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Horakova A, Konecna M, Anger M. Chromosome Division in Early Embryos-Is Everything under Control? And Is the Cell Size Important? Int J Mol Sci 2024; 25:2101. [PMID: 38396778 PMCID: PMC10889803 DOI: 10.3390/ijms25042101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/02/2024] [Accepted: 02/06/2024] [Indexed: 02/25/2024] Open
Abstract
Chromosome segregation in female germ cells and early embryonic blastomeres is known to be highly prone to errors. The resulting aneuploidy is therefore the most frequent cause of termination of early development and embryo loss in mammals. And in specific cases, when the aneuploidy is actually compatible with embryonic and fetal development, it leads to severe developmental disorders. The main surveillance mechanism, which is essential for the fidelity of chromosome segregation, is the Spindle Assembly Checkpoint (SAC). And although all eukaryotic cells carry genes required for SAC, it is not clear whether this pathway is active in all cell types, including blastomeres of early embryos. In this review, we will summarize and discuss the recent progress in our understanding of the mechanisms controlling chromosome segregation and how they might work in embryos and mammalian embryos in particular. Our conclusion from the current literature is that the early mammalian embryos show limited capabilities to react to chromosome segregation defects, which might, at least partially, explain the widespread problem of aneuploidy during the early development in mammals.
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Affiliation(s)
- Adela Horakova
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
- Faculty of Science, Masaryk University, 602 00 Brno, Czech Republic
| | - Marketa Konecna
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
- Faculty of Science, Masaryk University, 602 00 Brno, Czech Republic
| | - Martin Anger
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
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2
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Mihajlović AI, Byers C, Reinholdt L, FitzHarris G. Spindle assembly checkpoint insensitivity allows meiosis-II despite chromosomal defects in aged eggs. EMBO Rep 2023; 24:e57227. [PMID: 37795949 PMCID: PMC10626445 DOI: 10.15252/embr.202357227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 09/07/2023] [Accepted: 09/19/2023] [Indexed: 10/06/2023] Open
Abstract
Chromosome segregation errors in mammalian oocyte meiosis lead to developmentally compromised aneuploid embryos and become more common with advancing maternal age. Known contributors include age-related chromosome cohesion loss and spindle assembly checkpoint (SAC) fallibility in meiosis-I. But how effective the SAC is in meiosis-II and how this might contribute to age-related aneuploidy is unknown. Here, we developed genetic and pharmacological approaches to directly address the function of the SAC in meiosis-II. We show that the SAC is insensitive in meiosis-II oocytes and that as a result misaligned chromosomes are randomly segregated. Whilst SAC ineffectiveness in meiosis-II is not age-related, it becomes most prejudicial in oocytes from older females because chromosomes that prematurely separate by age-related cohesion loss become misaligned in meiosis-II. We show that in the absence of a robust SAC in meiosis-II these age-related misaligned chromatids are missegregated and lead to aneuploidy. Our data demonstrate that the SAC fails to prevent cell division in the presence of misaligned chromosomes in oocyte meiosis-II, which explains how age-related cohesion loss can give rise to aneuploid embryos.
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Affiliation(s)
| | - Candice Byers
- The Institute for Experiential AI, Roux InstituteNortheastern UniversityPortlandMEUSA
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3
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MacKenzie A, Vicory V, Lacefield S. Meiotic cells escape prolonged spindle checkpoint activity through kinetochore silencing and slippage. PLoS Genet 2023; 19:e1010707. [PMID: 37018287 PMCID: PMC10109492 DOI: 10.1371/journal.pgen.1010707] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 04/17/2023] [Accepted: 03/20/2023] [Indexed: 04/06/2023] Open
Abstract
To prevent chromosome mis-segregation, a surveillance mechanism known as the spindle checkpoint delays the cell cycle if kinetochores are not attached to spindle microtubules, allowing the cell additional time to correct improper attachments. During spindle checkpoint activation, checkpoint proteins bind the unattached kinetochore and send a diffusible signal to inhibit the anaphase promoting complex/cyclosome (APC/C). Previous work has shown that mitotic cells with depolymerized microtubules can escape prolonged spindle checkpoint activation in a process called mitotic slippage. During slippage, spindle checkpoint proteins bind unattached kinetochores, but the cells cannot maintain the checkpoint arrest. We asked if meiotic cells had as robust of a spindle checkpoint response as mitotic cells and whether they also undergo slippage after prolonged spindle checkpoint activity. We performed a direct comparison between mitotic and meiotic budding yeast cells that signal the spindle checkpoint through two different assays. We find that the spindle checkpoint delay is shorter in meiosis I or meiosis II compared to mitosis, overcoming a checkpoint arrest approximately 150 minutes earlier in meiosis than in mitosis. In addition, cells in meiosis I escape spindle checkpoint signaling using two mechanisms, silencing the checkpoint at the kinetochore and through slippage. We propose that meiotic cells undertake developmentally-regulated mechanisms to prevent persistent spindle checkpoint activity to ensure the production of gametes.
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Affiliation(s)
- Anne MacKenzie
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Victoria Vicory
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Soni Lacefield
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
- Department of Biochemistry and Cell Biology, the Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America
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4
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Chen P, Levy DL. Regulation of organelle size and organization during development. Semin Cell Dev Biol 2023; 133:53-64. [PMID: 35148938 PMCID: PMC9357868 DOI: 10.1016/j.semcdb.2022.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/20/2022] [Accepted: 02/01/2022] [Indexed: 12/11/2022]
Abstract
During early embryogenesis, as cells divide in the developing embryo, the size of intracellular organelles generally decreases to scale with the decrease in overall cell size. Organelle size scaling is thought to be important to establish and maintain proper cellular function, and defective scaling may lead to impaired development and disease. However, how the cell regulates organelle size and organization are largely unanswered questions. In this review, we summarize the process of size scaling at both the cell and organelle levels and discuss recently discovered mechanisms that regulate this process during early embryogenesis. In addition, we describe how some recently developed techniques and Xenopus as an animal model can be used to investigate the underlying mechanisms of size regulation and to uncover the significance of proper organelle size scaling and organization.
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Affiliation(s)
- Pan Chen
- Institute of Biochemistry and Molecular Biology, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, China.
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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5
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MacKenzie A, Vicory V, Lacefield S. Meiotic Cells Escape Prolonged Spindle Checkpoint Activity Through Premature Silencing and Slippage. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.02.522494. [PMID: 36711621 PMCID: PMC9881877 DOI: 10.1101/2023.01.02.522494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
To prevent chromosome mis-segregation, a surveillance mechanism known as the spindle checkpoint delays the cell cycle if kinetochores are not attached to spindle microtubules, allowing the cell additional time to correct improper attachments. During spindle checkpoint activation, checkpoint proteins bind the unattached kinetochore and send a diffusible signal to inhibit the anaphase promoting complex/cyclosome (APC/C). Previous work has shown that mitotic cells with depolymerized microtubules can escape prolonged spindle checkpoint activation in a process called mitotic slippage. During slippage, spindle checkpoint proteins bind unattached kinetochores, but the cells cannot maintain the checkpoint arrest. We asked if meiotic cells had as robust of a spindle checkpoint response as mitotic cells and whether they also undergo slippage after prolonged spindle checkpoint activity. We performed a direct comparison between mitotic and meiotic budding yeast cells that signal the spindle checkpoint due to a lack of either kinetochore-microtubule attachments or due to a loss of tension-bearing attachments. We find that the spindle checkpoint is not as robust in meiosis I or meiosis II compared to mitosis, overcoming a checkpoint arrest approximately 150 minutes earlier in meiosis. In addition, cells in meiosis I escape spindle checkpoint signaling using two mechanisms, silencing the checkpoint at the kinetochore and through slippage. We propose that meiotic cells undertake developmentally-regulated mechanisms to prevent persistent spindle checkpoint activity to ensure the production of gametes. AUTHOR SUMMARY Mitosis and meiosis are the two major types of cell divisions. Mitosis gives rise to genetically identical daughter cells, while meiosis is a reductional division that gives rise to gametes. Cell cycle checkpoints are highly regulated surveillance mechanisms that prevent cell cycle progression when circumstances are unfavorable. The spindle checkpoint promotes faithful chromosome segregation to safeguard against aneuploidy, in which cells have too many or too few chromosomes. The spindle checkpoint is activated at the kinetochore and then diffuses to inhibit cell cycle progression. Although the checkpoint is active in both mitosis and meiosis, most studies involving checkpoint regulation have been performed in mitosis. By activating the spindle checkpoint in both mitosis and meiosis in budding yeast, we show that cells in meiosis elicit a less persistent checkpoint signal compared to cells in mitosis. Further, we show that cells use distinct mechanisms to escape the checkpoint in mitosis and meiosis I. While cells in mitosis and meiosis II undergo anaphase onset while retaining checkpoint proteins at the kinetochore, cells in meiosis I prematurely lose checkpoint protein localization at the kinetochore. If the mechanism to remove the checkpoint components from the kinetochore is disrupted, meiosis I cells can still escape checkpoint activity. Together, these results highlight that cell cycle checkpoints are differentially regulated during meiosis to avoid long delays and to allow gametogenesis.
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Affiliation(s)
- Anne MacKenzie
- Department of Biology, Indiana University, Bloomington, IN USA
| | - Victoria Vicory
- Department of Biology, Indiana University, Bloomington, IN USA
| | - Soni Lacefield
- Department of Biology, Indiana University, Bloomington, IN USA,Department of Biochemistry and Cell Biology, the Geisel School of Medicine at Dartmouth, Hanover, NH USA,To whom correspondence should be addressed to Soni Lacefield:
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6
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Charalambous C, Webster A, Schuh M. Aneuploidy in mammalian oocytes and the impact of maternal ageing. Nat Rev Mol Cell Biol 2023; 24:27-44. [PMID: 36068367 DOI: 10.1038/s41580-022-00517-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/05/2022] [Indexed: 11/09/2022]
Abstract
During fertilization, the egg and the sperm are supposed to contribute precisely one copy of each chromosome to the embryo. However, human eggs frequently contain an incorrect number of chromosomes - a condition termed aneuploidy, which is much more prevalent in eggs than in either sperm or in most somatic cells. In turn, aneuploidy in eggs is a leading cause of infertility, miscarriage and congenital syndromes. Aneuploidy arises as a consequence of aberrant meiosis during egg development from its progenitor cell, the oocyte. In human oocytes, chromosomes often segregate incorrectly. Chromosome segregation errors increase in women from their mid-thirties, leading to even higher levels of aneuploidy in eggs from women of advanced maternal age, ultimately causing age-related infertility. Here, we cover the two main areas that contribute to aneuploidy: (1) factors that influence the fidelity of chromosome segregation in eggs of women from all ages and (2) factors that change in response to reproductive ageing. Recent discoveries reveal new error-causing pathways and present a framework for therapeutic strategies to extend the span of female fertility.
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Affiliation(s)
- Chloe Charalambous
- Department of Meiosis, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Alexandre Webster
- Department of Meiosis, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Melina Schuh
- Department of Meiosis, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
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7
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Wu T, Gu H, Luo Y, Wang L, Sang Q. Meiotic defects in human oocytes: Potential causes and clinical implications. Bioessays 2022; 44:e2200135. [PMID: 36207289 DOI: 10.1002/bies.202200135] [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: 07/07/2022] [Revised: 09/14/2022] [Accepted: 09/16/2022] [Indexed: 11/09/2022]
Abstract
Meiotic defects cause abnormal chromosome segregation leading to aneuploidy in mammalian oocytes. Chromosome segregation is particularly error-prone in human oocytes, but the mechanisms behind such errors remain unclear. To explain the frequent chromosome segregation errors, recent investigations have identified multiple meiotic defects and explained how these defects occur in female meiosis. In particular, we review the causes of cohesin exhaustion, leaky spindle assembly checkpoint (SAC), inherently unstable meiotic spindle, fragmented kinetochores or centromeres, abnormal aurora kinases (AURK), and clinical genetic variants in human oocytes. We mainly focus on meiotic defects in human oocytes, but also refer to the potential defects of female meiosis in mouse models.
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Affiliation(s)
- Tianyu Wu
- Institute of Pediatrics, Children's Hospital of Fudan University and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Hao Gu
- Institute of Pediatrics, Children's Hospital of Fudan University and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Yuxi Luo
- Institute of Pediatrics, Children's Hospital of Fudan University and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Lei Wang
- Institute of Pediatrics, Children's Hospital of Fudan University and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
| | - Qing Sang
- Institute of Pediatrics, Children's Hospital of Fudan University and Institutes of Biomedical Sciences, the State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, China
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8
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Ogonuki N, Kyogoku H, Hino T, Osawa Y, Fujiwara Y, Inoue K, Kunieda T, Mizuno S, Tateno H, Sugiyama F, Kitajima TS, Ogura A. Birth of mice from meiotically arrested spermatocytes following biparental meiosis in halved oocytes. EMBO Rep 2022; 23:e54992. [DOI: 10.15252/embr.202254992] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/01/2022] [Accepted: 04/19/2022] [Indexed: 01/05/2023] Open
Affiliation(s)
- Narumi Ogonuki
- Bioresource Engineering Division RIKEN BioResource Research Center Ibaraki Japan
| | - Hirohisa Kyogoku
- Laboratory for Chromosome Segregation RIKEN Center for Biosystems Dynamics Research Kobe Japan
- Graduate School of Agricultural Science Kobe University Kobe Japan
| | - Toshiaki Hino
- Department of Biological Sciences Asahikawa Medical University Asahikawa Japan
| | - Yuki Osawa
- Graduate School of Comprehensive Human Sciences University of Tsukuba Tsukuba Japan
| | - Yasuhiro Fujiwara
- Laboratory of Pathology and Development Institute for Quantitative Biosciences The University of Tokyo Tokyo Japan
| | - Kimiko Inoue
- Bioresource Engineering Division RIKEN BioResource Research Center Ibaraki Japan
- Graduate School of Life and Environmental Sciences University of Tsukuba Tsukuba Japan
| | - Tetsuo Kunieda
- Faculty of Veterinary Medicine Okayama University of Science Imabari Japan
| | - Seiya Mizuno
- Laboratory Animal Resource Center and Trans‐border Medical Research Center Faculty of Medicine University of Tsukuba Tsukuba Japan
| | - Hiroyuki Tateno
- Department of Biological Sciences Asahikawa Medical University Asahikawa Japan
| | - Fumihiro Sugiyama
- Laboratory Animal Resource Center and Trans‐border Medical Research Center Faculty of Medicine University of Tsukuba Tsukuba Japan
| | - Tomoya S Kitajima
- Laboratory for Chromosome Segregation RIKEN Center for Biosystems Dynamics Research Kobe Japan
| | - Atsuo Ogura
- Bioresource Engineering Division RIKEN BioResource Research Center Ibaraki Japan
- Graduate School of Life and Environmental Sciences University of Tsukuba Tsukuba Japan
- RIKEN Cluster for Pioneering Research Wako Japan
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9
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Bouftas N, Wassmann K. Working in close quarters: biparental meiosis in the oocyte. EMBO Rep 2022; 23:e55360. [PMID: 35620872 PMCID: PMC9253776 DOI: 10.15252/embr.202255360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In vitro fertilization (IVF) methods involve fertilizing haploid oocytes arrested in meiosis II with haploid sperm. An experimental IVF method had been developed in mice involving injection of diploid sperm nuclei into equally diploid oocytes (biparental meiosis) to increase the chance of reproduction in cases where haploid sperm cannot be obtained. However, this method had been shown to be highly error prone. In this issue of EMBO Reports, Ogonuki et al show that reducing ooplasm volume by half reduces the segregation errors and increases the likelihood of producing viable offsprings in mice (Ogonuki et al, 2022).
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Affiliation(s)
- Nora Bouftas
- Institut de Biologie Paris Seine Sorbonne Université Paris France
- CNRS UMR7622 Developmental Biology Lab Sorbonne Université Paris France
| | - Katja Wassmann
- Institut de Biologie Paris Seine Sorbonne Université Paris France
- CNRS UMR7622 Developmental Biology Lab Sorbonne Université Paris France
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10
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Anger M, Radonova L, Horakova A, Sekach D, Charousova M. Impact of Global Transcriptional Silencing on Cell Cycle Regulation and Chromosome Segregation in Early Mammalian Embryos. Int J Mol Sci 2021; 22:9073. [PMID: 34445775 PMCID: PMC8396661 DOI: 10.3390/ijms22169073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/14/2021] [Accepted: 08/18/2021] [Indexed: 11/17/2022] Open
Abstract
The onset of an early development is, in mammals, characterized by profound changes of multiple aspects of cellular morphology and behavior. These are including, but not limited to, fertilization and the merging of parental genomes with a subsequent transition from the meiotic into the mitotic cycle, followed by global changes of chromatin epigenetic modifications, a gradual decrease in cell size and the initiation of gene expression from the newly formed embryonic genome. Some of these important, and sometimes also dramatic, changes are executed within the period during which the gene transcription is globally silenced or not progressed, and the regulation of most cellular activities, including those mentioned above, relies on controlled translation. It is known that the blastomeres within an early embryo are prone to chromosome segregation errors, which might, when affecting a significant proportion of a cell within the embryo, compromise its further development. In this review, we discuss how the absence of transcription affects the transition from the oocyte to the embryo and what impact global transcriptional silencing might have on the basic cell cycle and chromosome segregation controlling mechanisms.
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Affiliation(s)
- Martin Anger
- Central European Institute of Technology, Department of Genetics and Reproduction, Veterinary Research Institute, 621 00 Brno, Czech Republic; (L.R.); (A.H.); (D.S.); (M.C.)
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11
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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: 1.3] [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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12
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Duro J, Nilsson J. SAC during early cell divisions: Sacrificing fidelity over timely division, regulated differently across organisms: Chromosome alignment and segregation are left unsupervised from the onset of development until checkpoint activity is acquired, varying from species to species. Bioessays 2020; 43:e2000174. [PMID: 33251610 DOI: 10.1002/bies.202000174] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 12/12/2022]
Abstract
Early embryogenesis is marked by a frail Spindle Assembly Checkpoint (SAC). The time of SAC acquisition varies depending on the species, cell size or a yet to be uncovered developmental timer. This means that for a specific number of divisions, biorientation of sister chromatids occurs unsupervised. When error-prone segregation is an issue, an aneuploidy-selective apoptosis system can come into play to eliminate chromosomally unbalanced cells resulting in healthy newborns. However, aneuploidy content can be too great to overcome, endangering viability. SAC generates a diffusible signal to lengthen time spent in mitosis if needed, ensuring correct chromosome segregation, a fundamental factor in the generation of euploid cells. Thus, it remains puzzling what benefit could come from delaying SAC acquisition till later in the development. In this review, we describe what is known on SAC acquisition in distinct species and highlight pending research as well as potential applications for such knowledge.
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Affiliation(s)
- Joana Duro
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, Copenhagen, Denmark
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13
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Mikwar M, MacFarlane AJ, Marchetti F. Mechanisms of oocyte aneuploidy associated with advanced maternal age. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2020; 785:108320. [PMID: 32800274 DOI: 10.1016/j.mrrev.2020.108320] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/24/2020] [Accepted: 06/29/2020] [Indexed: 12/30/2022]
Abstract
It is well established that maternal age is associated with a rapid decline in the production of healthy and high-quality oocytes resulting in reduced fertility in women older than 35 years of age. In particular, chromosome segregation errors during meiotic divisions are increasingly common and lead to the production of oocytes with an incorrect number of chromosomes, a condition known as aneuploidy. When an aneuploid oocyte is fertilized by a sperm it gives rise to an aneuploid embryo that, except in rare situations, will result in a spontaneous abortion. As females advance in age, they are at higher risk of infertility, miscarriage, or having a pregnancy affected by congenital birth defects such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Turner syndrome (monosomy X). Here, we review the potential molecular mechanisms associated with increased chromosome segregation errors during meiosis as a function of maternal age. Our review shows that multiple exogenous and endogenous factors contribute to the age-related increase in oocyte aneuploidy. Specifically, the weight of evidence indicates that recombination failure, cohesin deterioration, spindle assembly checkpoint (SAC) disregulation, abnormalities in post-translational modification of histones and tubulin, and mitochondrial dysfunction are the leading causes of oocyte aneuploidy associated with maternal aging. There is also growing evidence that dietary and other bioactive interventions may mitigate the effect of maternal aging on oocyte quality and oocyte aneuploidy, thereby improving fertility outcomes. Maternal age is a major concern for aneuploidy and genetic disorders in the offspring in the context of an increasing proportion of mothers having children at increasingly older ages. A better understanding of the mechanisms associated with maternal aging leading to aneuploidy and of intervention strategies that may mitigate these detrimental effects and reduce its occurrence are essential for preventing abnormal reproductive outcomes in the human population.
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Affiliation(s)
- Myy Mikwar
- Department of Biology, Carleton University, Ottawa, Ontario, Canada; Nutrition Research Division, Health Canada, Ottawa, Ontario, Canada
| | - Amanda J MacFarlane
- Department of Biology, Carleton University, Ottawa, Ontario, Canada; Nutrition Research Division, Health Canada, Ottawa, Ontario, Canada
| | - Francesco Marchetti
- Department of Biology, Carleton University, Ottawa, Ontario, Canada; Mechanistic Studies Division, Health Canada, Ottawa, Ontario, Canada.
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14
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Wesley CC, Mishra S, Levy DL. Organelle size scaling over embryonic development. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2020; 9:e376. [PMID: 32003549 DOI: 10.1002/wdev.376] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 12/19/2019] [Accepted: 01/08/2020] [Indexed: 12/13/2022]
Abstract
Cell division without growth results in progressive cell size reductions during early embryonic development. How do the sizes of intracellular structures and organelles scale with cell size and what are the functional implications of such scaling relationships? Model organisms, in particular Caenorhabditis elegans worms, Drosophila melanogaster flies, Xenopus laevis frogs, and Mus musculus mice, have provided insights into developmental size scaling of the nucleus, mitotic spindle, and chromosomes. Nuclear size is regulated by nucleocytoplasmic transport, nuclear envelope proteins, and the cytoskeleton. Regulators of microtubule dynamics and chromatin compaction modulate spindle and mitotic chromosome size scaling, respectively. Developmental scaling relationships for membrane-bound organelles, like the endoplasmic reticulum, Golgi, mitochondria, and lysosomes, have been less studied, although new imaging approaches promise to rectify this deficiency. While models that invoke limiting components and dynamic regulation of assembly and disassembly can account for some size scaling relationships in early embryos, it will be exciting to investigate the contribution of newer concepts in cell biology such as phase separation and interorganellar contacts. With a growing understanding of the underlying mechanisms of organelle size scaling, future studies promise to uncover the significance of proper scaling for cell function and embryonic development, as well as how aberrant scaling contributes to disease. This article is categorized under: Establishment of Spatial and Temporal Patterns > Regulation of Size, Proportion, and Timing Early Embryonic Development > Fertilization to Gastrulation Comparative Development and Evolution > Model Systems.
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Affiliation(s)
- Chase C Wesley
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Sampada Mishra
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming
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15
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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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16
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Akera T, Trimm E, Lampson MA. Molecular Strategies of Meiotic Cheating by Selfish Centromeres. Cell 2019; 178:1132-1144.e10. [PMID: 31402175 DOI: 10.1016/j.cell.2019.07.001] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 01/11/2019] [Accepted: 06/25/2019] [Indexed: 10/26/2022]
Abstract
Asymmetric division in female meiosis creates selective pressure favoring selfish centromeres that bias their transmission to the egg. This centromere drive can explain the paradoxical rapid evolution of both centromere DNA and centromere-binding proteins despite conserved centromere function. Here, we define a molecular pathway linking expanded centromeres to histone phosphorylation and recruitment of microtubule destabilizing factors, leading to detachment of selfish centromeres from spindle microtubules that would direct them to the polar body. Exploiting centromere divergence between species, we show that selfish centromeres in two hybrid mouse models use the same molecular pathway but modulate it differently to enrich destabilizing factors. Our results indicate that increasing microtubule destabilizing activity is a general strategy for drive in both models, but centromeres have evolved distinct mechanisms to increase that activity. Furthermore, we show that drive depends on slowing meiotic progression, suggesting that selfish centromeres can be suppressed by regulating meiotic timing.
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Affiliation(s)
- Takashi Akera
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Emily Trimm
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michael A Lampson
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA.
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17
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Lane S, Kauppi L. Meiotic spindle assembly checkpoint and aneuploidy in males versus females. Cell Mol Life Sci 2019; 76:1135-1150. [PMID: 30564841 PMCID: PMC6513798 DOI: 10.1007/s00018-018-2986-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 11/12/2018] [Accepted: 12/03/2018] [Indexed: 12/13/2022]
Abstract
The production of gametes (sperm and eggs in mammals) involves two sequential cell divisions, meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate to different daughter cells, and meiosis II resembles mitotic divisions in that sister chromatids separate. While in principle the process is identical in males and females, the time frame and susceptibility to chromosomal defects, including achiasmy and cohesion weakening, and the response to mis-segregating chromosomes are not. In this review, we compare and contrast meiotic spindle assembly checkpoint function and aneuploidy in the two sexes.
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Affiliation(s)
- Simon Lane
- Department of Chemistry and the Institute for Life Sciences, University of Southampton, Building 85, Highfield Campus, Southampton, SO171BJ, UK
| | - Liisa Kauppi
- Faculty of Medicine, University of Helsinki, Haartmaninkatu 8, 00014, Helsinki, Finland.
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19
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Cell-Size-Independent Spindle Checkpoint Failure Underlies Chromosome Segregation Error in Mouse Embryos. Curr Biol 2019; 29:865-873.e3. [PMID: 30773364 DOI: 10.1016/j.cub.2018.12.042] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/23/2018] [Accepted: 12/21/2018] [Indexed: 12/31/2022]
Abstract
Chromosome segregation errors during mammalian preimplantation development cause "mosaic" embryos comprising a mixture of euploid and aneuploid cells, which reduce the potential for a successful pregnancy [1-5], but why these errors are common is unknown. In most cells, chromosome segregation error is averted by the spindle assembly checkpoint (SAC), which prevents anaphase-promoting complex (APC/C) activation and anaphase onset until chromosomes are aligned with kinetochores attached to spindle microtubules [6, 7], but little is known about the SAC's role in the early mammalian embryo. In C. elegans, the SAC is weak in early embryos, and it strengthens during early embryogenesis as a result of progressively lessening cell size [8, 9]. Here, using live imaging, micromanipulation, gene knockdown, and pharmacological approaches, we show that this is not the case in mammalian embryos. Misaligned chromosomes in the early mouse embryo can recruit SAC components to mount a checkpoint signal, but this signal fails to prevent anaphase onset, leading to high levels of chromosome segregation error. We find that failure of the SAC to prolong mitosis is not attributable to cell size. We show that mild chemical inhibition of APC/C can extend mitosis, thereby allowing more time for correct chromosome alignment and reducing segregation errors. SAC-APC/C disconnect thus presents a mechanistic explanation for frequent chromosome segregation errors in early mammalian embryos. Moreover, our data provide proof of principle that modulation of the SAC-APC/C axis can increase the likelihood of error-free chromosome segregation in cultured mammalian embryos.
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20
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Regulation of the meiotic divisions of mammalian oocytes and eggs. Biochem Soc Trans 2018; 46:797-806. [PMID: 29934303 PMCID: PMC6103459 DOI: 10.1042/bst20170493] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 12/28/2022]
Abstract
Initiated by luteinizing hormone and finalized by the fertilizing sperm, the mammalian oocyte completes its two meiotic divisions. The first division occurs in the mature Graafian follicle during the hours preceding ovulation and culminates in an extreme asymmetric cell division and the segregation of the two pairs of homologous chromosomes. The newly created mature egg rearrests at metaphase of the second meiotic division prior to ovulation and only completes meiosis following a Ca2+ signal initiated by the sperm at gamete fusion. Here, we review the cellular events that govern the passage of the oocyte through meiosis I with a focus on the role of the spindle assembly checkpoint in regulating its timing. In meiosis II, we examine how the egg achieves its arrest and how the fertilization Ca2+ signal allows the initiation of embryo development.
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21
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Gerhold AR, Poupart V, Labbé JC, Maddox PS. Spindle assembly checkpoint strength is linked to cell fate in the Caenorhabditis elegans embryo. Mol Biol Cell 2018; 29:1435-1448. [PMID: 29688794 PMCID: PMC6014101 DOI: 10.1091/mbc.e18-04-0215] [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] [Indexed: 12/20/2022] Open
Abstract
The spindle assembly checkpoint (SAC) is a conserved mitotic regulator that preserves genome stability by monitoring kinetochore-microtubule attachments and blocking anaphase onset until chromosome biorientation is achieved. Despite its central role in maintaining mitotic fidelity, the ability of the SAC to delay mitotic exit in the presence of kinetochore-microtubule attachment defects (SAC "strength") appears to vary widely. How different cellular aspects drive this variation remains largely unknown. Here we show that SAC strength is correlated with cell fate during development of Caenorhabditis elegans embryos, with germline-fated cells experiencing longer mitotic delays upon spindle perturbation than somatic cells. These differences are entirely dependent on an intact checkpoint and only partially attributable to differences in cell size. In two-cell embryos, cell size accounts for half of the difference in SAC strength between the larger somatic AB and the smaller germline P1 blastomeres. The remaining difference requires asymmetric cytoplasmic partitioning downstream of PAR polarity proteins, suggesting that checkpoint-regulating factors are distributed asymmetrically during early germ cell divisions. Our results indicate that SAC activity is linked to cell fate and reveal a hitherto unknown interaction between asymmetric cell division and the SAC.
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Affiliation(s)
- Abigail R Gerhold
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Vincent Poupart
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Jean-Claude Labbé
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada.,Department of Pathology and Cell Biology, Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Paul S Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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