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Konar ESM, Mai K, Brachs S, Waghmare SG, Samarin AM, Policar T, Samarin AM. Evaluation of viability, developmental competence, and apoptosis-related transcripts during in vivo post-ovulatory oocyte aging in zebrafish Danio rerio (Hamilton, 1822). Front Vet Sci 2024; 11:1389070. [PMID: 38952806 PMCID: PMC11216024 DOI: 10.3389/fvets.2024.1389070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 05/30/2024] [Indexed: 07/03/2024] Open
Abstract
Introduction Post-ovulatory aging is a time-dependent deterioration of ovulated oocytes and a major limiting factor reducing the fitness of offspring. This process may lead to the activation of cell death pathways like apoptosis in oocytes. Methodology We evaluated oocyte membrane integrity, egg developmental competency, and mRNA abundance of apoptosis-related genes by RT-qPCR. Oocytes from zebrafish Danio rerio were retained in vivo at 28.5°C for 24 h post-ovulation (HPO). Viability was assessed using trypan blue (TB) staining. The consequences of in vivo oocyte aging on the developmental competence of progeny were determined by the embryo survival at 24 h post fertilization, hatching, and larval malformation rates. Results The fertilization, oocyte viability, and hatching rates were 91, 97, and 65% at 0 HPO and dropped to 62, 90, and 22% at 4 HPO, respectively. The fertilizing ability was reduced to 2% at 8 HPO, while 72% of oocytes had still intact plasma membranes. Among the apoptotic genes bcl-2 (b-cell lymphoma 2), bada (bcl2-associated agonist of cell death a), cathepsin D, cathepsin Z, caspase 6a, caspase 7, caspase 8, caspase 9, apaf1, tp53 (tumor protein p53), cdk1 (cyclin-dependent kinase 1) studied, mRNA abundance of anti-apoptotic bcl-2 decreased and pro-apoptotic cathepsin D increased at 24 HPO. Furthermore, tp53 and cdk1 mRNA transcripts decreased at 24 HPO compared to 0 HPO. Discussion Thus, TB staining did not detect the loss of oocyte competency if caused by aging. TB staining, however, could be used as a simple and rapid method to evaluate the quality of zebrafish oocytes before fertilization. Taken together, our results indicate the activation of cell death pathways in the advanced stages of oocyte aging in zebrafish.
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Affiliation(s)
- Essaikiammal Sodalai Muthu Konar
- Research Institute of Fish Culture and Hydrobiology, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Vodnany, Czechia
| | - Knut Mai
- Department of Endocrinology and Metabolism, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Berlin, Berlin, Germany
| | - Sebastian Brachs
- Department of Endocrinology and Metabolism, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Berlin, Berlin, Germany
| | - Swapnil Gorakh Waghmare
- Research Institute of Fish Culture and Hydrobiology, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Vodnany, Czechia
| | - Azadeh Mohagheghi Samarin
- Research Institute of Fish Culture and Hydrobiology, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Vodnany, Czechia
| | - Tomas Policar
- Research Institute of Fish Culture and Hydrobiology, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Vodnany, Czechia
| | - Azin Mohagheghi Samarin
- Research Institute of Fish Culture and Hydrobiology, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Vodnany, Czechia
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2
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Tokmakov AA, Teranishi R, Sato KI. Spontaneous Overactivation of Xenopus Frog Eggs Triggers Necrotic Cell Death. Int J Mol Sci 2024; 25:5321. [PMID: 38791359 PMCID: PMC11121189 DOI: 10.3390/ijms25105321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/01/2024] [Accepted: 05/03/2024] [Indexed: 05/26/2024] Open
Abstract
The excessive activation of frog eggs, referred to as overactivation, can be initiated by strong oxidative stress, leading to expedited calcium-dependent non-apoptotic cell death. Overactivation also occurs spontaneously, albeit at a low frequency, in natural populations of spawned frog eggs. Currently, the cytological and biochemical events of the spontaneous process have not been characterized. In the present study, we demonstrate that the spontaneous overactivation of Xenopus frog eggs, similarly to oxidative stress- and mechanical stress-induced overactivation, is characterized by the fast and irreversible contraction of the egg's cortical layer, an increase in egg size, the depletion of intracellular ATP, a drastic increase in the intracellular ADP/ATP ratio, and the degradation of M phase-specific cyclin B2. These events manifest in eggs in the absence of caspase activation within one hour of triggering overactivation. Importantly, substantial amounts of ATP and ADP leak from the overactivated eggs, indicating that plasma membrane integrity is compromised in these cells. The rupture of the plasma membrane and acute depletion of intracellular ATP explicitly define necrotic cell death. Finally, we report that egg overactivation can occur in the frog's genital tract. Our data suggest that mechanical stress may be a key factor promoting egg overactivation during oviposition in frogs.
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Affiliation(s)
- Alexander A. Tokmakov
- Institute of Advanced Technology, Faculty of Biology-Oriented Science and Technology, KinDai University, 930 Nishimitani, Kinokawa City 649-6493, Japan
| | - Ryuga Teranishi
- Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555, Japan;
| | - Ken-Ichi Sato
- Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555, Japan;
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Gagarinskiy E, Uteshev V, Fesenko E. Prolonged hypothermic storage of oocytes of the European common frog Rana temporaria in a gas mixture of oxygen and carbon monoxide. PLoS One 2023; 18:e0288370. [PMID: 37471400 PMCID: PMC10358915 DOI: 10.1371/journal.pone.0288370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 06/26/2023] [Indexed: 07/22/2023] Open
Abstract
The maximum hypothermic storage time of amphibian oocytes is several hours, which is due to the peculiarities of the structure of the cell envelope. The authors of this paper have already demonstrated the possibility of increasing the storage period of unfertilized oocytes of the common frog (Rana temporaria) up to 5-7 days. The aim of the current study was to determine the possibility of using a 6.5 atm gaseous mixture of carbon monoxide and oxygen, for prolonged hypothermic preservation of unfertilized oocytes for 4 to 12 days. After four days, oocytes stored under CO+O2 conditions exhibited fertilization and hatching rates that were 1.6 and 2.2-fold higher than control, respectively. While no oocytes in the control group survived to day twelve, oocytes held under CO +O2 gas exhibited a 39±14% (38 out of 99 oocytes in total) fertilization rate, however only 1±2% (1/99) of those hatched. This approach is promising for the storage of genetic material from female amphibians, particularly in respect to managing and restoring endangered species, but may also be applicable to oocytes of other classes of vertebrates.
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Affiliation(s)
- Evgeniy Gagarinskiy
- Institute of Cell Biophysics RAS - A Separate Subdivision of Federal Research Centre "Pushchino Scientific Centre for Biological Research RAS", Moscow, Russia
| | - Viktor Uteshev
- Institute of Cell Biophysics RAS - A Separate Subdivision of Federal Research Centre "Pushchino Scientific Centre for Biological Research RAS", Moscow, Russia
| | - Eugeny Fesenko
- Institute of Cell Biophysics RAS - A Separate Subdivision of Federal Research Centre "Pushchino Scientific Centre for Biological Research RAS", Moscow, Russia
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4
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Tokmakov AA, Morichika Y, Teranishi R, Sato KI. Oxidative Stress-Induced Overactivation of Frog Eggs Triggers Calcium-Dependent Non-Apoptotic Cell Death. Antioxidants (Basel) 2022; 11:antiox11122433. [PMID: 36552641 PMCID: PMC9774297 DOI: 10.3390/antiox11122433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022] Open
Abstract
Excessive activation of frog eggs (overactivation) is a pathological process that renders eggs unfertilizable. Its physiological inducers are unknown. Previously, oxidative stress was shown to cause time- and dose-dependent overactivation of Xenopus laevis frog eggs. Here, we demonstrate that the oxidative stress-induced egg overactivation is a calcium-dependent phenomenon which can be attenuated in the presence of the selective calcium chelator BAPTA. Degradation of cyclin B2, which is known to be initiated by calcium transient in fertilized or parthenogenetically activated eggs, can also be observed in the overactivated eggs. Decline in mitochondrial membrane potential, ATP depletion and termination of protein synthesis manifest in the eggs within one hour of triggering overactivation. These intracellular events occur in the absence of caspase activation. Furthermore, plasma membrane integrity is compromised in the overactivated eggs, as evidenced by ATP leakage and egg swelling. In sum, our data demonstrate that oxidative stress-induced overactivation of frog eggs causes fast and dramatic disruption of cellular homeostasis, resulting in robust and expedited cell death by a calcium-dependent non-apoptotic mechanism.
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Affiliation(s)
- Alexander A. Tokmakov
- Institute of Advanced Technoogy, Faculty of Biology-Oriented Science and Technology, KinDai University, 930 Nishimitani, Kinokawa City 649-6493, Japan
- Correspondence:
| | - Yudai Morichika
- Laboratory of Cell Signaling and Development, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
| | - Ryuga Teranishi
- Laboratory of Cell Signaling and Development, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
| | - Ken-Ichi Sato
- Laboratory of Cell Signaling and Development, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
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5
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Paitz RT, Dugas MB. Steroid levels in frog eggs: Manipulations, developmental changes, and implications for maternal steroid effects. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:293-302. [PMID: 34905660 DOI: 10.1002/jez.2566] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 11/21/2021] [Accepted: 11/23/2021] [Indexed: 06/14/2023]
Abstract
Exposure to maternally derived steroids during embryonic development can elicit phenotypic effects in the resulting offspring. Studies of maternal steroid effects, especially rich in mammals and birds, have offered exciting insights into the evolution of maternal effects in vertebrates. To extend this literature, we quantified levels of steroids in the eggs of four neotropical dendrobatid frogs that lay terrestrial clutches, a reproductive strategy that has evolved multiple times in amphibians. Building on our observational results, we then manipulated levels of pregnenolone and progesterone in eggs of one species and examined how this affected steroid levels during development. Eggs of all four species had detectable steroids levels, with progestogens being more abundant than androgens and glucocorticoids. Estrogens could not be detected. Immersion of frog eggs in a solution containing pregnenolone and progesterone resulted in elevated levels of both steroids early in development, but levels declined and were similar to those in unmanipulated eggs by the end of development. Treated eggs also exhibited a transient increase in levels of steroids that can be produced from pregnenolone and progesterone. Overall, our findings demonstrate that frog eggs contain steroids similar to what has been observed in other egg-laying vertebrates. During development, steroid levels are dynamic, further suggesting developing embryos regulate exposure to maternal steroids. These results set the stage for investigating the causes and consequences of maternal steroid effects in frogs.
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Affiliation(s)
- Ryan T Paitz
- School of Biological Sciences, Illinois State University, Normal, Illinois, USA
| | - Matthew B Dugas
- School of Biological Sciences, Illinois State University, Normal, Illinois, USA
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6
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Jevtić P, Elliott KW, Watkins SE, Sreter JA, Jovic K, Lehner IB, Baures PW, Tsavalas JG, Levy DL, Varga K. An insect antifreeze protein from Anatolica polita enhances the cryoprotection of Xenopus laevis eggs and embryos. J Exp Biol 2022; 225:jeb243662. [PMID: 35014670 PMCID: PMC8920033 DOI: 10.1242/jeb.243662] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 01/06/2022] [Indexed: 10/19/2022]
Abstract
Cryoprotection is of interest in many fields of research, necessitating a greater understanding of different cryoprotective agents. Antifreeze proteins have been identified that have the ability to confer cryoprotection in certain organisms. Antifreeze proteins are an evolutionary adaptation that contributes to the freeze resistance of certain fish, insects, bacteria and plants. These proteins adsorb to an ice crystal's surface and restrict its growth within a certain temperature range. We investigated the ability of an antifreeze protein from the desert beetle Anatolica polita, ApAFP752, to confer cryoprotection in the frog Xenopus laevis. Xenopus laevis eggs and embryos microinjected with ApAFP752 exhibited reduced damage and increased survival after a freeze-thaw cycle in a concentration-dependent manner. We also demonstrate that ApAFP752 localizes to the plasma membrane in eggs and embryonic blastomeres and is not toxic for early development. These studies show the potential of an insect antifreeze protein to confer cryoprotection in amphibian eggs and embryos.
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Affiliation(s)
- Predrag Jevtić
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - K. Wade Elliott
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Shelby E. Watkins
- Department of Chemistry, University of Wyoming, Laramie, WY 82071, USA
| | - Jonathan A. Sreter
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Katarina Jovic
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Ian B. Lehner
- Department of Chemistry, Keene State College, Keene, NH 03435, USA
| | - Paul W. Baures
- Department of Chemistry, Keene State College, Keene, NH 03435, USA
| | - John G. Tsavalas
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA
| | - Daniel L. Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | - Krisztina Varga
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
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7
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Modulation of Intracellular ROS and Senescence-Associated Phenotypes of Xenopus Oocytes and Eggs by Selective Antioxidants. Antioxidants (Basel) 2021; 10:antiox10071068. [PMID: 34356301 PMCID: PMC8301133 DOI: 10.3390/antiox10071068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/24/2021] [Accepted: 06/28/2021] [Indexed: 11/17/2022] Open
Abstract
Aging of oocytes and eggs diminishes their reproductive and developmental potential. It has been demonstrated previously that reactive oxygen species (ROS) contribute to accelerated aging of various cells. In the present study, we measured intracellular levels of ROS and investigated effects of several selective antioxidants (AOXs) on the viability and functional activity of aging oocytes and eggs of the African clawed frog Xenopus laevis. The fluorescent cell-permeable dye DCFDA, which is widely employed for ROS detection in cultured mammalian cells, was used to monitor ROS levels in the fresh and bench-aged oocytes and eggs by an optimized protocol. It was found that intracellular ROS contents were increased in frog oocytes and eggs aged for 48 h. It was further demonstrated using selective cell-permeable AOXs targeting different ROS-generating mechanisms, that the major source of ROS in Xenopus oocytes and eggs is the plasma membrane NADPH oxidase, and that mitochondrial generation contributes to the intracellular ROS content to a lesser extent. Targeted inhibition of NADPH oxidase with a natural organic compound apocynin reduced ROS levels significantly in Xenopus oocytes and eggs, maintained their normal phenotype and supported their functional competence. To our knowledge this is the first report concerning beneficial effects of apocynin on the isolated gamete cells, such as oocytes and eggs.
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8
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Tokmakov AA, Stefanov VE, Sato KI. Dissection of the Ovulatory Process Using ex vivo Approaches. Front Cell Dev Biol 2020; 8:605379. [PMID: 33363163 PMCID: PMC7755606 DOI: 10.3389/fcell.2020.605379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Accepted: 11/19/2020] [Indexed: 12/23/2022] Open
Abstract
Ovulation is a unique physiological phenomenon that is essential for sexual reproduction. It refers to the entire process of ovarian follicle responses to hormonal stimulation resulting in the release of mature fertilization-competent oocytes from the follicles and ovaries. Remarkably, ovulation in different species can be reproduced out-of-body with high fidelity. Moreover, most of the molecular mechanisms and signaling pathways engaged in this process have been delineated using in vitro ovulation models. Here, we provide an overview of the major molecular and cytological events of ovulation observed in frogs, primarily in the African clawed frog Xenopus laevis, using mainly ex vivo approaches, with the focus on meiotic oocyte maturation and follicle rupture. For the purpose of comparison and generalization, we also refer extensively to ovulation in other biological species, most notoriously, in mammals.
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Affiliation(s)
| | - Vasily E Stefanov
- Department of Biochemistry, Saint Petersburg State University, Saint Petersburg, Russia
| | - Ken-Ichi Sato
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan
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Effects of Ferrocenyl 4-(Imino)-1,4-Dihydro-quinolines on Xenopus laevis Prophase I - Arrested Oocytes: Survival and Hormonal-Induced M-Phase Entry. Int J Mol Sci 2020; 21:ijms21093049. [PMID: 32357477 PMCID: PMC7246863 DOI: 10.3390/ijms21093049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/20/2020] [Accepted: 04/23/2020] [Indexed: 01/14/2023] Open
Abstract
Xenopus oocytes were used as cellular and molecular sentinels to assess the effects of a new class of organometallic compounds called ferrocenyl dihydroquinolines that have been developed as potential anti-cancer agents. One ferrocenyl dihydroquinoline compound exerted deleterious effects on oocyte survival after 48 h of incubation at 100 μM. Two ferrocenyl dihydroquinoline compounds had an inhibitory effect on the resumption of progesterone induced oocyte meiosis, compared to controls without ferrocenyl groups. In these inhibited oocytes, no MPF (Cdk1/cyclin B) activity was detected by western blot analysis as shown by the lack of phosphorylation of histone H3. The dephosphorylation of the inhibitory Y15 residue of Cdk1 occurred but cyclin B was degraded. Moreover, two apoptotic death markers, the active caspase 3 and the phosphorylated histone H2, were detected. Only 7-chloro-1-ferrocenylmethyl-4-(phenylylimino)-1,4-dihydroquinoline (8) did not show any toxicity and allowed the assembly of a histologically normal metaphase II meiotic spindle while inhibiting the proliferation of cancer cell lines with a low IC50, suggesting that this compound appears suitable as an antimitotic agent.
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10
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Sato K, Tokmakov AA. Toward the understanding of biology of oocyte life cycle in Xenopus Laevis: No oocytes left behind. Reprod Med Biol 2020; 19:114-119. [PMID: 32273815 PMCID: PMC7138939 DOI: 10.1002/rmb2.12314] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 12/09/2019] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND For the past more than 25 years, we have been focusing on the developmental and reproductive biology of the female gametes, oocytes, and eggs, of the African clawed frog Xenopus laevis. METHODS The events associated with the life cycle of these cells can be classified into the four main categories: first, oogenesis and cell growth in the ovary during the first meiotic arrest; second, maturation and ovulation that occur simultaneously and result in the acquisition of fertilization competence and the second meiotic arrest; third, fertilization, that is sperm-induced transition from egg to zygote; and fourth, egg death after spontaneous activation in the absence of fertilizing sperm. MAIN FINDINGS Our studies have demonstrated that signal transduction system involving tyrosine kinase Src and other oocyte/egg membrane-associated molecules such as uroplakin III and some other cytoplasmic proteins such as mitogen-activated protein kinase (MAPK) play important roles for successful ovulation, maturation, fertilization, and initiation of embryonic development. CONCLUSION We summarize recent advances in understanding cellular and molecular mechanisms underlying life cycle events of the oocytes and eggs. Our further intention is to discuss and predict potentially promising impact of the recent findings on the challenges facing reproductive biology and medicine, as well as societal contexts.
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Affiliation(s)
- Ken‐ichi Sato
- Laboratory of Cell Signaling and DevelopmentDepartment of Industrial Life SciencesFaculty of Life SciencesKyoto Sangyo UniversityKyotoJapan
| | - Alexander A. Tokmakov
- Laboratory of Cell Signaling and DevelopmentDepartment of Industrial Life SciencesFaculty of Life SciencesKyoto Sangyo UniversityKyotoJapan
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11
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Hydrogen Sulfide Impairs Meiosis Resumption in Xenopus laevis Oocytes. Cells 2020; 9:cells9010237. [PMID: 31963573 PMCID: PMC7017156 DOI: 10.3390/cells9010237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 01/15/2020] [Accepted: 01/16/2020] [Indexed: 01/19/2023] Open
Abstract
The role of hydrogen sulfide (H2S) is addressed in Xenopus laevis oocytes. Three enzymes involved in H2S metabolism, cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase, were detected in prophase I and metaphase II-arrested oocytes and drove an acceleration of oocyte meiosis resumption when inhibited. Moreover, meiosis resumption is associated with a significant decrease in endogenous H2S. On another hand, a dose-dependent inhibition was obtained using the H2S donor, NaHS (1 and 5 mM). NaHS impaired translation. NaHS did not induce the dissociation of the components of the M-phase promoting factor (MPF), cyclin B and Cdk1, nor directly impacted the MPF activity. However, the M-phase entry induced by microinjection of metaphase II MPF-containing cytoplasm was diminished, suggesting upstream components of the MPF auto-amplification loop were sensitive to H2S. Superoxide dismutase and catalase hindered the effects of NaHS, and this sensitivity was partially dependent on the production of reactive oxygen species (ROS). In contrast to other species, no apoptosis was promoted. These results suggest a contribution of H2S signaling in the timing of amphibian oocytes meiosis resumption.
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12
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In Vitro Reconstruction of Xenopus Oocyte Ovulation. Int J Mol Sci 2019; 20:ijms20194766. [PMID: 31561408 PMCID: PMC6801927 DOI: 10.3390/ijms20194766] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/08/2019] [Accepted: 09/16/2019] [Indexed: 11/17/2022] Open
Abstract
Progesterone is widely used to induce maturation of isolated fully grown oocytes of the African clawed frog, Xenopus laevis. However, the hormone fails to release oocytes from the layer of surrounding follicle cells. Here, we report that maturation and follicle rupture can be recapitulated in vitro by treating isolated follicular oocytes with progesterone and low doses of the matrix metalloproteinase (MMP), collagenase, which are ineffective in the absence of the steroid. Using this in vitro ovulation model, we demonstrate that germinal vesicle breakdown (GVBD) and oocyte liberation from ovarian follicles occur synchronously during ovulation. Inhibition of the MAPK pathway in these experimental settings suppresses both GVBD and follicular rupture, whereas inhibition of MMP activity delays follicular rupture without affecting GVBD. These results highlight importance of MAPK and MMP activities in the ovulation process and provide the first evidence for their involvement in the release of oocytes from ovarian follicles in frogs. The in vitro ovulation model developed in our study can be employed for further dissection of ovulation.
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13
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Tokmakov AA, Akino K, Iguchi S, Iwasaki T, Stefanov VE, Sato KI. Autophosphorylation of MAP kinase disables the MAPK pathway in apoptotic Xenopus eggs. Biochem Biophys Res Commun 2019; 517:140-145. [PMID: 31320137 DOI: 10.1016/j.bbrc.2019.07.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 07/10/2019] [Indexed: 11/26/2022]
Abstract
Mitogen-activated protein kinases (MAPKs) are involved in the regulation of various cellular processes, including cell survival and apoptosis. Here, we report that Xenopus p42 MAPK becomes phosphorylated in apoptotic eggs, however this modification does not activate the enzyme. Using phosphorylation residue-specific antibodies, we demonstrate that this modification occurs on the Tyr residue in the MAPK activation segment, pinpointing the autophosphorylation mechanism. Notably, MAPK phosphorylation in apoptotic Xenopus eggs coincides with prominent intracellular acidification accompanying apoptosis in these cells. Furthermore, autophosphorylation of recombinant Xenopus MAPK is stimulated and phosphorylation of a protein substrate is inhibited under low pH conditions. Thus, acidic intracellular conditions inactivate MAPK and effectively disable the MAPK-mediated survival pathway in the apoptotic eggs. Given that cell acidification is a rather common feature of apoptosis, we hypothesize that stimulation of MAPK autophosphorylation and shutdown of the MAPK pathway may represent universal traits of apoptotic cell death.
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Affiliation(s)
| | - Kousuke Akino
- Graduate School of Science Faculty of Science, Kobe University, Japan
| | - Sho Iguchi
- Biosignal Research Center, Kobe University, Japan
| | - Tetsushi Iwasaki
- Graduate School of Science Faculty of Science, Kobe University, Japan; Biosignal Research Center, Kobe University, Japan
| | - Vasily E Stefanov
- Department of Biochemistry, Saint Petersburg State University, Russia
| | - Ken-Ichi Sato
- Faculty of Life Sciences, Kyoto Sangyo University, Japan
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14
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Biochemical Hallmarks of Oxidative Stress-Induced Overactivation of Xenopus Eggs. BIOMED RESEARCH INTERNATIONAL 2019; 2019:7180540. [PMID: 31341903 PMCID: PMC6634078 DOI: 10.1155/2019/7180540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/28/2019] [Accepted: 05/28/2019] [Indexed: 02/05/2023]
Abstract
Egg overactivation occurs with a low frequency in the populations of naturally ovulated frog eggs. At present, its natural inducers, molecular mechanisms, and intracellular events remain unknown. Using microscopic and biochemical analyses, we demonstrate here that high levels of hydrogen peroxide-induced oxidative stress can cause time- and dose-dependent overactivation of Xenopus eggs. Lipofuscin accumulation, decrease of soluble cytoplasmic protein content, and depletion of intracellular ATP were found to take place in the overactivated eggs. Progressive development of these processes suggests that egg overactivation unfolds in a sequential and ordered fashion.
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15
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Tokmakov AA, Sato KI. Activity and intracellular localization of senescence-associated β-galactosidase in aging Xenopus oocytes and eggs. Exp Gerontol 2019; 119:157-167. [PMID: 30769028 DOI: 10.1016/j.exger.2019.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/22/2019] [Accepted: 02/02/2019] [Indexed: 12/14/2022]
Abstract
Senescence-associated β-galactosidase (SA-β-gal) serves as a marker of senescence in aging somatic cells. However, little is known about SA-β-gal dynamics in aging gamete cells. To address this issue, here we investigated activity and intracellular localization of SA-β-gal in freshly obtained and aging oocytes and eggs of the African clawed frog Xenopus laevis. Data base mining revealed the presence of several homologous β-galactosidase sequences in the annotated Xenopus genome. Some of them were predicted to contain an N-terminal signal peptide sequence, suggesting enzyme translocation to cellular organelles. Biochemical and microscopic analyses confirmed SA-β-gal localization in the particulate and cytosolic fractions of oocytes and eggs. SA-β-gal activity was found to reside predominantly within a fraction of dense cytoplasmic granules that were extensively stained with the lysosome-specific dye LysoTracker Green DND-26 and had an average size of 8.9 ± 5.6 μm. These features identify the SA-β-gal-containing granules as a subpopulation of yolk platelets, specialized late endosomes or lysosomes that accumulate and store processed protein in frog oocytes. Further analysis revealed an increase of SA-β-gal activity in Xenopus eggs, but not in oocytes, aged in vitro over 48 h. Our data suggest that endosomal acidification during egg aging may be responsible for this increase.
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Affiliation(s)
- Alexander A Tokmakov
- Department of Molecular Biosciences, Kyoto Sangyo University, Kamigamo-motoyama, Kita-ku, Kyoto 603-8555, Japan.
| | - Ken-Ichi Sato
- Department of Molecular Biosciences, Kyoto Sangyo University, Kamigamo-motoyama, Kita-ku, Kyoto 603-8555, Japan.
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Sato KI, Tokmakov AA. Membrane Microdomains as Platform to Study Membrane-Associated Events During Oogenesis, Meiotic Maturation, and Fertilization in Xenopus laevis. Methods Mol Biol 2019; 1920:59-73. [PMID: 30737686 DOI: 10.1007/978-1-4939-9009-2_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Studies on the egg plasma membrane-associated tyrosine kinase Src have shed light on the identity of the molecular machinery that is responsible for gamete interaction and possibly fusion in African clawed frog Xenopus laevis. Here we describe our protocol for identifying and analyzing molecular and cellular machinery that contributes to a variety of biological processes in the course of oogenesis, oocyte maturation, egg fertilization, and early embryogenesis in Xenopus. Our current special interest is to evaluate the hypothesis that the oocyte/egg membrane microdomain (MD)-associated uroplakin III-Src system is responsible for mediating sperm-egg membrane interaction/fusion signal to the oocyte/egg cytoplasm to initiate embryonic and zygotic development in this species. Therefore, this chapter contains a brief introduction to biology of oocytes and eggs in Xenopus and addresses the following questions: (1) What is oocyte/egg MD? (2) Why do we study oocyte/egg MD? (3) How to manipulate oocyte/egg MD? (4) What has been achieved by oocyte/egg MD studies? (5) What are the next steps in oocyte/egg MD studies?
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Affiliation(s)
- Ken-Ichi Sato
- Faculty of Life Sciences, Laboratory of Cell Signaling and Development, Department of Molecular Biosciences, Kyoto Sangyo University, Kyoto, Japan.
| | - Alexander A Tokmakov
- Faculty of Life Sciences, Laboratory of Cell Signaling and Development, Department of Molecular Biosciences, Kyoto Sangyo University, Kyoto, Japan
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Dilsaver MR, Chen P, Thompson TA, Reusser T, Mukherjee RN, Oakey J, Levy DL. Emerin induces nuclear breakage in Xenopus extract and early embryos. Mol Biol Cell 2018; 29:3155-3167. [PMID: 30332321 PMCID: PMC6340207 DOI: 10.1091/mbc.e18-05-0277] [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: 11/17/2022] Open
Abstract
Emerin is an inner nuclear membrane protein often mutated in Emery–Dreifuss muscular dystrophy. Because emerin has diverse roles in nuclear mechanics, cytoskeletal organization, and gene expression, it has been difficult to elucidate its contribution to nuclear structure and disease pathology. In this study, we investigated emerin’s impact on nuclei assembled in Xenopus laevis egg extract, a simplified biochemical system that lacks potentially confounding cellular factors and activities. Notably, these extracts are transcriptionally inert and lack endogenous emerin and filamentous actin. Strikingly, emerin caused rupture of egg extract nuclei, dependent on the application of shear force. In egg extract, emerin localized to nonnuclear cytoplasmic membranes, and nuclear rupture was rescued by targeting emerin to the nucleus, disrupting its membrane association, or assembling nuclei with lamin A. Furthermore, emerin induced breakage of nuclei in early-stage X. laevis embryo extracts, and embryos microinjected with emerin were inviable, with ruptured nuclei. We propose that cytoplasmic membrane localization of emerin leads to rupture of nuclei that are more sensitive to mechanical perturbation, findings that may be relevant to early development and certain laminopathies.
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Affiliation(s)
- Matthew R Dilsaver
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Pan Chen
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Trey A Thompson
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - Traci Reusser
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071
| | - Richik N Mukherjee
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
| | - John Oakey
- Department of Chemical Engineering, University of Wyoming, Laramie, WY 82071
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
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Tokmakov AA, Sato KI, Stefanov VE. Postovulatory cell death: why eggs die via apoptosis in biological species with external fertilization. J Reprod Dev 2017; 64:1-6. [PMID: 29081453 PMCID: PMC5830352 DOI: 10.1262/jrd.2017-100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Spawned unfertilized eggs have been found to die by apoptosis in several species with external fertilization. However, there is no necessity for the externally laid eggs to degrade via this process, as apoptosis evolved as a mechanism to reduce the damaging effects of individual cell death on the whole organism. The recent observation of egg degradation in the genital tracts of some oviparous species provides a clue as to the physiological relevance of egg apoptosis in these animals. We hypothesize that egg apoptosis accompanies ovulation in species with external fertilization as a normal process to eliminate mature eggs retained in the genital tract after ovulation. Furthermore, apoptosis universally develops in ovulated eggs after spontaneous activation in the absence of fertilization. This paper provides an overview of egg apoptosis in several oviparous biological species, including frog, fish, sea urchin, and starfish.
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Affiliation(s)
| | - Ken-Ichi Sato
- Department of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan
| | - Vasily E Stefanov
- Department of Biochemistry, St. Petersburg State University, St. Petersburg 199034, Russia
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Tokmakov AA, Iguchi S, Iwasaki T, Fukami Y, Sato KI. Global decay of mRNA is a hallmark of apoptosis in aging Xenopus eggs. RNA Biol 2017; 14:339-346. [PMID: 28045588 PMCID: PMC5367254 DOI: 10.1080/15476286.2016.1276695] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Cytoplasmic mRNAs are specifically degraded in somatic cells as a part of early apoptotic response. However, no reports have been presented so far concerning mRNA fate in apoptotic gametes. In the present study, we analyzed the content of various cytoplasmic mRNAs in aging oocytes and eggs of the African clawed frog, Xenopus laevis. To circumvent large gene expression variation among the individual oocytes and eggs, single-cell monitoring of transcript levels has been implemented, using multiple cytoplasmic collections and reverse transcriptase quantitative PCR. It was found that numerous cytoplasmic mRNAs, coding for proteins classified in different functional types, are robustly degraded in apoptotic Xenopus eggs, but not in aging oocytes. mRNA degradation becomes evident in the eggs after meiotic exit at the time of cytochrome c release. A strong correlation between the length of PCR amplicon and specific transcript content was observed, suggesting endonucleolytic cleavage of mRNA. In addition, it was found that mRNA deadenylation also contributes to apoptotic mRNA degradation. Altogether, these findings indicate that the global decay of mRNA represents a hallmark of apoptosis in aging Xenopus eggs. To our knowledge, this is the first description of mRNA degradation in apoptotic gamete cells.
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Affiliation(s)
- Alexander A Tokmakov
- a Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo Motoyama , Kita ku , Kyoto , Japan.,b Graduate School of Science, Kobe University, Rokko dai , Nada , Kobe , Japan
| | - Sho Iguchi
- b Graduate School of Science, Kobe University, Rokko dai , Nada , Kobe , Japan
| | - Tetsushi Iwasaki
- b Graduate School of Science, Kobe University, Rokko dai , Nada , Kobe , Japan
| | - Yasuo Fukami
- b Graduate School of Science, Kobe University, Rokko dai , Nada , Kobe , Japan
| | - Ken-Ichi Sato
- a Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo Motoyama , Kita ku , Kyoto , Japan
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Tsuchiya Y, Murai S, Yamashita S. Dual inhibition of Cdc2 protein kinase activation during apoptosis inXenopusegg extracts. FEBS J 2015; 282:1256-70. [DOI: 10.1111/febs.13217] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 01/12/2015] [Accepted: 01/26/2015] [Indexed: 11/27/2022]
Affiliation(s)
- Yuichi Tsuchiya
- Department of Biochemistry; Toho University School of Medicine; Ota-ku Tokyo Japan
| | - Shin Murai
- Department of Biochemistry; Toho University School of Medicine; Ota-ku Tokyo Japan
| | - Shigeru Yamashita
- Department of Biochemistry; Toho University School of Medicine; Ota-ku Tokyo Japan
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Sato KI. Transmembrane signal transduction in oocyte maturation and fertilization: focusing on Xenopus laevis as a model animal. Int J Mol Sci 2014; 16:114-34. [PMID: 25546390 PMCID: PMC4307238 DOI: 10.3390/ijms16010114] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 12/15/2014] [Indexed: 11/16/2022] Open
Abstract
Fertilization is a cell biological phenomenon of crucial importance for the birth of new life in a variety of multicellular and sexual reproduction species such as algae, animal and plants. Fertilization involves a sequence of events, in which the female gamete "egg" and the male gamete "spermatozoon (sperm)" develop, acquire their functions, meet and fuse with each other, to initiate embryonic and zygotic development. Here, it will be briefly reviewed how oocyte cytoplasmic components are orchestrated to undergo hormone-induced oocyte maturation and sperm-induced activation of development. I then review how sperm-egg membrane interaction/fusion and activation of development in the fertilized egg are accomplished and regulated through egg coat- or egg plasma membrane-associated components, highlighting recent findings and future directions in the studies using Xenopus laevis as a model experimental animal.
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Affiliation(s)
- Ken-ichi Sato
- Laboratory of Cell Signaling and Development, Department of Molecular Biosciences, Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo-motoyama, Kita-ku, Kyoto 603-8555, Japan.
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Tokmakov AA, Hashimoto T, Hasegawa Y, Iguchi S, Iwasaki T, Fukami Y. Monitoring gene expression in a single Xenopus oocyte using multiple cytoplasmic collections and quantitative RT-PCR. FEBS J 2013; 281:104-14. [PMID: 24165194 DOI: 10.1111/febs.12576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 10/10/2013] [Accepted: 10/21/2013] [Indexed: 11/27/2022]
Abstract
Oocytes and eggs of the African clawed frog, Xenopus laevis, are commonly used in gene expression studies. However, monitoring transcript levels in the individual living oocytes remains challenging. To address this challenge, we used a technique based on multiple repeated collections of nanoliter volumes of cytoplasmic material from a single oocyte. Transcript quantification was performed by quantitative RT-PCR. The technique allowed monitoring of heterologous gene expression in a single oocyte without affecting its viability. We also used this approach to profile the expression of endogenous genes in living Xenopus oocytes. Although frog oocytes are traditionally viewed as a homogenous cell population, a significant degree of gene expression variation was observed among the individual oocytes. A lognormal distribution of transcript levels was revealed in the oocyte population. Finally, using this technique, we observed a dramatic decrease in the content of various cytoplasmic mRNAs in aging unfertilized eggs but not in oocytes, suggesting a link between mRNA degradation and egg apoptosis.
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Iguchi S, Iwasaki T, Fukami Y, Tokmakov AA. Unlaid Xenopus eggs degrade by apoptosis in the genital tract. BMC Cell Biol 2013; 14:11. [PMID: 23452868 PMCID: PMC3599861 DOI: 10.1186/1471-2121-14-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 02/28/2013] [Indexed: 01/09/2023] Open
Abstract
Background In several species with external fertilization, including frogs, laid unfertilized eggs were found to die by apoptosis outside of the animal body. However, there is no apparent reason for the externally laid eggs to degrade by this process, considering that apoptosis developed as a mechanism to reduce the damaging effect of individual cell death to the whole organism. Results Here, we demonstrate that a number of eggs are retained in the genital tract of the African clawed frog Xenopus laevis after gonadotropin-induced ovulation. The majority of these eggs exit meiotic arrest within 24 hours of hormone administration. Subsequently, post-meiotic eggs die in the frog genital tract by a well-defined apoptotic process. The hallmarks of egg degradation include prominent morphological changes, cytochrome c release, caspase activation, increase in ADP/ATP ratio, progressive intracellular acidification, egg swelling and all-out proteolysis of egg proteins. The sustained presence of post-apoptotic eggs in the genital tract of ageing frogs evidenced age-associated worsening of apoptotic clearance. Conclusions The direct observation of egg degradation in the Xenopus genital tract provides a clue to the physiological relevance of frog egg apoptosis. It works to eliminate the mature unlaid eggs retained in the animal body after ovulation. Our findings establish egg apoptosis as a major physiological process accompanying ovulation in frogs.
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Affiliation(s)
- Sho Iguchi
- Graduate School of Science, Rokko dai 1-1, Nada, Kobe 657-8501, Japan
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