1
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Dudka D, Dawicki-McKenna JM, Sun X, Beeravolu K, Akera T, Lampson MA, Black BE. Satellite DNA shapes dictate pericentromere packaging in female meiosis. Nature 2025; 638:814-822. [PMID: 39779853 PMCID: PMC11880906 DOI: 10.1038/s41586-024-08374-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 11/08/2024] [Indexed: 01/11/2025]
Abstract
The abundance and sequence of satellite DNA at and around centromeres is evolving rapidly despite the highly conserved and essential process through which the centromere directs chromosome inheritance1-3. The impact of such rapid evolution is unclear. Here we find that sequence-dependent DNA shape dictates packaging of pericentromeric satellites in female meiosis through a conserved DNA-shape-recognizing chromatin architectural protein, high mobility group AT-hook 1 (HMGA1)4,5. Pericentromeric heterochromatin in two closely related mouse species, M. musculus and M. spretus, forms on divergent satellites that differ by both density of narrow DNA minor grooves and HMGA1 recruitment. HMGA1 binds preferentially to M. musculus satellites, and depletion in M. musculus oocytes causes massive stretching of pericentromeric satellites, disruption of kinetochore organization and delays in bipolar spindle assembly. In M. musculus × spretus hybrid oocytes, HMGA1 depletion disproportionately impairs M. musculus pericentromeres and microtubule attachment to their kinetochores. Thus, DNA shape affects both pericentromere packaging and the segregation machinery. We propose that rapid evolution of centromere and pericentromere DNA does not disrupt these essential processes when the satellites adopt DNA shapes recognized by conserved architectural proteins (such as HMGA1). By packaging these satellites, architectural proteins become part of the centromeric and pericentromeric chromatin, suggesting an evolutionary strategy that lowers the cost of megabase-scale satellite expansion.
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Affiliation(s)
- Damian Dudka
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Jennine M Dawicki-McKenna
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Xueqi Sun
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Keagan Beeravolu
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Takashi Akera
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Michael A Lampson
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA.
- Penn Center for Genome Integrity, University of Pennsylvania, Philadelphia, PA, USA.
| | - Ben E Black
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Penn Center for Genome Integrity, University of Pennsylvania, Philadelphia, PA, USA.
- Epigenetics Institute, University of Pennsylvania, Philadelphia, PA, USA.
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2
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Asai K, Zhou Y, Takenouchi O, Kitajima TS. Artificial kinetochore beads establish a biorientation-like state in the spindle. Science 2024; 385:1366-1375. [PMID: 39298589 DOI: 10.1126/science.adn5428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 06/24/2024] [Accepted: 08/16/2024] [Indexed: 09/22/2024]
Abstract
Faithful chromosome segregation requires biorientation, where the pair of kinetochores on the chromosome establish bipolar microtubule attachment. The integrity of the kinetochore, a macromolecular complex built on centromeric DNA, is required for biorientation, but components sufficient for biorientation remain unknown. Here, we show that tethering the outer kinetochore heterodimer NDC80-NUF2 to the surface of apolar microbeads establishes their biorientation-like state in mouse cells. NDC80-NUF2 microbeads align at the spindle equator and self-correct alignment errors. The alignment is associated with stable bipolar microtubule attachment and is independent of the outer kinetochore proteins SPC24-SPC25, KNL1, the Mis12 complex, inner kinetochore proteins, and Aurora. Larger microbeads align more rapidly, suggesting a size-dependent biorientation mechanism. This study demonstrates a biohybrid kinetochore design for synthetic biorientation of microscale particles in cells.
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Affiliation(s)
- Kohei Asai
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Yuanzhuo Zhou
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Osamu Takenouchi
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Tomoya S Kitajima
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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3
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Tulek F, Kahraman A, Demirel C. Adjuvant letrozole administration in gonadotropin releasing hormone antagonist cycles do not affect ploidy status of embryos. J Gynecol Obstet Hum Reprod 2023; 52:102689. [PMID: 39491092 DOI: 10.1016/j.jogoh.2023.102689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 10/22/2023] [Accepted: 10/26/2023] [Indexed: 11/05/2024]
Abstract
OBJECTIVE To evaluate the effects of adjuvant letrozole administration on euploid embryo rates in gonadotropin releasing hormone (GnRH) antagonist cycles. METHODS This retrospective study was conducted by analyzing data of patients that underwent GnRH antagonist cycles with intra-cytoplasmic sperm injection (ICSI) and pre-implantation genetic testing for aneuploidy between 2013 and 2021. Study included a total of 713 patients which 84 of them were received adjuvant letrozole and 629 patients underwent ovulation induction without any adjuvant therapy. RESULTS In patients with letrozole administration, total dose of consumed gonadotropins were significantly lower (2166.80±738.82 IU vs. 2541.96±755.76 IU; p<0.001, respectively), and duration of stimulation was slightly longer (9.80±1.23 days vs. 9.53±1.38 days; p=0.037) in comparison to patients without letrozole administration. Overall euploidy rates were found similar among letrozole group and control group (28.02%±31.08% vs. 23.02%±30.87%; p=0.109). Similar rate of euploidy remained even after stratification of patients in accordance with female age. There was no significant difference in terms of live birth rates between letrozole administered group and control group (66.7% vs 62.2%, respectively). CONCLUSION Co-treatment with 5 mg/day letrozole for 5 days does not appear to affect euploidy rates of obtained embryos in GnRH antagonist cycles with ICSI.
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Affiliation(s)
- Firat Tulek
- Uskudar University, Faculty of Health Sciences, Department Obstetrics and Gynecology, Istanbul, Turkey; Acibadem Atasehir Hospital, Department of Obstetrics and Gynecology, Istanbul, Turkey.
| | - Alper Kahraman
- Haseki Training and Research Hospital, Department of Obstetrics and Gynecology, Istanbul, Turkey
| | - Cem Demirel
- Acibadem Atasehir Hospital, Department of Obstetrics and Gynecology, Istanbul, Turkey
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4
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Ozturk S. Molecular determinants of the meiotic arrests in mammalian oocytes at different stages of maturation. Cell Cycle 2022; 21:547-571. [PMID: 35072590 PMCID: PMC8942507 DOI: 10.1080/15384101.2022.2026704] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/21/2021] [Accepted: 01/03/2022] [Indexed: 01/26/2023] Open
Abstract
Mammalian oocytes undergo two rounds of developmental arrest during maturation: at the diplotene of the first meiotic prophase and metaphase of the second meiosis. These arrests are strictly regulated by follicular cells temporally producing the secondary messengers, cAMP and cGMP, and other factors to regulate maturation promoting factor (composed of cyclin B1 and cyclin-dependent kinase 1) levels in the oocytes. Out of these normally appearing developmental arrests, permanent arrests may occur in the oocytes at germinal vesicle (GV), metaphase I (MI), or metaphase II (MII) stage. This issue may arise from absence or altered expression of the oocyte-related genes playing key roles in nuclear and cytoplasmic maturation. Additionally, the assisted reproductive technology (ART) applications such as ovarian stimulation and in vitro culture conditions both of which harbor various types of chemical agents may contribute to forming the permanent arrests. In this review, the molecular determinants of developmental and permanent arrests occurring in the mammalian oocytes are comprehensively evaluated in the light of current knowledge. As number of permanently arrested oocytes at different stages is increasing in ART centers, potential approaches for inducing permanent arrests to obtain competent oocytes are discussed.
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Affiliation(s)
- Saffet Ozturk
- Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey
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5
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Wu T, Lane SIR, Morgan SL, Tang F, Jones KT. Loss of centromeric RNA activates the spindle assembly checkpoint in mammalian female meiosis I. J Cell Biol 2021; 220:212548. [PMID: 34379093 PMCID: PMC8360762 DOI: 10.1083/jcb.202011153] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 05/01/2021] [Accepted: 07/27/2021] [Indexed: 12/22/2022] Open
Abstract
The repetitive sequences of DNA centromeric regions form the structural basis for kinetochore assembly. Recently they were found to be transcriptionally active in mitosis, with their RNAs providing noncoding functions. Here we explore the role, in mouse oocytes, of transcripts generated from within the minor satellite repeats. Depletion of minor satellite transcripts delayed progression through meiosis I by activation of the spindle assembly checkpoint. Arrested oocytes had poorly congressed chromosomes, and centromeres were frequently split by microtubules. Thus, we have demonstrated that the centromeric RNA plays a specific role in female meiosis I compared with mitosis and is required for maintaining the structural integrity of centromeres. This may contribute to the high aneuploidy rates observed in female meiosis.
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Affiliation(s)
- Tianyu Wu
- Department of Central Laboratory, Clinical Laboratory, Jing'an District Centre Hospital of Shanghai, Shanghai Key Laboratory of Medical Epigenetics, International Laboratory of Medical Epigenetics and Metabolism and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Simon I R Lane
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Stephanie L Morgan
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, UK
| | - Feng Tang
- Discipline of Obstetrics and Gynecology, School of Medicine, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Keith T Jones
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK
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6
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Courtois A, Yoshida S, Takenouchi O, Asai K, Kitajima TS. Stable kinetochore-microtubule attachments restrict MTOC position and spindle elongation in oocytes. EMBO Rep 2021; 22:e51400. [PMID: 33655692 PMCID: PMC8024892 DOI: 10.15252/embr.202051400] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 01/14/2021] [Accepted: 01/28/2021] [Indexed: 01/13/2023] Open
Abstract
In mouse oocytes, acentriolar MTOCs functionally replace centrosomes and act as microtubule nucleation sites. Microtubules nucleated from MTOCs initially assemble into an unorganized ball‐like structure, which then transforms into a bipolar spindle carrying MTOCs at its poles, a process called spindle bipolarization. In mouse oocytes, spindle bipolarization is promoted by kinetochores but the mechanism by which kinetochore–microtubule attachments contribute to spindle bipolarity remains unclear. This study demonstrates that the stability of kinetochore–microtubule attachment is essential for confining MTOC positions at the spindle poles and for limiting spindle elongation. MTOC sorting is gradual and continues even in the metaphase spindle. When stable kinetochore–microtubule attachments are disrupted, the spindle is unable to restrict MTOCs at its poles and fails to terminate its elongation. Stable kinetochore fibers are directly connected to MTOCs and to the spindle poles. These findings suggest a role for stable kinetochore–microtubule attachments in fine‐tuning acentrosomal spindle bipolarity.
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Affiliation(s)
- Aurélien Courtois
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Shuhei Yoshida
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Osamu Takenouchi
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Kohei Asai
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan.,Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Tomoya S Kitajima
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan.,Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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7
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Abstract
Chromosome segregation errors in human oocytes lead to aneuploid embryos that cause infertility and birth defects. Here we provide an overview of the chromosome-segregation process in the mammalian oocyte, highlighting mechanistic differences between oocytes and somatic cells that render oocytes so prone to segregation error. These differences include the extremely large size of the oocyte cytoplasm, the unique geometry of meiosis-I chromosomes, idiosyncratic function of the spindle assembly checkpoint, and dramatically altered oocyte cell-cycle control and spindle assembly, as compared to typical somatic cells. We summarise recent work suggesting that aging leads to a further deterioration in fidelity of chromosome segregation by impacting multiple components of the chromosome-segregation machinery. In addition, we compare and contrast recent results from mouse and human oocytes, which exhibit overlapping defects to differing extents. We conclude that the striking propensity of the oocyte to mis-segregate chromosomes reflects the unique challenges faced by the spindle in a highly unusual cellular environment.
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Affiliation(s)
- Aleksandar I Mihajlović
- Centre Recherche CHUM and Department OBGYN, Université de Montreal, Montreal, Quebec, Canada
| | - Greg FitzHarris
- Centre Recherche CHUM and Department OBGYN, Université de Montreal, Montreal, Quebec, Canada.
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8
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Costa MFA, Ohkura H. The molecular architecture of the meiotic spindle is remodeled during metaphase arrest in oocytes. J Cell Biol 2019; 218:2854-2864. [PMID: 31278080 PMCID: PMC6719438 DOI: 10.1083/jcb.201902110] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/21/2019] [Accepted: 06/19/2019] [Indexed: 11/25/2022] Open
Abstract
Before fertilization, oocytes of most species undergo a long, natural arrest in metaphase. Before this, prometaphase I is also prolonged, due to late stable kinetochore-microtubule attachment. How oocytes stably maintain the dynamic spindle for hours during these periods is poorly understood. Here we report that the bipolar spindle changes its molecular architecture during the long prometaphase/metaphase I in Drosophila melanogaster oocytes. By generating transgenic flies expressing GFP-tagged spindle proteins, we found that 14 of 25 spindle proteins change their distribution in the bipolar spindle. Among them, microtubule cross-linking kinesins, MKlp1/Pavarotti and kinesin-5/Klp61F, accumulate to the spindle equator in late metaphase. We found that the late equator accumulation of MKlp1/Pavarotti is regulated by a mechanism distinct from that in mitosis. While MKlp1/Pavarotti contributes to the control of spindle length, kinesin-5/Klp61F is crucial for maintaining a bipolar spindle during metaphase I arrest. Our study provides novel insight into how oocytes maintain a bipolar spindle during metaphase arrest.
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Affiliation(s)
- Mariana F A Costa
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Hiroyuki Ohkura
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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9
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Spindle assembly and chromosome dynamics during oocyte meiosis. Curr Opin Cell Biol 2019; 60:53-59. [PMID: 31082633 DOI: 10.1016/j.ceb.2019.03.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 03/18/2019] [Accepted: 03/20/2019] [Indexed: 12/26/2022]
Abstract
Organisms that reproduce sexually utilize a specialized form of cell division called meiosis to reduce their chromosome number by half to generate haploid gametes. Meiosis in females is especially error-prone, and this vulnerability has a profound impact on human health: it is estimated that 10-25% of human embryos are chromosomally abnormal, and the vast majority of these defects arise from problems with the female reproductive cells (oocytes). Here, we highlight recent studies that explore how these important cells divide. Although we focus on work in the model organism Caenorhabditis elegans, we also discuss complementary studies in other organisms that together provide new insights into this crucial form of cell division.
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10
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Abstract
Oocytes of many species lack centrioles and therefore form acentriolar spindles. Despite the necessity of oocyte meiosis for successful reproduction, how these spindles mediate accurate chromosome segregation is poorly understood. We have gained insight into this process through studies of the kinesin-4 family member Kif4 in mouse oocytes. We found that Kif4 localizes to chromosomes through metaphase and then largely redistributes to the spindle midzone during anaphase, transitioning from stretches along microtubules to distinct ring-like structures; these structures then appear to fuse together by telophase. Kif4’s binding partner PRC1 and MgcRacGAP, a component of the centralspindlin complex, have a similar localization pattern, demonstrating dynamic spindle midzone organization in oocytes. Kif4 knockdown results in defective midzone formation and longer spindles, revealing new anaphase roles for Kif4 in mouse oocytes. Moreover, inhibition of Aurora B/C kinases results in Kif4 mislocalization and causes anaphase defects. Taken together, our work reveals essential roles for Kif4 during the meiotic divisions, furthering our understanding of mechanisms promoting accurate chromosome segregation in acentriolar oocytes.
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Affiliation(s)
- Carissa M Heath
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Sarah M Wignall
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
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11
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Levasseur MD, Thomas C, Davies OR, Higgins JMG, Madgwick S. Aneuploidy in Oocytes Is Prevented by Sustained CDK1 Activity through Degron Masking in Cyclin B1. Dev Cell 2019; 48:672-684.e5. [PMID: 30745144 PMCID: PMC6416240 DOI: 10.1016/j.devcel.2019.01.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 10/22/2018] [Accepted: 12/29/2018] [Indexed: 01/10/2023]
Abstract
Successful mitosis requires that cyclin B1:CDK1 kinase activity remains high until chromosomes are correctly aligned on the mitotic spindle. It has therefore been unclear why, in mammalian oocyte meiosis, cyclin B1 destruction begins before chromosome alignment is complete. Here, we resolve this paradox and show that mouse oocytes exploit an imbalance in the ratio of cyclin B1 to CDK1 to control CDK1 activity; early cyclin B1 destruction reflects the loss of an excess of non-CDK1-bound cyclin B1 in late prometaphase, while CDK1-bound cyclin B1 is destroyed only during metaphase. The ordered destruction of the two forms of cyclin B1 is brought about by a previously unidentified motif that is accessible in free cyclin B1 but masked when cyclin B1 is in complex with CDK1. This protects the CDK1-bound fraction from destruction in prometaphase, ensuring a period of prolonged CDK1 activity sufficient to achieve optimal chromosome alignment and prevent aneuploidy. In mouse oocytes, an excess of cyclin B1 preserves CDK1 activity A motif in non-CDK1-bound cyclin B1 confers preferential APC/C targeting Non-CDK1-bound cyclin B1 is gradually destroyed before CDK1-bound cyclin B1 Prolonged CDK1 activity assists the spindle checkpoint and prevents aneuploidy
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Affiliation(s)
- Mark D Levasseur
- Cell Division Biology Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Christopher Thomas
- Cell Division Biology Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Owen R Davies
- Cell Division Biology Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Jonathan M G Higgins
- Cell Division Biology Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Suzanne Madgwick
- Cell Division Biology Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
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12
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Hoshino Y. Updating the markers for oocyte quality evaluation: intracellular temperature as a new index. Reprod Med Biol 2018; 17:434-441. [PMID: 30377396 PMCID: PMC6194278 DOI: 10.1002/rmb2.12245] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/07/2018] [Accepted: 08/09/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The developmental competence of an embryo is principally dictated by the oocyte. Usually, oocyte selection is based on morphological properties; however, all morphological criteria that are currently used for the grading and screening of oocytes are not able to eliminate the subjectivity. Despite recent studies of the molecular factors related to oocyte quality, it is technically difficult to develop an index based on these factors, and new indices that reflect intracellular conditions are necessary. METHODS Morphological and molecular factors influencing developmental competence were comprehensively reviewed, and intracellular temperature was evaluated as a new marker of oocyte quality. MAIN FINDINGS The intracellular temperature of mature oocytes was high in fresh oocytes and decreased with time after polar body release. Under the same conditions, the intracellular temperature and its distribution differed among oocytes, suggesting that temperature represents the state of each oocyte. CONCLUSION Intracellular temperature is advantageous as an objective and quantitative indicator of oocyte quality. Further studies should evaluate the link between temperature and cellular phenomena to establish its use as an indicator of quality.
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Affiliation(s)
- Yumi Hoshino
- Graduate School of Biosphere ScienceHiroshima UniversityHiroshimaJapan
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13
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Marin D, Nguyen AL, Scott RT, Schindler K. Using Mouse Oocytes to Assess Human Gene Function During Meiosis I. J Vis Exp 2018. [PMID: 29708548 DOI: 10.3791/57442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Embryonic aneuploidy is the major genetic cause of infertility in humans. Most of these events originate during female meiosis, and albeit positively correlated with maternal age, age alone is not always predictive of the risk of generating an aneuploid embryo. Therefore, gene variants might account for incorrect chromosome segregation during oogenesis. Given that access to human oocytes is limited for research purposes, a series of assays were developed to study human gene function during meiosis I using mouse oocytes. First, messenger RNA (mRNA) of the gene and gene variant of interest are microinjected into prophase I-arrested mouse oocytes. After allowing time for expression, oocytes are synchronously released into meiotic maturation to complete meiosis I. By tagging the mRNA with a sequence of a fluorescent reporter, such as green fluorescent protein (Gfp), the localization of the human protein can be assessed in addition to the phenotypic alterations. For example, gain or loss of function can be investigated by establishing experimental conditions that challenge the gene product to fix meiotic errors. Although this system is advantageous in investigating human protein function during oogenesis, adequate interpretation of results should be undertaken given that protein expression is not at endogenous levels and, unless controlled for (i.e. knocked out or down), murine homologs are also present in the system.
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Affiliation(s)
- Diego Marin
- IVI-RMA New Jersey; Jefferson College of Biomedical Sciences, Thomas Jefferson University
| | | | - Richard T Scott
- IVI-RMA New Jersey; Jefferson College of Biomedical Sciences, Thomas Jefferson University
| | - Karen Schindler
- Department of Genetics, Rutgers, The State University of New Jersey;
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14
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Kitajima TS. Mechanisms of kinetochore-microtubule attachment errors in mammalian oocytes. Dev Growth Differ 2018; 60:33-43. [PMID: 29318599 PMCID: PMC11520954 DOI: 10.1111/dgd.12410] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/03/2017] [Accepted: 10/04/2017] [Indexed: 12/21/2022]
Abstract
Proper kinetochore-microtubule attachment is essential for correct chromosome segregation. Therefore, cells normally possess multiple mechanisms for the prevention of errors in kinetochore-microtubule attachments and for selective stabilization of correct attachments. However, the oocyte, a cell that produces an egg through meiosis, exhibits a high frequency of errors in kinetochore-microtubule attachments. These attachment errors predispose oocytes to chromosome segregation errors, resulting in aneuploidy in eggs. This review aims to provide possible explanations for the error-prone nature of oocytes by examining key differences among other cell types in the mechanisms for the establishment of kinetochore-microtubule attachments.
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Affiliation(s)
- Tomoya S. Kitajima
- Laboratory for Chromosome SegregationRIKEN Center for Developmental BiologyKobe650‐0047Japan
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15
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Greaney J, Wei Z, Homer H. Immunofluorescence Staining of K-Fibers in Mouse Oocytes Using Cold Fixation. Methods Mol Biol 2018; 1818:77-87. [PMID: 29961257 DOI: 10.1007/978-1-4939-8603-3_9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The kinetochore is a multiprotein complex that assembles on centromeric DNA and constitutes the main attachment interface between chromosomes and microtubules of the spindle apparatus. Kinetochores also provide the platform for integrating the surveillance mechanism known as the spindle assembly checkpoint (SAC) that regulates the timing of anaphase onset. Saturation of microtubule binding sites on kinetochores displaces SAC proteins leading to loss of SAC-mediated inhibition and the triggering of anaphase. Microtubule binding sites become saturated by bundles of microtubules attached in an end-on manner to kinetochores, termed kinetochore fibers or K-fibers. The appearance of K-fibers therefore signifies the completion of attachment between kinetochores and microtubules and the silencing of the SAC. Here we describe a method involving cold-fixation for immunostaining and imaging K-fibers during meiosis I in mouse oocytes.
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Affiliation(s)
- Jessica Greaney
- Christopher Chen Oocyte Biology Research Laboratory, UQ Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia
| | - Zhe Wei
- Christopher Chen Oocyte Biology Research Laboratory, UQ Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia
| | - Hayden Homer
- Christopher Chen Oocyte Biology Research Laboratory, UQ Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia.
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16
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Jaramillo-Lambert A, Fabritius AS, Hansen TJ, Smith HE, Golden A. The Identification of a Novel Mutant Allele of topoisomerase II in Caenorhabditis elegans Reveals a Unique Role in Chromosome Segregation During Spermatogenesis. Genetics 2016; 204:1407-1422. [PMID: 27707787 PMCID: PMC5161275 DOI: 10.1534/genetics.116.195099] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 09/30/2016] [Indexed: 01/03/2023] Open
Abstract
Topoisomerase II alleviates DNA entanglements that are generated during mitotic DNA replication, transcription, and sister chromatid separation. In contrast to mitosis, meiosis has two rounds of chromosome segregation following one round of DNA replication. In meiosis II, sister chromatids segregate from each other, similar to mitosis. Meiosis I, on the other hand, segregates homologs, which requires pairing, synapsis, and recombination. The exact role that topoisomerase II plays during meiosis is unknown. In a screen reexamining Caenorhabditis elegans legacy mutants isolated 30 years ago, we identified a novel allele of the gene encoding topoisomerase II, top-2(it7). In this study, we demonstrate that top-2(it7) males produce dead embryos, even when fertilizing wild-type oocytes. Characterization of early embryonic events indicates that fertilization is successful and sperm components are transmitted to the embryo. However, sperm chromatin is not detected in these fertilized embryos. Examination of top-2(it7) spermatogenic germ lines reveals that the sperm DNA fails to segregate properly during anaphase I of meiosis, resulting in anucleate sperm. top-2(it7) chromosome-segregation defects observed during anaphase I are not due to residual entanglements incurred during meiotic DNA replication and are not dependent on SPO-11-induced double-strand DNA breaks. Finally, we show that TOP-2 associates with chromosomes in meiotic prophase and that chromosome association is disrupted in the germ lines of top-2(it7) mutants.
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Affiliation(s)
- Aimee Jaramillo-Lambert
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Amy S Fabritius
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Tyler J Hansen
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Harold E Smith
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Andy Golden
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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17
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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: 154] [Impact Index Per Article: 17.1] [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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18
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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: 35] [Impact Index Per Article: 3.9] [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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19
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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: 0.4] [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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20
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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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21
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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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22
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Głuszek AA, Cullen CF, Li W, Battaglia RA, Radford SJ, Costa MF, McKim KS, Goshima G, Ohkura H. The microtubule catastrophe promoter Sentin delays stable kinetochore-microtubule attachment in oocytes. J Cell Biol 2015; 211:1113-20. [PMID: 26668329 PMCID: PMC4687879 DOI: 10.1083/jcb.201507006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 11/12/2015] [Indexed: 01/08/2023] Open
Abstract
The critical step in meiosis is to attach homologous chromosomes to the opposite poles. In mouse oocytes, stable microtubule end-on attachments to kinetochores are not established until hours after spindle assembly, and phosphorylation of kinetochore proteins by Aurora B/C is responsible for the delay. Here we demonstrated that microtubule ends are actively prevented from stable attachment to kinetochores until well after spindle formation in Drosophila melanogaster oocytes. We identified the microtubule catastrophe-promoting complex Sentin-EB1 as a major factor responsible for this delay. Without this activity, microtubule ends precociously form robust attachments to kinetochores in oocytes, leading to a high proportion of homologous kinetochores stably attached to the same pole. Therefore, regulation of microtubule ends provides an alternative novel mechanism to delay stable kinetochore-microtubule attachment in oocytes.
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Affiliation(s)
- A Agata Głuszek
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - C Fiona Cullen
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Wenjing Li
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | | | | | - Mariana F Costa
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
| | - Kim S McKim
- Waksman Institute, Rutgers University, Piscataway, NJ 08854
| | - Gohta Goshima
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Hiroyuki Ohkura
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK
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23
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Radford SJ, Hoang TL, Głuszek AA, Ohkura H, McKim KS. Lateral and End-On Kinetochore Attachments Are Coordinated to Achieve Bi-orientation in Drosophila Oocytes. PLoS Genet 2015; 11:e1005605. [PMID: 26473960 PMCID: PMC4608789 DOI: 10.1371/journal.pgen.1005605] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 09/24/2015] [Indexed: 11/21/2022] Open
Abstract
In oocytes, where centrosomes are absent, the chromosomes direct the assembly of a bipolar spindle. Interactions between chromosomes and microtubules are essential for both spindle formation and chromosome segregation, but the nature and function of these interactions is not clear. We have examined oocytes lacking two kinetochore proteins, NDC80 and SPC105R, and a centromere-associated motor protein, CENP-E, to characterize the impact of kinetochore-microtubule attachments on spindle assembly and chromosome segregation in Drosophila oocytes. We found that the initiation of spindle assembly results from chromosome-microtubule interactions that are kinetochore-independent. Stabilization of the spindle, however, depends on both central spindle and kinetochore components. This stabilization coincides with changes in kinetochore-microtubule attachments and bi-orientation of homologs. We propose that the bi-orientation process begins with the kinetochores moving laterally along central spindle microtubules towards their minus ends. This movement depends on SPC105R, can occur in the absence of NDC80, and is antagonized by plus-end directed forces from the CENP-E motor. End-on kinetochore-microtubule attachments that depend on NDC80 are required to stabilize bi-orientation of homologs. A surprising finding was that SPC105R but not NDC80 is required for co-orientation of sister centromeres at meiosis I. Together, these results demonstrate that, in oocytes, kinetochore-dependent and -independent chromosome-microtubule attachments work together to promote the accurate segregation of chromosomes.
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Affiliation(s)
- Sarah J. Radford
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Tranchau L. Hoang
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - A. Agata Głuszek
- The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Hiroyuki Ohkura
- The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Kim S. McKim
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
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24
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Chmátal L, Yang K, Schultz RM, Lampson MA. Spatial Regulation of Kinetochore Microtubule Attachments by Destabilization at Spindle Poles in Meiosis I. Curr Biol 2015; 25:1835-41. [PMID: 26166779 DOI: 10.1016/j.cub.2015.05.013] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 05/08/2015] [Accepted: 05/08/2015] [Indexed: 12/27/2022]
Abstract
To ensure accurate chromosome segregation in cell division, erroneous kinetochore-microtubule (MT) attachments are recognized and destabilized . Improper attachments typically lack tension between kinetochores and are positioned off-center on the spindle. Low tension is a widely accepted mechanism for recognizing errors , but whether chromosome position regulates MT attachments has been difficult to test. We exploited a meiotic system in which kinetochores attached to opposite spindle poles differ in their interactions with MTs and therefore position and tension can be uncoupled. In this system, homologous chromosomes are positioned off-center on the spindle in oocytes in meiosis I, while under normal tension, as a result of crossing mouse strains with different centromere strengths, manifested by unequal kinetochore protein levels. We show that proximity to spindle poles destabilizes kinetochore-MTs and that stable attachments are restored by inhibition of Aurora A kinase at spindle poles. During the correction of attachment errors, kinetochore-MTs detach near spindle poles to allow formation of correct attachments. We propose that chromosome position on the spindle provides spatial cues for the fidelity of cell division.
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Affiliation(s)
- Lukáš Chmátal
- Department of Biology, University of Pennsylvania, 433 South University Avenue, Philadelphia, PA 19104, USA
| | - Karren Yang
- Department of Biology, University of Pennsylvania, 433 South University Avenue, Philadelphia, PA 19104, USA
| | - Richard M Schultz
- Department of Biology, University of Pennsylvania, 433 South University Avenue, Philadelphia, PA 19104, USA.
| | - Michael A Lampson
- Department of Biology, University of Pennsylvania, 433 South University Avenue, Philadelphia, PA 19104, USA.
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25
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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: 128] [Impact Index Per Article: 12.8] [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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26
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Muscat CC, Torre-Santiago KM, Tran MV, Powers JA, Wignall SM. Kinetochore-independent chromosome segregation driven by lateral microtubule bundles. eLife 2015; 4:e06462. [PMID: 26026148 PMCID: PMC4481507 DOI: 10.7554/elife.06462] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/28/2015] [Indexed: 12/17/2022] Open
Abstract
During cell division, chromosomes attach to spindle microtubules at sites called kinetochores, and force generated at the kinetochore-microtubule interface is the main driver of chromosome movement. Surprisingly, kinetochores are not required for chromosome segregation on acentrosomal spindles in Caenorhabditis elegans oocytes, but the mechanism driving chromosomes apart in their absence is not understood. In this study, we show that lateral microtubule–chromosome associations established during prometaphase remain intact during anaphase to facilitate separation, defining a novel form of kinetochore-independent segregation. Chromosome dynamics during congression and segregation are controlled by opposing forces; plus-end directed forces are mediated by a protein complex that forms a ring around the chromosome center and dynein on chromosome arms provides a minus-end force. At anaphase onset, ring removal shifts the balance between these forces, triggering poleward movement along lateral microtubule bundles. This represents an elegant strategy for controlling chromosomal movements during cell division distinct from the canonical kinetochore-driven mechanism. DOI:http://dx.doi.org/10.7554/eLife.06462.001 An animal's genetic material is packaged into structures called chromosomes. Most animals have two sets of chromosomes: one from each parent. Sperm and egg cells must contain half the number of chromosomes compared to other cells in the body, so that when they fuse, the resulting embryo receives a full complement of chromosomes. Egg and sperm cells are made via a type of cell division called meiosis. In meiosis, the genetic material of a cell is copied once but then the cell divides twice. Therefore, at the end of the two divisions, the resulting sperm or egg cells contain half the number of chromosomes as the original cell. During cell division, the genetic material is separated by a structure called the spindle apparatus. The spindle is made of protein filaments called microtubules. At each end of the spindle, there is a cluster of microtubule ends, known as a ‘pole’. The other ends of the microtubules extend out towards the center of the spindle, where they overlap with the microtubules from the opposite pole. The chromosomes line up in the center of the spindle and then the chromosomes are separated, with half moving to one spindle pole, and half to the other. In most forms of cell division, the microtubules attach to the chromosomes via sites called kinetochores. However, it was recently discovered that kinetochores are not required to separate chromosomes to make egg cells in the worm C. elegans, suggesting that these chromosomes associate with the spindle in a different way. Muscat, Torre-Santiago et al. have now used high-resolution imaging to look at this chromosome separation process in more detail and to figure out how the chromosomes separate when C. elegans forms egg cells. The experiments revealed that the chromosomes move within the spindle along parallel microtubule bundles, much like trains moving along a track. The chromosomes are moved into position at the center of the spindle by a ring-shaped group (or ‘complex’) of proteins that forms around the center of each chromosome. The protein complex comes off the chromosomes as they separate, and a motor protein called dynein walks along the microtubules to pull the separated chromosomes to the poles. Muscat, Torre-Santiago et al.'s findings thus show that meiosis in C. elegans during the production of egg cells works in a very different way to other types of cell division. In the future, it will be important to understand how dynein and the ring-shaped complex are regulated, as this may shed light on what causes mistakes in the separation of genetic material during meiosis, which can lead to infertility, miscarriages, and birth defects in humans and other animals. DOI:http://dx.doi.org/10.7554/eLife.06462.002
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Affiliation(s)
- Christina C Muscat
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | | | - Michael V Tran
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - James A Powers
- Light Microscopy Imaging Center, Indiana University, Bloomington, United States
| | - Sarah M Wignall
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
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27
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Yoshida S, Kaido M, Kitajima TS. Inherent Instability of Correct Kinetochore-Microtubule Attachments during Meiosis I in Oocytes. Dev Cell 2015; 33:589-602. [PMID: 26028219 DOI: 10.1016/j.devcel.2015.04.020] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 03/03/2015] [Accepted: 04/24/2015] [Indexed: 01/08/2023]
Abstract
A model for mitosis suggests that correct kinetochore-microtubule (KT-MT) attachments are stabilized by spatial separation of the attachment sites from Aurora B kinase through sister KT stretching. However, the spatiotemporal regulation of attachment stability during meiosis I (MI) in oocytes remains unclear. Here, we found that in mouse oocytes, Aurora B and C (B/C) are located in close proximity to KT-MT attachment sites after bivalent stretching due to an intrinsic property of the MI chromosomes. The Aurora B/C activity destabilizes correct attachments while allowing a considerable amount of incorrect attachments to form. KT-MT attachments are eventually stabilized through KT dephosphorylation by PP2A-B56 phosphatase, which is progressively recruited to KTs depending on the BubR1 phosphorylation resulting from the timer Cdk1 and independent of bivalent stretching. Thus, oocytes lack a mechanism for coordinating bivalent stretching and KT phosphoregulation during MI, which may explain the high frequency of KT-MT attachment errors.
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Affiliation(s)
- Shuhei Yoshida
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan
| | - Masako Kaido
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan
| | - Tomoya S Kitajima
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
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28
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A comparative analysis of spindle morphometrics across metazoans. Curr Biol 2015; 25:1542-50. [PMID: 26004761 DOI: 10.1016/j.cub.2015.04.036] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/15/2015] [Accepted: 04/16/2015] [Indexed: 11/21/2022]
Abstract
Cell division in all eukaryotes depends on function of the spindle, a microtubule-based structure that segregates chromosomes to generate daughter cells in mitosis or haploid gametes in meiosis. Spindle size adapts to changes in cell size and shape, which vary dramatically across species and within a multicellular organism, but the nature of scaling events and their underlying mechanisms are poorly understood. Cell size variations are most pronounced in early animal development, as egg diameters range from tens of microns up to millimeters across animal phyla, and decrease several orders of magnitude during rapid reductive divisions. During early embryogenesis in the model organisms X. laevis and C. elegans, the spindle scales with cell size [1, 2], a phenomenon regulated by molecules that modulate microtubule dynamics [3-6], as well as by limiting cytoplasmic volume [7, 8]. However, it is not known to what extent spindle scaling is conserved across organisms and among different cell types. Here we show that in a range of metazoan phyla, mitotic spindle length decreased with cell size across an ∼30-fold difference in zygote size. Maximum spindle length varied, but linear spindle scaling occurred similarly in all species once embryonic cell diameter reduced to 140 μm. In contrast, we find that the female meiotic spindle does not scale as closely to egg size, adopting a more uniform size across species that most likely reflects its specialized function. Our analysis reveals that spindle morphometrics change abruptly, within one cell cycle, at the transition from meiosis to mitosis in most animals.
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29
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Fellmeth JE, Gordon D, Robins CE, Scott RT, Treff NR, Schindler K. Expression and characterization of three Aurora kinase C splice variants found in human oocytes. Mol Hum Reprod 2015; 21:633-44. [PMID: 25995441 PMCID: PMC4518136 DOI: 10.1093/molehr/gav026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/14/2015] [Indexed: 12/31/2022] Open
Abstract
Chromosome segregation is an extensively choreographed process yet errors still occur frequently in female meiosis, leading to implantation failure, miscarriage or offspring with developmental disorders. Aurora kinase C (AURKC) is a component of the chromosome passenger complex and is highly expressed in gametes. Studies in mouse oocytes indicate that AURKC is required to regulate chromosome segregation during meiosis I; however, little is known about the functional significance of AURKC in human oocytes. Three splice variants of AURKC exist in testis tissue. To determine which splice variants human oocytes express, we performed quantitative real-time PCR using single oocytes and found expression of all three variants. To evaluate the functional differences between the variants, we created green fluorescent protein-tagged constructs of each variant to express in oocytes from Aurkc(-/-) mice. By quantifying metaphase chromosome alignment, cell cycle progression, phosphorylation of INCENP and microtubule attachments to kinetochores, we found that AURKC_v1 was the most capable of the variants at supporting metaphase I chromosome segregation. AURKC_v3 localized to chromosomes properly and supported cell cycle progression to metaphase II, but its inability to correct erroneous microtubule attachments to kinetochores meant that chromosome segregation was not as accurate compared with the other two variants. Finally, when we expressed the three variants simultaneously, error correction was more robust than when they were expressed on their own. Therefore, oocytes express three variants of AURKC that are not functionally equivalent in supporting meiosis, but fully complement meiosis when expressed simultaneously.
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Affiliation(s)
- Jessica E Fellmeth
- Department of Genetics, Rutgers University, 145 Bevier Road, Piscataway, NJ 08854, USA
| | - Derek Gordon
- Department of Genetics, Rutgers University, 145 Bevier Road, Piscataway, NJ 08854, USA
| | - Christian E Robins
- Reproductive Medicine Associates of New Jersey, Basking Ridge, NJ 07960, USA
| | - Richard T Scott
- Reproductive Medicine Associates of New Jersey, Basking Ridge, NJ 07960, USA
| | - Nathan R Treff
- Department of Genetics, Rutgers University, 145 Bevier Road, Piscataway, NJ 08854, USA Reproductive Medicine Associates of New Jersey, Basking Ridge, NJ 07960, USA
| | - Karen Schindler
- Department of Genetics, Rutgers University, 145 Bevier Road, Piscataway, NJ 08854, USA
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Riepsamen A, Wu L, Lau L, Listijono D, Ledger W, Sinclair D, Homer H. Nicotinamide impairs entry into and exit from meiosis I in mouse oocytes. PLoS One 2015; 10:e0126194. [PMID: 25938585 PMCID: PMC4418673 DOI: 10.1371/journal.pone.0126194] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 03/30/2015] [Indexed: 11/18/2022] Open
Abstract
Following exit from meiosis I, mammalian oocytes immediately enter meiosis II without an intervening interphase, accompanied by rapid reassembly of a bipolar spindle that maintains condensed chromosomes in a metaphase configuration (metaphase II arrest). Here we study the effect of nicotinamide (NAM), a non-competitive pan-sirtuin inhibitor, during meiotic maturation in mouse oocytes. Sirtuins are a family of seven NAD+-dependent deacetylases (Sirt1-7), which are involved in multiple cellular processes and are emerging as important regulators in oocytes and embryos. We found that NAM significantly delayed entry into meiosis I associated with delayed accumulation of the Cdk1 co-activator, cyclin B1. GVBD was also inhibited by the Sirt2-specific inhibitor, AGK2, and in a very similar pattern to NAM, supporting the notion that as in somatic cells, NAM inhibits sirtuins in oocytes. NAM did not affect subsequent spindle assembly, chromosome alignment or the timing of first polar body extrusion (PBE). Unexpectedly, however, in the majority of oocytes with a polar body, chromatin was decondensed and a nuclear structure was present. An identical phenotype was observed when flavopiridol was used to induce Cdk1 inactivation during late meiosis I prior to PBE, but not if Cdk1 was inactivated after PBE when metaphase II arrest was already established, altogether indicating that NAM impaired establishment rather than maintenance of metaphase II arrest. During meiosis I exit in NAM-treated medium, we found that cyclin B1 levels were lower and inhibitory Cdk1 phosphorylation was increased compared with controls. Although activation of the anaphase-promoting complex-Cdc20 (APC-Cdc20) occurred on-time in NAM-treated oocytes, Cdc20 levels were higher in very late meiosis I, pointing to exaggerated APC-Cdc20-mediated proteolysis as a reason for lower cyclin B1 levels. Collectively, therefore, our data indicate that by disrupting Cdk1 regulation, NAM impairs entry into meiosis I and the establishment of metaphase II arrest.
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Affiliation(s)
- Angelique Riepsamen
- School of Women’s & Children’s Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Lindsay Wu
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Laurin Lau
- School of Women’s & Children’s Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Dave Listijono
- School of Women’s & Children’s Health, University of New South Wales, Sydney, New South Wales, Australia
| | - William Ledger
- School of Women’s & Children’s Health, University of New South Wales, Sydney, New South Wales, Australia
| | - David Sinclair
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
- Genetics Department, Harvard Medical School, Boston, Massachusetts, United States of America
- Glenn Labs for the Biological Mechanisms of Aging, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Hayden Homer
- School of Women’s & Children’s Health, University of New South Wales, Sydney, New South Wales, Australia
- * E-mail:
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31
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Solc P, Kitajima TS, Yoshida S, Brzakova A, Kaido M, Baran V, Mayer A, Samalova P, Motlik J, Ellenberg J. Multiple requirements of PLK1 during mouse oocyte maturation. PLoS One 2015; 10:e0116783. [PMID: 25658810 PMCID: PMC4319955 DOI: 10.1371/journal.pone.0116783] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 12/12/2014] [Indexed: 11/19/2022] Open
Abstract
Polo-like kinase 1 (PLK1) orchestrates multiple events of cell division. Although PLK1 function has been intensively studied in centriole-containing and rapidly cycling somatic cells, much less is known about its function in the meiotic divisions of mammalian oocytes, which arrest for a long period of time in prophase before meiotic resumption and lack centrioles for spindle assembly. Here, using specific small molecule inhibition combined with live mouse oocyte imaging, we comprehensively characterize meiotic PLK1's functions. We show that PLK1 becomes activated at meiotic resumption on microtubule organizing centers (MTOCs) and later at kinetochores. PLK1 is required for efficient meiotic resumption by promoting nuclear envelope breakdown. PLK1 is also needed to recruit centrosomal proteins to acentriolar MTOCs to promote normal spindle formation, as well as for stable kinetochore-microtubule attachment. Consequently, PLK1 inhibition leads to metaphase I arrest with misaligned chromosomes activating the spindle assembly checkpoint (SAC). Unlike in mitosis, the metaphase I arrest is not bypassed by the inactivation of the SAC. We show that PLK1 is required for the full activation of the anaphase promoting complex/cyclosome (APC/C) by promoting the degradation of the APC/C inhibitor EMI1 and is therefore essential for entry into anaphase I. Moreover, our data suggest that PLK1 is required for proper chromosome segregation and the maintenance of chromosome condensation during the meiosis I-II transition, independently of the APC/C. Thus, our results define the meiotic roles of PLK1 in oocytes and reveal interesting differential requirements of PLK1 between mitosis and oocyte meiosis in mammals.
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Affiliation(s)
- Petr Solc
- Institute of Animal Physiology and Genetics, Libechov, Czech Republic
| | - Tomoya S. Kitajima
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe, Japan
| | - Shuhei Yoshida
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe, Japan
| | - Adela Brzakova
- Institute of Animal Physiology and Genetics, Libechov, Czech Republic
| | - Masako Kaido
- Laboratory for Chromosome Segregation, RIKEN Center for Developmental Biology, Kobe, Japan
| | | | - Alexandra Mayer
- Institute of Animal Physiology and Genetics, Libechov, Czech Republic
| | - Pavlina Samalova
- Institute of Animal Physiology and Genetics, Libechov, Czech Republic
| | - Jan Motlik
- Institute of Animal Physiology and Genetics, Libechov, Czech Republic
| | - Jan Ellenberg
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
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Ohkura H. Meiosis: an overview of key differences from mitosis. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a015859. [PMID: 25605710 DOI: 10.1101/cshperspect.a015859] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Meiosis is the specialized cell division that generates gametes. In contrast to mitosis, molecular mechanisms and regulation of meiosis are much less understood. Meiosis shares mechanisms and regulation with mitosis in many aspects, but also has critical differences from mitosis. This review highlights these differences between meiosis and mitosis. Recent studies using various model systems revealed differences in a surprisingly wide range of aspects, including cell-cycle regulation, recombination, postrecombination events, spindle assembly, chromosome-spindle interaction, and chromosome segregation. Although a great degree of diversity can be found among organisms, meiosis-specific processes, and regulation are generally conserved.
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Affiliation(s)
- Hiroyuki Ohkura
- The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
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33
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Gorbsky GJ. The spindle checkpoint and chromosome segregation in meiosis. FEBS J 2015; 282:2471-87. [PMID: 25470754 DOI: 10.1111/febs.13166] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/01/2014] [Indexed: 12/30/2022]
Abstract
The spindle checkpoint is a key regulator of chromosome segregation in mitosis and meiosis. Its function is to prevent precocious anaphase onset before chromosomes have achieved bipolar attachment to the spindle. The spindle checkpoint comprises a complex set of signaling pathways that integrate microtubule dynamics, biomechanical forces at the kinetochores, and intricate regulation of protein interactions and post-translational modifications. Historically, many key observations that gave rise to the initial concepts of the spindle checkpoint were made in meiotic systems. In contrast with mitosis, the two distinct chromosome segregation events of meiosis present a special challenge for the regulation of checkpoint signaling. Preservation of fidelity in chromosome segregation in meiosis, controlled by the spindle checkpoint, also has a significant impact in human health. This review highlights the contributions from meiotic systems in understanding the spindle checkpoint as well as the role of checkpoint signaling in controlling the complex divisions of meiosis.
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Affiliation(s)
- Gary J Gorbsky
- Cell Cycle & Cancer Biology, Oklahoma Medical Research Foundation, OK, USA
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34
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Liu D, Shao H, Wang H, Liu XJ. Meiosis I in Xenopus oocytes is not error-prone despite lacking spindle assembly checkpoint. Cell Cycle 2014; 13:1602-6. [PMID: 24646611 DOI: 10.4161/cc.28562] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The spindle assembly checkpoint, SAC, is a surveillance mechanism to control the onset of anaphase during cell division. SAC prevents anaphase initiation until all chromosome pairs have achieved bipolar attachment and aligned at the metaphase plate of the spindle. In doing so, SAC is thought to be the key mechanism to prevent chromosome nondisjunction in mitosis and meiosis. We have recently demonstrated that Xenopus oocyte meiosis lacks SAC control. This prompted the question of whether Xenopus oocyte meiosis is particularly error-prone. In this study, we have karyotyped a total of 313 Xenopus eggs following in vitro oocyte maturation. We found no hyperploid egg, out of 204 metaphase II eggs with countable chromosome spreads. Therefore, chromosome nondisjunction is very rare during Xenopus oocyte meiosis I, despite the lack of SAC.
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Affiliation(s)
- Dandan Liu
- State Key Laboratory of Reproductive Biology; Institute of Zoology; Chinese Academy of Sciences; Beijing, China; University of Chinese Academy of Sciences; Beijing, China; Ottawa Hospital Research Institute; The Ottawa Hospital - General Campus; Ottawa, Ontario, Canada
| | - Hua Shao
- Ottawa Hospital Research Institute; The Ottawa Hospital - General Campus; Ottawa, Ontario, Canada
| | - Hongmei Wang
- State Key Laboratory of Reproductive Biology; Institute of Zoology; Chinese Academy of Sciences; Beijing, China
| | - X Johné Liu
- Ottawa Hospital Research Institute; The Ottawa Hospital - General Campus; Ottawa, Ontario, Canada; Department of Biochemistry, Microbiology, and Immunology and Department of Obstetrics and Gynecology; University of Ottawa; Ottawa, Ontario, Canada
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35
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Selective disruption of aurora C kinase reveals distinct functions from aurora B kinase during meiosis in mouse oocytes. PLoS Genet 2014; 10:e1004194. [PMID: 24586209 PMCID: PMC3937256 DOI: 10.1371/journal.pgen.1004194] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 01/06/2014] [Indexed: 11/19/2022] Open
Abstract
Aurora B kinase (AURKB) is the catalytic subunit of the chromosomal passenger complex (CPC), an essential regulator of chromosome segregation. In mitosis, the CPC is required to regulate kinetochore microtubule (K-MT) attachments, the spindle assembly checkpoint, and cytokinesis. Germ cells express an AURKB homolog, AURKC, which can also function in the CPC. Separation of AURKB and AURKC function during meiosis in oocytes by conventional approaches has not been successful. Therefore, the meiotic function of AURKC is still not fully understood. Here, we describe an ATP-binding-pocket-AURKC mutant, that when expressed in mouse oocytes specifically perturbs AURKC-CPC and not AURKB-CPC function. Using this mutant we show for the first time that AURKC has functions that do not overlap with AURKB. These functions include regulating localized CPC activity and regulating chromosome alignment and K-MT attachments at metaphase of meiosis I (Met I). We find that AURKC-CPC is not the sole CPC complex that regulates the spindle assembly checkpoint in meiosis, and as a result most AURKC-perturbed oocytes arrest at Met I. A small subset of oocytes do proceed through cytokinesis normally, suggesting that AURKC-CPC is not the sole CPC complex during telophase I. But, the resulting eggs are aneuploid, indicating that AURKC is a critical regulator of meiotic chromosome segregation in female gametes. Taken together, these data suggest that mammalian oocytes contain AURKC to efficiently execute meiosis I and ensure high-quality eggs necessary for sexual reproduction.
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36
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Abstract
Mammalian oocytes are particularly error prone in segregating their chromosomes during their two meiotic divisions. This results in the creation of an embryo that has inherited the wrong number of chromosomes: it is aneuploid. The incidence of aneuploidy rises significantly with maternal age and so there is much interest in understanding this association and the underlying causes of aneuploidy. The spindle assembly checkpoint, a surveillance mechanism that operates in all cells to prevent chromosome mis-segregation, and the cohesive ties that hold those chromosomes together, have thus both been the subject of intensive investigation in oocytes. It is possible that a lowered sensitivity of the spindle assembly checkpoint to certain types of chromosome attachment error may endow oocytes with an innate susceptibility to aneuploidy, which is made worse by an age-related loss in the factors that hold the chromosomes together.
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Affiliation(s)
- Keith T Jones
- Centre for Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK.
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37
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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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38
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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: 5.4] [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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39
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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: 4.2] [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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40
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Sun SC, Kim NH. Molecular mechanisms of asymmetric division in oocytes. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2013; 19:883-897. [PMID: 23764118 DOI: 10.1017/s1431927613001566] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In contrast to symmetric division in mitosis, mammalian oocyte maturation is characterized by asymmetric cell division that produces a large egg and a small polar body. The asymmetry results from oocyte polarization, which includes spindle positioning, migration, and cortical reorganization, and this process is critical for fertilization and the retention of maternal components for early embryo development. Although actin dynamics are involved in this process, the molecular mechanism underlying this remained unclear until the use of confocal microscopy and live cell imaging became widespread in recent years. Information obtained through a PubMed database search of all articles published in English between 2000 and 2012 that included the phrases "oocyte, actin, spindle migration," "oocyte, actin, polar body," or "oocyte, actin, asymmetric division" was reviewed. The actin nucleation factor actin-related protein 2/3 complex and its nucleation-promoting factors, formins and Spire, and regulators such as small GTPases, partitioning-defective/protein kinase C, Fyn, microRNAs, cis-Golgi apparatus components, myosin/myosin light-chain kinase, spindle stability regulators, and spindle assembly checkpoint regulators, play critical roles in asymmetric cell division in oocytes. This review summarizes recent findings on these actin-related regulators in mammalian oocyte asymmetric division and outlines a complete signaling pathway.
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Affiliation(s)
- Shao-Chen Sun
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
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41
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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: 63] [Impact Index Per Article: 5.3] [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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42
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Abstract
In this issue of Developmental Cell, Gui and Homer (2013) report that the proper execution of meiosis I in mouse oocytes requires the stabilization of cyclin B2 by the kinetochore protein Hec1, revealing unanticipated functions for both proteins.
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Affiliation(s)
- Christopher S Campbell
- Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92037, USA
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43
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Shao H, Li R, Ma C, Chen E, Liu XJ. Xenopus oocyte meiosis lacks spindle assembly checkpoint control. ACTA ACUST UNITED AC 2013; 201:191-200. [PMID: 23569212 PMCID: PMC3628510 DOI: 10.1083/jcb.201211041] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In contrast to the situation in mammalian oocytes, the metaphase-to-anaphase transition in frog oocytes is not regulated by a spindle assembly checkpoint. The spindle assembly checkpoint (SAC) functions as a surveillance mechanism to detect chromosome misalignment and to delay anaphase until the errors are corrected. The SAC is thought to control mitosis and meiosis, including meiosis in mammalian eggs. However, it remains unknown if meiosis in the eggs of nonmammalian vertebrate species is also regulated by SAC. Using a novel karyotyping technique, we demonstrate that complete disruption of spindle microtubules in Xenopus laevis oocytes did not affect the bivalent-to-dyad transition at the time oocytes are undergoing anaphase I. These oocytes also acquired the ability to respond to parthenogenetic activation, which indicates proper metaphase II arrest. Similarly, oocytes exhibiting monopolar spindles, via inhibition of aurora B or Eg5 kinesin, underwent monopolar anaphase on time and without additional intervention. Therefore, the metaphase-to-anaphase transition in frog oocytes is not regulated by SAC.
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Affiliation(s)
- Hua Shao
- Ottawa Hospital Research Institute, The Ottawa Hospital, Ottawa, Ontario K1H BL6, Canada
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44
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Kogasaka Y, Hoshino Y, Hiradate Y, Tanemura K, Sato E. Distribution and association of mTOR with its cofactors, raptor and rictor, in cumulus cells and oocytes during meiotic maturation in mice. Mol Reprod Dev 2013; 80:334-48. [DOI: 10.1002/mrd.22166] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 02/12/2013] [Indexed: 01/26/2023]
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45
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Pomerantz Y, Elbaz J, Ben-Eliezer I, Reizel Y, David Y, Galiani D, Nevo N, Navon A, Dekel N. From ubiquitin-proteasomal degradation to CDK1 inactivation: requirements for the first polar body extrusion in mouse oocytes. FASEB J 2012; 26:4495-505. [PMID: 22859367 DOI: 10.1096/fj.12-209866] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Completion of the first meiotic division, manifested by extrusion of the first polar body (PBI), depends on proteasomal degradation of cyclin B1 and securin and the subsequent respective CDK1 inactivation and chromosome segregation. We aimed at identifying the polyubiquitin signal that mediates proteasomal action and at a better characterization of the role of CDK1 inactivation at this stage of meiosis. Microinjections of mutated ubiquitin proteins into mouse oocytes revealed that interference with lysine-11 polyubiquitin chains abrogated chromosome segregation and reduced PBI extrusion by 63% as compared to WT ubiquitin-injected controls. Inactivation of CDK1 in oocytes arrested at first metaphase by a proteasome inhibitor fully rescued PBI extrusion. However, removal of CDK1 inhibition failed to allow progression to the second metaphase, rather, inducing PBI reengulfment in 62% of the oocytes. Inhibition of either PLK1 or MEK1/2 during the first anaphase changed spindle dimensions. The PLK1 inhibitor also blocked PBI emission and prevented RhoA translocation. Our results identified lysine-11 rather than the canonic lysine-48 ubiquitin chains as the degradation signal in oocytes resuming meiosis, further disclosing that CDK1 inactivation is necessary and sufficient for PBI emission. This information significantly contributes to our understanding of faulty chromosome segregation that may lead to aneuploidy.
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Affiliation(s)
- Yael Pomerantz
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
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46
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Actin cytoskeleton in cell polarity and asymmetric division during mouse oocyte maturation. Cytoskeleton (Hoboken) 2012; 69:727-37. [DOI: 10.1002/cm.21048] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/18/2012] [Accepted: 06/21/2012] [Indexed: 12/22/2022]
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47
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The chromosomal passenger complex is required for meiotic acentrosomal spindle assembly and chromosome biorientation. Genetics 2012; 192:417-29. [PMID: 22865736 DOI: 10.1534/genetics.112.143495] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
During meiosis in the females of many species, spindle assembly occurs in the absence of the microtubule-organizing centers called centrosomes. In the absence of centrosomes, the nature of the chromosome-based signal that recruits microtubules to promote spindle assembly as well as how spindle bipolarity is established and the chromosomes orient correctly toward the poles is not known. To address these questions, we focused on the chromosomal passenger complex (CPC). We have found that the CPC localizes in a ring around the meiotic chromosomes that is aligned with the axis of the spindle at all stages. Using new methods that dramatically increase the effectiveness of RNA interference in the germline, we show that the CPC interacts with Drosophila oocyte chromosomes and is required for the assembly of spindle microtubules. Furthermore, chromosome biorientation and the localization of the central spindle kinesin-6 protein Subito, which is required for spindle bipolarity, depend on the CPC components Aurora B and Incenp. Based on these data we propose that the ring of CPC around the chromosomes regulates multiple aspects of meiotic cell division including spindle assembly, the establishment of bipolarity, the recruitment of important spindle organization factors, and the biorientation of homologous chromosomes.
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48
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Shao H, Ma C, Zhang X, Li R, Miller AL, Bement WM, Liu XJ. Aurora B regulates spindle bipolarity in meiosis in vertebrate oocytes. Cell Cycle 2012; 11:2672-80. [PMID: 22751439 DOI: 10.4161/cc.21016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Aurora B (Aur-B) plays multiple roles in mitosis, of which the best known are to ensure bi-orientation of sister chromatids by destabilizing incorrectly attached kinetochore microtubules and to participate in cytokinesis. Studies in Xenopus egg extracts, however, have indicated that Aur-B and the chromosome passenger complex play an important role in stabilizing chromosome-associated spindle microtubules. Aur-B stabilizes spindle microtubules in the egg extracts by inhibiting the catastrophe kinesin MCAK. Whether or not Aur-B plays a similar role in intact oocytes remains unknown. Here we have employed a dominant-negative Aur-B mutant (Aur-B122R, in which the ATP-binding lysine(122) is replaced with arginine) to investigate the function of Aur-B in spindle assembly in Xenopus oocytes undergoing meiosis. Overexpression of Aur-B122R results in short bipolar spindles or monopolar spindles, with higher concentrations of Aur-B122R producing mostly the latter. Simultaneous inhibition of MCAK translation in oocytes overexpressing Aur-B122R results in suppression of monopolar phenotype, suggesting that Aur-B regulates spindle bipolarity by inhibiting MCAK. Furthermore, recombinant MCAK-4A protein, which lacks all four Aur-B phosphoryaltion sites and is therefore insensitive to Aur-B inhibition but not wild-type MCAK, recapitulated the monopolar phenotype in the oocytes. These results suggest that in vertebrate oocytes that lack centrosomes, one major function of Aur-B is to stabilize chromosome-associated spindle microtubules to ensure spindle bipolarity.
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Affiliation(s)
- Hua Shao
- Ottawa Hospital Research Institute, Ottawa Hospital Civic Campus, Ottawa, ON, Canada
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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: 1.3] [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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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: 113] [Impact Index Per Article: 8.7] [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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