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Jiang Y, Adhikari D, Li C, Zhou X. Spatiotemporal regulation of maternal mRNAs during vertebrate oocyte meiotic maturation. Biol Rev Camb Philos Soc 2023; 98:900-930. [PMID: 36718948 DOI: 10.1111/brv.12937] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 01/15/2023] [Accepted: 01/17/2023] [Indexed: 02/01/2023]
Abstract
Vertebrate oocytes face a particular challenge concerning the regulation of gene expression during meiotic maturation. Global transcription becomes quiescent in fully grown oocytes, remains halted throughout maturation and fertilization, and only resumes upon embryonic genome activation. Hence, the oocyte meiotic maturation process is largely regulated by protein synthesis from pre-existing maternal messenger RNAs (mRNAs) that are transcribed and stored during oocyte growth. Rapidly developing genome-wide techniques have greatly expanded our insights into the global translation changes and possible regulatory mechanisms during oocyte maturation. The storage, translation, and processing of maternal mRNAs are thought to be regulated by factors interacting with elements in the mRNA molecules. Additionally, posttranscriptional modifications of mRNAs, such as methylation and uridylation, have recently been demonstrated to play crucial roles in maternal mRNA destabilization. However, a comprehensive understanding of the machineries that regulate maternal mRNA fate during oocyte maturation is still lacking. In particular, how the transcripts of important cell cycle components are stabilized, recruited at the appropriate time for translation, and eliminated to modulate oocyte meiotic progression remains unclear. A better understanding of these mechanisms will provide invaluable insights for the preconditions of developmental competence acquisition, with important implications for the treatment of infertility. This review discusses how the storage, localization, translation, and processing of oocyte mRNAs are regulated, and how these contribute to oocyte maturation progression.
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Affiliation(s)
- Yanwen Jiang
- College of Animal Science, Jilin University, 5333 Xian Road, Changchun, 130062, China
| | - Deepak Adhikari
- Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, 19 Innovation Walk, Melbourne, VIC, 3800, Australia
| | - Chunjin Li
- College of Animal Science, Jilin University, 5333 Xian Road, Changchun, 130062, China
| | - Xu Zhou
- College of Animal Science, Jilin University, 5333 Xian Road, Changchun, 130062, China
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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: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [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,CONTACT Saffet Ozturk Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya07070, Turkey
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Onuma A, Fujioka YA, Fujii W, Sugiura K, Naito K. Expression and function of exportin 6 in full-grown and growing porcine oocytes. J Reprod Dev 2019; 65:407-412. [PMID: 31204365 PMCID: PMC6815735 DOI: 10.1262/jrd.2019-040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Exportin 6, which functions specifically in the nuclear export of actin family proteins, has been reported to be absent in immature Xenopus oocytes, which have a huge
nucleus containing a large amount of actin. In mammalian oocytes, however, the presence and the function of exportin 6 remain uninvestigated. In this study, we assessed the expression and
effects of exportin 6 on meiotic resumption in porcine oocytes after cloning porcine exportin 6 cDNA and carrying out overexpression and expression inhibition by mRNA and antisense RNA
injection, respectively. We found for the first time that exportin 6 was expressed in mammalian full-grown germinal-vesicle-stage oocytes and was involved in the nuclear export of actin. In
contrast, exportin 6 was absent from the growing oocytes, which are meiotically incompetent and maintain the germinal-vesicle structure in the long term; the regulatory mechanism appeared to
be active degradation. We examined the effects of exportin 6 on meiotic resumption of porcine oocytes and noted that its expression did not affect the onset time but increased the rate of
germinal vesicle breakdown at 24 h via regulation of the nuclear actin level, which directly influences the physical strength of the germinal-vesicle membrane. Our results suggest that
exportin 6 affects the nuclear transport of actin and meiotic resumption in mammalian oocytes.
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Affiliation(s)
- Asuka Onuma
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Yoshie A Fujioka
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Wataru Fujii
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Koji Sugiura
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Kunihiko Naito
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
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Onuma A, Fujioka YA, Fujii W, Sugiura K, Naito K. Effects of exportin 1 on nuclear transport and meiotic resumption in porcine full-grown and growing oocytes. Biol Reprod 2018; 98:501-509. [PMID: 29228114 DOI: 10.1093/biolre/iox168] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 12/07/2017] [Indexed: 12/17/2023] Open
Abstract
Exportin 1 (XPO1) is a nuclear transport receptor involved in the nuclear export of majority proteins in somatic cells. In mammalian oocytes, however, only the presence of XPO1 has been reported at mRNA and protein levels, and the definitive functions of XPO1 and its effects on the meiotic maturation of oocytes have never been directly examined. In the present study, the expression state and the nuclear-export function of porcine XPO1 were analyzed in porcine oocytes. In addition, we investigated the effects of the overexpression and inhibition of XPO1 on meiotic regulation in full-grown and growing oocytes by mRNA injection and inhibitor treatment. Endogenous XPO1 was stably expressed in porcine oocytes during the germinal vesicle (GV) stage, and the expression of exogenous XPO1 significantly decreased the nuclear localization of XPO1 cargos, snurportin 1, and WEE1B. Inhibition of XPO1 by a specific inhibitor, leptomycin B, delayed the GV breakdown (GVBD), whereas the overexpression of XPO1 by mRNA injection accelerated the GVBD. XPO1 overexpression overcame the meiotic arrest induced by WEE1B expression in full-grown oocytes. Surprisingly, the GVBD of porcine growing oocytes, which could not resume meiosis by the maturation culture in vitro, was induced by the expression of exogenous XPO1. These results showed the presence of XPO1 and its function as a nuclear export receptor in mammalian oocytes, including growing oocytes, and they suggest that the regulation of nuclear transport has a large influence on the GV maintenance and meiotic resumption of oocytes.
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Affiliation(s)
- Asuka Onuma
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Yoshie A Fujioka
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Wataru Fujii
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Koji Sugiura
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Kunihiko Naito
- Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
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Fujioka YA, Onuma A, Fujii W, Sugiura K, Naito K. Contributions of UBE2C and UBE2S to meiotic progression of porcine oocytes. J Reprod Dev 2018; 64:253-259. [PMID: 29576589 PMCID: PMC6021604 DOI: 10.1262/jrd.2018-006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Vertebrate oocytes arrested at the first meiotic prophase must proceed to the second meiotic metaphase (MII) before fertilization. This meiotic process requires the precise control of
protein degradation. Part of the protein degradation in oocytes is controlled by members of the ubiquitin-conjugating enzyme family, UBE2C and UBE2S, which are known to participate in
mono-ubiquitination and poly-ubiquitination, respectively. Although UBE2 enzymes have been well studied in mitosis, their contribution to mammalian oocyte meiosis is relatively unknown and
has been studied only in mice. Here, we investigated the contribution of UBE2C and UBE2S to porcine oocyte maturation using an RNA injection method. Overexpression of UBE2S prevented MII
arrest of oocytes and led to the formation of a pronucleus (PN) at 48 h of culture. This effect was also observed for prolonged cultures of UBE2C-overexpressing oocytes, suggesting the
effectiveness of poly-ubiquitination in the rapid escape from M-phase in porcine oocytes. Although the inhibition of either UBE2C or UBE2S by antisense RNA (asRNA) injection had no effect on
oocyte maturation, asRNA-injected oocytes showed inhibited PN formation after parthenogenetic activation. These results indicated that ubiquitination of certain factors by UBE2S and UBE2C
plays a role in the escape from MII arrest in porcine oocytes. Further investigations to identify the factors and how mono- and/or poly-ubiquitination contributes to protein degradation
could provide a better understanding of UBE2 roles in oocyte maturation.
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Affiliation(s)
- Yoshie A Fujioka
- Laboratory of Applied Genetics, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Asuka Onuma
- Laboratory of Applied Genetics, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Wataru Fujii
- Laboratory of Applied Genetics, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Koji Sugiura
- Laboratory of Applied Genetics, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Kunihiko Naito
- Laboratory of Applied Genetics, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
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