1
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Liu C, Liu H, Luo Y, Lu T, Fu X, Cui S, Zhu S, Hou Y. The extracellular calcium-sensing receptor promotes porcine egg activation via calcium/calmodulin-dependent protein kinase II. Mol Reprod Dev 2020; 87:598-606. [PMID: 32017318 DOI: 10.1002/mrd.23322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 12/27/2019] [Indexed: 12/24/2022]
Abstract
Extracellular calcium is required for intracellular Ca2+ oscillations needed for egg activation, but the regulatory mechanism is still poorly understood. The present study was designed to demonstrate the function of calcium-sensing receptor (CASR), which could recognize extracellular calcium as first messenger, during porcine egg activation. CASR expression was markedly upregulated following egg activation. Functionally, the addition of CASR agonist NPS R-568 significantly enhanced pronuclear formation rate, while supplementation of CASR antagonist NPS2390 compromised egg activation. There was no change in NPS R-568 group compared with control group when the egg activation was performed without extracellular calcium addition. The addition of NPS2390 precluded the activation-dependent [Ca2+ ]i rise. When egg activation was conducted in intracellular Ca2+ chelator BAPTA-AM and NPS R-568 containing medium, CASR function was abolished. Meanwhile, CASR activation increased the level of the [Ca2+ ]i effector p-CAMKII, and the presence of KN-93, an inhibitor of CAMKII, significantly reduced the CASR-mediated increasement of pronuclear formation rate. Furthermore, the increase of CASR expression following activation was reversed by inhibiting CAMKII activity, supporting a positive feedback loop between CAMKII and CASR. Altogether, these findings provide a new pathway of egg activation about CASR, as the extracellular Ca2+ effector, promotes egg activation via its downstream effector and upstream regulator CAMKII.
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Affiliation(s)
- Cong Liu
- School of Basic Medical Science, Wuhan University, Wuhan, China
| | - Huage Liu
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Yan Luo
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Tengfei Lu
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xiangwei Fu
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Sheng Cui
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Shien Zhu
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yunpeng Hou
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
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2
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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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3
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Karabulut S, Aksünger Ö, Ata C, Sağıroglu Y, Keskin İ. Artificial oocyte activation with calcium ionophore for frozen sperm cycles. Syst Biol Reprod Med 2018; 64:381-388. [PMID: 29620419 DOI: 10.1080/19396368.2018.1452311] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Fertilization problems are the major problems that may be faced in 30-55% of the patients during an intracytoplasmic sperm injection (ICSI) cycle. A successful oocyte activation depends on factors related to both sperm and oocyte, and one of the important factors that mediates the process is Ca2+ concentration within the oocyte. Artificial oocyte activation (AOA) is a method used for fertilization problems that commonly involve the usage of Ca2+ ionophores and is usually used in problems such as total fertilization failure (TFF) and globozoospermia. The aim of the present study was to investigate possible effects of AOA for different groups of patients with fertilization failure. Four groups of patients (previous TFF, low oocyte number, severe sperm quality, and frozen sperm (FS) group) that underwent ICSI with AOA were included in the study. All groups had similar control groups with same indications except TFF, where AOA was not performed. Fertilization rates were significantly higher in the TFF group than those observed in other AOA groups. Fertilization rates and quality of embryos observed in the remaining AOA groups were higher than those of the controls, which were statistically insignificant. Prgenancy rates were higher in all AOA groups compared to the controls, although the differences were significant in FS group only. Quality of embryos and pregnancy rates were lower in the TFF group compared to the remaining AOA groups indicating possible concomitant problems. Fertilization rates, quality of embryos and pregnancy rates seemed to be increased in all indication groups suggesting that not only TFF patients but also a wide variety of patients with different indications may benefit from AOA. ABBREVIATIONS ICSI: Intracytoplasmic sperm injection; ARTs: Assisted reproductive techniques; Ca: Calcium; AOA: Artificial oocyte activation; TFF: Total fertilization failures; OAT: Oligoasthenoteratozoospemia; IVF: In vitro fertilization; SOAT: Severe OAT; LON: Low ooctye number; FS: Frozen sperm; hCG: human chorionic gonadotrophin; PVP: polyvinylpyrrolidone; HSA: human serum albumin.
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Affiliation(s)
- Seda Karabulut
- a School of Medicine , İstanbul Medipol University , İstanbul.,b REMER (Regenerative and Restorative Medicine Research Center) , İstanbul Medipol University , İstanbul , Turkey
| | - Özlem Aksünger
- c Memorial Antalya Hastanesi/Tüp Bebek Merkezi , Antalya , Turkey
| | - Can Ata
- c Memorial Antalya Hastanesi/Tüp Bebek Merkezi , Antalya , Turkey
| | - Yusuf Sağıroglu
- d IVF Unit , Florence Nightingale Hospital Kadıkoy , İstanbul , Turkey
| | - İlknur Keskin
- a School of Medicine , İstanbul Medipol University , İstanbul.,b REMER (Regenerative and Restorative Medicine Research Center) , İstanbul Medipol University , İstanbul , Turkey
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4
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Roychoudhury S, Maldonado-Rosas I, Agarwal A, Esteves SC, Henkel R, Sharma R. Human sperm handling in intracytoplasmic sperm injection processes: In vitro studies on mouse oocyte activation, embryo development competence and sperm oxidation-reduction potential. Andrologia 2018; 50:e12943. [PMID: 29315724 DOI: 10.1111/and.12943] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2017] [Indexed: 02/28/2024] Open
Abstract
Polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) are routinely used in handling spermatozoa for intracytoplasmic sperm injection (ICSI). As there are still concerns about possible adverse effects on the embryo, this study investigated sperm handling in a mouse ICSI model to (i) evaluate oocyte activation after injection of spermatozoa selected for rotational or linear motion in PVP; (ii) assess the effect of sperm selection in PVP, HA and medium on oocyte activation; (iii) examine the effects of PVP and HA on parthenogenetic oocyte activation and embryo development; and (iv) assess the oxidation-reduction potential (ORP) of spermatozoa exposed to PVP, HA or medium. Oocyte activation was higher when spermatozoa exhibited rotational motion rather than linear motion (79% vs. 52%; p = .05). There was no difference in oocyte activation and embryo development after parthenogenetic oocyte activation after sperm injection using PVP, HA or medium-incubated spermatozoa. PVP-selected spermatozoa exhibited lower (p < .0001) ORP levels than using HA. Thus, results indicate that the sperm handling method and the type of medium used impact ICSI outcomes. Overall, sperm incubation in PVP, HA and medium yields similar outcomes with regard to oocyte activation and embryo development. However, PVP provides more antioxidative protection than HA and should therefore be preferred for sperm manipulation.
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Affiliation(s)
- S Roychoudhury
- American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA
- Department of Life Science and Bioinformatics, Assam University, Silchar, India
| | | | - A Agarwal
- American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA
| | - S C Esteves
- ANDROFERT, Center for Male Reproduction, Campinas, Brazil
| | - R Henkel
- Department of Medical Bioscience, University of the Western Cape, Bellville, South Africa
| | - R Sharma
- American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA
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5
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Zhang QH, Yuen WS, Adhikari D, Flegg JA, FitzHarris G, Conti M, Sicinski P, Nabti I, Marangos P, Carroll J. Cyclin A2 modulates kinetochore-microtubule attachment in meiosis II. J Cell Biol 2017; 216:3133-3143. [PMID: 28819014 PMCID: PMC5626527 DOI: 10.1083/jcb.201607111] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 07/04/2017] [Accepted: 07/28/2017] [Indexed: 12/17/2022] Open
Abstract
Cyclin A2 is a crucial mitotic Cdk regulatory partner that coordinates entry into mitosis and is then destroyed in prometaphase within minutes of nuclear envelope breakdown. The role of cyclin A2 in female meiosis and its dynamics during the transition from meiosis I (MI) to meiosis II (MII) remain unclear. We found that cyclin A2 decreases in prometaphase I but recovers after the first meiotic division and persists, uniquely for metaphase, in MII-arrested oocytes. Conditional deletion of cyclin A2 from mouse oocytes has no discernible effect on MI but leads to disrupted MII spindles and increased merotelic attachments. On stimulation of exit from MII, there is a dramatic increase in lagging chromosomes and an inhibition of cytokinesis. These defects are associated with an increase in microtubule stability in MII spindles, suggesting that cyclin A2 mediates the fidelity of MII by maintaining microtubule dynamics during the rapid formation of the MII spindle.
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Affiliation(s)
- Qing-Hua Zhang
- Development and Stem Cell Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia .,Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Wai Shan Yuen
- Development and Stem Cell Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia.,Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Deepak Adhikari
- Development and Stem Cell Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia.,Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Jennifer A Flegg
- Monash Academy for Cross and Interdisciplinary Mathematical Applications, Monash University, Melbourne, Victoria, Australia
| | - Greg FitzHarris
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec, Canada.,Department of Obstetrics and Gynaecology, University of Montréal, Montréal, Québec, Canada
| | - Marco Conti
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Center for Reproductive Sciences, University of California, San Francisco, San Francisco, CA
| | - Piotr Sicinski
- Dana-Farber Cancer Institute, Boston, MA.,Department of Genetics, Harvard Medical School, Boston, MA
| | - Ibtissem Nabti
- Department of Cell and Developmental Biology, University College London, London, England, UK.,Division of Science, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Petros Marangos
- Department of Cell and Developmental Biology, University College London, London, England, UK.,Department of Biological Applications and Technology, University of Ioannina, Ioannina, Greece.,Department of Biomedical Research, Institute of Molecular Biology and Biotechnology-Foundation for Research and Technology, Ioannina, Greece
| | - John Carroll
- Development and Stem Cell Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia .,Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia.,Department of Cell and Developmental Biology, University College London, London, England, UK
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6
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Li R, Leblanc J, He K, Liu XJ. Spindle function in Xenopus oocytes involves possible nanodomain calcium signaling. Mol Biol Cell 2016; 27:3273-3283. [PMID: 27582389 PMCID: PMC5170860 DOI: 10.1091/mbc.e16-05-0338] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/25/2016] [Indexed: 11/11/2022] Open
Abstract
Injection of dibromo-BAPTA caused immediate collapse of meiotic spindles in frog oocytes. In contrast, EGTA had no effect on the spindle or polar body emission. The disruption of spindle integrity by the fast but not slow calcium chelators suggests that meiotic spindle function in the oocytes involves nanodomain calcium signaling. Intracellular calcium transients are a universal phenomenon at fertilization and are required for egg activation, but the exact role of Ca2+ in second-polar-body emission remains unknown. On the other hand, similar calcium transients have not been demonstrated during oocyte maturation, and yet, manipulating intracellular calcium levels interferes with first-polar-body emission in mice and frogs. To determine the precise role of calcium signaling in polar body formation, we used live-cell imaging coupled with temporally precise intracellular calcium buffering. We found that BAPTA-based calcium chelators cause immediate depolymerization of spindle microtubules in meiosis I and meiosis II. Surprisingly, EGTA at similar or higher intracellular concentrations had no effect on spindle function or polar body emission. Using two calcium probes containing permutated GFP and the calcium sensor calmodulin (Lck-GCaMP3 and GCaMP3), we demonstrated enrichment of the probes at the spindle but failed to detect calcium increase during oocyte maturation at the spindle or elsewhere. Finally, endogenous calmodulin was found to colocalize with spindle microtubules throughout all stages of meiosis. Our results—most important, the different sensitivities of the spindle to BAPTA and EGTA—suggest that meiotic spindle function in frog oocytes requires highly localized, or nanodomain, calcium signaling.
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Affiliation(s)
- Ruizhen Li
- Ottawa Hospital Research Institute, Ottawa Hospital-General Campus, Ottawa, ON K1H 8L6, Canada
| | - Julie Leblanc
- Ottawa Hospital Research Institute, Ottawa Hospital-General Campus, Ottawa, ON K1H 8L6, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
| | - Kevin He
- Ottawa Hospital Research Institute, Ottawa Hospital-General Campus, Ottawa, ON K1H 8L6, Canada
| | - X Johné Liu
- Ottawa Hospital Research Institute, Ottawa Hospital-General Campus, Ottawa, ON K1H 8L6, Canada .,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.,Department of Obstetrics and Gynaecology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
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7
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Nikiforaki D, Vanden Meerschaut F, de Roo C, Lu Y, Ferrer-Buitrago M, de Sutter P, Heindryckx B. Effect of two assisted oocyte activation protocols used to overcome fertilization failure on the activation potential and calcium releasing pattern. Fertil Steril 2016; 105:798-806.e2. [DOI: 10.1016/j.fertnstert.2015.11.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/21/2015] [Accepted: 11/02/2015] [Indexed: 12/22/2022]
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8
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Gonzalez-Garcia JR, Bradley J, Nomikos M, Paul L, Machaty Z, Lai FA, Swann K. The dynamics of MAPK inactivation at fertilization in mouse eggs. J Cell Sci 2014; 127:2749-60. [PMID: 24741069 PMCID: PMC4058113 DOI: 10.1242/jcs.145045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Egg activation at fertilization in mammals is initiated by prolonged Ca(2+) oscillations that trigger the completion of meiosis and formation of pronuclei. A fall in mitogen-activated protein kinase (MAPK) activity is essential for pronuclear formation, but the precise timing and mechanism of decline are unknown. Here, we have measured the dynamics of MAPK pathway inactivation during fertilization of mouse eggs using novel chemiluminescent MAPK activity reporters. This reveals that the MAPK activity decrease begins during the Ca(2+) oscillations, but MAPK does not completely inactivate until after pronuclear formation. The MAPKs present in eggs are Mos, MAP2K1 and MAP2K2 (MEK1 and MEK2, respectively) and MAPK3 and MAPK1 (ERK1 and ERK2, respectively). Notably, the MAPK activity decline at fertilization is not explained by upstream destruction of Mos, because a decrease in the signal from a Mos-luciferase reporter is not associated with egg activation. Furthermore, Mos overexpression does not affect the timing of MAPK inactivation or pronuclear formation. However, the late decrease in MAPK could be rapidly reversed by the protein phosphatase inhibitor, okadaic acid. These data suggest that the completion of meiosis in mouse zygotes is driven by an increased phosphatase activity and not by a decline in Mos levels or MEK activity.
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Affiliation(s)
- Jose Raul Gonzalez-Garcia
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Josephine Bradley
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK
| | - Michail Nomikos
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Laboni Paul
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK
| | - Zoltan Machaty
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - F Anthony Lai
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Karl Swann
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
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9
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Nikiforaki D, Vanden Meerschaut F, Qian C, De Croo I, Lu Y, Deroo T, Van den Abbeel E, Heindryckx B, De Sutter P. Oocyte cryopreservation and in vitro culture affect calcium signalling during human fertilization. Hum Reprod 2013; 29:29-40. [DOI: 10.1093/humrep/det404] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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10
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Liu XJ. Polar body emission. Cytoskeleton (Hoboken) 2012; 69:670-85. [PMID: 22730245 DOI: 10.1002/cm.21041] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/15/2012] [Accepted: 05/21/2012] [Indexed: 12/13/2022]
Abstract
Generation of a haploid female germ cell, the egg, consists of two rounds of asymmetric cell division (meiosis I and meiosis II), yielding two diminutive and nonviable polar bodies and a large haploid egg. Animal eggs are also unique in the lack of centrioles and therefore form meiotic spindles without the pre-existence of the two dominant microtubule organizing centers (centrosomes) found in mitosis. Meiotic spindle assembly is further complicated by the unique requirement of sister chromatid mono-oriented in meiosis I. Nonetheless, the eggs appear to adopt many of the same proteins and mechanisms described in mitosis, with necessary modifications to accommodate their special needs. Unraveling these special modifications will not only help understanding animal reproduction, but should also enhance our understanding of cell division in general.
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Affiliation(s)
- X Johné Liu
- Chronic Disease Program, Ottawa Hospital Research Institute, Ottawa Hospital Civic Campus, 1053 Carling Avenue, Ottawa, K1Y 4E9, Canada.
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11
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Ca2+ signaling during mammalian fertilization: requirements, players, and adaptations. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a006767. [PMID: 21441584 DOI: 10.1101/cshperspect.a006767] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Changes in the intracellular concentration of calcium ([Ca(2+)](i)) represent a vital signaling mechanism enabling communication among cells and between cells and the environment. The initiation of embryo development depends on a [Ca(2+)](i) increase(s) in the egg, which is generally induced during fertilization. The [Ca(2+)](i) increase signals egg activation, which is the first stage in embryo development, and that consist of biochemical and structural changes that transform eggs into zygotes. The spatiotemporal patterns of [Ca(2+)](i) at fertilization show variability, most likely reflecting adaptations to fertilizing conditions and to the duration of embryonic cell cycles. In mammals, the focus of this review, the fertilization [Ca(2+)](i) signal displays unique properties in that it is initiated after gamete fusion by release of a sperm-derived factor and by periodic and extended [Ca(2+)](i) responses. Here, we will discuss the events of egg activation regulated by increases in [Ca(2+)](i), the possible downstream targets that effect these egg activation events, and the property and identity of molecules both in sperm and eggs that underpin the initiation and persistence of the [Ca(2+)](i) responses in these species.
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12
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Yu Y, Dumollard R, Rossbach A, Lai FA, Swann K. Redistribution of mitochondria leads to bursts of ATP production during spontaneous mouse oocyte maturation. J Cell Physiol 2010; 224:672-80. [PMID: 20578238 PMCID: PMC3149123 DOI: 10.1002/jcp.22171] [Citation(s) in RCA: 175] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
During mammalian oocyte maturation there are marked changes in the distribution of mitochondria that supply the majority of the cellular ATP. Such redistribution of mitochondria is critical for oocyte quality, as oocytes with a poor developmental potential display aberrant mitochondrial distribution and lower ATP levels. Here we have investigated the dynamics of mitochondrial ATP production throughout spontaneous mouse oocyte maturation, using live measurements of cytosolic and mitochondrial ATP levels. We have observed three distinct increases in cytosolic ATP levels temporally associated with discrete events of oocyte maturation. These changes in cytosolic ATP levels are mirrored by changes in mitochondrial ATP levels, suggesting that mitochondrial ATP production is stimulated during oocyte maturation. Strikingly, these changes in ATP levels correlate with the distribution of mitochondria undergoing translocation to the peri-nuclear region and aggregation into clusters. Mitochondrial clustering during oocyte maturation was concomitant with the formation of long cortical microfilaments and could be disrupted by cytochalasin B treatment. Furthermore, the ATP production bursts observed during oocyte maturation were also inhibited by cytochalasin B suggesting that mitochondrial ATP production is stimulated during oocyte maturation by microfilament-driven, sub-cellular targeting of mitochondria. J. Cell. Physiol. 224: 672–680, 2010. © 2010 Wiley-Liss, Inc.
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Affiliation(s)
- Yuansong Yu
- Department of Obstetrics and Gynaecology, School of Medicine, Cardiff University, Heath Park, Cardiff, UK.
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13
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Sterthaus O, Skoczylas E, De Geyter C, Bürki K, Ledermann B. Evaluation of in vitro cultured rat oocytes, from different strains, by spindle morphology and maturation-promoting-factor activity combined with nuclear-transfer experiments. CLONING AND STEM CELLS 2009; 11:463-72. [PMID: 19751114 DOI: 10.1089/clo.2009.0014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Although successful nuclear transfer (NT) has been reported in the rat 6 years ago, somatic cell nuclear transfer (SCNT) in the rat could not be repeated. Our experiments with rat SCNT reveal the difficulties related to rat cloning. We first focussed on the most appropriate rat strain that could be used as an oocyte donor. Then we describe how rat oocytes can be kept in a nonactivated state during in vitro culture, because the latter undergo spontaneous partial activation through rapid extrusion of the second polar body after isolation from the oviduct. In the SCNT experiments performed with the one-step manipulation technique it was possible to produce rat embryos, which developed in vivo up to the blastocyst stage. In addition, we identified the implantation sites of SCNT rat embryos reconstructed with Sprague-Dawley (SD) oocytes. Furthermore, different rat strains were used as oocyte donors and their oocytes were cultured under different conditions to establish a stable nonactivating oocyte culture system. The ratio of activated to nonactivated oocytes was measured by spindle-stability and maturation promoting factor (MPF) activity. These measurements indicated that a substrain of the SD rat strain, the so-called OFA-SD strain, is the one providing the most stable oocytes, when their oocytes are cultured in the presence of the proteasome inhibitor MG132. However, it was not possible to obtain any implantation sites with reconstructed oocytes derived from the OFA-SD strain transferred to foster mothers. This goal was not achieved, even when the trichostatin A (TSA) treatment was used, which is known to enhance the cloning efficiency of reconstructed mouse, porcine, bovine, and rabbit oocytes both in vitro and in vivo by enhancing the reprogramming efficiency of the recipient nucleus.
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Affiliation(s)
- Oliver Sterthaus
- Institute of Laboratory Animal Science, University of Zurich, Zurich, Switzerland.
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14
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Varghese AC, Peter Nagy Z, Agarwal A. Current trends, biological foundations and future prospects of oocyte and embryo cryopreservation. Reprod Biomed Online 2009. [DOI: 10.1016/s1472-6483(10)60181-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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15
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Current trends, biological foundations and future prospects of oocyte and embryo cryopreservation. Reprod Biomed Online 2009; 19:126-40. [DOI: 10.1016/s1472-6483(10)60056-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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16
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Ajduk A, Ciemerych MA, Nixon V, Swann K, Maleszewski M. Fertilization differently affects the levels of cyclin B1 and M-phase promoting factor activity in maturing and metaphase II mouse oocytes. Reproduction 2008; 136:741-52. [DOI: 10.1530/rep-08-0271] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fertilization affects levels of cyclin B1 and M-phase promoting factor (MPF) activity in maturing and metaphase II mouse oocytes in two distinct ways. In metaphase II oocytes, it leads to a Ca2+-dependent, continuous degradation of cyclin B1 and inactivation of cyclin dependent kinase (CDC2A)–cyclin B1 complex (MPF). In this paper, we show that neither mono- nor polyspermic fertilization of prometaphase I and metaphase I oocytes triggered degradation of cyclin B1. However, polyspermic fertilization of prometaphase I oocytes led to a transient decrease in MPF activity that lasted for 2 h. The inactivation of MPF in polyspermic prometaphase I oocytes did not depend on the fertilization-induced increase in the cytoplasmic concentration of free Ca2+ions, but was caused, at least in part, by dephosphorylation of CDC2A at threonine 161 (Thr161). We found that polyspermic fertilization did not affect glutathione levels in prometaphase I oocytes, and concluded that the decrease in MPF activity and dephosphorylation of CDC2A at Thr161 in polyspermic prometaphase I oocytes were not caused by a change in the redox status of the cell induced by an introduction of excessive amount of sperm protamines. Instead, we propose that inactivation of MPF activity in polyspermic maturing oocytes is caused by a change in nucleo-cytoplasmic ratio that leads to a ‘titration’ of kinases and phosphatases responsible for keeping MPF in an active state. This idea is supported by the finding that oocytes fused with thymocytes rather than spermatozoa also showed a transient decrease in MPF activity.
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17
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Marangos P, Carroll J. Securin regulates entry into M-phase by modulating the stability of cyclin B. Nat Cell Biol 2008; 10:445-51. [PMID: 18364698 DOI: 10.1038/ncb1707] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 01/18/2008] [Indexed: 11/09/2022]
Abstract
Timely progression into mitosis is necessary for normal cell division. This transition is sensitive to the levels of cyclin B, the regulatory subunit of the master mitotic kinase, Cdk1. Cyclin B accumulates during G2 and prophase when its rate of destruction by the anaphase promoting complex (APC) is low. Securin is also an APC substrate and is known for its role in inactivating the cohesin-cleaving enzyme, separase, until the metaphase to anaphase transition. Here we show that securin has an additional role in cell-cycle regulation, that of modulating the timing of entry into M-phase. In mouse oocytes, excess securin caused stabilization of cyclin B and precocious entry into M-phase. Depletion of securin increased cyclin B degradation, resulting in delayed progression into M-phase. This effect required APC activity and was reversed by expression of wild-type securin. These data reveal a role for securin at the G2-M transition and suggest a more general mechanism whereby physiological levels of co-competing APC substrates function in modulating the timing of cell-cycle transitions.
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Affiliation(s)
- Petros Marangos
- Department of Cell and Developmental Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, UK.
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18
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Trichlorfon-induced polyploidy and nondisjunction in mouse oocytes from preantral follicle culture. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2008; 651:114-24. [DOI: 10.1016/j.mrgentox.2007.10.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 10/28/2007] [Indexed: 11/17/2022]
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19
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Tomashov-Matar R, Levi M, Shalgi R. The involvement of Src family kinases (SFKs) in the events leading to resumption of meiosis. Mol Cell Endocrinol 2008; 282:56-62. [PMID: 18166263 DOI: 10.1016/j.mce.2007.11.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Ovulated mammalian eggs remain arrested at the second meiotic metaphase (MII) until fertilization. The fertilizing spermatozoon initiates a sequence of biochemical events, collectively referred to as 'egg activation', which overcome this arrest. The initial observable change within the activated egg is a transient rise in intracellular Ca2+ concentration ([Ca2+]i) followed by cortical granule exocytosis (CGE) and resumption of the second meiotic division (RMII). To date, the mechanism by which the fertilizing spermatozoon activates the signaling pathways upstream to the Ca2+ release and the manner by which the signals downstream to Ca2+ release evoke RMII are not well documented. Protein tyrosine kinases (PTKs) were suggested as possible inducers of some aspects of egg activation. Src family kinases (SFKs) constitute a large family of evolutionarily conserved PTKs that mediate crucial biological functions. At present, the theory that one or more SFKs are necessary and sufficient for Ca2+ regulation at fertilization is documented in eggs of marine invertebrates. The mechanism leading to Ca2+ release during fertilization is less established in mammalian eggs. A controversy still exists as to whether SFKs within the mammalian egg are sufficient and/or necessary for Ca2+ release, or whether they play a role during egg activation via other signaling pathways. This article summarizes the possible signaling pathways involved upstream to Ca2+ release but focuses mainly on the involvement of SFKs downstream to Ca2+ release toward RMII, in invertebrate and vertebrate eggs.
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Affiliation(s)
- R Tomashov-Matar
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
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20
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Kubiak JZ, Chesnel F, Richard-Parpaillon L, Bazile F, Pascal A, Polanski Z, Sikora-Polaczek M, Maciejewska Z, Ciemerych MA. Temporal regulation of the first mitosis in Xenopus and mouse embryos. Mol Cell Endocrinol 2008; 282:63-9. [PMID: 18178304 DOI: 10.1016/j.mce.2007.11.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cell cycle regulation in Eukaryotes is based on common molecular actors and mechanisms. However, the canonical cell cycle is modified in certain cells. Such modifications play a key role in oocyte maturation and embryonic development. They can be achieved either by introduction of new components, pathways, substrates, changed interactions between them, or by elimination of some factors inherited by the cells from previous developmental stages. Here we discuss a particular temporal regulation of the first embryonic M-phase of Xenopus and mouse embryos. These two examples help to understand better the general regulation of M-phase of the cell cycle.
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Affiliation(s)
- Jacek Z Kubiak
- CNRS/University of Rennes 1, Institute of Genetics & Development, UMR 6061, Mitosis & Meiosis Group, Faculty of Medicine, 2 Ave. Prof. Léon Bernard, CS 34317, 35043 Rennes Cedex, France.
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21
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Mitalipov SM, Zhou Q, Byrne JA, Ji WZ, Norgren RB, Wolf DP. Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling. Hum Reprod 2007; 22:2232-42. [PMID: 17562675 DOI: 10.1093/humrep/dem136] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Somatic cell nuclear transfer (SCNT) requires cytoplast-mediated reprogramming of the donor nucleus. Cytoplast factors such as maturation promoting factor are implicated based on their involvement in nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC). Given prior difficulties in SCNT in primates using conventional protocols, we hypothesized that the ability of cytoplasts to induce nuclear remodeling was instrumental in efficient reprogramming. METHODS NEBD and PCC in monkey (Macaca mulatta) SCNT embryos were monitored by lamin A/C immunolabeling. RESULTS Initially, a persistent lamin A/C signal from donor cell nuclei after fusion with cytoplasts was observed indicative of incomplete NEBD following SCNT and predictive of developmental arrest. We then identified fluorochrome-assisted enucleation and donor cell electrofusion as likely candidates for inducing premature cytoplast activation and a consequent lack of nuclear remodeling. Modified protocols designed to prevent premature cytoplast activation during SCNT showed robust NEBD and PCC. Coincidently, over 20% of SCNT embryos reconstructed with fetal fibroblasts progressed to blastocysts. Similar results were obtained with other somatic cells. Reconstructed blastocysts displayed patterns of Oct-4 expression similar to fertilized embryos reflecting successful reprogramming. CONCLUSIONS Our results represent a significant breakthrough in elucidating the role of nuclear remodeling events in reprogramming following SCNT.
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Affiliation(s)
- S M Mitalipov
- Division of Reproductive Sciences, Oregon National Primate Research Center, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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22
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Nanassy L, Lee K, Javor A, Machaty Z. Changes in MPF and MAPK activities in porcine oocytes activated by different methods. Theriogenology 2007; 68:146-52. [PMID: 17524467 DOI: 10.1016/j.theriogenology.2007.04.044] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Accepted: 04/04/2007] [Indexed: 11/29/2022]
Abstract
The effect of different oocyte activation methods on the dynamics of M-phase promoting factor (MPF) and mitogen-activated protein kinase (MAPK) activity in porcine oocytes were examined. Three activativation methods were tested: (1) electroporation (EP); (2) electroporation combined with butyrolactone I (BL), an inhibitor of cdc2 and cdk2 kinases; (3) electroporation followed by a treatment with cycloheximide (CHX), a protein synthesis blocker. The activity of cdc2 in MII oocytes was 0.067+/-0.011pmol/oocyte/min (mean+/-S.E.M.), which by 1h decreased in every treatment group (P<0.05) and stayed at low levels until 6h post-activation, approximately the time of pronuclear formation. The initial MAPK activity (0.123+/-0.017pmol/oocyte/min) also decreased 1h after each type of activation treatment (P<0.005). However, in the electroporation only group, activity reached its lowest level at 3h; thereafter, it started to recover and at later time points, MAPK activity did not differ from that in non-treated oocytes (P>0.1). In contrast, oocytes where electroporation was followed by protein kinase or protein synthesis inhibition had low MAPK activity by the time pronuclei were to be formed. Pronuclear formation in these groups (86.3+/-3.3% for EP+BL and 87.6+/-3.7% for EP+CHX) was higher compared to that found in the EP-only oocytes (69.4+/-3.3%; P<0.05). These findings demonstrated that electroporation alone efficiently triggered the inactivation of MPF but not that of MAPK. In order to achieve low MAPK activity to allow high frequency of pronuclear formation, electroporation should be followed by a treatment that inhibits protein synthesis or specific protein kinases. The combined activation methods provided stimuli that efficiently induced both MPF and MAPK inactivation and triggered pronuclear formation with high frequencies.
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Affiliation(s)
- L Nanassy
- Department of Animal Breeding Science, Center of Agricultural Sciences, University of Debrecen, Böszörményi Street 138, Debrecen, Hungary
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23
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Borissenko L, Groll M. 20S proteasome and its inhibitors: crystallographic knowledge for drug development. Chem Rev 2007; 107:687-717. [PMID: 17316053 DOI: 10.1021/cr0502504] [Citation(s) in RCA: 332] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ljudmila Borissenko
- Charité (CCM), Institut für Biochemie, AG Strukturforschung, Monbijoustrasse 2, 10117 Berlin, Germany
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24
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Gardner DK, Sheehan CB, Rienzi L, Katz-Jaffe M, Larman MG. Analysis of oocyte physiology to improve cryopreservation procedures. Theriogenology 2007; 67:64-72. [PMID: 17049589 DOI: 10.1016/j.theriogenology.2006.09.012] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In contrast to the preimplantation mammalian embryo, it has been notoriously difficult to cryopreserve the metaphase II oocyte. The ability to store oocytes successfully at -196 degrees C has numerous practical and financial advantages, together with ethical considerations, and will positively impact animal breeding programs and assisted conception in the human. Differences in membrane permeability and in physiology are two main reasons why successful oocyte cryopreservation has remained elusive. It is proposed, therefore, that rather than relying on technologies already established for the preimplantation embryo, the development of cryopreservation techniques suitable for the mammalian oocyte needs to take into account the idiosyncratic physiology of this cell. Analysis of intracellular calcium, for example, has revealed that exposure to conventional permeating cryoprotectants, such as propanediol, ethylene glycol and DMSO, all independently result in an increase in calcium, which in turn has the potential to initiate oocyte activation, culminating in zona hardening. Quantification of the metabolome and proteome of the oocyte has revealed that whereas slow freezing has a dramatic effect on cell physiology, vitrification appears to have limited effect. This is plausibly achieved by the limited exposure to cryoprotectants. Analysis of meiotic spindle dynamics and embryo development following IVF, also indicate that vitrification is less traumatic than slow freezing, and therefore has the greatest potential for successful oocyte cryopreservation.
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Affiliation(s)
- David K Gardner
- Colorado Center for Reproductive Medicine, Englewood, CO 80113, USA.
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25
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Malcuit C, Fissore RA. Activation of fertilized and nuclear transfer eggs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 591:117-31. [PMID: 17176559 DOI: 10.1007/978-0-387-37754-4_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In all animal species, initiation of embryonic development occurs shortly after the joining together of the gametes from each of the sexes. The first of these steps, referred to as "egg activation", is a series of molecular events that results in the syngamy of the two haploid genomes and the beginning of cellular divisions for the new diploid embryo. For many years it has been known that the incoming sperm drives this process, as an unfertilized egg will remain dormant until it can no longer sustain normal metabolic processes. Until recently, it was also believed that the sperm was the only cell capable of creating a viable embryo and offspring. Recent advances in cell biology have allowed researchers to not only understand the molecular mechanisms of egg activation, but to exploit the use of pharmacological agents to bypass sperm-induced egg activation for the creation of animals by somatic cell nuclear transfer. This chapter will focus on the molecular events of egg activation in mammals as they take place during fertilization, and will discuss how these mechanisms are successfully bypassed in processes such as somatic cell nuclear transfer.
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Affiliation(s)
- Christopher Malcuit
- Department of Veterinary and Animal Sciences, Paige Laboratory, University of Massachusetts, Amherst, Massachusetts 01003, USA
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26
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Marangos P, Verschuren EW, Chen R, Jackson PK, Carroll J. Prophase I arrest and progression to metaphase I in mouse oocytes are controlled by Emi1-dependent regulation of APC(Cdh1). ACTA ACUST UNITED AC 2006; 176:65-75. [PMID: 17190794 PMCID: PMC2063628 DOI: 10.1083/jcb.200607070] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mammalian oocytes are arrested in prophase of the first meiotic division. Progression into the first meiotic division is driven by an increase in the activity of maturation-promoting factor (MPF). In mouse oocytes, we find that early mitotic inhibitor 1 (Emi1), an inhibitor of the anaphase-promoting complex (APC) that is responsible for cyclin B destruction and inactivation of MPF, is present at prophase I and undergoes Skp1–Cul1–F-box/βTrCP-mediated destruction immediately after germinal vesicle breakdown (GVBD). Exogenous Emi1 or the inhibition of Emi1 destruction in prophase-arrested oocytes leads to a stabilization of cyclin B1–GFP that is sufficient to trigger GVBD. In contrast, the depletion of Emi1 using morpholino oligonucleotides increases cyclin B1–GFP destruction, resulting in an attenuation of MPF activation and a delay of entry into the first meiotic division. Finally, we show that Emi1-dependent effects on meiosis I require the presence of Cdh1. These observations reveal a novel mechanism for the control of entry into the first meiotic division: an Emi1-dependent inhibition of APCCdh1.
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Affiliation(s)
- Petros Marangos
- Department of Physiology, University College London, London WC1E 6BT, England, UK.
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27
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Larman MG, Sheehan CB, Gardner DK. Calcium-free vitrification reduces cryoprotectant-induced zona pellucida hardening and increases fertilization rates in mouse oocytes. Reproduction 2006; 131:53-61. [PMID: 16388009 DOI: 10.1530/rep.1.00878] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Despite the success of embryo cyropreservation, routine oocyte freezing has proved elusive with only around 200 children born since the first reported birth in 1986. The reason for the poor efficiency is unclear, but evidence of zona pellucida hardening following oocyte freezing indicates that current protocols affect oocyte physiology. Here we report that two cryoprotectants commonly used in vitrification procedures, dimethyl sulfoxide (DMSO) and ethylene glycol, cause a large transient increase in intracellular calcium concentration in mouse metaphase II (MII) oocytes comparable to the initial increase triggered at fertilization. Removal of extracellular calcium from the medium failed to affect the response exacted by DMSO challenge, but significantly reduced the ethylene glycol-induced calcium increase. These results suggest that the source of the DMSO-induced calcium increase is solely from the internal calcium pool, as opposed to ethylene glycol that causes an influx of calcium across the plasma membrane from the external medium. By carrying out vitrification in calcium-free media, it was found that zona hardening is significantly reduced and subsequent fertilization and development to the two-cell stage significantly increased. Furthermore, such calcium-free treatment appears not to affect the embryo adversely, as shown by development rates to the blastocyst stage and cell number/allocation. Since zona hardening is one of the early activation events normally triggered by the sperm-induced calcium increases observed at fertilization, it is possible that other processes are negatively affected by the calcium rise caused by cryoprotectants used during oocyte freezing, which might explain the current poor efficiency of this technique.
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Affiliation(s)
- Mark G Larman
- Colorado Center for Reproductive Medicine, 799 East Hampden Avenue, Suite 520, Englewood, 80113, USA
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28
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Abstract
Fertilization in all species studied to date induces an increase in the intracellular concentration of free calcium ions ([Ca2+]i) within the egg. In mammals, this [Ca2+]i signal is delivered in the form of long-lasting [Ca2+]i oscillations that begin shortly after fusion of the gametes and persist beyond the time of completion of meiosis. While not fully elucidated, recent evidence supports the notion that the sperm delivers into the ooplasm a trigger of oscillations, the so-called sperm factor (SF). The recent discovery that mammalian sperm harbor a specific phospholipase C (PLC), PLCzeta has consolidated this view. The fertilizing sperm, and presumably PLCzeta promote Ca2+ release in eggs via the production of inositol 1,4,5-trisphosphate (IP3), which binds and gates its receptor, the type-1 IP3 receptor, located on the endoplasmic reticulum, the Ca2+ store of the cell. Repetitive Ca2+ release in this manner results in a positive cumulative effect on downstream signaling molecules that are responsible for the completion of all the events comprising egg activation. This review will discuss recent advances in our understanding of how [Ca2+]i oscillations are initiated and regulated in mammals, highlight areas of discrepancies, and emphasize the need to better characterize the downstream molecular cascades that are dependent on [Ca2+]i oscillations and that may impact embryo development.
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Affiliation(s)
- Christopher Malcuit
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
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29
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Abstract
Mammalian eggs arrest at metaphase of the second meiotic division (MetII). Sperm break this arrest by inducing a series of Ca2+spikes that last for several hours. During this time cell cycle resumption is induced, sister chromatids undergo anaphase and the second polar body is extruded. This is followed by decondensation of the chromatin and the formation of pronuclei. Ca2+spiking is both the necessary and solely sufficient sperm signal to induce full egg activation. How MetII arrest is established, how the Ca2+spiking is induced and how the signal is transduced into cell cycle resumption are the topics of this review. Although the roles of most components of the signal transduction pathway remain to be fully investigated, here I present a model in which a sperm-specific phospholipase C (PLCζ) generates Ca2+spikes to activate calmodulin-dependent protein kinase II and so switch on the Anaphase-Promoting Complex/Cyclosome (APC/C). APC/C activation leads to securin and cyclin B1 degradation and in so doing allows sister chromatids to be segregated and to decondense.
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Affiliation(s)
- Keith T Jones
- Institute for Cell and Molecular Biosciences, The Medical School, Framlington Place, University of Newcastle, Newcastle, NE2 4HH, UK.
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30
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FitzHarris G, Larman M, Richards C, Carroll J. An increase in [Ca2+]i is sufficient but not necessary for driving mitosis in early mouse embryos. J Cell Sci 2005; 118:4563-75. [PMID: 16179613 DOI: 10.1242/jcs.02586] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An increase in intracellular Ca2+ concentration ([Ca2+]i) has been shown to drive sea-urchin embryos and some fibroblasts through nuclear-envelope breakdown (NEBD) and the metaphase-to-anaphase transition. Mitotic Ca2+ transients can be pan-cellular global events or localized to the perinuclear region. It is not known whether Ca2+ is a universal regulator of mitosis or whether its role is confined to specific cell types. To test the hypothesis that Ca2+ is a universal regulator of mitosis, we have investigated the role of Ca2+ in mitosis in one-cell mouse embryos. Fertilized embryos generate Ca2+ transients during the first mitotic division. Imposing a Ca2+ transient by photorelease of inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] resulted in acceleration of mitosis entry, suggesting that a [Ca2+]i increase is capable of triggering mitosis. Mitotic Ca2+ transients were inhibited using three independent approaches: injection of intracellular Ca2+ buffers; downregulation of Ins(1,4,5)P3 receptors; and removal of extracellular Ca2+. None of the interventions had any effects on the timing of NEBD or cytokinesis. The possibility that NEBD is driven by localized perinuclear Ca2+ transients was examined using two-photon microscopy but no Ca2+-dependent increases in fluorescence were found to precede NEBD. Finally, the second mitotic division took place in the absence of any detectable [Ca2+]i increase. Thus, although an induced [Ca2+]i increase can accelerate mitosis entry, neither cytosolic nor perinuclear [Ca2+] increases appear to be necessary for progression through mitosis in mouse embryos.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels/metabolism
- Calcium Signaling/physiology
- Chelating Agents/chemistry
- Chelating Agents/metabolism
- Embryo, Mammalian/cytology
- Embryo, Mammalian/physiology
- Female
- Fertilization/physiology
- Fluorescent Dyes/chemistry
- Fluorescent Dyes/metabolism
- Fura-2/chemistry
- Fura-2/metabolism
- Inositol 1,4,5-Trisphosphate/chemistry
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Mice
- Microinjections
- Microscopy, Fluorescence
- Mitosis/physiology
- Receptors, Cytoplasmic and Nuclear/metabolism
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Affiliation(s)
- Greg FitzHarris
- Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK
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