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Bennabi I, Terret ME, Verlhac MH. Meiotic spindle assembly and chromosome segregation in oocytes. J Cell Biol 2016; 215:611-619. [PMID: 27879467 PMCID: PMC5147004 DOI: 10.1083/jcb.201607062] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 10/10/2016] [Accepted: 11/02/2016] [Indexed: 11/22/2022] Open
Abstract
Centrosomes play a key role in organizing the microtubule spindle that separates chromosomes during mitosis. Bennabi et al. review how microtubule spindle formation and chromosomal segregation also occur in oocytes during cell division by meiosis despite the absence of centrosomes. Oocytes accumulate maternal stores (proteins, mRNAs, metabolites, etc.) during their growth in the ovary to support development after fertilization. To preserve this cytoplasmic maternal inheritance, they accomplish the difficult task of partitioning their cytoplasm unequally while dividing their chromosomes equally. Added to this complexity, most oocytes, for reasons still speculative, lack the major microtubule organizing centers that most cells use to assemble and position their spindles, namely canonical centrosomes. In this review, we will address recent work on the mechanisms of meiotic spindle assembly and chromosome alignment/segregation in female gametes to try to understand the origin of errors of oocyte meiotic divisions. The challenge of oocyte divisions appears indeed not trivial because in both mice and humans oocyte meiotic divisions are prone to chromosome segregation errors, a leading cause of frequent miscarriages and congenital defects.
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Affiliation(s)
- Isma Bennabi
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
| | - Marie-Emilie Terret
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
| | - Marie-Hélène Verlhac
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
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52
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Radford SJ, Nguyen AL, Schindler K, McKim KS. The chromosomal basis of meiotic acentrosomal spindle assembly and function in oocytes. Chromosoma 2016; 126:351-364. [PMID: 27837282 DOI: 10.1007/s00412-016-0618-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 12/20/2022]
Abstract
Several aspects of meiosis are impacted by the absence of centrosomes in oocytes. Here, we review four aspects of meiosis I that are significantly affected by the absence of centrosomes in oocyte spindles. One, microtubules tend to assemble around the chromosomes. Two, the organization of these microtubules into a bipolar spindle is directed by the chromosomes. Three, chromosome bi-orientation and attachment to microtubules from the correct pole require modification of the mechanisms used in mitotic cells. Four, chromosome movement to the poles at anaphase cannot rely on polar anchoring of spindle microtubules by centrosomes. Overall, the chromosomes are more active participants during acentrosomal spindle assembly in oocytes, compared to mitotic and male meiotic divisions where centrosomes are present. The chromosomes are endowed with information that can direct the meiotic divisions and dictate their own behavior in oocytes. Processes beyond those known from mitosis appear to be required for their bi-orientation at meiosis I. As mitosis occurs without centrosomes in many systems other than oocytes, including all plants, the concepts discussed here may not be limited to oocytes. The study of meiosis in oocytes has revealed mechanisms that are operating in mitosis and will probably continue to do so.
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Affiliation(s)
- Sarah J Radford
- Waksman Institute, 190 Frelinghuysen Rd, Piscataway, NJ, 08854, USA
| | | | - Karen Schindler
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA
| | - Kim S McKim
- Waksman Institute, 190 Frelinghuysen Rd, Piscataway, NJ, 08854, USA.
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA.
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53
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Olferiev M, Jacek E, Kirou KA, Crow MK. Novel molecular signatures in mononuclear cell populations from patients with systemic lupus erythematosus. Clin Immunol 2016; 172:34-43. [PMID: 27576056 DOI: 10.1016/j.clim.2016.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 08/22/2016] [Indexed: 12/12/2022]
Abstract
To gain novel insights into the immunopathogenesis of systemic lupus erythematosus we have analyzed gene expression data from isolated CD4+ T cells, CD8+ T cells, CD19+ B cells, and CD56+ NK-cell enriched peripheral blood cell fractions from patients and healthy donors. As predicted, type I interferon-inducible gene transcripts are overexpressed in all populations. Transcripts preferentially expressed in SLE CD4+ and CD8+ T cells include those associated with Tregulatory and Th17 effector cell programs, respectively, but in each case additional transcripts predicted to limit differentiation of those effector cells are detected. Evidence for involvement of the Wnt/β-catenin pathway was observed in both B and T cell fractions, and novel transcripts were identified in each cell population. These data point to disrupted T effector cell differentiation and the Wnt/β-catenin pathway as contributors to immune dysfunction in SLE while further supporting a central role for the type I interferon pathway in lupus.
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Affiliation(s)
- Mikhail Olferiev
- Mary Kirkland Center for Lupus Research, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA
| | - Elzbieta Jacek
- Mary Kirkland Center for Lupus Research, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA
| | - Kyriakos A Kirou
- Mary Kirkland Center for Lupus Research, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA
| | - Mary K Crow
- Mary Kirkland Center for Lupus Research, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
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54
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Balboula AZ, Nguyen AL, Gentilello AS, Quartuccio SM, Drutovic D, Solc P, Schindler K. Haspin kinase regulates microtubule-organizing center clustering and stability through Aurora kinase C in mouse oocytes. J Cell Sci 2016; 129:3648-3660. [PMID: 27562071 DOI: 10.1242/jcs.189340] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 08/17/2016] [Indexed: 12/16/2022] Open
Abstract
Meiotic oocytes lack classic centrosomes and, therefore, bipolar spindle assembly depends on clustering of acentriolar microtubule-organizing centers (MTOCs) into two poles. However, the molecular mechanism regulating MTOC assembly into two poles is not fully understood. The kinase haspin (also known as GSG2) is required to regulate Aurora kinase C (AURKC) localization at chromosomes during meiosis I. Here, we show that inhibition of haspin perturbed MTOC clustering into two poles and the stability of the clustered MTOCs. Furthermore, we show that AURKC localizes to MTOCs in mouse oocytes. Inhibition of haspin perturbed the localization of AURKC at MTOCs, and overexpression of AURKC rescued the MTOC-clustering defects in haspin-inhibited oocytes. Taken together, our data uncover a role for haspin as a regulator of bipolar spindle assembly by regulating AURKC function at acentriolar MTOCs in oocytes.
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Affiliation(s)
- Ahmed Z Balboula
- Department of Genetics, 145 Bevier Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8082, USA Theriogenology Department, Faculty of Veterinary Medicine, Mansoura University, 60 Elgomhoria Street, 35516 Mansoura, Egypt
| | - Alexandra L Nguyen
- Department of Genetics, 145 Bevier Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8082, USA
| | - Amanda S Gentilello
- Department of Genetics, 145 Bevier Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8082, USA
| | - Suzanne M Quartuccio
- Department of Genetics, 145 Bevier Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8082, USA
| | - David Drutovic
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Rumburská 89, 277 21, Liběchov, Czech Republic
| | - Petr Solc
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Rumburská 89, 277 21, Liběchov, Czech Republic
| | - Karen Schindler
- Department of Genetics, 145 Bevier Road, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8082, USA
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55
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Bury L, Coelho PA, Glover DM. From Meiosis to Mitosis: The Astonishing Flexibility of Cell Division Mechanisms in Early Mammalian Development. Curr Top Dev Biol 2016; 120:125-71. [PMID: 27475851 DOI: 10.1016/bs.ctdb.2016.04.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The execution of female meiosis and the establishment of the zygote is arguably the most critical stage of mammalian development. The egg can be arrested in the prophase of meiosis I for decades, and when it is activated, the spindle is assembled de novo. This spindle must function with the highest of fidelity and yet its assembly is unusually achieved in the absence of conventional centrosomes and with minimal influence of chromatin. Moreover, its dramatic asymmetric positioning is achieved through remarkable properties of the actin cytoskeleton to ensure elimination of the polar bodies. The second meiotic arrest marks a uniquely prolonged metaphase eventually interrupted by egg activation at fertilization to complete meiosis and mark a period of preparation of the male and female pronuclear genomes not only for their entry into the mitotic cleavage divisions but also for the imminent prospect of their zygotic expression.
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Affiliation(s)
- L Bury
- University of Cambridge, Cambridge, United Kingdom.
| | - P A Coelho
- University of Cambridge, Cambridge, United Kingdom
| | - D M Glover
- University of Cambridge, Cambridge, United Kingdom
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56
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Wallberg A, Pirk CW, Allsopp MH, Webster MT. Identification of Multiple Loci Associated with Social Parasitism in Honeybees. PLoS Genet 2016; 12:e1006097. [PMID: 27280405 PMCID: PMC4900560 DOI: 10.1371/journal.pgen.1006097] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 05/10/2016] [Indexed: 12/20/2022] Open
Abstract
In colonies of the honeybee Apis mellifera, the queen is usually the only reproductive female, which produces new females (queens and workers) by laying fertilized eggs. However, in one subspecies of A. mellifera, known as the Cape bee (A. m. capensis), worker bees reproduce asexually by thelytoky, an abnormal form of meiosis where two daughter nucleii fuse to form single diploid eggs, which develop into females without being fertilized. The Cape bee also exhibits a suite of phenotypes that facilitate social parasitism whereby workers lay such eggs in foreign colonies so their offspring can exploit their resources. The genetic basis of this switch to social parasitism in the Cape bee is unknown. To address this, we compared genome variation in a sample of Cape bees with other African populations. We find genetic divergence between these populations to be very low on average but identify several regions of the genome with extreme differentiation. The regions are strongly enriched for signals of selection in Cape bees, indicating that increased levels of positive selection have produced the unique set of derived phenotypic traits in this subspecies. Genetic variation within these regions allows unambiguous genetic identification of Cape bees and likely underlies the genetic basis of social parasitism. The candidate loci include genes involved in ecdysteroid signaling and juvenile hormone and dopamine biosynthesis, which may regulate worker ovary activation and others whose products localize at the centrosome and are implicated in chromosomal segregation during meiosis. Functional analysis of these loci will yield insights into the processes of reproduction and chemical signaling in both parasitic and non-parasitic populations and advance understanding of the process of normal and atypical meiosis.
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Affiliation(s)
- Andreas Wallberg
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
- * E-mail: (AW); (MTW)
| | - Christian W. Pirk
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Mike H. Allsopp
- Plant Protection Research Institute, Agricultural Research Council, Stellenbosch, South Africa
| | - Matthew T. Webster
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
- * E-mail: (AW); (MTW)
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57
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Intra-spindle Microtubule Assembly Regulates Clustering of Microtubule-Organizing Centers during Early Mouse Development. Cell Rep 2016; 15:54-60. [PMID: 27052165 DOI: 10.1016/j.celrep.2016.02.087] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 01/14/2016] [Accepted: 02/24/2016] [Indexed: 11/20/2022] Open
Abstract
Errors during cell division in oocytes and early embryos are linked to birth defects in mammals. Bipolar spindle assembly in early mouse embryos is unique in that three or more acentriolar microtubule-organizing centers (MTOCs) are initially formed and are then clustered into two spindle poles. Using a knockout mouse and live imaging of spindles in embryos, we demonstrate that MTOC clustering during the blastocyst stage requires augmin, a critical complex for MT-dependent MT nucleation within the spindle. Functional analyses in cultured cells with artificially increased numbers of centrosomes indicate that the lack of intra-spindle MT nucleation, but not loss of augmin per se or overall reduction of spindle MTs, is the cause of clustering failure. These data suggest that onset of mitosis with three or more MTOCs is turned into a typical bipolar division through augmin-dependent intra-spindle MT assembly.
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58
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Verlhac MH. Mother centrioles are kicked out so that starfish zygote can grow. J Cell Biol 2016; 212:759-61. [PMID: 27002168 PMCID: PMC4810309 DOI: 10.1083/jcb.201602053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 11/22/2022] Open
Abstract
Most oocytes eliminate their centrioles during meiotic divisions through unclear mechanisms. In this issue, Borrego-Pinto et al. (2016. J Cell. Biol. http://dx.doi.org/10.1083/jcb.201510083) show that mother centrioles need to be eliminated from starfish oocytes by extrusion into the polar bodies for successful embryo development.
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Affiliation(s)
- Marie-Hélène Verlhac
- Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique-UMR7241, and Institut National de la Santé et de la Recherche Médicale-U1050, Paris F-75005, France
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59
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Abstract
Sexual reproduction is essential for many organisms to propagate themselves. It requires the formation of haploid female and male gametes: oocytes and sperms. These specialized cells are generated through meiosis, a particular type of cell division that produces cells with recombined genomes that differ from their parental origin. In this review, we highlight the end process of female meiosis, the divisions per se, and how they can give rise to a functional female gamete preparing itself for the ensuing zygotic development. In particular, we discuss why such an essential process in the propagation of species is so poorly controlled, producing a strong percentage of abnormal female gametes in the end. Eventually, we examine aspects related to the lack of centrosomes in female oocytes, the asymmetry in size of the mammalian oocyte upon division, and in mammals the direct consequences of these long-lived cells in the ovary.
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60
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Urquhart KR, Zhao Y, Baker JA, Lu Y, Yan L, Cook MN, Jones BC, Hamre KM, Lu L. A novel heat shock protein alpha 8 (Hspa8) molecular network mediating responses to stress- and ethanol-related behaviors. Neurogenetics 2016; 17:91-105. [PMID: 26780340 DOI: 10.1007/s10048-015-0470-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 12/10/2015] [Indexed: 12/15/2022]
Abstract
Genetic differences mediate individual differences in susceptibility and responses to stress and ethanol, although, the specific molecular pathways that control these responses are not fully understood. Heat shock protein alpha 8 (Hspa8) is a molecular chaperone and member of the heat shock protein family that plays an integral role in the stress response and that has been implicated as an ethanol-responsive gene. Therefore, we assessed its role in mediating responses to stress and ethanol across varying genetic backgrounds. The hippocampus is an important mediator of these responses, and thus, was examined in the BXD family of mice in this study. We conducted bioinformatic analyses to dissect genetic factors modulating Hspa8 expression, identify downstream targets of Hspa8, and examined its role. Hspa8 is trans-regulated by a gene or genes on chromosome 14 and is part of a molecular network that regulates stress- and ethanol-related behaviors. To determine additional components of this network, we identified direct or indirect targets of Hspa8 and show that these genes, as predicted, participate in processes such as protein folding and organic substance metabolic processes. Two phenotypes that map to the Hspa8 locus are anxiety-related and numerous other anxiety- and/or ethanol-related behaviors significantly correlate with Hspa8 expression. To more directly assay this relationship, we examined differences in gene expression following exposure to stress or alcohol and showed treatment-related differential expression of Hspa8 and a subset of the members of its network. Our findings suggest that Hspa8 plays a vital role in genetic differences in responses to stress and ethanol and their interactions.
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Affiliation(s)
- Kyle R Urquhart
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Yinghong Zhao
- Department of Neurology, Affiliated Hospital of Nantong University, Nantong, Jiangsu, China
| | - Jessica A Baker
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Ye Lu
- The International Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Lei Yan
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Melloni N Cook
- Department of Psychology, University of Memphis, Memphis, TN, 38152, USA
| | - Byron C Jones
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
| | - Kristin M Hamre
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, 38163, USA.
| | - Lu Lu
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, 38163, USA. .,Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38163, USA. .,Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College of Nantong University, Nantong, China.
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61
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Chaigne A, Campillo C, Voituriez R, Gov NS, Sykes C, Verlhac MH, Terret ME. F-actin mechanics control spindle centring in the mouse zygote. Nat Commun 2016; 7:10253. [PMID: 26727405 PMCID: PMC4725770 DOI: 10.1038/ncomms10253] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 11/20/2015] [Indexed: 01/01/2023] Open
Abstract
Mitotic spindle position relies on interactions between astral microtubules nucleated by centrosomes and a rigid cortex. Some cells, such as mouse oocytes, do not possess centrosomes and astral microtubules. These cells rely only on actin and on a soft cortex to position their spindle off-centre and undergo asymmetric divisions. While the first mouse embryonic division also occurs in the absence of centrosomes, it is symmetric and not much is known on how the spindle is positioned at the exact cell centre. Using interdisciplinary approaches, we demonstrate that zygotic spindle positioning follows a three-step process: (1) coarse centring of pronuclei relying on the dynamics of an F-actin/Myosin-Vb meshwork; (2) fine centring of the metaphase plate depending on a high cortical tension; (3) passive maintenance at the cell centre. Altogether, we show that F-actin-dependent mechanics operate the switch between asymmetric to symmetric division required at the oocyte to embryo transition.
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Affiliation(s)
- Agathe Chaigne
- CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe labellisée Ligue contre le Cancer, Paris F-75005, France
| | - Clément Campillo
- Université Evry Val d'Essonne, LAMBE, Boulevard F Mitterrand, Evry 91025, France
| | | | - Nir S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Cécile Sykes
- CNRS-UMR168, Paris F-75248, France.,UPMC, 4 Place Jussieu, Paris F-75248, France.,Institut Curie, Centre de Recherche, Laboratoire Physico-Chimie, Paris F-75248, France
| | - Marie-Hélène Verlhac
- CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe labellisée Ligue contre le Cancer, Paris F-75005, France
| | - Marie-Emilie Terret
- CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe labellisée Ligue contre le Cancer, Paris F-75005, France
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62
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Kwon M. Using Cell Culture Models of Centrosome Amplification to Study Centrosome Clustering in Cancer. Methods Mol Biol 2016; 1413:367-392. [PMID: 27193861 DOI: 10.1007/978-1-4939-3542-0_23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The link between centrosome amplification and cancer has been recognized for more than a century, raising many key questions about the biology of both normal and cancer cells. In particular, the presence of extra centrosomes imposes a great challenge to a dividing cell by increasing the likelihood of catastrophic multipolar divisions. Only recently have we begun to understand how cancer cells successfully divide by clustering their extra centrosomes for bipolar division. Several hurdles to dissecting centrosome clustering include limitations in the methodologies used to quantify centrosome amplification, and the lack of appropriate cell culture models. Here, we describe how to accurately assess centrosome number and create isogenic cell lines with or without centrosome amplification. We then describe how imaging of cell division in these cell culture models leads to identification of the molecular machinery uniquely required for cells with extra centrosomes. These approaches have led to the identification of molecular targets for selective cancer therapeutics that can kill cancer cells with extra centrosomes without affecting normal cells with two centrosomes. We further anticipate that the approaches described here will be broadly applicable for studying the causes and consequences of centrosome amplification in a variety of contexts across cancer pathophysiology, such as cell migration and metastasis.
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Affiliation(s)
- Mijung Kwon
- Howard Hughes Medical Institute, Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA.
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63
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Clift D, Schuh M. A three-step MTOC fragmentation mechanism facilitates bipolar spindle assembly in mouse oocytes. Nat Commun 2015; 6:7217. [PMID: 26147444 PMCID: PMC4501430 DOI: 10.1038/ncomms8217] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 04/20/2015] [Indexed: 12/20/2022] Open
Abstract
Assembly of a bipolar microtubule spindle is essential for accurate chromosome segregation. In somatic cells, spindle bipolarity is determined by the presence of exactly two centrosomes. Remarkably, mammalian oocytes do not contain canonical centrosomes. This study reveals that mouse oocytes assemble a bipolar spindle by fragmenting multiple acentriolar microtubule-organizing centres (MTOCs) into a high number of small MTOCs to be able to then regroup and merge them into two equal spindle poles. We show that MTOCs are fragmented in a three-step process. First, PLK1 triggers a decondensation of the MTOC structure. Second, BicD2-anchored dynein stretches the MTOCs into fragmented ribbons along the nuclear envelope. Third, KIF11 further fragments the MTOCs following nuclear envelope breakdown so that they can be evenly distributed towards the two spindle poles. Failure to fragment MTOCs leads to defects in spindle assembly, which delay chromosome individualization and congression, putting the oocyte at risk of aneuploidy. Mitotic spindles assemble from two centrosomes, but oocytes lack centrosomes so how their spindles assemble is unclear. Here Clift and Schuh show that multiple acentriolar microtubule-organizing centres fragment in a three-step process to facilitate bipolar spindle assembly in mouse oocytes.
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Affiliation(s)
- Dean Clift
- Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Melina Schuh
- Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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64
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Turning the headlights on novel cancer biomarkers: Inspection of mechanics underlying intratumor heterogeneity. Mol Aspects Med 2015; 45:3-13. [PMID: 26024970 DOI: 10.1016/j.mam.2015.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/20/2015] [Indexed: 01/20/2023]
Abstract
Although the existence of intratumoral heterogeneity (ITH) in the expression of common biomarkers has been described by pathologists since the late 1890s, we have only recently begun to fathom the staggering extent and near ubiquity of this phenomenon. From the tumor's perspective, ITH provides a stabilizing diversity that allows for the evolution of aggressive cancer phenotypes. As the weight of the evidence correlating ITH to poor prognosis burgeons, it has become increasingly important to determine the mechanisms by which a tumor acquires ITH, find clinically-adaptable means to quantify ITH and design strategies to deal with the numerous profound clinical ramifications that ITH forces upon us. Elucidation of the drivers of ITH could enable development of novel biomarkers whose interrogation might permit quantitative evaluation of the ITH inherent in a tumor in order to predict the poor prognosis risk associated with that tumor. This review proposes centrosome amplification (CA), aided and abetted by centrosome clustering mechanisms, as a critical driver of chromosomal instability (CIN) that makes a key contribution to ITH generation. Herein we also evaluate how a tumor's inherent mitotic propensity, which reflects the cell cycling kinetics within the tumor's proliferative cells, functions as the indispensable engine underpinning CIN, and determines the rate of CIN. We thus expound how the forces of centrosome amplification and mitotic propensity collaborate to sculpt the genetic landscape of a tumor and spawn extensive subclonal diversity. As such, centrosome amplification and mitotic propensity profiles could serve as clinically facile and powerful prognostic biomarkers that would enable more accurate risk segmentation of patients and design of individualized therapies.
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65
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Godinho SA, Pellman D. Causes and consequences of centrosome abnormalities in cancer. Philos Trans R Soc Lond B Biol Sci 2015; 369:rstb.2013.0467. [PMID: 25047621 DOI: 10.1098/rstb.2013.0467] [Citation(s) in RCA: 245] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Centrosome amplification is a hallmark of cancer. However, despite significant progress in recent years, we are still far from understanding how centrosome amplification affects tumorigenesis. Boveri's hypothesis formulated more than 100 years ago was that aneuploidy induced by centrosome amplification promoted tumorigenesis. Although the hypothesis remains appealing 100 years later, it is also clear that the role of centrosome amplification in cancer is more complex than initially thought. Here, we review how centrosome abnormalities are generated in cancer and the mechanisms cells employ to adapt to centrosome amplification, in particular centrosome clustering. We discuss the different mechanisms by which centrosome amplification could contribute to tumour progression and the new advances in the development of therapies that target cells with extra centrosomes.
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Affiliation(s)
- S A Godinho
- Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - D Pellman
- Howard Hughes Medical Institute, Dana-Farber Cancer Institute, and Pediatric Hematology/Oncology, Children's Hospital, Boston, MA 02115, USA Department of Pediatric Oncology, Dana-Farber Cancer Institute, and Pediatric Hematology/Oncology, Children's Hospital, Boston, MA 02115, USA Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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66
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Active diffusion positions the nucleus in mouse oocytes. Nat Cell Biol 2015; 17:470-9. [PMID: 25774831 DOI: 10.1038/ncb3131] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 02/09/2015] [Indexed: 12/14/2022]
Abstract
In somatic cells, the position of the cell centroid is dictated by the centrosome. The centrosome is instrumental in nucleus positioning, the two structures being physically connected. Mouse oocytes have no centrosomes, yet harbour centrally located nuclei. We demonstrate how oocytes define their geometric centre in the absence of centrosomes. Using live imaging of oocytes, knockout for the formin 2 actin nucleator, with off-centred nuclei, together with optical trapping and modelling, we discover an unprecedented mode of nucleus positioning. We document how active diffusion of actin-coated vesicles, driven by myosin Vb, generates a pressure gradient and a propulsion force sufficient to move the oocyte nucleus. It promotes fluidization of the cytoplasm, contributing to nucleus directional movement towards the centre. Our results highlight the potential of active diffusion, a prominent source of intracellular transport, able to move large organelles such as nuclei, providing in vivo evidence of its biological function.
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67
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Wang J, Li J, Santana-Santos L, Shuda M, Sobol RW, Van Houten B, Qian W. A novel strategy for targeted killing of tumor cells: Induction of multipolar acentrosomal mitotic spindles with a quinazolinone derivative mdivi-1. Mol Oncol 2014; 9:488-502. [PMID: 25458053 DOI: 10.1016/j.molonc.2014.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 10/07/2014] [Accepted: 10/08/2014] [Indexed: 01/05/2023] Open
Abstract
Traditional antimitotic drugs for cancer chemotherapy often have undesired toxicities to healthy tissues, limiting their clinical application. Developing novel agents that specifically target tumor cell mitosis is needed to minimize the toxicity and improve the efficacy of this class of anticancer drugs. We discovered that mdivi-1 (mitochondrial division inhibitor-1), which was originally reported as an inhibitor of mitochondrial fission protein Drp1, specifically disrupts M phase cell cycle progression only in human tumor cells, but not in non-transformed fibroblasts or epithelial cells. The antimitotic effect of mdivi-1 is Drp1 independent, as mdivi-1 induces M phase abnormalities in both Drp1 wild-type and Drp1 knockout SV40-immortalized/transformed MEF cells. We also identified that the tumor transformation process required for the antimitotic effect of mdivi-1 is downstream of SV40 large T and small t antigens, but not hTERT-mediated immortalization. Mdivi-1 induces multipolar mitotic spindles in tumor cells regardless of their centrosome numbers. Acentrosomal spindle poles, which do not contain the bona-fide centrosome components γ-tubulin and centrin-2, were found to contribute to the spindle multipolarity induced by mdivi-1. Gene expression profiling revealed that the genes involved in oocyte meiosis and assembly of acentrosomal microtubules are highly expressed in tumor cells. We further identified that tumor cells have enhanced activity in the nucleation and assembly of acentrosomal kinetochore-attaching microtubules. Mdivi-1 inhibited the integration of acentrosomal microtubule-organizing centers into centrosomal asters, resulting in the development of acentrosomal mitotic spindles preferentially in tumor cells. The formation of multipolar acentrosomal spindles leads to gross genome instability and Bax/Bak-dependent apoptosis. Taken together, our studies indicate that inducing multipolar spindles composing of acentrosomal poles in mitosis could achieve tumor-specific antimitotic effect, and mdivi-1 thus represents a novel class of compounds as acentrosomal spindle inducers (ASI).
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Affiliation(s)
- Jingnan Wang
- Tsinghua University School of Medicine, Tsinghua University, Haidian District, Beijing 100084, China
| | - Jianfeng Li
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine and Hillman Cancer Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA
| | - Lucas Santana-Santos
- Biomedical Informatics, and Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Masahiro Shuda
- Molecular Virology Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA
| | - Robert W Sobol
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine and Hillman Cancer Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA; Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15213, USA
| | - Bennett Van Houten
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine and Hillman Cancer Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA.
| | - Wei Qian
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine and Hillman Cancer Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA.
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68
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Affiliation(s)
- Marie-Emilie Terret
- CIRB; Collège de France and CNRS-UMR7241 and INSERM-U1050; Paris, France; Equipe Labellisée Ligue Contre le Cancer; Paris, France; Memolife Laboratory of Excellence and Paris Science Lettre; Paris, France
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69
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Howe K, FitzHarris G. Recent insights into spindle function in mammalian oocytes and early embryos. Biol Reprod 2013; 89:71. [PMID: 23966320 DOI: 10.1095/biolreprod.113.112151] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Errors in chromosome segregation in oocytes and early embryos lead to embryo aneuploidy, which contributes to early pregnancy loss. At the heart of chromosome segregation is the spindle, a dynamic biomechanical machine fashioned from microtubules, which is tasked with gathering and sorting chromosomes and dispatching them to the daughter cells at the time of cell division. Understanding the causes of segregation error in the oocyte and early embryo will undoubtedly hinge on a thorough understanding of the mechanism of spindle assembly and function in these highly specialized cellular environments. The recent advent of live imaging approaches to observe chromosome segregation in real-time in oocytes and embryos, paired with gene-silencing techniques and specific inhibition for assessing the function of a protein of interest, has led to a substantial advance in our understanding of chromosome segregation in early mammalian development. These studies have uncovered numerous mechanistic differences between oocytes, embryos, and traditional model systems. In addition, a flurry of recent studies using naturally aged mice as the model for human aging have begun to shed light on the increased levels of aneuploidy seen in embryos from older mothers. Here we review these recent developments and consider what has been learned about the causes of chromosome missegregation in early development.
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Affiliation(s)
- Katie Howe
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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70
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Self-assembly and sorting of acentrosomal microtubules by TACC3 facilitate kinetochore capture during the mitotic spindle assembly. Proc Natl Acad Sci U S A 2013; 110:15295-300. [PMID: 24003142 DOI: 10.1073/pnas.1312382110] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kinetochore capture by dynamic kinetochore microtubule fibers (K fibers) is essential for proper chromosome alignment and accurate distribution of the replicated genome during cell division. Although this capture process has been extensively studied, the mechanisms underlying the initiation of this process and the proper formation of the K fibers remain largely unknown. Here we show that transforming acidic coiled-coil-containing protein 3 (TACC3) is essential for kinetochore capture and proper K-fiber formation in HeLa cells. To observe the assembly of acentrosomal microtubules more clearly, the cells were released from higher concentrations of nocodazole into zero or lower concentrations. We find that small acentrosomal TACC3-microtubule aster formation near the kinetochores and binding of the asters with the kinetochores are the initial steps of the kinetochore capture by the acentrosomal microtubules, and that the sorting of kinetochore-captured acentrosomal microtubules with centrosomal microtubules leads to the capture of kinetochore by centrosomal microtubules from both spindle poles. We demonstrate that the sorting of the TACC3-associated microtubules with the centrosomal microtubules is a crucial process for spindle assembly and chromosome movement. These findings, which are also supported in the unperturbed mitosis without nocodazole, reveal a critical TACC3-dependent acentrosomal microtubule nucleation and sorting process to regulate kinetochore-microtubule connections and provide deep insight into the mechanisms of mitotic spindle assembly and chromosome alignment.
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71
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Clift D, Schuh M. Restarting life: fertilization and the transition from meiosis to mitosis. Nat Rev Mol Cell Biol 2013; 14:549-62. [PMID: 23942453 PMCID: PMC4021448 DOI: 10.1038/nrm3643] [Citation(s) in RCA: 185] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Fertilization triggers a complex cellular programme that transforms two highly specialized meiotic germ cells, the oocyte and the sperm, into a totipotent mitotic embryo. Linkages between sister chromatids are remodelled to support the switch from reductional meiotic to equational mitotic divisions; the centrosome, which is absent from the egg, is reintroduced; cell division shifts from being extremely asymmetric to symmetric; genomic imprinting is selectively erased and re-established; and protein expression shifts from translational control to transcriptional control. Recent work has started to reveal how this remarkable transition from meiosis to mitosis is achieved.
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Affiliation(s)
- Dean Clift
- Medical Research Council Laboratory of Molecular Biology (MRC LMB), Cambridge CB2 0QH, UK
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72
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Rebuilding MTOCs upon centriole loss during mouse oogenesis. Dev Biol 2013; 382:48-56. [PMID: 23954884 DOI: 10.1016/j.ydbio.2013.07.029] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 07/25/2013] [Accepted: 07/30/2013] [Indexed: 11/21/2022]
Abstract
The vast majority of animal cells contain canonical centrosomes as a main microtubule-organizing center defined by a central pair of centrioles. As a rare and striking exception to this rule, vertebrate oocytes loose their centrioles at an early step of oogenesis. At the end of oogenesis, centrosomes are eventually replaced by numerous acentriolar microtubule-organizing centers (MTOCs) that shape the spindle poles during meiotic divisions. The mechanisms involved in centrosome and acentriolar MTOCs metabolism in oocytes have not been elucidated yet. In addition, little is known about microtubule organization and its impact on intracellular architecture during the oocyte growth phase following centrosome disassembly. We have investigated this question in the mouse by coupling immunofluorescence and live-imaging approaches. We show that growing oocytes contain dispersed pericentriolar material, responsible for microtubule assembly and distribution all over the cell. The gradual enlargement of PCM foci eventually leads in competent oocytes to the formation of big perinuclear MTOCs and to the assembly of large microtubule asters emanating from the close vicinity of the nucleus. Upon meiosis resumption, perinuclear MTOCs spread around the nuclear envelope, which in parallel is remodelled before breaking-down, via a MT- and dynein-dependent mechanism. Only fully competent oocytes are able to perform this dramatic reorganization at NEBD. Therefore, the MTOC-MT reorganization that we describe is one of key feature of mouse oocyte competency.
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73
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Davydenko O, Schultz RM, Lampson MA. Increased CDK1 activity determines the timing of kinetochore-microtubule attachments in meiosis I. ACTA ACUST UNITED AC 2013; 202:221-9. [PMID: 23857768 PMCID: PMC3718970 DOI: 10.1083/jcb.201303019] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The slow increase in CDK1 activity in meiosis I acts as a timing mechanism to allow stable kinetochore–microtubule attachments only after bipolar spindle formation, thus preventing attachment errors. Chromosome segregation during cell division depends on stable attachment of kinetochores to spindle microtubules. Mitotic spindle formation and kinetochore–microtubule (K-MT) capture typically occur within minutes of nuclear envelope breakdown. In contrast, during meiosis I in mouse oocytes, formation of the acentrosomal bipolar spindle takes 3–4 h, and stabilization of K-MT attachments is delayed an additional 3–4 h. The mechanism responsible for this delay, which likely prevents stabilization of erroneous attachments during spindle formation, is unknown. Here we show that during meiosis I, attachments are regulated by CDK1 activity, which gradually increases through prometaphase and metaphase I. Partial reduction of CDK1 activity delayed formation of stable attachments, whereas a premature increase in CDK1 activity led to precocious formation of stable attachments and eventually lagging chromosomes at anaphase I. These results indicate that the slow increase in CDK1 activity in meiosis I acts as a timing mechanism to allow stable K-MT attachments only after bipolar spindle formation, thus preventing attachment errors.
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Affiliation(s)
- Olga Davydenko
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
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74
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A soft cortex is essential for asymmetric spindle positioning in mouse oocytes. Nat Cell Biol 2013; 15:958-66. [PMID: 23851486 DOI: 10.1038/ncb2799] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 06/03/2013] [Indexed: 12/19/2022]
Abstract
At mitosis onset, cortical tension increases and cells round up, ensuring correct spindle morphogenesis and orientation. Thus, cortical tension sets up the geometric requirements of cell division. On the contrary, cortical tension decreases during meiotic divisions in mouse oocytes, a puzzling observation because oocytes are round cells, stable in shape, that actively position their spindles. We investigated the pathway leading to reduction in cortical tension and its significance for spindle positioning. We document a previously uncharacterized Arp2/3-dependent thickening of the cortical F-actin essential for first meiotic spindle migration to the cortex. Using micropipette aspiration, we show that cortical tension decreases during meiosis I, resulting from myosin-II exclusion from the cortex, and that cortical F-actin thickening promotes cortical plasticity. These events soften and relax the cortex. They are triggered by the Mos-MAPK pathway and coordinated temporally. Artificial cortex stiffening and theoretical modelling demonstrate that a soft cortex is essential for meiotic spindle positioning.
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75
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Abstract
The anaphase-promoting complex or cyclosome (APC/C) orchestrates a meticulously controlled sequence of proteolytic events critical for proper cell cycle progression, the details of which have been most extensively elucidated during mitosis. It has become apparent, however, that the APC/C, particularly when acting in concert with its Cdh1 co-activator (APC/C(Cdh1)), executes a staggeringly diverse repertoire of functions that extend its remit well outside the bounds of mitosis. Findings over the past decade have not only earmarked mammalian oocyte maturation as one such case in point but have also begun to reveal a complex pattern of APC/C regulation that underpins many of the oocyte's unique developmental attributes. This review will encompass the latest findings pertinent to the APC/C, especially APC/C(Cdh1), in mammalian oocytes and how its activity and substrates shape the stop-start tempo of female mammalian first meiotic division and the challenging requirement for assembling spindles in the absence of centrosomes.
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Affiliation(s)
- Hayden Homer
- Mammalian Oocyte and Embryo Research Laboratory, Cell and Developmental Biology, UCL, London WC1E 6BT, UK.
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76
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Aurora kinase inhibitors reveal mechanisms of HURP in nucleation of centrosomal and kinetochore microtubules. Proc Natl Acad Sci U S A 2013; 110:E1779-87. [PMID: 23610398 DOI: 10.1073/pnas.1220523110] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The overexpression of Aurora kinases in multiple tumors makes these kinases appealing targets for the development of anticancer therapies. This study identified two small molecules with a furanopyrimidine core, IBPR001 and IBPR002, that target Aurora kinases and induce a DFG conformation change at the ATP site of Aurora A. Our results demonstrate the high potency of the IBPR compounds in reducing tumorigenesis in a colorectal cancer xenograft model in athymic nude mice. Human hepatoma up-regulated protein (HURP) is a substrate of Aurora kinase A, which plays a crucial role in the stabilization of kinetochore fibers. This study used the IBPR compounds as well as MLN8237, a proven Aurora A inhibitor, as chemical probes to investigate the molecular role of HURP in mitotic spindle formation. These compounds effectively eliminated HURP phosphorylation, thereby revealing the coexistence and continuous cycling of HURP between unphosphorylated and phosphorylated forms that are associated, respectively, with microtubules emanating from centrosomes and kinetochores. Furthermore, these compounds demonstrate a spatial hierarchical preference for HURP in the attachment of microtubules extending from the mother to the daughter centrosome. The finding of inequality in the centrosomal microtubules revealed by these small molecules provides a versatile tool for the discovery of new cell-division molecules for the development of antitumor drugs.
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77
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Gui L, Homer H. Hec1-dependent cyclin B2 stabilization regulates the G2-M transition and early prometaphase in mouse oocytes. Dev Cell 2013; 25:43-54. [PMID: 23541922 PMCID: PMC3659288 DOI: 10.1016/j.devcel.2013.02.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Revised: 01/20/2013] [Accepted: 02/14/2013] [Indexed: 01/06/2023]
Abstract
The functions of the Ndc80/Hec1 subunit of the highly conserved Ndc80 kinetochore complex are normally restricted to M phase when it exerts a pivotal kinetochore-based role. Here, we find that in mouse oocytes, depletion of Hec1 severely compromises the G2-M transition because of impaired activation of cyclin-dependent kinase 1 (Cdk1). Unexpectedly, impaired M phase entry is due to instability of the Cdk1-activating subunit, cyclin B2, which cannot be covered by cyclin B1. Hec1 protects cyclin B2 from destruction by the Cdh1-activated anaphase-promoting complex (APCCdh1) and remains important for cyclin B2 stabilization during early M phase, required for the initial stages of acentrosomal spindle assembly. By late M phase, however, Hec1 and cyclin B2 become uncoupled, and although Hec1 remains stable, APCCdc20 triggers cyclin B2 destruction. These data identify another dimension to Hec1 function centered on M phase entry and early prometaphase progression and challenge the view that cyclin B2 is completely dispensable in mammals.
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Affiliation(s)
- Liming Gui
- Mammalian Oocyte and Embryo Research Laboratory, Cell and Developmental Biology, UCL, London WC1E 6BT, UK
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78
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Yamagata K, FitzHarris G. 4D imaging reveals a shift in chromosome segregation dynamics during mouse pre-implantation development. Cell Cycle 2012; 12:157-65. [PMID: 23255117 DOI: 10.4161/cc.23052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cells of the early developing mammalian embryo frequently mis-segregate chromosomes during cell division, causing daughter cells to inherit an erroneous numbers of chromosomes. Why the embryo is so susceptible to errors is unknown, and the mechanisms that embryos employ to accomplish chromosome segregation are poorly understood. Chromosome segregation is performed by the spindle, a fusiform-shaped microtubule-based transient organelle. Here we present a detailed analysis of 4D fluorescence-confocal data sets of live embryos progressing from the one-cell embryo stage through to blastocyst in vitro, providing some of the first mechanistic insights into chromosome segregation in the mammalian embryo. We show that chromosome segregation occurs as a combined result of poleward chromosome motion (anaphase-A) and spindle elongation (anaphase-B), which occur simultaneously at the time of cell division. Unexpectedly, however, regulation of the two anaphase mechanisms changes significantly between the first and second embryonic mitoses. In one-cell embryos, the velocity of anaphase-A chromosome motion and the velocity and overall extent of anaphase-B spindle elongation are significantly constrained compared with later stages. As a result chromosomes are delivered close to the center of the forming two-cell stage blastomeres at the end of the first mitosis. In subsequent divisions, anaphase-B spindle elongation is faster and more extensive, resulting in the delivery of chromosomes to the distal plasma membrane of the newly forming blastomeres. Metaphase spindle length scales with cell size from the two-cell stage onwards, but is substantially shorter in the first mitosis than in the second mitosis, and the duration of mitosis-1 is substantially greater than subsequent divisions. Thus, there is a striking and unexpected shift in the approach to cell division between the first and second mitotic divisions, which likely reflects adaptations to the unique environment within the developing embryo.
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Affiliation(s)
- Kazuo Yamagata
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
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79
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PROL4 Elevates The Sensitivity of Lung Cancer Cell LTEP-a-2 to Cisplatin Treatment*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2011.00567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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80
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Solc P, Baran V, Mayer A, Bohmova T, Panenkova-Havlova G, Saskova A, Schultz RM, Motlik J. Aurora kinase A drives MTOC biogenesis but does not trigger resumption of meiosis in mouse oocytes matured in vivo. Biol Reprod 2012; 87:85. [PMID: 22837479 DOI: 10.1095/biolreprod.112.101014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Aurora kinase A (AURKA) is an important mitotic kinase involved in the G2/M transition, centrosome maturation and separation, and spindle formation in somatic cells. We used transgenic models that specifically overexpress in mouse oocytes either wild-type (WT-AURKA) or a catalytically inactive (kinase-dead) (KD-AURKA) AURKA to gain new insights regarding the role of AURKA during oocyte maturation. AURKA activation occurs shortly after hCG administration that initiates maturation in vivo. Although AURKA activity is increased in WT-AURKA oocytes, resumption of meiosis is not observed in the absence of hCG administration. Control oocytes contain one to three microtubule organizing centers (MTOCs; centrosome equivalent) at prophase I. At the time of germinal vesicle breakdown (GVBD), the first visible marker of resumption of meiosis, the MTOC number increases. In WT-AURKA oocytes, the increase in MTOC number occurs prematurely but transiently without GVBD, whereas the increase in MTOC number does not occur in control and KD-AURKA oocytes. AURKA activation is biphasic with the initial activation not requiring CDC25B-CDK1 activity, whereas full activation, which is essential for the increase in MTOCs number, depends on CDK1 activity. AURKA activity also influences spindle length and regulates, independent of its protein kinase activity, the amount of MTOC associated with gamma-tubulin. Both WT-AURKA and KD-AURKA transgenic mice have normal fertility during first 6 mo of life. These results suggest that although AURKA is not a trigger kinase for G2/M transition in mouse oocytes, it regulates MTOC number and spindle length, and, independent of its protein kinase activity, gamma-tubulin recruitment to MTOCs.
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Affiliation(s)
- Petr Solc
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Libechov, Czech Republic.
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81
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Holt JE, Lane SIR, Jennings P, García-Higuera I, Moreno S, Jones KT. APC(FZR1) prevents nondisjunction in mouse oocytes by controlling meiotic spindle assembly timing. Mol Biol Cell 2012; 23:3970-81. [PMID: 22918942 PMCID: PMC3469513 DOI: 10.1091/mbc.e12-05-0352] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The APC activator FZR1 has a role in controlling the timing of meiosis I spindle assembly. Oocytes lacking FZR1 undergo accelerated meiosis I, associated with earlier spindle assembly checkpoint satisfaction and APCCDC20 activity, resulting in high rates of aneuploidy. FZR1 is an anaphase-promoting complex (APC) activator best known for its role in the mitotic cell cycle at M-phase exit, in G1, and in maintaining genome integrity. Previous studies also established that it prevents meiotic resumption, equivalent to the G2/M transition. Here we report that mouse oocytes lacking FZR1 undergo passage through meiosis I that is accelerated by ∼1 h, and this is due to an earlier onset of spindle assembly checkpoint (SAC) satisfaction and APCCDC20 activity. However, loss of FZR1 did not compromise SAC functionality; instead, earlier SAC satisfaction was achieved because the bipolar meiotic spindle was assembled more quickly in the absence of FZR1. This novel regulation of spindle assembly by FZR1 led to premature bivalent attachment to microtubules and loss of kinetochore-bound MAD2. Bivalents, however, were observed to congress poorly, leading to nondisjunction rates of 25%. We conclude that in mouse oocytes FZR1 controls the timing of assembly of the bipolar spindle and in so doing the timing of SAC satisfaction and APCCDC20 activity. This study implicates FZR1 as a major regulator of prometaphase whose activity helps to prevent chromosome nondisjunction.
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Affiliation(s)
- Janet E Holt
- School of Biomedical Sciences, University of Newcastle, Callaghan, NSW 2308, Australia.
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82
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Liu XJ. Polar body emission. Cytoskeleton (Hoboken) 2012; 69:670-85. [PMID: 22730245 DOI: 10.1002/cm.21041] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/15/2012] [Accepted: 05/21/2012] [Indexed: 12/13/2022]
Abstract
Generation of a haploid female germ cell, the egg, consists of two rounds of asymmetric cell division (meiosis I and meiosis II), yielding two diminutive and nonviable polar bodies and a large haploid egg. Animal eggs are also unique in the lack of centrioles and therefore form meiotic spindles without the pre-existence of the two dominant microtubule organizing centers (centrosomes) found in mitosis. Meiotic spindle assembly is further complicated by the unique requirement of sister chromatid mono-oriented in meiosis I. Nonetheless, the eggs appear to adopt many of the same proteins and mechanisms described in mitosis, with necessary modifications to accommodate their special needs. Unraveling these special modifications will not only help understanding animal reproduction, but should also enhance our understanding of cell division in general.
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Affiliation(s)
- X Johné Liu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa Hospital Civic Campus, 1053 Carling Avenue, Ottawa, K1Y 4E9, Canada.
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83
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Gui L, Homer H. Spindle assembly checkpoint signalling is uncoupled from chromosomal position in mouse oocytes. Development 2012; 139:1941-6. [PMID: 22513372 PMCID: PMC3347686 DOI: 10.1242/dev.078352] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/02/2012] [Indexed: 12/19/2022]
Abstract
The spindle assembly checkpoint (SAC) averts aneuploidy by coordinating proper bipolar chromosomal attachment with anaphase-promoting complex/cyclosome (APC/C)-mediated securin and cyclin B1 destruction required for anaphase onset. The generation of a Mad2-based signal at kinetochores is central to current models of SAC-based APC/C inhibition. During mitosis, kinetochores of polar-displaced chromosomes, which are at greatest risk of mis-segregating, recruit the highest levels of Mad2, thereby ensuring that SAC activation is proportionate to aneuploidy risk. Paradoxically, although an SAC operates in mammalian oocytes, meiosis I (MI) is notoriously error prone and polar-displaced chromosomes do not prevent anaphase onset. Here we find that Mad2 is not preferentially recruited to the kinetochores of polar chromosomes of wild-type mouse oocytes, in which polar chromosomes are rare, or of oocytes depleted of the kinesin-7 motor CENP-E, in which polar chromosomes are more abundant. Furthermore, in CENP-E-depleted oocytes, although polar chromosomal displacement intensified during MI and the capacity to form stable end-on attachments was severely compromised, all kinetochores nevertheless became devoid of Mad2. Thus, it is possible that the ability of the SAC to robustly discriminate chromosomal position might be compromised by the propensity of oocyte kinetochores to become saturated with unproductive attachments, thereby predisposing to aneuploidy. Our data also reveal novel functions for CENP-E in oocytes: first, CENP-E stabilises BubR1, thereby impacting MI progression; and second, CENP-E mediates bi-orientation by promoting kinetochore reorientation and preventing chromosomal drift towards the poles.
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Affiliation(s)
- Liming Gui
- Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Hayden Homer
- Cell and Developmental Biology, University College London, London WC1E 6BT, UK
- Institute for Women’s Health, University College London, London WC1E 6BT, UK
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84
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Error-prone mammalian female meiosis from silencing the spindle assembly checkpoint without normal interkinetochore tension. Proc Natl Acad Sci U S A 2012; 109:E1858-67. [PMID: 22552228 DOI: 10.1073/pnas.1204686109] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is well established that chromosome segregation in female meiosis I (MI) is error-prone. The acentrosomal meiotic spindle poles do not have centrioles and are not anchored to the cortex via astral microtubules. By Cre recombinase-mediated removal in oocytes of the microtubule binding site of nuclear mitotic apparatus protein (NuMA), which is implicated in anchoring microtubules at poles, we determine that without functional NuMA, microtubules lose connection to MI spindle poles, resulting in highly disorganized early spindle assembly. Subsequently, very long spindles form with hyperfocused poles. The kinetochores of homologs make attachments to microtubules in these spindles but with reduced tension between them and accompanied by alignment defects. Despite this, the spindle assembly checkpoint is normally silenced and the advance to anaphase I and first polar body extrusion takes place without delay. Females without functional NuMA in oocytes are sterile, producing aneuploid eggs with altered chromosome number. These findings establish that in mammalian MI, the spindle assembly checkpoint is unable to sustain meiotic arrest in the presence of one or few misaligned and/or misattached kinetochores with reduced interkinetochore tension, thereby offering an explanation for why MI in mammals is so error-prone.
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85
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Acentrosomal spindle assembly and chromosome segregation during oocyte meiosis. Trends Cell Biol 2012; 22:241-9. [PMID: 22480579 DOI: 10.1016/j.tcb.2012.02.007] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 02/28/2012] [Accepted: 02/29/2012] [Indexed: 11/24/2022]
Abstract
The ability to reproduce relies in most eukaryotes on specialized cells called gametes. Gametes are formed by the process of meiosis in which, after a single round of replication, two successive cell divisions reduce the ploidy of the genome. Fusion of gametes at fertilization reconstitutes diploidy. In most animal species, chromosome segregation during female meiosis occurs on spindles assembled in the absence of the major microtubule-organizing center, the centrosome. In mammals, oocyte meiosis is error prone and underlies most birth aneuploidies. Here, we review recent work on acentrosomal spindle formation and chromosome alignment/separation during oocyte meiosis in different animal models.
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Ma N, Titus J, Gable A, Ross JL, Wadsworth P. TPX2 regulates the localization and activity of Eg5 in the mammalian mitotic spindle. ACTA ACUST UNITED AC 2011; 195:87-98. [PMID: 21969468 PMCID: PMC3187703 DOI: 10.1083/jcb.201106149] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
TPX2 promotes mitotic spindle formation by enhancing Eg5 accumulation on microtubules and limiting motor activity. Mitotic spindle assembly requires the regulated activity of numerous spindle-associated proteins. In mammalian cells, the Kinesin-5 motor Eg5 interacts with the spindle assembly factor TPX2, but how this interaction contributes to spindle formation and function is not established. Using bacterial artificial chromosome technology, we generated cells expressing TPX2 lacking the Eg5 interaction domain. Spindles in these cells were highly disorganized with multiple spindle poles. The TPX2–Eg5 interaction was required for kinetochore fiber formation and contributed to Eg5 localization to spindle microtubules but not spindle poles. Microinjection of the Eg5-binding domain of TPX2 resulted in spindle elongation, indicating that the interaction of Eg5 with TPX2 reduces motor activity. Consistent with this possibility, we found that TPX2 reduced the velocity of Eg5-dependent microtubule gliding, inhibited microtubule sliding, and resulted in the accumulation of motor on microtubules. These results establish a novel function of TPX2 in regulating the location and activity of the mitotic motor Eg5.
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Affiliation(s)
- Nan Ma
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
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Krämer A, Maier B, Bartek J. Centrosome clustering and chromosomal (in)stability: a matter of life and death. Mol Oncol 2011; 5:324-35. [PMID: 21646054 DOI: 10.1016/j.molonc.2011.05.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/06/2011] [Accepted: 05/11/2011] [Indexed: 01/28/2023] Open
Abstract
Centrosome abnormalities occur commonly in cancer, and contribute to chromosomal instability and tumorigenesis. New evidence on a phylogenetically conserved mechanism termed 'centrosomal clustering' provides exciting insights into how cells with supernumerary centrosomes adapt to avoid lethal multipolar divisions. Here, we highlight the emerging molecular basis of centrosome clustering, and its impact on asymmetric divisions of stem cells, chromosomal (in)stability and malignant transformation. Finally, pharmacological inhibition of centrosome clustering promises to selectively target tumor cells.
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Affiliation(s)
- Alwin Krämer
- Clinical Cooperation Unit Molecular Hematology/Oncology, German Cancer Research Center, Department of Internal Medicine V, University of Heidelberg, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany.
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