertilization is discussed with regard to specific mRNAs.
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Affiliation(s)
- M Stewart
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
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20
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Affiliation(s)
- R P Elinson
- Department of Zoology, University of Toronto, Canada
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21
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Affiliation(s)
- W R Jeffery
- Department of Zoology, University of Texas, Austin 78712
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22
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Charbonneau M, Grandin N. The egg of Xenopus laevis: a model system for studying cell activation. CELL DIFFERENTIATION AND DEVELOPMENT : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF DEVELOPMENTAL BIOLOGISTS 1989; 28:71-93. [PMID: 2692788 DOI: 10.1016/0922-3371(89)90045-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- M Charbonneau
- Laboratoire de Biologie et Génétique du Développement, Université de Rennes, France
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23
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Speksnijder JE, Jong K, Wisselaar HA, Linnemans WAM, Dohmen MR. The ultrastructural organization of the isolated cortex in eggs ofNassarius reticulatus (Mollusca). ACTA ACUST UNITED AC 1989; 198:119-128. [DOI: 10.1007/bf02438936] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/1989] [Accepted: 05/26/1989] [Indexed: 11/30/2022]
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Nakazato S, Ikenishi K. Monoclonal antibody production against a subcellular fraction of vegetal pole cytoplasm containing the germ plasm of Xenopus 2-cell eggs. CELL DIFFERENTIATION AND DEVELOPMENT : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF DEVELOPMENTAL BIOLOGISTS 1989; 27:163-74. [PMID: 2679981 DOI: 10.1016/0922-3371(89)90697-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In attempts to understand the molecular nature of substances localized in the germ plasm (GP), monoclonal antibodies against a subcellular fraction of vegetal pole cytoplasm containing the GP of Xenopus 2-cell eggs were produced. The monoclonal antibody produced by the hybridoma cell line (designated as no 48) reacted specifically with the GP of embryos at the cleavage stages. Beyond the gastrula stage, the antibody reacted with not only the GP of germ line cells but also the cytoplasm of somatic cells. By immunoblotting analysis with two-dimensional (2-D) gel the antibody was shown to react with two protein spots of approx. 40 kDa, with a pI of 6.0-6.5.
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Affiliation(s)
- S Nakazato
- Department of Biology, Faculty of Science, Osaka City University, Japan
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25
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Boyle JA, Ernst SG. Sea urchin oocytes possess elaborate cortical arrays of microfilaments, microtubules, and intermediate filaments. Dev Biol 1989; 134:72-84. [PMID: 2471666 DOI: 10.1016/0012-1606(89)90079-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Extensive arrays of microfilaments, microtubules and cytokeratin-type intermediate filaments were detected in the cortex of Strongylocentrotus droebachiensis oocytes using fluorescently labeled antibodies on both cortex and whole mount preparations. All three filament systems undergo dramatic structural reorganization during meiotic maturation of the egg. Microfilaments form a dense meshwork within the cortex of the oocyte. After meiosis, the filaments rearrange and shorten, resulting in a more loosely organized network. Both cortical microtubules and microtubules associated with a microtubule-organizing center are observed within the oocyte. After meiosis, the number and length of the cortical microtubules gradually diminish. A microtubule organizing center is found situated between the germinal vesicle and the plasma membrane in many oocytes. A network of filaments extends from the microtubule organizing center and radiates peripherally toward the germinal vesicle, presumably marking the animal pole. Cytokeratin-like intermediate filaments form a reticular network within the oocyte cortex, then solubilize during meiosis. In whole mounts of oocytes there is a single focal center of cytokeratin staining from which filaments radiate. Indirect immunofluorescence experiments, using anti-tubulin and anti-cytokeratin antibodies simultaneously, reveal the intermediate filament focal center to be localized within the microtubule organizing center. These results demonstrate the presence of a complex cortical cytoskeleton in premeiotic eggs of the sea urchin, Strongylocentrotus droebachiensis.
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Affiliation(s)
- J A Boyle
- Department of Biology, Tufts University, Medford, Massachusetts 02155
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