1
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Hua LL, Casas C, Mikawa T. Mitotic Antipairing of Homologous Chromosomes. Results Probl Cell Differ 2022; 70:191-220. [PMID: 36348108 PMCID: PMC9731508 DOI: 10.1007/978-3-031-06573-6_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chromosome organization is highly dynamic and plays an essential role during cell function. It was recently found that pairs of the homologous chromosomes are continuously separated at mitosis and display a haploid (1n) chromosome set, or "antipairing," organization in human cells. Here, we provide an introduction to the current knowledge of homologous antipairing in humans and its implications in human disease.
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Affiliation(s)
- Lisa L. Hua
- Department of Biology, Sonoma State University, San Francisco
| | - Christian Casas
- Department of Biology, Sonoma State University, San Francisco
| | - Takashi Mikawa
- Department of Anatomy, Cardiovascular Research Institute, University of California, San Francisco,Corresponding author:
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2
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Pierron M, Kalbfuss N, Borrego-Pinto J, Lénárt P, Gönczy P. Centriole foci persist in starfish oocytes despite Polo-like kinase 1 inactivation or loss of microtubule nucleation activity. Mol Biol Cell 2020; 31:873-880. [PMID: 32073992 PMCID: PMC7185973 DOI: 10.1091/mbc.e19-06-0346] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 02/05/2020] [Accepted: 02/11/2020] [Indexed: 11/29/2022] Open
Abstract
Centrioles must be eliminated or inactivated from the oocyte to ensure that only the two functional centrioles contributed by the sperm are present in the zygote. Such removal can occur during oogenesis, as in Drosophila, where departure of Polo kinase from centrosomes leads to loss of microtubule nucleating activity and centriole removal. In other species, oocyte-derived centrioles are removed around the time of fertilization through incompletely understood mechanisms. Here, we use confocal imaging of live starfish oocytes and zygotes expressing markers of microtubule nucleating activity and centrioles to investigate this question. We first assay the role of Polo-like kinase 1 (Plk1) in centriole elimination. We find that although Plk1 localizes around oocyte-derived centrioles, kinase impairment with BI-2536 does not protect centrioles from removal in the bat star Patiria miniata. Moreover, we uncover that all four oocyte-derived centrioles lose microtubule nucleating activity when retained experimentally in the zygote of the radiate star Asterias forbesi. Interestingly, two such centrioles nevertheless retain the centriolar markers mEGFP::PACT and pmPoc1::mEGFP. Together, these findings indicate that centrioles can persist when Plk1 activity is impaired, as well as when microtubule nucleating activity is lacking, uncovering further diversity in the mechanisms governing centriole removal.
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Affiliation(s)
- Marie Pierron
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nils Kalbfuss
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Joana Borrego-Pinto
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg, Germany
| | - Péter Lénárt
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg, Germany
- Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
| | - Pierre Gönczy
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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3
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Abstract
Gametogenesis in animal oocytes reduces the diploid genome content of germline precursors to a haploid state in gametes by discarding ¾ of the duplicated chromosomes through a sequence of two meiotic cell divisions called meiosis I and II. The assembly of the microtubule-based spindle structure that mediates this reduction in genome content remains poorly understood compared to our knowledge of mitotic spindle assembly and function. In this review, we consider the diversity of oocyte meiotic spindle assembly and structure across animal phylogeny, review recent advances in our understanding of how animal oocytes assemble spindles in the absence of the centriole-based microtubule-organizing centers that dominate mitotic spindle assembly, and discuss different models for how chromosomes are captured and moved to achieve chromosome segregation during oocyte meiotic cell division.
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Affiliation(s)
- Aaron F Severson
- Department of Biological, Geological, and Environmental Sciences, Center for Gene Regulation in Health and Disease, Cleveland State University, Cleveland, Ohio, USA
| | - George von Dassow
- Oregon Institute of Marine Biology, University of Oregon, Charleston, Oregon, USA
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA.
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4
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Mikeladze-Dvali T, von Tobel L, Strnad P, Knott G, Leonhardt H, Schermelleh L, Gönczy P. Analysis of centriole elimination during C. elegans oogenesis. Development 2012; 139:1670-9. [PMID: 22492357 PMCID: PMC4074223 DOI: 10.1242/dev.075440] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/29/2012] [Indexed: 01/04/2023]
Abstract
Centrosomes are the principal microtubule organizing centers (MTOCs) of animal cells and comprise a pair of centrioles surrounded by pericentriolar material (PCM). Centriole number must be carefully regulated, notably to ensure bipolar spindle formation and thus faithful chromosome segregation. In the germ line of most metazoan species, centrioles are maintained during spermatogenesis, but eliminated during oogenesis. Such differential behavior ensures that the appropriate number of centrioles is present in the newly fertilized zygote. Despite being a fundamental feature of sexual reproduction in metazoans, the mechanisms governing centriole elimination during oogenesis are poorly understood. Here, we investigate this question in C. elegans. Using antibodies directed against centriolar components and serial-section electron microscopy, we establish that centrioles are eliminated during the diplotene stage of the meiotic cell cycle. Moreover, we show that centriole elimination is delayed upon depletion of the helicase CGH-1. We also find that somatic cells make a minor contribution to this process, and demonstrate that the germ cell karyotype is important for timely centriole elimination. These findings set the stage for a mechanistic dissection of centriole elimination in a metazoan organism.
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Affiliation(s)
| | | | | | - Graham Knott
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL) Lausanne, 1015 Switzerland
| | | | | | - Pierre Gönczy
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL) Lausanne, 1015 Switzerland
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5
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Kinesin-1 prevents capture of the oocyte meiotic spindle by the sperm aster. Dev Cell 2012; 22:788-98. [PMID: 22465668 DOI: 10.1016/j.devcel.2012.01.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 12/03/2011] [Accepted: 01/12/2012] [Indexed: 11/20/2022]
Abstract
Centrioles are lost during oogenesis and inherited from the sperm at fertilization. In the zygote, the centrioles recruit pericentriolar proteins from the egg to form a mature centrosome that nucleates a sperm aster. The sperm aster then captures the female pronucleus to join the maternal and paternal genomes. Because fertilization occurs before completion of female meiosis, some mechanism must prevent capture of the meiotic spindle by the sperm aster. Here we show that in wild-type Caenorhabditis elegans zygotes, maternal pericentriolar proteins are not recruited to the sperm centrioles until after completion of meiosis. Depletion of kinesin-1 heavy chain or its binding partner resulted in premature centrosome maturation during meiosis and growth of a sperm aster that could capture the oocyte meiotic spindle. Kinesin prevents recruitment of pericentriolar proteins by coating the sperm DNA and centrioles and thus prevents triploidy by a nonmotor mechanism.
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6
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Snook RR, Hosken DJ, Karr TL. The biology and evolution of polyspermy: insights from cellular and functional studies of sperm and centrosomal behavior in the fertilized egg. Reproduction 2011; 142:779-92. [PMID: 21964827 DOI: 10.1530/rep-11-0255] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recent studies of centrosome biogenesis, microtubule dynamics, and their management point to their role in mediating conditions such as aging and cancer. Centrosome dysfunction is also a hallmark of pathological polyspermy. Polyspermy occurs when the oocyte is penetrated by more than one sperm and can be pathological because an excess of centrosomes compromises development. However, in some taxa, multiple sperm enter the egg with no apparent adverse effect on zygote viability. Thus, some taxa can manage excess centrosomes and represent cases of non-pathological polyspermy. While these two forms of polyspermy have long been known, we argue that there is limited understanding of the proximate and ultimate processes that underlie this taxonomic variation in the outcome of polyspermy and that studying this variation could help uncover the control and role(s) of centrosomes during fertilization in particular, but also mitosis in general. To encourage such studies we: 1) describe taxonomic differences in the outcome of polyspermy, 2) discuss mechanistic aspects of reproductive biology that may contribute to the different consequences of polyspermy, and 3) outline the potential selective events that could lead to the evolution of variation in polyspermy outcomes. We suggest that novel insights into centrosome biology may occur by cooperative studies between reproductive and evolutionary biologists focusing on the mechanisms generating variation in the fitness consequences of polyspermy, and in the taxonomic distribution of all these events. The consequent discoveries of these studies may lead to informative insights into cancer and aging along with other centrosome-related diseases and syndromes.
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Affiliation(s)
- Rhonda R Snook
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.
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Abstract
The notion of nucleic acids in the spindle, and particularly, the centrosome has a long history of inquiry, doubt, and debate. However, the association of specific RNAs with these structures is now confirmed by several investigators. What their presence means for the assembly, function, and evolution of the cell division apparatus is not known; but with newly available information and probes, these are questions that can finally be addressed. The present article summarizes the history of this field, what we know about the molecules in question, and in light of these findings, emphasizes the need to view the cell division apparatus for what it is by definition, a ribonucleoprotein complex.
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Alliegro MA, Henry JJ, Alliegro MC. Rediscovery of the nucleolinus, a dynamic RNA-rich organelle associated with the nucleolus, spindle, and centrosomes. Proc Natl Acad Sci U S A 2010; 107:13718-23. [PMID: 20643950 PMCID: PMC2922224 DOI: 10.1073/pnas.1008469107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nucleolinus is an RNA-rich compartment, closely apposed to or embedded within the nucleolus. Discovered over 150 y ago, fewer than two dozen articles have been published on the nucleolinus, probably because complex histochemical stains are required for its visualization in the great majority of cells. The nucleolinus has been reported in invertebrate oocytes, mammalian and amphibian epithelial cells, neurons, and several transformed cell lines. A prominent nucleolinus, clearly visible with transmitted light microscopes at 10x magnification, is present in each oocyte of the surf clam, Spisula solidissima. We observed a consistent relationship between the nucleolinus and the developing meiotic apparatus following Spisula oocyte activation. Through sonication and sucrose gradient fractionation of purified oocyte nuclei, we isolated nucleolini, extracted their RNA, and prepared an in situ riboprobe (NLi-1), which is associated specifically with the nucleolinus, confirming its unique composition. Other in situ observations revealed a NLi-1 and nucleolinar association with the developing spindle and centrosomes. Laser microsurgery that targeted the nucleolinus resulted in failed meiotic cell division in parthenogenetically activated oocytes and failed mitosis in fertilized oocytes. Although the nucleolinus may be a forgotten organelle, its demonstrated role in spindle formation suggests it deserves renewed attention.
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Affiliation(s)
- Mary Anne Alliegro
- Josephine Bay Paul Center, The Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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9
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Terada Y, Schatten G, Hasegawa H, Yaegashi N. Essential Roles of the Sperm Centrosome in Human Fertilization: Developing the Therapy for Fertilization Failure due to Sperm Centrosomal Dysfunction. TOHOKU J EXP MED 2010; 220:247-58. [DOI: 10.1620/tjem.220.247] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Yukihiro Terada
- Department of Obstetrics and Gynecology, Tohoku University School of Medicine
| | - Gerald Schatten
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine
| | - Hisataka Hasegawa
- Department of Obstetrics and Gynecology, Tohoku University School of Medicine
| | - Nobuo Yaegashi
- Department of Obstetrics and Gynecology, Tohoku University School of Medicine
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10
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Abstract
Tight regulation of centrosome duplication is critical to ensure that centrosome number doubles once and only once per cell cycle. Superimposed onto this centrosome duplication cycle is a functional centrosome cycle in which they alternate between phases of quiescence and robust microtubule (MT) nucleation and MT-anchoring activities. In vertebrate cycling cells, interphase centrioles accumulate less pericentriolar material (PCM), reducing their MT nucleation capacity. In mitosis, centrosomes mature, accumulating more PCM to increase their nucleation and anchoring capacities to form robust MT asters. Interestingly, functional cycles of centrosomes can be altered to suit the cell's needs. Some interphase centrosomes function as a microtubule-organizing center by increasing their ability to anchor MTs to form centrosomal radial arrays. Other interphase centrosomes maintain their MT nucleation capacity but reduce/eliminate their MT-anchoring capacity. Recent work demonstrates that Drosophila cells take this to the extreme, whereby centrioles lose all detectable PCM during interphase, offering an explanation as to how centrosome-deficient flies develop to adulthood. Drosophila stem cells further modify the functional cycle by differentially regulating their two centrioles - a situation that seems important for stem cell asymmetric divisions, as misregulation of centrosome duplication in stem/progenitor cells can promote tumor formation. Here, we review recent findings that describe variations in the functional cycle of centrosomes.
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Affiliation(s)
- Nasser M Rusan
- Department of Biology, University of North Carolina at Chapel Hill, CB#3280, Coker Hall, Chapel Hill, NC 27599, USA.
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11
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Schnackenberg BJ, Palazzo RE, Marzluff WF. Cyclin E/Cdk2 is required for sperm maturation, but not DNA replication, in early sea urchin embryos. Genesis 2007; 45:282-91. [PMID: 17458867 DOI: 10.1002/dvg.20291] [Citation(s) in RCA: 13] [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 cell cycle is driven by the activity of cyclin/cdk complexes. In somatic cells, cyclin E/cdk2 oscillates throughout the cell cycle and has been shown to promote S-phase entry and initiation of DNA replication. In contrast, cyclin E/cdk2 activity remains constant throughout the early embryonic development of the sea urchin and localizes to the sperm nucleus following fertilization. We now show that cyclin E localization to the sperm nucleus following fertilization is not unique to the sea urchin, but also occurs in the surf clam, and inhibition of cyclin E/cdk2 activity by roscovitine inhibits the morphological changes indicative of male pronuclear maturation in sea urchin zygotes. Finally, we show that inhibition of cyclin E/cdk2 activity does not block DNA replication in the early cleavage cycles of the sea urchin. We conclude that cyclin E/cdk2 activity is required for male pronuclear maturation, but not for initiation of DNA replication in early sea urchin development.
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Affiliation(s)
- Bradley J Schnackenberg
- Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
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12
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Rebollo E, Sampaio P, Januschke J, Llamazares S, Varmark H, González C. Functionally unequal centrosomes drive spindle orientation in asymmetrically dividing Drosophila neural stem cells. Dev Cell 2007; 12:467-74. [PMID: 17336911 DOI: 10.1016/j.devcel.2007.01.021] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Revised: 01/24/2007] [Accepted: 01/29/2007] [Indexed: 12/24/2022]
Abstract
Stem cell asymmetric division requires tight control of spindle orientation. To study this key process, we have recorded Drosophila larval neural stem cells (NBs) engineered to express fluorescent reporters for microtubules, pericentriolar material (PCM), and centrioles. We have found that early in the cell cycle, the two centrosomes become unequal: one organizes an aster that stays near the apical cortex for most of the cell cycle, while the other loses PCM and microtubule-organizing activity, and moves extensively throughout the cell until shortly before mitosis when, located near the basal cortex, it recruits PCM and organizes the second mitotic aster. Upon division, the apical centrosome remains in the stem cell, while the other goes into the differentiating daughter. Apical aster maintenance requires the function of Pins. These results reveal that spindle orientation in Drosophila larval NBs is determined very early in the cell cycle, and is mediated by asymmetric centrosome function.
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Affiliation(s)
- Elena Rebollo
- Cell Division Group, Institute for Research in Biomedicine, Parc Científic Barcelona, C/ Josep Samitier 1-5, 08028 Barcelona, Spain
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13
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Abstract
Tissue stem cells play a key role in tissue maintenance. Drosophila melanogaster central brain neuroblasts are excellent models for stem cell asymmetric division. Earlier work showed that their mitotic spindle orientation is established before spindle formation. We investigated the mechanism by which this occurs, revealing a novel centrosome cycle. In interphase, the two centrioles separate, but only one is active, retaining pericentriolar material and forming a “dominant centrosome.” This centrosome acts as a microtubule organizing center (MTOC) and remains stationary, forming one pole of the future spindle. The second centriole is inactive and moves to the opposite side of the cell before being activated as a centrosome/MTOC. This is accompanied by asymmetric localization of Polo kinase, a key centrosome regulator. Disruption of centrosomes disrupts the high fidelity of asymmetric division. We propose a two-step mechanism to ensure faithful spindle positioning: the novel centrosome cycle produces a single interphase MTOC, coarsely aligning the spindle, and spindle–cortex interactions refine this alignment.
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Affiliation(s)
- Nasser M Rusan
- Department of Biology and 2Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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14
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Riparbelli MG, Giordano R, Callaini G. Centrosome inheritance in the parthenogenetic egg of the collembolan Folsomia candida. Cell Tissue Res 2006; 326:861-72. [PMID: 16906420 DOI: 10.1007/s00441-006-0253-x] [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] [Received: 02/21/2006] [Accepted: 05/18/2006] [Indexed: 11/24/2022]
Abstract
Unfertilized eggs commonly lack centrioles, which are usually provided by the male gamete at fertilization, and are unable to assemble functional reproducing centrosomes. However, some insect species lay eggs that develop to adulthood without a contribution from sperm. We report that the oocyte of the parthenogenetic collembolan Folsomia candida is able to self-assemble microtubule-based asters in the absence of pre-existing maternal centrosomes. The asters, which develop near the innermost pole of the meiotic apparatus, interact with the female chromatin to form the first mitotic spindle. The appearance of microtubule-based asters in the cytoplasm of the activated Folsomia oocyte might represent a conserved mechanism for centrosome formation during insect parthenogenesis. We also report that the architecture of the female meiotic apparatus and the structure of the mitotic spindles during the early embryonic divisions are unusual in comparison with that of insects.
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15
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Zelena D, Filaretova L, Mergl Z, Barna I, Tóth ZE, Makara GB. Hypothalamic paraventricular nucleus, but not vasopressin, participates in chronic hyperactivity of the HPA axis in diabetic rats. Am J Physiol Endocrinol Metab 2006; 290:E243-50. [PMID: 16144820 DOI: 10.1152/ajpendo.00118.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diabetes mellitus (DM), as chronic stress activates the hypothalamo-pituitary-adrenocortical axis. We examined whether arginine vasopressin (AVP) and the hypothalamic paraventricular nucleus (PVN) participate in DM-induced chronic stress symptoms. AVP-deficient Brattleboro or PVN-lesioned Wistar rats were used with heterozygous or sham-operated controls. The rats were studied 2 wk after a single injection of streptozotocin. The appearance of DM (enhanced water consumption and blood glucose elevation) and the chronic stress-like somatic changes (body weight decrease, thymus involution, adrenal gland hypertrophy) were not influenced by the lack of AVP. By contrast, PVN lesion significantly attenuated DM-induced thymus involution and adrenal gland hypertrophy as well as the increase in water consumption. The corticotropin-releasing hormone mRNA in PVN was diminished by DM and elevated by the lack of AVP without interaction. DM elevated the proopiomelanocortin (POMC) mRNA in the anterior lobe of the pituitary. The lack of AVP had no effect, whereas lesioning the PVN significantly diminished the elevation. The elevated basal corticosterone plasma levels detectable in DM were influenced neither by the lack of AVP nor by lesioning the PVN. Thus the lack of AVP had no influence on DM-induced chronic stress symptoms, but lesioning the PVN attenuated part of them. However, the lack of elevation in POMC mRNA after PVN lesion, together with the maintained corticosterone elevation, suggests that direct adrenal gland activation occurs in untreated DM.
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Affiliation(s)
- Dóra Zelena
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Szigony 43, Hungary.
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16
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Obata M, Komaru A. Specific location of sperm mitochondria in mussel Mytilus galloprovincialis zygotes stained by MitoTracker. Dev Growth Differ 2005; 47:255-63. [PMID: 15921500 DOI: 10.1111/j.1440-169x.2005.00801.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In Mytilidae, mitochondrial DNA (mtDNA) in the offspring is inherited from male and female parents. Sperm mitochondria are only incorporated into the testes. This phenomenon is called doubly uniparental inheritance (DUI). Sperm mitochondria should locate in the primordial germ cell during development to maintain DUI. However, the mechanism of sperm mitochondria localization is still unknown. To reveal the mechanism, we followed the location of sperm mitochondria in Mytilus galloprovincialis zygotes fertilized with sperm stained by MitoTracker. Just after fertilization, sperm mitochondria, which were found to enter eggs from various sites, remained at sperm entry point. Five sperm mitochondria located at the male pronucleus. After pronuclear expansion, sperm mitochondria migrated to the center of the egg together with the male pronucleus. At anaphase of cleavage-I, the distribution pattern of sperm mitochondria was divided into two patterns. In pattern A, sperm mitochondria located in the equatorial region of the eggs. In pattern B, sperm mitochondria migrated and divided into two groups with chromosomes. From observations of colchicine-treated eggs, we suggest that sperm mitochondria migration from fertilization to anaphase of cleavage-I depends on the microtubules. The difference between pattern A and pattern B may be caused by whether sperm mitochondria migrated or not by the microtubules at cleavage-I.
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Affiliation(s)
- Mayu Obata
- Faculty of Bioresources, Mie University, 1515, Kamihama, Tsu City, Mie Prefecture 514-8507, Japan.
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17
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Yuba-Kubo A, Kubo A, Hata M, Tsukita S. Gene knockout analysis of two gamma-tubulin isoforms in mice. Dev Biol 2005; 282:361-73. [PMID: 15893303 DOI: 10.1016/j.ydbio.2005.03.031] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2004] [Revised: 03/14/2005] [Accepted: 03/16/2005] [Indexed: 11/19/2022]
Abstract
Gamma-tubulin regulates the nucleation of microtubules, but knowledge of its functions in vivo is still fragmentary. Here, we report the identification of two closely related gamma-tubulin isoforms, TUBG1 and TUBG2, in mice, and the generation of TUBG1- and TUBG2-deficient mice. TUBG1 was expressed ubiquitously, whereas TUBG2 was primarily detected in the brain. The development of TUBG1-deficient (Tubg1-/-) embryos stopped at the morula/blastocyst stages due to a characteristic mitotic arrest: the mitotic spindle was highly disorganized, and disorganized spindles showed one or two pole-like foci of bundled MTs that were surrounded by condensed chromosomes. TUBG2 was expressed in blastocysts, but could not rescue the TUBG1 deficiency. By contrast, TUBG2-deficient (Tubg2-/-) mice were born, grew, and intercrossed normally. In the brain of wild-type mice, TUBG2 was expressed in approximately the same amount as TUBG1, but no histological abnormalities were found in the Tubg2-/- brain. These findings indicated that TUBG1 and TUBG2 are not functionally equivalent in vivo, that TUBG1 corresponds to conventional gamma-tubulin, and that TUBG2 may have some unidentified function in the brain.
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Affiliation(s)
- Akiko Yuba-Kubo
- Solution Oriented Research for Science and Technology, Japan Science and Technology Corporation, Sakyo-ku, Kyoto 606-8501, Japan
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18
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Pielak RM, Hawkins C, Pyie A, Bautista J, Lee KG, Cohen WD. Polar body formation in Spisula oocytes: function of the peripheral aster. THE BIOLOGICAL BULLETIN 2005; 209:21-30. [PMID: 16110091 DOI: 10.2307/3593139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Activated Spisula oocytes proceed through meiotic stages rapidly and in near synchrony, providing an excellent system for analyzing polar body formation. Our previous studies suggested that cortical spreading of the metaphase peripheral aster determines spatial features of the cortical F-actin ring that is generated prior to extrusion of the polar body. We tested this hypothesis by experimentally altering the number and cortical contact patterns of peripheral asters. Such alteration was achieved by (a) lovastatin-induced arrest at metaphase I, with and without hexylene glycol modification, followed by washout; and (b) cytochalasin-D inhibition of extrusion of the first polar body, with washout before extrusion of the second polar body. Both methods induced simultaneous formation of two or more cortically spreading asters, correlated with subsequent formation of double, or even triple, overlapping F-actin rings during anaphase. Regardless of pattern, ring F-actin was deposited near regions of greatest astral microtubule density, indicating that microtubules provided a positive stimulus to which the cortex responded indiscriminately. These results strongly support the proposed causal relationship between peripheral aster spreading and biogenesis of the F-actin ring involved in polar body formation.
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Affiliation(s)
- Rafal M Pielak
- Department of Biological Sciences, Hunter College, New York, New York, USA
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19
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Riparbelli MG, Tagu D, Bonhomme J, Callaini G. Aster self-organization at meiosis: a conserved mechanism in insect parthenogenesis? Dev Biol 2005; 278:220-30. [PMID: 15649474 DOI: 10.1016/j.ydbio.2004.11.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 11/08/2004] [Accepted: 11/08/2004] [Indexed: 11/18/2022]
Abstract
Unfertilized eggs usually lack maternal centrosomes and cannot develop without sperm contribution. However, several insect species lay eggs that develop to adulthood as unfertilized in the absence of a preexisting centrosome. We report that the oocyte of the parthenogenetic viviparous pea aphid Acyrthosiphon pisum is able to self-organize microtubule-based asters, which in turn interact with the female chromatin to form the first mitotic spindle. This mode of reproduction provides a good system to investigate how the oocyte can assemble new centrosomes and how their number can be exactly monitored. We propose that the cooperative interaction of motor proteins and randomly nucleated surface microtubules could lead to the formation of aster-like structures in the absence of pre-existing centrosomes. Recruitment of material along the microtubules might contribute to the accumulation of pericentriolar material and centriole precursors at the focus of the asters, thus leading to the formation of true centrosomes. The appearance of microtubule asters at the surface of activated oocytes could represent a possible common mechanism for centrosome formation during insect parthenogenesis.
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Tei J, Kani S, Hanai K, Miyaguchi T, Yamamoto K. Formation of polar-body-like structures induced in polyspermic starfish oocytes that had been inseminated at the germinal vesicle stage. Dev Growth Differ 2004; 46:439-47. [PMID: 15606489 DOI: 10.1111/j.1440-169x.2004.00760.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Immature starfish oocytes, which are arrested at the first meiotic prophase and contain a large nucleus called the germinal vesicle (GV), are known to accept multiple sperm on insemination. We found that if these polyspermic starfish oocytes are induced to mature, they often form small protrusion(s) adjacent to the first polar body emitted shortly earlier. We refer to these protrusion(s) as 'polar-body-like structures (PLS).' Fluorescent staining of PLS indicated that they were not merely cytoplasmic protrusions, but contained some chromatin. Maturing process of these polyspermic oocytes was examined by immnofluorescent staining, which showed that: (i) numerous sperm asters were observed after the onset of GV breakdown; (ii) before the first polar body (PB1) emission, a complex microtubular structure resembling a multipolar spindle was formed; and (iii) several isolated asters were observed after PB1 emission. These results indicate that PLS formation may be induced by interaction of meiosis-I spindle with paternal centrosomes incorporated at GV stage.
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Affiliation(s)
- Jinsei Tei
- Department of Biological Diversity and Resources, Faculty of Agriculture, Gifu University, Gifu 501-1193, Japan
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21
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Abstract
How do cells regulate centrosome number? A canonical duplication cycle generates two centrosomes from one in most proliferating cells. Centrioles are key to this process, and molecules such as centrins, SAS-4 and ZYG-1 govern daughter centriole formation. Cdk2 activity probably couples centrosome duplication with the S phase, and a licensing mechanism appears to limit centrosome duplication to once per cell cycle. However, such mechanisms must be altered in some cells – for example, spermatocytes – in which centrosome duplication and DNA replication are uncoupled. There are also alternative pathways of centrosome biogenesis. For example, one centrosome is reconstituted from two gametes at fertilization; in this case, the most common strategy involves differential contributions of centrioles and pericentriolar material (PCM) from each gamete. Furthermore, centrioles can sometimes form de novo from no apparent template. This occurs, for instance, in the early mouse embryo and in parthenogenetic species and might rely on a pre-existing seed that resides within PCM but is not visible by ultrastructural analysis.
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Affiliation(s)
- Marie Delattre
- Swiss Institute for Experimental Cancer Research (ISREC), CH-1066 Epalinges/Lausanne, Switzerland
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22
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Zhang QY, Tamura M, Uetake Y, Washitani-Nemoto S, Nemoto SI. Regulation of the paternal inheritance of centrosomes in starfish zygotes. Dev Biol 2004; 266:190-200. [PMID: 14729488 DOI: 10.1016/j.ydbio.2003.10.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In most animals, fertilized eggs inherit one centrosome from a meiosis-II spindle of oocytes and another centrosome from the sperm. However, since first proposed by Boveri [Sitzungsber. Ges. Morph. Phys. Münch. 3 (1887) 151-164] at the turn of the last century, it has been believed that only the paternal (sperm) centrosome provides the division poles for mitosis in animal zygotes. This uniparental (paternal) inheritance of centrosomes is logically based on the premise that the maternal (egg) centrosome is lost before the onset of the first mitosis. For the processes of the selective loss of the maternal centrosome, three models have been proposed: One stresses the intrinsic factors within the centrosome itself; the other two emphasize external factors such as cytoplasmic conditions or the sperm centrosome. In the present study, we have examined the validity of one of the models in which the sperm centrosome overwhelms the maternal centrosomes. Because centrosomes cast off into both the first and the second polar bodies (PB) are known to retain the capacity for reproduction and cell-division pole formation, we observed the behavior of those PB centrosomes with reproductive capacity and the sperm centrosome in the same zygotic cytoplasm. We prepared two kinds of fertilized eggs that contain reproductive maternal centrosomes, (1) by micromanipulative transplantation of the PB centrosomes into fertilized eggs, and (2) by suppression of the PB extrusions of fertilized eggs with cytochalasin B. In both types of eggs, the PB centrosomes could double and form cell-division poles, indicating that they are not suppressed by the sperm centrosome, which in turn indicates that selective loss of the maternal centrosome is due to intrinsic factors within the centrosomes themselves.
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Affiliation(s)
- Qui Yan Zhang
- Department of Biology, Faculty of Science, Ochanomizu University, Otsuka, Bunkyo, Tokyo 112-8610, Japan
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23
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Twomey C, Wattam SL, Pillai MR, Rapley J, Baxter JE, Fry AM. Nek2B stimulates zygotic centrosome assembly in Xenopus laevis in a kinase-independent manner. Dev Biol 2004; 265:384-98. [PMID: 14732400 DOI: 10.1016/j.ydbio.2003.10.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Pronuclear migration and formation of the first mitotic spindle depend upon assembly of a functional zygotic centrosome. For most animals, this involves both paternal and maternal contributions as sperm basal bodies are converted into centrosomes competent for microtubule nucleation through recruitment of egg proteins. Nek2B is a vertebrate NIMA-related protein kinase required for centrosome assembly, as its depletion from egg extracts delays microtubule aster formation from sperm basal bodies. Using Xenopus as a model system, we now show that protein expression of Nek2B begins during mid-oogenesis and increases further upon oocyte maturation. This is regulated, at least in part, at the level of protein translation. Nek2B protein is weakly phosphorylated in mitotic egg extracts but its recruitment to the sperm basal body, which occurs independently of its kinase activity, stimulates its phosphorylation, possibly through sequestration from a phosphatase present in mitotic egg cytoplasm. Importantly, although Nek2B is not required to organize acentrosomal microtubule asters, we show that addition of either active or kinase-dead recombinant Nek2B can restore centrosome assembly in a dose-dependent manner to a depleted extract. These results support a model in which maternal Nek2B acts to promote assembly of a functional zygotic centrosome in a kinase-independent manner.
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Affiliation(s)
- Ciara Twomey
- Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
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24
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Abstract
The Drosophila egg contains all the components required to properly execute the early mitotic divisions but is unable to assemble a functional centrosome without a sperm-provided basal body. We show that 65% of unfertilized eggs obtained from a laboratory strain of Drosophila mercatorum can spontaneously assemble a number of cytoplasmic asters after activation, most of them duplicating in a cell cycle-dependent manner. Such asters are formed by a polarized array of microtubules that have their Asp-associated minus-ends converging at a main focus, where centrioles and typical centrosomal antigens are found. Aster assembly is spatially restricted to the anterior region of the oocyte. When fertilized, the parthenogenetic egg forms the poles of the gonomeric spindle by using the sperm-provided basal body, despite the presence within the same cytoplasm of maternal centrosomes. Thirty-five percent of parthenogenetic eggs and all unfertilized and fertilized eggs from the sibling bisexually reproducing D. mercatorum strain do not contain cytoplasmic asters. Thus, the Drosophila eggs have the potential for de novo formation of functional centrosomes independent of preexisting centrioles, but some control mechanisms preventing their spontaneous assembly must exist. We speculate that the release of the block preventing centrosome self-assembly could be a landmark for ensuring parthenogenetic reproduction.
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25
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Lambert JD, Nagy LM. Asymmetric inheritance of centrosomally localized mRNAs during embryonic cleavages. Nature 2002; 420:682-6. [PMID: 12478296 DOI: 10.1038/nature01241] [Citation(s) in RCA: 188] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2002] [Accepted: 10/10/2002] [Indexed: 12/28/2022]
Abstract
During development, different cell fates are generated by cell-cell interactions or by the asymmetric distribution of patterning molecules. Asymmetric inheritance is known to occur either through directed transport along actin microfilaments into one daughter cell or through capture of determinants by a region of the cortex inherited by one daughter. Here we report a third mechanism of asymmetric inheritance in a mollusc embryo. Different messenger RNAs associate with centrosomes in different cells and are subsequently distributed asymmetrically during division. The segregated mRNAs are diffusely distributed in the cytoplasm and then localize, in a microtubule-dependent manner, to the pericentriolar matrix. During division, they dissociate from the core mitotic centrosome and move by means of actin filaments to the presumptive animal daughter cell cortex. In experimental cells with two interphase centrosomes, mRNAs accumulate on the correct centrosome, indicating that differences between centrosomes control mRNA targeting. Blocking the accumulation of mRNAs on the centrosome shows that this event is required for subsequent cortical localization. These events produce a complex pattern of mRNA localization, in which different messages distinguish groups of cells with the same birth order rank and similar developmental potentials.
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Affiliation(s)
- J David Lambert
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA
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26
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Affiliation(s)
- Kevin F O'Connell
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Building 8, Room 2A07, Bethesda, Maryland, MD 20892, USA.
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27
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Marescalchi O, Zauli C, Scali V. Centrosome dynamics and inheritance in related sexual and parthenogenetic Bacillus (Insecta Phasmatodea). Mol Reprod Dev 2002; 63:89-95. [PMID: 12211065 DOI: 10.1002/mrd.10177] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In animals, some general features of centrosome dynamics and inheritance have been widely recognized. The most acknowledged model assigns to sperm the contribution of a centriole to the fertilized egg, which in turn provides the pericentriolar materials, including gamma-tubulin, recruiting them from the cytoplasm: the main zygote microtubule organizing center (MTOC) is thus reconstituted to organize first the spermaster and then the full first embryonic spindle. Obviously the model cannot apply to parthenogenetic systems, which actually rely on egg components alone. In stick insects of the Bacillus genus, the spindle of both somatic and germ cells is clearly anastral, therefore we have been investigating their centrosome in sexual and parthenogenetic taxa by analyzing its component dynamics and transmission through the use of monoclonal beta- and gamma-tubulin antibodies and transmission electron microscopy (TEM). It has been shown that in sexually reproducing species the spermatozoon does not contribute the centriole, so that the egg wholly provides the MTOC and the ensuing anastral spindle of the embryo: MTs appear to derive from pronuclear chromatin surroundings and no asters are observed. The parthenogenetic embryo development is the same as the sexual one if syngamy is excepted. The parthenogenetic mechanism realized by these panoistic insects appears to differ from that observed in the meroistic hymenopteran and drosophilid species, where the embryo spindle derives from asters formed in the egg cortex. In stick insects, the lack of sperm contribution to embryonic centrosome appears to be a major trait accounting for the widespread occurrence of facultative and obligate parthenogenesis within the order.
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28
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Ishibashi R, Komaru A, Ookubo K, Kiyomoto M. The second meiosis occurs in cytochalasin D-treated eggs of Corbicula leana even though it is not observed in control androgenetic eggs because the maternal chromosomes and centrosomes are extruded at first meiosis. Dev Biol 2002; 244:37-43. [PMID: 11900457 DOI: 10.1006/dbio.2002.0590] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hermaphroditic freshwater clam Corbicula leana reproduces by androgenesis. In the control (androgenetic development), all maternal chromosomes and maternal centrosomes at the meiotic poles were extruded as the two first polar bodies, and subsequently, second meiosis did not occur. But, in C. leana eggs treated with cytochalasin D (CD) to inhibit polar body extrusion, the second meiosis occurred. At metaphase-I, the spindle showed the typical bipolar structure and two spheroid centrosomes were located at its poles. All the maternal chromosomes were divided at anaphase-I, but they were not extruded as polar bodies due to the effects of CD. After completion of first meiosis, the maternal centrosomes split into four. At the second meiosis, twin or tetrapolar spindles were formed and two groups of maternal chromosomes divided into four sets of chromosomes. After the second meiosis, the spindle disassociated and the four maternal centrosomes disappeared. Four groups of maternal chromosomes transformed into the four female pronuclei. Male and female pronuclei became metaphase chromosomes of the first mitosis. The present study clearly indicates that typical meiosis systems still proceed in androgenetic triploid C. leana. We conclude that the androgenetic form may have arisen from the meiotic form.
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Affiliation(s)
- R Ishibashi
- Faculty of Bioresources, Mie University, Tsu, Mie, 514-8507, Japan
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29
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Minshall N, Thom G, Standart N. A conserved role of a DEAD box helicase in mRNA masking. RNA (NEW YORK, N.Y.) 2001; 7:1728-42. [PMID: 11780630 PMCID: PMC1370213 DOI: 10.1017/s135583820101158x] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Clam p82 is a member of the cytoplasmic polyadenylation element-binding protein (CPEB) family of RNA-binding proteins and serves dual functions in regulating gene expression in early development. In the oocyte, p82/CPEB is a translational repressor, whereas in the activated egg, it acts as a polyadenylation factor. Coimmunoprecipitations were performed with p82 antibodies in clam oocyte and egg lysates to identify stage-regulated accessory factors. p47 coprecipitates with p82 from oocyte lysates in an RNA-dependent manner and is absent from egg lysate p92-bound material. Clam p47 is a member of the RCK/p54 family of DEAD box RNA helicases. Xp54, the Xenopus homolog, with bona fide helicase activity, is an abundant and integral component of stored mRNP in oocytes (Ladomery et al., 1997). In oocytes, clam p47 and p82/CPEB are found in large cytoplasmic mRNP complexes. Whereas the helicase level is constant during embryogenesis, in contrast to CPEB, clam p47 translocates to nuclei at the two-cell stage. To address the role of this class of helicase in masking, Xp54 was tethered via 3' UTR MS2-binding sites to firefly luciferase, following microinjection of fusion protein and nonadenylated reporter mRNAs into Xenopus oocytes. Tethered helicase repressed luciferase translation three- to fivefold and, strikingly, mutations in two helicase motifs (DEAD--> DQAD and HRIGR-->HRIGQ), activated translation three- to fourfold, relative to MS2. These data suggest that this helicase family represses translation of maternal mRNA in early development, and that its activity may be attenuated during meiotic maturation, prior to cytoplasmic polyadenylation.
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Affiliation(s)
- N Minshall
- Department of Biochemistry, University of Cambridge, United Kingdom
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30
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Tamura M, Nemoto S. Reproductive maternal centrosomes are cast off into polar bodies during maturation division in starfish oocytes. Exp Cell Res 2001; 269:130-9. [PMID: 11525646 DOI: 10.1006/excr.2001.5305] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Animal egg inherits a maternal centrosome from the meiosis-II spindle and sperm can introduce another centrosome at fertilization. It has been believed that in most animals only the sperm centrosome provides the division poles for mitosis in zygotes. This uniparental (paternal) inheritance of the centrosome must depend on the loss of the maternal centrosome. In starfish, suppression of polar body (PB) extrusion is a prerequisite for induction of parthenogenesis (Washitani-Nemoto et al. (1994) Dev. Biol. 163, 293-301), suggesting that the centrosomes cast off into PBs have reproducing capacity. Due to the absence of centriole duplication in meiosis II of starfish oocytes, each centrosome of a meiosis-II spindle has only one single centriole, whereas in meiosis I each has a pair of centrioles (Sluder et al. (1989) Dev. Biol. 131, 567-579; Kato et al. (1990) Dev. Growth Differ. 32, 41-49). Hence, the first PB (PB1) has two centrioles, whereas the second PB (PB2) and the mature egg have only one centriole, respectively. The present study examined the reproductive capacity of PB centrosomes by transplanting them into artificially activated eggs, and then the recipient egg nucleus with the surrounding cytoplasm was removed. A transplanted PB2 centrosome with a single centriole formed a monopolar spindle at the first mitosis, followed by formation of a bipolar spindle in the next mitosis, leading to actual cleavage and subsequent development. This proves the reproducing capacity of the single centriole in the PB2 centrosome. The behavior of the transplanted PB1 centrosome was exactly the same as in the PB2 centrosome, in spite of the difference in the number of centrioles. These results clearly show that four maternal centrioles are heterogeneous in duplicating capacity, during meiosis only one centriole in each of the centrosomes of a meiosis-I spindle pole retains duplicating capacity, the reproductive centrioles are successively cast off into PBs, and finally a mature egg inheriting a nonreproductive centriole alone is formed, and the presence of a single reproductive centriole is sufficient condition for embryonic development in starfish.
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Affiliation(s)
- M Tamura
- Department of Biology, Ochanomizu University, Bunkyo, Tokyo, 112-8610, Japan.
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31
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O'Connell KF, Caron C, Kopish KR, Hurd DD, Kemphues KJ, Li Y, White JG. The C. elegans zyg-1 Gene Encodes a Regulator of Centrosome Duplication with Distinct Maternal and Paternal Roles in the Embryo. Cell 2001; 105:547-58. [PMID: 11371350 DOI: 10.1016/s0092-8674(01)00338-5] [Citation(s) in RCA: 214] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Centrosome duplication is a critical step in assembly of the bipolar mitotic spindle, but the molecular mechanisms regulating this process during the cell cycle and during animal development are poorly understood. Here, we report that the zyg-1 gene of Caenorhabditis elegans is an essential regulator of centrosome duplication. ZYG-1 is a protein kinase specifically required for daughter centriole formation that localizes transiently to centrosomes and acts at least one cell cycle prior to each spindle assembly event. In the embryo, ZYG-1 participates in a unique regulatory scheme whereby paternal ZYG-1 regulates duplication and bipolar spindle assembly during the first cell cycle, and maternal ZYG-1 regulates these processes thereafter. ZYG-1 is therefore a key molecular component of the centrosome/centriole duplication process.
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Affiliation(s)
- K F O'Connell
- Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706, USA.
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32
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Tram U, Sullivan W. Reciprocal inheritance of centrosomes in the parthenogenetic hymenopteran Nasonia vitripennis. Curr Biol 2000; 10:1413-9. [PMID: 11102802 DOI: 10.1016/s0960-9822(00)00795-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND In the majority of animals, the centrosome-the microtubule-organizing center of the cell-is assembled from components of both the sperm and the egg. How the males of the insect order Hymenoptera acquire centrosomes is a mystery, as they originate from virgin birth. RESULTS To address this issue, we observed centrosome, spindle and nuclear behavior in real time during early development in the parthenogenetic hymenopteran Nasonia vitripennis. Female meiosis was identical in unfertilized eggs. Centrosomes were assembled before the first mitotic division but were inherited differently in unfertilized and fertilized eggs. In both, large numbers of asters appeared at the cortex of the egg after completion of meiosis. In unfertilized eggs, the asters migrated inwards and two of them became stably associated with the female pronucleus and the remaining cytoplasmic asters rapidly disappeared. In fertilized eggs, the Nasonia sperm brought in paternally derived centrosomes, similar to Drosophila melanogaster. At pronuclear fusion, the diploid zygotic nucleus was associated only with paternally derived centrosomes. None of the cytoplasmic asters associated with the zygotic nucleus and, as in unfertilized eggs, they rapidly degenerated. CONCLUSIONS Selection and migration of the female pronucleus is independent of the sperm and its aster. Unfertilized male eggs inherit maternal centrosomes whereas fertilized female eggs inherit paternal centrosomes. This is the first system described in which centrosomes are reciprocally inherited. The results suggest the existence of a previously undescribed mechanism for regulating centrosome number in the early embryo.
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Affiliation(s)
- U Tram
- University of California, Santa Cruz, Department of Biology, Sinsheimer Labs, Santa Cruz, California 95064, USA
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33
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Abstract
We reported previously that inhibition of MAP kinase during meiosis in Urechis caupo eggs caused premature sperm aster formation and we reviewed indirect evidence that the suppression of sperm asters by MAPK during meiosis might be a universal mechanism (M. C. Gould and J. L. Stephano, 1999, Dev. Biol. 216, 348-358). We tested this proposition with oyster (Crassostrea gigas) and starfish (Asterina miniata) eggs, utilizing the MEK inhibitors U0126 and PD98059. Centrosomes, asters, and meiotic spindles were visualized by normal epifluorescence and confocal microscopy following indirect immunocytochemical staining for anti-beta-tubulin. When MAPK activation was inhibited, sperm asters in both species developed prematurely and tended to move toward the egg centrosomes, sometimes even fusing with the egg spindle or centrosomes. Meiotic spindles and polar body formation were also abnormal when MAPK was inhibited.
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Affiliation(s)
- J L Stephano
- Instituto de Biología Celular y Molecular, Universidad Autónoma de Baja California, Ensenada, Baja California, 22800, Mexico
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Schnackenberg BJ, Hull DR, Balczon RD, Palazzo RE. Reconstitution of microtubule nucleation potential in centrosomes isolated from Spisula solidissima oocytes. J Cell Sci 2000; 113 ( Pt 6):943-53. [PMID: 10683143 DOI: 10.1242/jcs.113.6.943] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Treatment of isolated Spisula solidissima centrosomes with KI removes (gamma)-tubulin, 25 nm rings, and their microtubule nucleation potential, revealing the presence of a filamentous lattice, the ‘centromatrix’. Treatment of this centromatrix with Spisula oocyte extract results in the binding of (gamma)-tubulin and 25 nm rings, and the recovery of microtubule nucleation potential. Fractionation of this extract resulted in the separation of elements that are required for the recovery of microtubule nucleation potential. We show that some, but not all, of the elements needed cosediment with microtubules. Further, extracts prepared from activated (meiotic) and non-activated (interphase) Spisula oocytes, CHO cells blocked in S phase, Drosophila embryos and Xenopus oocytes all support the recovery of microtubule nucleation potential by the Spisula centromatrix. These results demonstrate that components necessary for centrosome-dependent microtubule nucleation are functionally conserved and abundant in both interphase and meiotic/mitotic cytoplasm.
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Affiliation(s)
- B J Schnackenberg
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
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35
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Abstract
Centrioles are the organizing centers around which centrosomes assemble. Despite a century of study, the molecular details of centriole function and assembly remain largely unknown. Recent work has exploited the unique advantages of unicellular algae to reveal proteins that play central roles in centriole biology.
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Affiliation(s)
- W F Marshall
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA.
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36
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Abstract
Although MAP kinase is an important regulatory enzyme in many somatic cells, almost nothing is known about its functions during meiosis, except in frog and mouse oocytes. We investigated MAPK activation and function in oocytes of the marine worm Urechis caupo that are fertilized at meiotic prophase. Activity was first detected at 4-6 min after fertilization in immunoblots with anti-active MAPK, prior to germinal vesicle breakdown (GVBD). MAPK activation did not require new protein synthesis and was dependent on the increases in both intracellular pH and intracellular Ca(2+) that normally occur during activation. When MAPK activation was inhibited with PD98059 or U0126, GVBD still occurred, but meiosis was abnormal and there was a dramatic premature enlargement of sperm asters, which normally do not appear until second polar body formation. Failure of polar body formation and premature sperm aster enlargement also occurred when MAPK activation was inhibited by an entirely different treatment which involved lowering the pH of external seawater to interrupt the normal cytoplasmic pH increase. Thus, in Urechis, active MAPK appears to be required for (1) normal meiotic divisions and (2) suppressing the paternal centrosome until after the egg completes meiosis, a general phenomenon whose mechanism has been unknown.
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Affiliation(s)
- M C Gould
- Facultad de Ciencias, Universidad Autónoma de Baja California, Ensenada, B.C., 22800, Mexico
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