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Stein P, Savy V, Williams AM, Williams CJ. Modulators of calcium signalling at fertilization. Open Biol 2020; 10:200118. [PMID: 32673518 PMCID: PMC7574550 DOI: 10.1098/rsob.200118] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/18/2020] [Indexed: 12/16/2022] Open
Abstract
Calcium (Ca2+) signals initiate egg activation across the animal kingdom and in at least some plants. These signals are crucial for the success of development and, in the case of mammals, health of the offspring. The mechanisms associated with fertilization that trigger these signals and the molecules that regulate their characteristic patterns vary widely. With few exceptions, a major contributor to fertilization-induced elevation in cytoplasmic Ca2+ is release from endoplasmic reticulum stores through the IP3 receptor. In some cases, Ca2+ influx from the extracellular space and/or release from alternative intracellular stores contribute to the rise in cytoplasmic Ca2+. Following the Ca2+ rise, the reuptake of Ca2+ into intracellular stores or efflux of Ca2+ out of the egg drive the return of cytoplasmic Ca2+ back to baseline levels. The molecular mediators of these Ca2+ fluxes in different organisms include Ca2+ release channels, uptake channels, exchangers and pumps. The functions of these mediators are regulated by their particular activating mechanisms but also by alterations in their expression and spatial organization. We discuss here the molecular basis for modulation of Ca2+ signalling at fertilization, highlighting differences across several animal phyla, and we mention key areas where questions remain.
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Affiliation(s)
- Paula Stein
- Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Virginia Savy
- Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Audrey M. Williams
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Carmen J. Williams
- Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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Wang H, Paulson EE, Ma L, Ross PJ, Schultz RM. Paternal genome rescues mouse preimplantation embryo development in the absence of maternally-recruited EZH2 activity. Epigenetics 2019; 14:94-108. [PMID: 30661456 DOI: 10.1080/15592294.2019.1570771] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Enhancer of zeste homolog 2 (EZH2), a component of the PRC2 complex, trimethylates H3K27, a transcriptionally repressive histone mark. EZH2 is encoded by a dormant maternal mRNA and inhibiting the maturation-associated increase in EZH2 activity using either a combined siRNA/morpholino approach or a small molecule inhibitor (GSK343) inhibits development of diploidized parthenotes to the blastocyst stage but not inseminated eggs, with longer GSK343 treatments leading to progressively greater inhibition of development. GSK343 treatment also results in a decrease in H3K27me3 and a decrease in global transcription in 2-cell parthenotes but not 2-cell embryos derived from inseminated eggs. RNA-sequencing revealed the relative abundance of ~100 zygotically-expressed transcripts is decreased by GSK treatment in parthenotes, but not in embryos, with many of the affected transcripts encoding proteins involved in transcription. A previous study found that parthenotes deficient in maternal Ezh2 readily develop to the blastocyst stage. To reconcile these differences we propose that the H3K27me3 state present in the zygote needs to be faithfully propagated following DNA replication in at least one pronucleus, otherwise development is compromised.
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Affiliation(s)
- Huili Wang
- a Institute of Animal Science , Jiangsu Academy of Agricultural Sciences , Nanjing , China.,b Department of Anatomy, Physiology, and Cell Biology , University of California Davis , Davis , CA , USA.,c Department of Animal Science , University of California Davis , Davis , CA , USA
| | - Erika E Paulson
- c Department of Animal Science , University of California Davis , Davis , CA , USA
| | - Libing Ma
- d School of Life Science and Technology , Inner Mongolia University of Science & Technology , Baotou , China
| | - Pablo J Ross
- c Department of Animal Science , University of California Davis , Davis , CA , USA
| | - Richard M Schultz
- b Department of Anatomy, Physiology, and Cell Biology , University of California Davis , Davis , CA , USA.,e Department of Biology , University of Pennsylvania , Philadelphia , PA , USA
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Kasowitz SD, Ma J, Anderson SJ, Leu NA, Xu Y, Gregory BD, Schultz RM, Wang PJ. Nuclear m6A reader YTHDC1 regulates alternative polyadenylation and splicing during mouse oocyte development. PLoS Genet 2018; 14:e1007412. [PMID: 29799838 PMCID: PMC5991768 DOI: 10.1371/journal.pgen.1007412] [Citation(s) in RCA: 339] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 06/07/2018] [Accepted: 05/14/2018] [Indexed: 12/31/2022] Open
Abstract
The N6-methyladenosine (m6A) modification is the most prevalent internal RNA modification in eukaryotes. The majority of m6A sites are found in the last exon and 3' UTRs. Here we show that the nuclear m6A reader YTHDC1 is essential for embryo viability and germline development in mouse. Specifically, YTHDC1 is required for spermatogonial development in males and for oocyte growth and maturation in females; Ythdc1-deficient oocytes are blocked at the primary follicle stage. Strikingly, loss of YTHDC1 leads to extensive alternative polyadenylation in oocytes, altering 3' UTR length. Furthermore, YTHDC1 deficiency causes massive alternative splicing defects in oocytes. The majority of splicing defects in mutant oocytes are rescued by introducing wild-type, but not m6A-binding-deficient, YTHDC1. YTHDC1 is associated with the pre-mRNA 3' end processing factors CPSF6, SRSF3, and SRSF7. Thus, YTHDC1 plays a critical role in processing of pre-mRNA transcripts in the oocyte nucleus and may have similar non-redundant roles throughout fetal development.
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Affiliation(s)
- Seth D. Kasowitz
- Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, United States of America
| | - Jun Ma
- Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, United States of America
- Department of Biology, University of Pennsylvania, Philadelphia, United States of America
| | - Stephen J. Anderson
- Department of Biology, University of Pennsylvania, Philadelphia, United States of America
| | - N. Adrian Leu
- Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, United States of America
| | - Yang Xu
- Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, United States of America
| | - Brian D. Gregory
- Department of Biology, University of Pennsylvania, Philadelphia, United States of America
| | - Richard M. Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, United States of America
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, United States of America
| | - P. Jeremy Wang
- Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, United States of America
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Jimenez R, Melo EO, Davydenko O, Ma J, Mainigi M, Franke V, Schultz RM. Maternal SIN3A regulates reprogramming of gene expression during mouse preimplantation development. Biol Reprod 2015; 93:89. [PMID: 26353893 DOI: 10.1095/biolreprod.115.133504] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 08/27/2015] [Indexed: 12/20/2022] Open
Abstract
The oocyte-to-embryo transition entails genome activation and a dramatic reprogramming of gene expression that is required for continued development. Superimposed on genome activation and reprogramming is development of a transcriptionally repressive state at the level of chromatin structure. Inducing global histone hyperacetylation relieves this repression and histone deacetylases 1 and 2 (HDAC1 and HDAC2) are involved in establishing the repressive state. Because SIN3A is an HDAC1/2-containing complex, we investigated whether it is involved in reprogramming gene expression during the course of genome activation. We find that Sin3a mRNA is recruited during maturation and that inhibiting its recruitment not only inhibits development beyond the 2-cell stage but also compromises the fidelity of reprogramming gene expression. The SIN3A that is synthesized during oocyte maturation reaches a maximum level in the mid-1-cell embryo and is essentially absent by the mid-2-cell stage. Overexpressing SIN3A in 1-cell embryos has no obvious effect on pre- and postimplantation development. These results provide a mechanism by which reprogramming can occur using a maternally inherited transcription machinery, namely, recruitment of mRNAs encoding transcription factors and chromatin remodelers, such as SIN3A.
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Affiliation(s)
- Richard Jimenez
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Eduardo O Melo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Olga Davydenko
- Department of Obstetrics and Gynecology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Monica Mainigi
- Department of Obstetrics and Gynecology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Vedran Franke
- Bioinformatics Group, Division of Biology, Faculty of Science, Zagreb University, Zagreb, Croatia
| | - Richard M Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
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Ma J, Fukuda Y, Schultz RM. Mobilization of Dormant Cnot7 mRNA Promotes Deadenylation of Maternal Transcripts During Mouse Oocyte Maturation. Biol Reprod 2015; 93:48. [PMID: 26134871 DOI: 10.1095/biolreprod.115.130344] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/10/2015] [Indexed: 11/01/2022] Open
Abstract
Maternal mRNAs in oocytes are remarkably stable. In mouse, oocyte maturation triggers a transition from mRNA stability to instability. This transition is a critical event in the oocyte-to-embryo transition in which a differentiated oocyte loses its identity as it is transformed into totipotent blastomeres. We previously demonstrated that phosphorylation of MSY2, an RNA-binding protein, and mobilization of mRNAs encoding the DCP1A-DCP2 decapping complex contribute to maternal mRNA destruction during meiotic maturation. We report here that Cnot7, Cnot6l, and Pan2, key components of deadenylation machinery, are also dormant maternal mRNAs that are recruited during oocyte maturation. Inhibiting the maturation-associated increase in CNOT7 (or CNOT6L) using a small interference RNA approach inhibits mRNA deadenylation, whereas inhibiting the increase in PAN2 has little effect. Reciprocally, expressing CNOT7 (or CNOT6L) in oocytes prevented from resuming meiosis initiates deadenylation of mRNAs. These effects on deadenylation are also observed when the total amount of poly (A) is quantified. Last, inhibiting the increase in CNOT7 protein results in an ~70% decrease in transcription in 2-cell embryos.
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Affiliation(s)
- Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yusuke Fukuda
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Richard M Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania
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Stein P, Rozhkov NV, Li F, Cárdenas FL, Davydenk O, Vandivier LE, Gregory BD, Hannon GJ, Schultz RM. Essential Role for endogenous siRNAs during meiosis in mouse oocytes. PLoS Genet 2015; 11:e1005013. [PMID: 25695507 PMCID: PMC4335007 DOI: 10.1371/journal.pgen.1005013] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 01/20/2015] [Indexed: 11/21/2022] Open
Abstract
The RNase III enzyme DICER generates both microRNAs (miRNAs) and endogenous short interfering RNAs (endo-siRNAs). Both small RNA species silence gene expression post-transcriptionally in association with the ARGONAUTE (AGO) family of proteins. In mammals, there are four AGO proteins (AGO1-4), of which only AGO2 possesses endonucleolytic activity. siRNAs trigger endonucleolytic cleavage of target mRNAs, mediated by AGO2, whereas miRNAs cause translational repression and mRNA decay through association with any of the four AGO proteins. Dicer deletion in mouse oocytes leads to female infertility due to defects during meiosis I. Because mouse oocytes express both miRNAs and endo-siRNAs, this phenotype could be due to the absence of either class of small RNA, or both. However, we and others demonstrated that miRNA function is suppressed in mouse oocytes, which suggested that endo-siRNAs, not miRNAs, are essential for female meiosis. To determine if this was the case we generated mice that express a catalytically inactive knock-in allele of Ago2 (Ago2ADH) exclusively in oocytes and thereby disrupted the function of siRNAs. Oogenesis and hormonal response are normal in Ago2ADH oocytes, but meiotic maturation is impaired, with severe defects in spindle formation and chromosome alignment that lead to meiotic catastrophe. The transcriptome of these oocytes is widely perturbed and shows a highly significant correlation with the transcriptome of Dicer null and Ago2 null oocytes. Expression of the mouse transcript (MT), the most abundant transposable element in mouse oocytes, is increased. This study reveals that endo-siRNAs are essential during meiosis I in mouse females, demonstrating a role for endo-siRNAs in mammals.
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Affiliation(s)
- Paula Stein
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Nikolay V. Rozhkov
- Cold Spring Harbor Laboratory, Watson School of Biological Sciences and Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States of America
| | - Fan Li
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Fabián L. Cárdenas
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Olga Davydenk
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Lee E. Vandivier
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Brian D. Gregory
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Gregory J. Hannon
- Cold Spring Harbor Laboratory, Watson School of Biological Sciences and Howard Hughes Medical Institute, Cold Spring Harbor, New York, United States of America
- CRUK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, United Kingdom
| | - Richard M. Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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Filges I, Manokhina I, Peñaherrera MS, McFadden DE, Louie K, Nosova E, Friedman JM, Robinson WP. Recurrent triploidy due to a failure to complete maternal meiosis II: whole-exome sequencing reveals candidate variants. Mol Hum Reprod 2014; 21:339-46. [PMID: 25504873 DOI: 10.1093/molehr/gau112] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 12/05/2014] [Indexed: 01/16/2023] Open
Abstract
Triploidy is a relatively common cause of miscarriage; however, recurrent triploidy has rarely been reported. A healthy 34-year-old woman was ascertained because of 18 consecutive miscarriages with triploidy found in all 5 karyotyped losses. Molecular results in a sixth loss were also consistent with triploidy. Genotyping of markers near the centromere on multiple chromosomes suggested that all six triploid conceptuses occurred as a result of failure to complete meiosis II (MII). The proband's mother had also experienced recurrent miscarriage, with a total of 18 miscarriages. Based on the hypothesis that an inherited autosomal-dominant maternal predisposition would explain the phenotype, whole-exome sequencing of the proband and her parents was undertaken to identify potential candidate variants. After filtering for quality and rarity, potentially damaging variants shared between the proband and her mother were identified in 47 genes. Variants in genes coding for proteins implicated in oocyte maturation, oocyte activation or polar body extrusion were then prioritized. Eight of the most promising candidate variants were confirmed by Sanger sequencing. These included a novel change in the PLCD4 gene, and a rare variant in the OSBPL5 gene, which have been implicated in oocyte activation upon fertilization and completion of MII. Several variants in genes coding proteins playing a role in oocyte maturation and early embryonic development were also identified. The genes identified may be candidates for the study in other women experiencing recurrent triploidy or recurrent IVF failure.
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Affiliation(s)
- I Filges
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4 Medical Genetics, Department of Biomedicine, University Hospital Basel, Basel 4031, Switzerland
| | - I Manokhina
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4
| | - M S Peñaherrera
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4
| | - D E McFadden
- Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4 Department of Pathology, University of British Columbia, Vancouver, BC, Canada V6T 2B5
| | - K Louie
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4
| | - E Nosova
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC, Canada V5Z 4H4 Centre for Applied Neurogenetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - J M Friedman
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4
| | - W P Robinson
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada V6T 1Z3 Child and Family Research Institute, Vancouver, BC, Canada V5Z 4H4
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Liu W, Stein P, Cheng X, Yang W, Shao NY, Morrisey EE, Schultz RM, You J. BRD4 regulates Nanog expression in mouse embryonic stem cells and preimplantation embryos. Cell Death Differ 2014; 21:1950-60. [PMID: 25146928 DOI: 10.1038/cdd.2014.124] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/10/2014] [Accepted: 07/13/2014] [Indexed: 01/06/2023] Open
Abstract
Bromodomain-containing protein 4 (BRD4) is an important epigenetic reader implicated in the pathogenesis of a number of different cancers and other diseases. Brd4-null mouse embryos die shortly after implantation and are compromised in their ability to maintain the inner cell mass, which gives rise to embryonic stem cells (ESCs). Here we report that BRD4 regulates expression of the pluripotency factor Nanog in mouse ESCs and preimplantation embryos, as well as in human ESCs and embryonic cancer stem cells. Inhibition of BRD4 function using a chemical inhibitor, small interfering RNAs, or a dominant-negative approach suppresses Nanog expression, and abolishes the self-renewal ability of ESCs. We also find that BRD4 associates with BRG1 (brahma-related gene 1, aka Smarca4 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a, member 4)), a key regulator of ESC self-renewal and pluripotency, in the Nanog regulatory regions to regulate Nanog expression. Our study identifies Nanog as a novel BRD4 target gene, providing new insights for the biological function of BRD4 in stem cells and mouse embryos. Knowledge gained from these non-cancerous systems will facilitate future investigations of how Brd4 dysfunction leads to cancers.
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Affiliation(s)
- W Liu
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - P Stein
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - X Cheng
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - W Yang
- Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - N-Y Shao
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - E E Morrisey
- Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - R M Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - J You
- Department of Microbiology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
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Histone deacetylase 2 (HDAC2) regulates chromosome segregation and kinetochore function via H4K16 deacetylation during oocyte maturation in mouse. PLoS Genet 2013; 9:e1003377. [PMID: 23516383 PMCID: PMC3597510 DOI: 10.1371/journal.pgen.1003377] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 01/29/2013] [Indexed: 01/26/2023] Open
Abstract
Changes in histone acetylation occur during oocyte development and maturation, but the role of specific histone deacetylases in these processes is poorly defined. We report here that mice harboring Hdac1−/+/Hdac2−/− or Hdac2−/− oocytes are infertile or sub-fertile, respectively. Depleting maternal HDAC2 results in hyperacetylation of H4K16 as determined by immunocytochemistry—normal deacetylation of other lysine residues of histone H3 or H4 is observed—and defective chromosome condensation and segregation during oocyte maturation occurs in a sub-population of oocytes. The resulting increased incidence of aneuploidy likely accounts for the observed sub-fertility of mice harboring Hdac2−/− oocytes. The infertility of mice harboring Hdac1−/+/Hdac2−/−oocytes is attributed to failure of those few eggs that properly mature to metaphase II to initiate DNA replication following fertilization. The increased amount of acetylated H4K16 likely impairs kinetochore function in oocytes lacking HDAC2 because kinetochores in mutant oocytes are less able to form cold-stable microtubule attachments and less CENP-A is located at the centromere. These results implicate HDAC2 as the major HDAC that regulates global histone acetylation during oocyte development and, furthermore, suggest HDAC2 is largely responsible for the deacetylation of H4K16 during maturation. In addition, the results provide additional support that histone deacetylation that occurs during oocyte maturation is critical for proper chromosome segregation. Oocyte development is becoming of increasing interest not only in the broad research community but also within the general public due, in part, to the ever increasing demand for and use of assisted reproductive technologies (ART) to treat human infertility, and because the oocyte-to-embryo transition encompasses a natural reprogramming of gene expression, a process central to forming iPS cells. Dramatic changes in chromatin structure and gene expression occur during oocyte development, but the role of such changes in generating oocytes that are capable of maturing, being fertilized, and giving rise to offspring is very poorly understood. Histone deacetylases (HDACs) are critically involved in modulating chromatin structure. Here, we describe the effect of specifically deleting the gene encoding Hdac2 in mouse oocytes and find the fertility of female mice harboring such oocytes is compromised. Although such mutant oocytes can grow they fail to mature properly to become an egg. The primary defect is that histone H4 acetylated on lysine 16 fails to become deacetylated as the oocyte matures to become an egg, with the consequence that the ability of chromosomes to interact with spindle microtubules is compromised, which in turn leads to improper chromosome segregation.
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Ma J, Flemr M, Strnad H, Svoboda P, Schultz RM. Maternally recruited DCP1A and DCP2 contribute to messenger RNA degradation during oocyte maturation and genome activation in mouse. Biol Reprod 2013; 88:11. [PMID: 23136299 DOI: 10.1095/biolreprod.112.105312] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The oocyte-to-zygote transition entails transforming a highly differentiated oocyte into totipotent blastomeres and represents one of the earliest obstacles that must be successfully hurdled for continued development. Degradation of maternal mRNAs, which likely lies at the heart of this transition, is characterized by a transition from mRNA stability to instability during oocyte maturation. Although phosphorylation of the oocyte-specific RNA-binding protein MSY2 during maturation is implicated in making maternal mRNAs more susceptible to degradation, mechanisms underlying mRNA degradation during oocyte maturation remain poorly understood. We report that DCP1A and DCP2, proteins responsible for decapping mRNA, are encoded by maternal mRNAs recruited for translation during maturation via cytoplasmic polyadenylation elements located in their 3' untranslated regions. Both DCP1A and DCP2 are phosphorylated during maturation, with CDC2A being the kinase likely responsible for both, although MAPK may be involved in DCP1A phosphorylation. Inhibiting accumulation of DCP1A and DCP2 by RNA interference or morpholinos decreases not only degradation of mRNAs during meiotic maturation but also transcription of the zygotic genome. The results indicate that maternally recruited DCP1A and DCP2 are critical players in the transition from mRNA stability to instability during meiotic maturation and that proper maternal mRNA degradation must be successful to execute the oocyte-to-zygote transition.
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Affiliation(s)
- Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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11
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Xia M, He H, Wang Y, Liu M, Zhou T, Lin M, Zhou Z, Huo R, Zhou Q, Sha J. PCBP1 is required for maintenance of the transcriptionally silent state in fully grown mouse oocytes. Cell Cycle 2012; 11:2833-42. [PMID: 22801551 DOI: 10.4161/cc.21169] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Global transcriptional silencing in fully grown oocytes is a critical event during mammalian oogenesis. However, how this event is regulated remains elusive. Here, we provide evidence that poly(rC)-binding protein 1 (PCBP1), a protein found by us previously to be present in metaphase II (MII) mouse oocytes, participates in maintenance of the transcriptionally silent state in fully grown mouse oocytes. Knocking down Pcbp1 by microinjection of its specific siRNAs into fully grown germinal vesicle (GV) oocytes resulted in remarkable changes in their transcriptional state, including the disequilibrium between the number of oocytes with an NSN (non-surrounded nucleolus) and those with a SN (surrounded nucleolus), and obvious transcriptional reactiviation in oocytes with a SN configuration as evidenced by BrUTP incorporation assay and immunofluorescent labeling of phosphorylated RNA polymerase II CTD and trimethylated H3 lysine 4, markers for active transcription. Furthermore, in a comprehensive microarray analysis of the preovulatory oocyte transcriptome, an incredible number of nearly 4,000 transcripts were upregulated in the Pcbp1 knockdown groups. These data indicate that lack of the function of PCBP1 disrupts the quiescent status of transcription in the fully grown oocytes, and hence supporting a role of this protein in the regulation of global transcriptional silcencing in fully grown mouse oocytes.
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Affiliation(s)
- Meng Xia
- State Key Laboratory of Reproductive Medicine, Department of Histology and Embryology, Nanjing Medical University, Nanjing, China
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Boccaccio A, Frassanito MC, Lamberti L, Brunelli R, Maulucci G, Monaci M, Papi M, Pappalettere C, Parasassi T, Sylla L, Ursini F, De Spirito M. Nanoscale characterization of the biomechanical hardening of bovine zona pellucida. J R Soc Interface 2012; 9:2871-82. [PMID: 22675161 DOI: 10.1098/rsif.2012.0269] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The zona pellucida (ZP) is an extracellular membrane surrounding mammalian oocytes. The so-called zona hardening plays a key role in fertilization process, as it blocks polyspermy, which may also be caused by an increase in the mechanical stiffness of the ZP membrane. However, structural reorganization mechanisms leading to ZP's biomechanical hardening are not fully understood yet. Furthermore, a correct estimate of the elastic properties of the ZP is still lacking. Therefore, the aim of the present study was to investigate the biomechanical behaviour of ZP membranes extracted from mature and fertilized bovine oocytes to better understand the mechanisms involved in the structural reorganization of the ZP that may lead to the biomechanical hardening of the ZP. For that purpose, a hybrid procedure is developed by combining atomic force microscopy nanoindentation measurements, nonlinear finite element analysis and nonlinear optimization. The proposed approach allows us to determine the biomechanical properties of the ZP more realistically than the classical analysis based on Hertz's contact theory, as it accounts for the nonlinearity of finite indentation process, hyperelastic behaviour and material heterogeneity. Experimental results show the presence of significant biomechanical hardening induced by the fertilization process. By comparing various hyperelastic constitutive models, it is found that the Arruda-Boyce eight-chain model best describes the biomechanical response of the ZP. Fertilization leads to an increase in the degree of heterogeneity of membrane elastic properties. The Young modulus changes sharply within a superficial layer whose thickness is related to the characteristic distance between cross-links in the ZP filamentous network. These findings support the hypothesis that biomechanical hardening of bovine ZP is caused by an increase in the number of inter-filaments cross-links whose density should be higher in the ZP inner side.
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Affiliation(s)
- Antonio Boccaccio
- Dipartimento di Ingegneria Meccanica e Gestionale, Politecnico di Bari, , Bari 70126, Italy
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13
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Dey SR, Deb GK, Ha AN, Lee JI, Bang JI, Lee KL, Kong IK. Coculturing denuded oocytes during the in vitro maturation of bovine cumulus oocyte complexes exerts a synergistic effect on embryo development. Theriogenology 2011; 77:1064-77. [PMID: 22153275 DOI: 10.1016/j.theriogenology.2011.10.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 10/03/2011] [Accepted: 10/08/2011] [Indexed: 11/25/2022]
Abstract
The present study examined the effect of coculturing cumulus oocyte complexes (COCs) and denuded oocytes (DOs) during in vitro maturation (IVM) on nuclear and cytoplasmic maturation, zona pellucida (ZP) hardening, the pattern of fertilization and glutathione peroxidase 1 (GPX1) gene expression in the oocyte. Furthermore, the rate of embryonic development and the quality of blastocysts were examined for both COCs and DOs. Three IVM conditions were studied: 1) the coculture of 12 COCs and 60 DOs, 2) COC control with 12 COCs, and 3) DO control with 60 DOs. The IVM was performed in a 120-μl droplet of TCM199-based IVM medium. Following IVM, in vitro fertilization (IVF) and in vitro culture (IVC) were conducted separately for the COCs and DOs (DO coculture) from the IVM coculture group. Coculturing COCs and DOs increased the percentage of oocytes reaching the blastocyst stage and the total number of cells per blastocyst in both the COC coculture (44.4 ± 8.6 vs 26.7 ± 9.7%, P < 0.01, and 137.9 ± 24.9 vs 121.7 ± 21.1, P < 0.05) and the DO coculture (20.5 ± 5.0 vs 11.1 ± 2.5%, P < 0.01, and 121.9 ± 27.5 vs 112.3 ± 33.2, P < 0.05) compared to their respective control groups. The synergistic effects of coculturing were detected as increased nuclear and cytoplasmic maturation, the prevention of ZP hardening, increased monospermic fertilization and increased expression of GPX1 in the oocytes in response to endogenous oocyte-secreted factors. In conclusion, coculturing COCs and DOs may be an effective culture system for both intact COCs and immature DOs.
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Affiliation(s)
- S R Dey
- Division of Applied Life Science (BK21 Program), Graduate School of Gyeongsang, National University, Republic of Korea
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14
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Abstract
Cortical granules are membrane bound organelles located in the cortex of unfertilized oocytes. Following fertilization, cortical granules undergo exocytosis to release their contents into the perivitelline space. This secretory process, which is calcium dependent and SNARE protein-mediated pathway, is known as the cortical reaction. After exocytosis, the released cortical granule proteins are responsible for blocking polyspermy by modifying the oocytes' extracellular matrices, such as the zona pellucida in mammals. Mammalian cortical granules range in size from 0.2 um to 0.6 um in diameter and different from most other regulatory secretory organelles in that they are not renewed once released. These granules are only synthesized in female germ cells and transform an egg upon sperm entry; therefore, this unique cellular structure has inherent interest for our understanding of the biology of fertilization. Cortical granules are long thought to be static and awaiting in the cortex of unfertilized oocytes to be stimulated undergoing exocytosis upon gamete fusion. Not till recently, the dynamic nature of cortical granules is appreciated and understood. The latest studies of mammalian cortical granules document that this organelle is not only biochemically heterogeneous, but also displays complex distribution during oocyte development. Interestingly, some cortical granules undergo exocytosis prior to fertilization; and a number of granule components function beyond the time of fertilization in regulating embryonic cleavage and preimplantation development, demonstrating their functional significance in fertilization as well as early embryonic development. The following review will present studies that investigate the biology of cortical granules and will also discuss new findings that uncover the dynamic aspect of this organelle in mammals.
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Affiliation(s)
- Min Liu
- Department of Life Science and Graduate Institute of Biotechnology, Private Chinese Culture University, Taipei, Republic of China.
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15
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Medvedev S, Pan H, Schultz RM. Absence of MSY2 in mouse oocytes perturbs oocyte growth and maturation, RNA stability, and the transcriptome. Biol Reprod 2011; 85:575-83. [PMID: 21613634 DOI: 10.1095/biolreprod.111.091710] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Messenger RNA is remarkably stable during oocyte growth, thus enabling mRNAs to accumulate during the growth phase and thereby provide mRNAs that support early embryonic development. MSY2, a germ cell-specific RNA-binding protein, is implicated in regulating mRNA stability. MSY2 is essential for development because female Msy2(-/-) mice are infertile. We describe here the characterization of Msy2(-/-) oocytes. Mutant oocytes grow more slowly during the first wave of folliculogenesis, and maturation to and arrest at metaphase II is severely compromised because of aberrant spindle formation and chromosome congression. Consistent with MSY2 conferring mRNA stability is that the amount of poly(A)-containing RNA is reduced by ~25% in mutant oocytes. Stability of an exogenous mRNA injected into mutant oocytes is lower than when compared to their wild-type counterparts, and moreover, expression of wild-type MSY2 in mutant oocytes increases mRNA stability, whereas injection of a mutant form of MSY2 not capable of binding RNA does not. Transcription quiescence that normally occurs during the course of oocyte growth is not observed in mutant oocytes, and the transcriptome of mutant oocytes is markedly perturbed. These results, and those of previous studies, strongly implicate a central role of MSY2 in regulating mRNA stability.
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Affiliation(s)
- Sergey Medvedev
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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16
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Pan H, Schultz RM. Sox2 modulates reprogramming of gene expression in two-cell mouse embryos. Biol Reprod 2011; 85:409-16. [PMID: 21543769 DOI: 10.1095/biolreprod.111.090886] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Sox2 is a key gene that controls transcriptional networks required for pluripotency. The role of Sox2 in the developmental transition of a highly differentiated oocyte to totipotent blastomeres of the early preimplantation embryo, however, is not known. We report that Sox2, which is localized in the nucleus, is first zygotically expressed during the 2-cell stage and that its expression dramatically increases between the morula and blastocyst stages. Injecting a cRNA encoding Sox2 into 1-cell embryos resulted in overexpression of SOX2 by approximately 70% and developmental arrest at the 2-cell stage, whereas injecting cRNAs encoding Pou5f1, Myc (also known as c-Myc), or Klf4 has little effect on the ability of 2-cell embryos to cleave to the 4-cell stage. Global transcription assessed by bromo uridine triphosphate incorporation is reduced by approximately 15%, and transcript profiling revealed that approximately 15% of zygotically expressed genes are dramatically repressed in 2-cell embryos overexpressing SOX2. Furthermore, overexpressing a dominant-negative SOX2 perturbs reprogramming of gene expression in 2-cell embryos, though to a much lesser extent than that observed following overexpression of SOX2, and leads to developmental failure after the 2-cell stage but before the 8-cell stage. Results of these experiments implicate Sox2 as a critical transcriptional regulator in the oocyte-to-embryo transition that entails formation of totipotent blastomeres and indicate that the amount of Sox2 is critical for successful execution of this transition.
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Affiliation(s)
- Hua Pan
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
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17
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N-glycosylation of zona glycoproteins during meiotic maturation is involved in sperm-zona pellucida interactions of porcine oocytes. Theriogenology 2011; 75:1146-52. [DOI: 10.1016/j.theriogenology.2010.11.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 11/22/2010] [Accepted: 11/22/2010] [Indexed: 11/22/2022]
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18
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LAY KM, OSHIRO R, ARASAKI C, ASHIZAWA K, TATEMOTO H. Role of Acidification Elicited by Sialylation and Sulfation of Zona Glycoproteins During Oocyte Maturation in Porcine Sperm-zona Pellucida Interactions. J Reprod Dev 2011; 57:744-51. [DOI: 10.1262/jrd.11-057h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Khin Mar LAY
- Science of Bioresource Production, The United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima 890-0065, Japan
| | - Ryuko OSHIRO
- Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan
| | - Chiemi ARASAKI
- Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan
| | - Koji ASHIZAWA
- Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan
| | - Hideki TATEMOTO
- Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan
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19
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Ikawa M, Inoue N, Benham AM, Okabe M. Fertilization: a sperm's journey to and interaction with the oocyte. J Clin Invest 2010; 120:984-94. [PMID: 20364096 DOI: 10.1172/jci41585] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mammalian fertilization comprises sperm migration through the female reproductive tract, biochemical and morphological changes to sperm, and sperm-egg interaction in the oviduct. Recent gene knockout approaches in mice have revealed that many factors previously considered important for fertilization are largely dispensable, or if they are essential, they have an unexpected function. These results indicate that what has been observed in in vitro fertilization (IVF) differs significantly from what occurs during "physiological" fertilization. This Review focuses on the advantages of studying fertilization using gene-manipulated animals and highlights an emerging molecular mechanism of mammalian fertilization.
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Affiliation(s)
- Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Yamadaoka 3-1, Suita, Osaka, 565-0871, Japan
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20
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Ma J, Flemr M, Stein P, Berninger P, Malik R, Zavolan M, Svoboda P, Schultz RM. MicroRNA activity is suppressed in mouse oocytes. Curr Biol 2010; 20:265-70. [PMID: 20116252 DOI: 10.1016/j.cub.2009.12.042] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 12/02/2009] [Accepted: 12/16/2009] [Indexed: 11/30/2022]
Abstract
MicroRNAs (miRNAs) are small endogenous RNAs that typically imperfectly base pair with 3' untranslated regions (3'UTRs) and mediate translational repression and mRNA degradation. Dicer, which generates small RNAs in the miRNA and RNA interference (RNAi) pathways, is essential for meiotic maturation of mouse oocytes. We found that 3'UTRs of transcripts upregulated in Dicer1(-/-) oocytes are not enriched in miRNA binding sites, implicating a weak impact of miRNAs on the maternal transcriptome. Therefore, we tested the ability of endogenous miRNAs to mediate RNA-like cleavage or translational repression of reporter mRNAs. In contrast to somatic cells, endogenous miRNAs in oocytes poorly repressed translation of mRNA reporters, whereas their RNAi-like activity was much less affected. Reporter mRNA carrying let-7-binding sites failed to localize to P body-like structures in oocytes. Our data suggest that miRNA function is downregulated during oocyte development, an idea supported by normal meiotic maturation of oocytes lacking Dgcr8, which is required for the miRNA but not the RNAi pathway (Suh et al. [1], this issue of Current Biology). Suppressing miRNA function during oocyte growth is likely an early event in reprogramming gene expression during the transition of a differentiated oocyte into pluripotent blastomeres of the embryo.
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Affiliation(s)
- Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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21
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Shuda K, Schindler K, Ma J, Schultz RM, Donovan PJ. Aurora kinase B modulates chromosome alignment in mouse oocytes. Mol Reprod Dev 2010; 76:1094-105. [PMID: 19565641 DOI: 10.1002/mrd.21075] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The elevated incidence of aneuploidy in human oocytes warrants study of the molecular mechanisms regulating proper chromosome segregation. The Aurora kinases are a well-conserved family of serine/threonine kinases that are involved in proper chromosome segregation during mitosis and meiosis. Here we report the expression and localization of all three Aurora kinase homologs, AURKA, AURKB, and AURKC, during meiotic maturation of mouse oocytes. AURKA, the most abundantly expressed homolog, localizes to the spindle poles during meiosis I (MI) and meiosis II (MII), whereas AURKB is concentrated at kinetochores, specifically at metaphase of MI (Met I). The germ cell-specific homolog, AURKC, is found along the entire length of chromosomes during both meiotic divisions. Maturing oocytes in the presence of the small molecule pan-Aurora kinase inhibitor, ZM447439 results in defects in meiotic progression and chromosome alignment at both Met I and Met II. Over-expression of AURKB, but not AURKA or AURKC, rescues the chromosome alignment defect suggesting that AURKB is the primary Aurora kinase responsible for regulating chromosome dynamics during meiosis in mouse oocytes.
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Affiliation(s)
- Kristy Shuda
- Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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22
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Abstract
A block to polyspermy is required for successful fertilisation and embryo survival in mammals. A higher incidence of polyspermy is observed during in vitro fertilisation (IVF) compared with the in vivo situation in several species. Two groups of mechanisms have traditionally been proposed as contributing to the block to polyspermy in mammals: oviduct-based mechanisms, avoiding a massive arrival of spermatozoa in the proximity of the oocyte, and egg-based mechanisms, including changes in the membrane and zona pellucida (ZP) in reaction to the fertilising sperm. Additionally, a mechanism has been described recently which involves modifications of the ZP in the oviduct before the oocyte interacts with spermatozoa, termed "pre-fertilisation zona pellucida hardening". This mechanism is mediated by the oviductal-specific glycoprotein (OVGP1) secreted by the oviductal epithelial cells around the time of ovulation, and is reinforced by heparin-like glycosaminoglycans (S-GAGs) present in oviductal fluid. Identification of the molecules contributing to the ZP modifications in the oviduct will improve our knowledge of the mechanisms of sperm-egg interaction and could help to increase the success of IVF systems in domestic animals and humans.
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Affiliation(s)
- Pilar Coy
- Department of Physiology, Faculty of Veterinary, University of Murcia, Spain.
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23
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Abstract
The final steps of oogenesis occur during oocyte maturation that generates fertilization-competent haploid eggs capable of supporting embryonic development. Cyclin-dependent kinase 1 (CDK1) drives oocyte maturation and its activity and actions on substrates are tightly regulated. CDC14 is a dual-specificity phosphatase that reduces CDK1 activity and reverses the actions of CDK1 during mitosis. In budding yeast, Cdc14 is essential for meiosis, but it is not known whether its mammalian homolog CDC14A is required for meiosis in females. Here, we report that CDC14A is concentrated in the nucleus of meiotically incompetent mouse oocytes but is dispersed throughout meiotically competent oocytes. During meiotic progression CDC14A has no specific sub-cellular localization except between metaphase of meiosis I (Met I) and metaphase of meiosis II (Met II) when it co-localizes with the central portion of the meiotic spindle. Overexpression of CDC14A generally delays meiotic progression after resumption of meiosis whereas microinjection of oocytes with an antibody against CDC14A specifically delays exit from Met I. Each of these perturbations generates eggs with chromosome alignment abnormalities and eggs that were injected with the CDC14A antibody had an elevated incidence of aneuploidy. Collectively, these data suggest that CDC14A regulates oocyte maturation and functions to promote the meiosis I-to-meiosis II transition as its homolog does in budding yeast.
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Affiliation(s)
- Karen Schindler
- Department of Biology; University of Pennsylvania; Philadelphia, PA USA
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24
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Schindler K, Schultz RM. CDC14B acts through FZR1 (CDH1) to prevent meiotic maturation of mouse oocytes. Biol Reprod 2009; 80:795-803. [PMID: 19129509 DOI: 10.1095/biolreprod.108.074906] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Meiotic maturation in oocytes is a prolonged process that is unique because of cell cycle arrests at prophase of meiosis I (MI) and at metaphase of meiosis II (MII). Fluctuations in cyclin-dependent kinase 1 (CDK1/CDC2A) activity govern meiotic progression, yet little is known about how these fluctuations are achieved. CDC14 is a highly conserved dual-specificity phosphatase that counteracts the function of proteins phosphorylated by CDK. Mammals contain two CDC14 homologs, CDC14A and CDC14B. We report that CDC14B localizes with the meiotic spindle in mouse oocytes, and (unlike somatic cells) it does not localize in the nucleolus. Oocytes that overexpress CDC14B are significantly delayed in resuming meiosis and fail to progress to MII, whereas oocytes depleted of CDC14B spontaneously resume meiosis under conditions that normally inhibit meiotic resumption. Depletion of FZR1 (CDH1), a regulatory subunit of the anaphase-promoting complex/cyclosome that targets cyclin B1 (CCNB1) for ubiquitin-mediated proteolysis, partially restores normal timing of meiotic resumption in oocytes with excess CDC14B. These studies also reveal that experimentally altering CDC14B levels generates eggs with abnormal spindles and with chromosome alignment perturbations. Our data indicate that CDC14B is a negative regulator of meiotic resumption and may regulate MI in mouse oocytes.
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Affiliation(s)
- Karen Schindler
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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25
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Ihara M, Stein P, Schultz RM. UBE2I (UBC9), a SUMO-conjugating enzyme, localizes to nuclear speckles and stimulates transcription in mouse oocytes. Biol Reprod 2008; 79:906-13. [PMID: 18703419 DOI: 10.1095/biolreprod.108.070474] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Sumoylation is a posttranslational modification in which SUMO (small ubiquitin-related modifier) proteins are covalently attached to their substrates. In vertebrates, developmental roles for sumoylation have been studied, but the function of sumoylation during mammalian oocyte growth and maturation is not known. As a prelude to conducting studies on the role of sumoylation during oocyte development, we analyzed the temporal and spatial pattern of expression of UBE2I, a SUMO-conjugating E2 enzyme. Immunocytochemical analysis of UBE2I revealed a punctate nuclear staining pattern, with transcriptionally quiescent, fully grown, GV-intact oocytes having larger UBE2I-containing bodies than transcriptionally active, meiotically incompetent growing oocytes. Inhibiting transcription in incompetent oocytes resulted in an increase in the size of the UBE2I-containing bodies. Overexpression of either wild-type UBE2I or catalytically inactive UBE2I resulted in an increase in the size of the UBE2I-containing bodies but also an increase in BrUTP incorporation, suggesting that transcriptional activation by UBE2I is independent of its catalytic activity. Although UBE2I-containing bodies did not completely colocalize with SUMO1 or SUMO2 and SUMO3, which were localized mainly on the nuclear membrane and in the nucleoplasm, UBE2I strikingly colocalized with SFRS2, which is a component of nuclear speckles and critical for mRNA processing. These results suggest a novel function for UBE2I and therefore sumoylation in gene expression.
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Affiliation(s)
- Motomasa Ihara
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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26
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Ma P, Schultz RM. Histone deacetylase 1 (HDAC1) regulates histone acetylation, development, and gene expression in preimplantation mouse embryos. Dev Biol 2008; 319:110-20. [PMID: 18501342 DOI: 10.1016/j.ydbio.2008.04.011] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 04/07/2008] [Accepted: 04/07/2008] [Indexed: 11/19/2022]
Abstract
Superimposed on activation of the embryonic genome in preimplantation mouse embryos is the formation of a chromatin-mediated transcriptionally repressive state that arises in the late two-cell embryo and becomes more pronounced with development. In this study, we investigated expression and function of Class I histone deacetylases (HDAC) HDAC1, HDAC2, and HDAC3 during preimplantation development. HDAC1 is likely a major deacetylase in preimplantation embryos and its expression inversely correlates with changes in the acetylation state of histone H4K5 during preimplantation development. RNAi-mediated reduction of HDAC1 leads to hyperacetylation of histone H4 and a developmental delay even though expression of HDAC2 and HDAC3 is significantly induced in Hdac1-suppressed embryos; increased expression of p21(Cip1/Waf) may contribute to the observed developmental delay. RNAi-mediated reduction of HDAC2 has no noticeable effect on preimplantation development, suggesting that individual HDACs have distinct functions during preimplantation development. Although RNAi-mediated targeting of Hdac3 mRNA was very efficient, maternal HDAC3 protein was stable during preimplantation development, thereby preventing an examination of its role. HDAC1 knockdown does not increase the rate of global transcription in late 2-cell embryos, but does result in elevated levels of expression of a subset of genes; this increased expression correlates with hyperacetylation of histone H4. Results of these experiments suggest that HDAC1 is involved in the development of a transcriptionally repressive state that initiates in 2-cell embryos.
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Affiliation(s)
- Pengpeng Ma
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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27
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Ducibella T, Fissore R. The roles of Ca2+, downstream protein kinases, and oscillatory signaling in regulating fertilization and the activation of development. Dev Biol 2008; 315:257-79. [PMID: 18255053 DOI: 10.1016/j.ydbio.2007.12.012] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 12/12/2007] [Accepted: 12/13/2007] [Indexed: 12/12/2022]
Abstract
Reviews in Developmental Biology have covered the pathways that generate the all-important intracellular calcium (Ca(2+)) signal at fertilization [Miyazaki, S., Shirakawa, H., Nakada, K., Honda, Y., 1993a. Essential role of the inositol 1,4,5-trisphosphate receptor/Ca(2+) release channel in Ca(2+) waves and Ca(2+) oscillations at fertilization of mammalian eggs. Dev. Biol. 158, 62-78; Runft, L., Jaffe, L., Mehlmann, L., 2002. Egg activation at fertilization: where it all begins. Dev. Biol. 245, 237-254] and the different temporal responses of Ca(2+) in many organisms [Stricker, S., 1999. Comparative biology of calcium signaling during fertilization and egg activation in animals. Dev. Biol. 211, 157-176]. Those reviews raise the importance of identifying how Ca(2+) causes the events of egg activation (EEA) and to what extent these temporal Ca(2+) responses encode developmental information. This review covers recent studies that have analyzed how these Ca(2+) signals are interpreted by specific proteins, and how these proteins regulate various EEA responsible for the onset of development. Many of these proteins are protein kinases (CaMKII, PKC, MPF, MAPK, MLCK) whose activity is directly or indirectly regulated by Ca(2+), and whose amount increases during late oocyte maturation. We cover biochemical progress in defining the signaling pathways between Ca(2+) and the EEA, as well as discuss how oscillatory or multiple Ca(2+) signals are likely to have specific advantages biochemically and/or developmentally. These emerging concepts are put into historical context, emphasizing that key contributions have come from many organisms. The intricate interdependence of Ca(2+), Ca(2+)-dependent proteins, and the EEA raise many new questions for future investigations that will provide insight into the extent to which fertilization-associated signaling has long-range implications for development. In addition, answers to these questions should be beneficial to establishing parameters of egg quality for human and animal IVF, as well as improving egg activation protocols for somatic cell nuclear transfer to generate stem cells and save endangered species.
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Affiliation(s)
- Tom Ducibella
- Department of OB/GYN, Tufts-New England Medical Center, Boston, MA 02111, USA.
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28
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Coy P, Grullon L, Canovas S, Romar R, Matas C, Aviles M. Hardening of the zona pellucida of unfertilized eggs can reduce polyspermic fertilization in the pig and cow. Reproduction 2007; 135:19-27. [DOI: 10.1530/rep-07-0280] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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29
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Romanova LG, Anger M, Zatsepina OV, Schultz RM. Implication of nucleolar protein SURF6 in ribosome biogenesis and preimplantation mouse development. Biol Reprod 2006; 75:690-6. [PMID: 16855206 DOI: 10.1095/biolreprod.106.054072] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The step-wise assembly of a functional nucleolus, which occurs over the first few cell cycles during preimplantation development, is poorly understood. In this study, we examined the function of the evolutionary conserved nucleolar protein SURF6 in preimplantation mouse embryo development. Immunocytochemical analyses revealed that the localization of SURF6 was similar but not identical to those of fibrillarin and B23/nucleophosmin 1, which are involved in rRNA processing and ribosome biogenesis in mammalian somatic cells. Surf6 mRNA, which is expressed in oocytes and maternally inherited in the zygote, reached a peak level of expression during the 8-cell stage of embryo development, at which time rDNA is highly transcribed. Knock-down of Surf6 mRNA by RNAi led to a decrease in both the mRNA and protein levels, and resulted in developmental arrest at the 8-cell/morula stage, as well as a decrease in the level of 18S rRNA. These results suggest that Surf6 is essential for mouse preimplantation development, presumably by regulating ribosome biogenesis.
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Affiliation(s)
- Ludmila G Romanova
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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30
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Yan W, Ma L, Stein P, Pangas SA, Burns KH, Bai Y, Schultz RM, Matzuk MM. Mice deficient in oocyte-specific oligoadenylate synthetase-like protein OAS1D display reduced fertility. Mol Cell Biol 2005; 25:4615-24. [PMID: 15899864 PMCID: PMC1140637 DOI: 10.1128/mcb.25.11.4615-4624.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The double-stranded RNA (dsRNA)-induced interferon response is a defense mechanism against viral infection. Upon interferon activation by dsRNA, 2',5'-oligoadenylate synthetase 1 (OAS1A) is induced; it binds dsRNA and converts ATP into 2',5'-linked oligomers of adenosine (called 2-5A), which activate RNase L that in turn degrades viral and cellular RNAs. In a screen to identify oocyte-specific genes, we identified a novel murine cDNA encoding an ovary-specific 2',5'-oligoadenylate synthetase-like protein, OAS1D, which displays 59% identity with OAS1A. OAS1D is predominantly cytoplasmic and is exclusively expressed in growing oocytes and early embryos. Like OAS1A, OAS1D binds the dsRNA mimetic poly(I-C), but unlike OAS1A, it lacks 2'-5' adenosine linking activity. OAS1D interacts with OAS1A and inhibits the enzymatic activity of OAS1A. Mutant mice lacking OAS1D (Oas1d(-/-)) display reduced fertility due to defects in ovarian follicle development, decreased efficiency of ovulation, and eggs that are fertilized arrest at the one-cell stage. These effects are exacerbated after activation of the interferon/OAS1A/RNase L pathway by poly(I-C). We propose that OAS1D suppresses the interferon/OAS/RNase L-mediated cellular destruction by interacting with OAS1A during oogenesis and early embryonic development.
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Affiliation(s)
- Wei Yan
- Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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31
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Nipper RW, Chennothukuzhi V, Tutuncu L, Williams CJ, Gerton GL, Moss SB. Differential RNA expression and polyribosome loading of alternative transcripts of the Akap4 gene in murine spermatids. Mol Reprod Dev 2005; 70:397-405. [PMID: 15685631 DOI: 10.1002/mrd.20224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An X chromosome-linked gene, Akap4, is expressed only during spermiogenesis and encodes the major fibrous sheath protein of the mouse sperm flagellum. All sperm contain the AKAP4 protein even though only X chromosome-bearing spermatids express the gene, indicating that the Akap4 mRNA and/or protein must be shared among the conjoined spermatids via the intercellular bridges. There are two mouse Akap4 cDNA clones, Akap82 and Fsc1, which represent mRNAs that arise by alternative processing of a single gene. Although Akap82 and Fsc1 encode identical mature proteins, they differ in their 5' UTRs. We hypothesized that the expression pattern of these two mRNAs might be relevant to the issue of mRNA and/or protein transport into adjacent spermatids. Expression of both transcripts began in round spermatids, but the amount of the Akap82 transcript in condensing spermatids increased twofold relative to Fsc1. Significantly, only the Akap82 transcript was found on polyribosomes and translated in spermatids. These results indicate that the Akap82 transcript and/or its protein must be shared among the conjoined X and Y chromosome-bearing spermatids. Although Fsc1 was not polysomal, both the Akap82 and Fsc1 transcripts were deadenylated during spermiogenesis, suggesting that deadenylation is not always correlated with loading of mRNAs onto polyribosomes in germ cells. The distinct 5' UTR sequences in Akap82 and Fsc1 did not differ in their ability to regulate translation of reporter constructs either in vivo or in vitro. Antisense RNA transcripts complementary to both the Akap82 and Fsc1 mRNAs were present, suggesting that translatability may be regulated by these RNAs.
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Affiliation(s)
- Rick W Nipper
- Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA
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Tatemoto H, Muto N, Yim SD, Nakada T. Anti-Hyaluronidase Oligosaccharide Derived from Chondroitin Sulfate A Effectively Reduces Polyspermy During In Vitro Fertilization of Porcine Oocytes1. Biol Reprod 2005; 72:127-34. [PMID: 15342356 DOI: 10.1095/biolreprod.104.032813] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The present study was conducted to examine the effects of chondroitin sulfate A-derived oligosaccharide (ChSAO) on hyaluronidase activity and in vitro fertilization (IVF) parameters. The activity of hyaluronidase extracted from preincubated boar sperm was completely blocked by ChSAO at concentrations of 10 microg/ml or higher. After in vitro maturation of porcine cumulus-oocyte complexes, some oocytes were freed from their cumulus cells, and cumulus-intact or cumulus-free oocytes were inseminated with sperm in IVF medium containing various concentrations of ChSAO (0.1-100 microg/ml). In cumulus-intact oocytes, the penetration and the polyspermy rates (39% and 28%, respectively) were significantly decreased by treatment with 100 microg/ml ChSAO compared with those of oocytes treated without ChSAO (63% and 52%, respectively). On the contrary, in cumulus-free oocytes, the addition of 10-100 microg/ml ChSAO significantly reduced the polyspermy rate compared with the control (25-30% versus 53%, respectively), whereas ChSAO had no effect on sperm penetration. Interestingly, ChSAO added to IVF medium significantly decreased the number of sperm bound to the zona pellucida (ZP) of cumulus-free oocytes in a concentration-dependent manner between 0.1 and 100 microg/ml. However, ChSAO had no effect on the time course change in ZP modification after oocyte activation by electrostimulation and the incidence of the acrosome-reacted sperm. Treatment with 100 microg/ml ChSAO during IVF of cumulus-free oocytes significantly increased the proportion of development to the blastocyst stage after in vitro insemination. Therefore, the present findings indicate that hyaluronidase-inhibitory ChSAO is an efficient probe for promoting normal fertilization process in terms of an effective decrease in the incidence of polyspermy during IVF of porcine oocytes.
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Affiliation(s)
- Hideki Tatemoto
- Department of Bioproduction, Faculty of Agriculture, University of the Ryukyus, Nishihara-cho, Okinawa 903-0213, Japan.
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Knott JG, Kurokawa M, Fissore RA, Schultz RM, Williams CJ. Transgenic RNA interference reveals role for mouse sperm phospholipase Czeta in triggering Ca2+ oscillations during fertilization. Biol Reprod 2004; 72:992-6. [PMID: 15601914 DOI: 10.1095/biolreprod.104.036244] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A sperm-specific phospholipase (PL) C, termed PLCzeta, is proposed to be the soluble sperm factor that induces Ca(2+) oscillations in mammalian eggs and, thus, initiates egg activation in vivo. We report that sperm from transgenic mice expressing short hairpin RNAs targeting PLCzeta mRNA have reduced amounts of PLCzeta protein. Sperm derived from these transgenic mice trigger patterns of Ca(2+) oscillations following fertilization in vitro that terminate prematurely. Consistent with the perturbation in patterns of Ca(2+) oscillations is the finding that mating of transgenic founder males to females results in lower rates of egg activation and no transgenic offspring. These data strongly suggest that PLCzeta is the physiological trigger of Ca(2+) oscillations required for activation of development.
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Affiliation(s)
- Jason G Knott
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Anger M, Stein P, Schultz RM. CDC6 requirement for spindle formation during maturation of mouse oocytes. Biol Reprod 2004; 72:188-94. [PMID: 15385409 DOI: 10.1095/biolreprod.104.035451] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A master regulator of DNA replication, CDC6 also functions in the DNA-replication checkpoint by preventing DNA rereplication. Cyclin-dependent kinases (CDKs) regulate the amount and localization of CDC6 throughout the cell cycle; CDC6 phosphorylation after DNA replication initiation leads to its proteolysis in yeast or translocation to the cytoplasm in mammals. Overexpression of CDC6 during the late S phase prevents entry into the M phase by activating CHEK1 kinase that then inactivates CDK1/cyclin B, which is essential for the G2/M-phase transition. We analyzed the role of CDC6 during resumption of meiosis in mouse oocytes, which are arrested in the first meiotic prophase with low CDK1/cyclin B activity; this is similar to somatic cells at the G2/M-phase border. Overexpression of CDC6 in mouse oocytes does not prevent resumption of meiosis. The RNA interference-mediated knockdown of CDC6, however, reveals a new and unexpected function for CDC6; namely, it is essential for spindle formation in mouse oocytes.
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Affiliation(s)
- Martin Anger
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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Yu J, Deng M, Medvedev S, Yang J, Hecht NB, Schultz RM. Transgenic RNAi-mediated reduction of MSY2 in mouse oocytes results in reduced fertility. Dev Biol 2004; 268:195-206. [PMID: 15031116 DOI: 10.1016/j.ydbio.2003.12.020] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2003] [Revised: 12/16/2003] [Accepted: 12/17/2003] [Indexed: 11/19/2022]
Abstract
MSY2 is implicated in regulating the stability and translation of maternal mRNAs during mouse oogenesis. We report here that by driving the expression of a transgene encoding an Msy2 hairpin dsRNA in growing oocytes using the oocyte-specific Zp3 promoter, the amount of MSY2 protein was reduced by at least 60% in fully grown oocytes. The decrease appeared specific because no decrease was observed in either non-targeted mRNAs or proteins. Fertility of transgenic females was severely reduced. Although transgenic eggs could be inseminated, the eggs did not exhibit the normal series of oscillations in intracellular Ca2+, resume meiosis, undergo cortical granule exocytosis, or ZP2 cleavage to ZP2f. Transgenic oocytes also displayed a higher incidence of both the non-surrounded nucleolus chromatin morphology, and abnormal meiotic spindle formation was observed following oocyte maturation. Transgenic oocytes contained less total mRNA (approximately 75-80% that of non-transgenic oocytes) and displayed a reduced level of protein synthesis. Moreover, several of the maturation-associated changes in protein synthesis failed to occur in the transgenic oocytes. These results support a role for MSY2 in stabilizing maternal mRNAs in growing oocytes, a process essential to generate meiotically and developmentally competent oocytes.
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Affiliation(s)
- Junying Yu
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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36
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Xu Z, Williams CJ, Kopf GS, Schultz RM. Maturation-associated increase in IP3 receptor type 1: role in conferring increased IP3 sensitivity and Ca2+ oscillatory behavior in mouse eggs. Dev Biol 2003; 254:163-71. [PMID: 12591238 DOI: 10.1016/s0012-1606(02)00049-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Maturation of mouse oocytes is accompanied by an increase in sensitivity to inositol 1,4,5-trisphosphate (IP(3))-mediated release of intracellular calcium. To test the hypothesis that the maturation-associated 1.5- to 2.0-fold increase in the mass of the type 1 IP(3) receptor (IP(3)R-1) confers this increase in IP(3) sensitivity, we employed RNA interference to prevent this change in IP(3)R-1 protein level. Microinjection into germinal vesicle (GV)-intact oocytes of dsRNA corresponding to the IP(3)R-1 sequence resulted in a >90% reduction in the amount of maternal IP(3)R-1 mRNA and prevented the maturation-associated increase in the mass of the IP(3)R-1 protein. These injected oocytes matured to metaphase II, and there was no effect on the maturation-associated increases in p34(cdc2)/cyclin B kinase and MAP kinase activities or the global pattern of protein synthesis. IP(3)-induced cortical granule exocytosis was significantly decreased in these eggs when compared with controls previously injected with enhanced green fluorescent protein (EGFP) dsRNA. Following insemination, the IP(3)R-1 dsRNA-injected eggs displayed significantly fewer Ca(2+) transients than controls, and the duration of the first Ca(2+) transient was about half that of controls. These results support the hypothesis that the maturation-associated increase in the mass of IP(3)R-1 confers the increase in IP(3)-sensitivity that is observed following oocyte maturation and is necessary for the proper Ca(2+) oscillatory pattern following insemination.
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Affiliation(s)
- Zhe Xu
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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37
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Stein P, Svoboda P, Anger M, Schultz RM. RNAi: mammalian oocytes do it without RNA-dependent RNA polymerase. RNA (NEW YORK, N.Y.) 2003; 9:187-92. [PMID: 12554861 PMCID: PMC1370384 DOI: 10.1261/rna.2860603] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2002] [Accepted: 10/23/2002] [Indexed: 05/19/2023]
Abstract
Studies in mutant organisms deficient in RNA interference (RNAi) and related post-transcriptional gene silencing implicated a role for a single class of RNA-dependent RNA polymerases (RdRp). Nevertheless, sequence homologs to these RdRps have not been found in coelomate organisms such as Drosophila or mammals. This lack of homologous sequences does not exclude that an RdRp functions in RNAi in these organisms because an RdRp could be acquired by horizontal transfer from an RNA virus. In fact, such a sequence is found in mice (Aquarius) and we observe that it is expressed in mouse oocytes and early embryos, which exhibit RNAi. We report here that cordycepin, an inhibitor of RNA synthesis, does not prevent Mos double-strand RNA (dsRNA) to target endogenous Mos mRNA in mouse oocytes and that targeting a chimeric Mos-EGFP mRNA with dsRNA to EGFP does not reduce the endogenous Mos mRNA, but does target the chimeric mRNA. These results indicate that an RdRp is not involved in dsRNA-mediated mRNA degradation in mammalian oocytes, and possibly in mammals in general, and therefore that only homologous sequences to the dsRNA are targeted for degradation.
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Affiliation(s)
- Paula Stein
- Department of Biology, University of Pennsylvania, 415 South University Avenue, Philadelphia, PA 19104-6018, USA
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38
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Ma J, Zhou H, Su L, Ji W. Effects of exogenous double-stranded RNA on the basonuclin gene expression in mouse oocytes. ACTA ACUST UNITED AC 2002; 45:593-603. [DOI: 10.1007/bf02879747] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2001] [Indexed: 11/28/2022]
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Nixon VL, Levasseur M, McDougall A, Jones KT. Ca(2+) oscillations promote APC/C-dependent cyclin B1 degradation during metaphase arrest and completion of meiosis in fertilizing mouse eggs. Curr Biol 2002; 12:746-50. [PMID: 12007419 DOI: 10.1016/s0960-9822(02)00811-4] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cyclin B1, the regulatory component of M phase-promoting factor (MPF), is degraded during the metaphase-anaphase transition in an anaphase-promoting complex/cyclosome (APC/C)-dependent process. MPF activity is stable in eggs, and a sperm-triggered Ca(2+) signal is needed to promote cyclin degradation. In frogs, a single Ca(2+) spike promotes cell cycle resumption, but, in mammals, the Ca(2+) signal is more complex, consisting of a series of spikes that stop several hours after sperm fusion. Using dual imaging in mouse eggs, we have examined how the Ca(2+) signal generates cyclin B1 destruction using destructible and nondestructible GFP-tagged constructs. APC/C activity was present in unfertilized eggs, giving cyclin B1 a half-life of 1.15 +/- 0.28 hr. However, APC/C-dependent cyclin degradation was elevated 6-fold when sperm raised cytosolic Ca(2+) levels above 600 nM. This activation was transitory since cyclin B1 levels recovered between Ca(2+) spikes. For continued cyclin degradation at basal Ca(2+) levels, multiple spikes were needed. APC/C-mediated degradation was observed until eggs had completed meiosis with the formation of pronuclei, and, at this time, Ca(2+) spikes stopped. Therefore, the physiological need for a repetitive Ca(2+) signal in mammals is to ensure long-term cyclin destruction during a protracted exit from meiosis.
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Affiliation(s)
- Victoria L Nixon
- Department of Physiological Sciences, The Medical School, Framlington Place, University of Newcastle, Newcastle NE2 4HH, United Kingdom
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40
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Abstract
At fertilization in mammals, the spermatozoon triggers a series of Ca(2+) oscillations that are essential for activating the oocyte. The reason why the spermatozoon triggers Ca(2+) oscillations, as opposed to a single Ca(2+) increase, is unknown. However, there is evidence that more than one Ca(2+) increase is required for efficient rates of pronuclear formation. In addition, the pattern of Ca(2+) oscillations may affect later development. It is not known how the spermatozoon triggers Ca(2+) release in the oocyte, but it may act by introducing a cytosolic factor after gamete membrane fusion has taken place. This factor is characterized by its ability to cause Ca(2+) oscillations and is referred to as an oscillogen. The protein components that make up the sperm oscillogen remain unclear.
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Affiliation(s)
- Karl Swann
- Department of Anatomy and Developmental Biology, University College, Gower Street, London WC1E 6BT, UK
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41
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Svoboda P, Stein P, Schultz RM. RNAi in mouse oocytes and preimplantation embryos: effectiveness of hairpin dsRNA. Biochem Biophys Res Commun 2001; 287:1099-104. [PMID: 11587535 DOI: 10.1006/bbrc.2001.5707] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
RNA interference (RNAi), the targeted mRNA degradation by double-stranded RNA (dsRNA), is a useful tool for studying gene function in several organisms. Here we report results of experiments with mammalian dsRNA expression vectors that are suitable to study gene function in mouse oocytes and preimplantation embryos. The plasmid vectors were constructed to contain the SV40 small intron, EGFP coding sequence to permit detection of expression, and an inverted repeat to mos mRNA that would form a hairpin dsRNA. Results of the experiments indicated that (i) hairpin dsRNA was just as effective as dsRNA (i.e., annealed sense and antisense RNA) in promoting the destruction of targeted mRNA, (ii) the EGFP marker could be expressed from the construct, and (iii) the distance of the SV40 intron from the inverted repeat was critical for the transcribed RNA to function in RNAi.
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Affiliation(s)
- P Svoboda
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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42
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Abstract
Translational control plays a central role during oocyte maturation and early embryogenesis, as these processes occur in the absence of transcription. MSY2, a member of a multifunctional Y-box protein family, is implicated in repressing the translation of paternal mRNAs. Here, we characterize MSY2 expression in mouse oocytes and preimplantation embryos. Northern blot analysis indicates that MSY2 expression is highly restricted and essentially confined to the oocyte in the female mouse. MSY2 transcript and protein, as assessed by reverse transcription-polymerase chain reaction and immunoblotting, respectively, are expressed in growing oocytes, metaphase II-arrested eggs, and 1-cell embryos, but then are degraded by the late 2-cell stage; no expression is detectable in the blastocysts. During oocyte maturation, MSY2 is phosphorylated and following fertilization it is dephosphorylated. Quantification of the mass amount of MSY2 reveals that it represents 2% of the total protein in the fully grown oocyte, i.e., it is a very abundant protein. Both endogenous MSY2 and MSY2-enhanced green fluorescent protein (EGFP), which is synthesized following microinjection of an mRNA encoding MSY2-EGFP, are primarily localized in the cytoplasm, and about 75% of the MSY2 remains associated with oocyte cytoskeletal preparations. Results of these studies are consistent with the proposal that MSY2 functions by stabilizing and/or repressing the translation of maternal mRNAs.
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Affiliation(s)
- J Yu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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43
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da Silva CP, Guse AH. Intracellular Ca(2+) release mechanisms: multiple pathways having multiple functions within the same cell type? BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1498:122-33. [PMID: 11108956 DOI: 10.1016/s0167-4889(00)00089-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The elevation of the cytosolic and nuclear Ca(2+) concentration is a fundamental signal transduction mechanism in almost all eukaryotic cells. Interestingly, three Ca(2+)-mobilising second messengers, D-myo-inositol 1,4,5-trisphosphate (InsP(3)), cyclic adenosine diphosphoribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP(+)) were identified in a phylogenetically wide range of different organisms. Moreover, in an as yet very limited number of cell types, sea urchin eggs, mouse pancreatic acinar cells, and human Jurkat T-lymphocytes, all three Ca(2+)-mobilising ligands have been shown to be involved in the generation of Ca(2+) signals. This situation raises the question why during evolution all three messengers have been conserved in the same cell type. From a theoretical point of view the following points may be considered: (i) redundant mechanisms ensuring intact Ca(2+) signalling even if one system does not work, (ii) the need for subcellularly localised Ca(2+) elevations to obtain a certain physiological response of the cell, and (iii) tight control of a physiological response of the cell by a temporal sequence of Ca(2+) signalling events. These theoretical considerations are compared to the current knowledge regarding the three messengers in sea urchin eggs, mouse pancreatic acinar cells, and human Jurkat T lymphocytes.
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Affiliation(s)
- C P da Silva
- University of Hamburg, University Clinic Hamburg-Eppendorf, Institute for Medical Biochemistry and Molecular Biology, Division of Cellular Signal Transduction, Grindelallee 117, D-20146, Hamburg, Germany
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44
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Funahashi H, Ekwall H, Rodriguez-Martinez H. Zona reaction in porcine oocytes fertilized in vivo and in vitro as seen with scanning electron microscopy. Biol Reprod 2000; 63:1437-42. [PMID: 11058549 DOI: 10.1095/biolreprod63.5.1437] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Morphological changes in zona pellucidae (ZP) isolated from in vitro-matured (IVM) and ovulated porcine oocytes were compared before or after fertilization in vitro and in vivo, respectively, by using scanning electron microscopy (SEM). The ZP of some ovulated or IVM oocytes and in vivo- or in vitro-fertilized (IVF) zygotes were equally split into two halves while immersed in an enzyme-inhibitor solution, using a surgical blade. After washing, intact and ZP halves were fixed in 1% glutaraldehyde solution in 0.1 M cacodylate buffer, processed, and examined using SEM. The outer surface of ZP in ovulated oocytes had a mesh-like structure. The outer morphology in IVM oocytes was more smooth although the mesh-like structure was still visible at high magnification. In in vivo zygotes and IVM-IVF zygotes, this lysed, mesh-like structure was more obvious. The inner surface of ZP had some small depressions (orifices). The mean number of orifices per 100 micrometer(2) of ZP surface was larger in IVM oocytes as compared to ovulated ones. The number of orifices per 100 micrometer(2) decreased in IVM-IVF zygotes as compared to IVM oocytes; whereas, in vivo zygotes did not differ from ovulated oocytes. The mean diameter of intact ZP as well as their mean thickness was greater in ovulated oocytes than IVM oocytes. The mean thickness of the ZP was larger in ovulated oocytes than IVM ones. The ZP thickness was larger in zygotes than in in vivo oocytes, whereas that of IVM-IVF zygotes did not differ from that of IVM oocytes. These results indicate that the morphology of ZP and the ZP reaction at sperm penetration appears to be much different between IVM oocytes and ovulated ones.
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Affiliation(s)
- H Funahashi
- Department of Animal Science, Faculty of Agriculture, Okayama University, Okayama 700-8530 Japan.
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45
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Svoboda P, Stein P, Hayashi H, Schultz RM. Selective reduction of dormant maternal mRNAs in mouse oocytes by RNA interference. Development 2000; 127:4147-56. [PMID: 10976047 DOI: 10.1242/dev.127.19.4147] [Citation(s) in RCA: 282] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Specific mRNA degradation mediated by double-stranded RNA (dsRNA), which is termed RNA interference (RNAi), is a useful tool with which to study gene function in several systems. We report here that in mouse oocytes, RNAi provides a suitable and robust approach to study the function of dormant maternal mRNAs. Mos (originally known as c-mos) and tissue plasminogen activator (tPA, Plat) mRNAs are dormant maternal mRNAs that are recruited during oocyte maturation; translation of Mos mRNA results in the activation of MAP kinase. dsRNA directed towards Mos or Plat mRNAs in mouse oocytes effectively results in the specific reduction of the targeted mRNA in both a time- and concentration-dependent manner. Moreover, dsRNA is more potent than either sense or antisense RNAs. Targeting the Mos mRNA results in inhibiting the appearance of MAP kinase activity and can result in parthenogenetic activation. Mos dsRNA, therefore, faithfully phenocopies the Mos null mutant. Targeting the Plat mRNA with Plat dsRNA results in inhibiting production of tPA activity. Finally, effective reduction of the Mos and Plat mRNA is observed with stoichiometric amounts of Mos and Plat dsRNA, respectively.
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Affiliation(s)
- P Svoboda
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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46
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Stein P, Schultz RM. Initiation of a chromatin-based transcriptionally repressive state in the preimplantation mouse embryo: lack of a primary role for expression of somatic histone H1. Mol Reprod Dev 2000; 55:241-8. [PMID: 10657042 DOI: 10.1002/(sici)1098-2795(200003)55:3<241::aid-mrd1>3.0.co;2-t] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A chromatin-based transcriptionally repressive state develops during the two-cell stage in preimplantation mouse embryos. Correlated with the initial formation of this state is the expression of somatic histone H1, which could confer repression by promoting the formation of a transcriptionally repressive chromatin structure. To ascertain if the expression of histone H1 could play such a primary role in initiating the formation of this transcriptionally repressive state, the endogenous pool of somatic histone H1 in the two-cell embryo was greatly expanded by injection of 25 or 100 pg of histone H1 at the one-cell stage. The expression of the transcription-requiring complex, which is an accepted marker for genome activation, was then assessed during the two-cell stage. No significant inhibition was noted following the injection of 25 pg of histone H1. A transient inhibition was observed following injection of 100 pg, but this was likely due to a delay in cleavage to the two-cell stage. We conclude that it is unlikely that the expression of somatic histone H1 is a major factor in the initial establishment of the chromatin-based transcriptionally repressive state that accompanies genome activation.
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Affiliation(s)
- P Stein
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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47
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Tatemoto H, Terada T. Analysis of zona pellucida modifications due to cortical granule exocytosis in single porcine oocytes, using enhanced chemiluminescence. Theriogenology 1999; 52:629-40. [PMID: 10734362 DOI: 10.1016/s0093-691x(99)00158-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The present study was carried out to determine whether modification of zona pellucida (ZP) of a single oocyte following the cortical granule (CG) exocytosis induced by electrical stimulation could be analyzed using enhanced chemiluminescent (ECL) detection of the biotinylated ZP in a porcine oocyte. When a biotinylated ZP derived from a single oocyte matured in vitro was subjected to SDS-PAGE, 3 major bands (ZP1, ZP2 and ZP3) were observed following ECL detection. In these oocytes, CGs staining with fluorescein isothiocyanate (FITC)-labeled peanut agglutinin (FITC-PNA) had formed a monolayer underlying the plasma membrane. Electrical stimulation to induce artificial activation caused a decline in the fluorescent intensity of the CGs with a concomitant decrease in the amounts of ZP1 and ZP2 bands. However, the mobility changes of ZP1 and ZP2 on SDS-PAGE were not found under the inhibitory condition of the CG exocytosis in which oocytes were treated with ethylene glycol-bis(beta-aminoethyl ether) N, N, N',N'-tetraacetic acid (EGTA) or 1, 2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid tetrakis(acetoxymethyl) ester (BAPTA/AM). In addition, when a time-dependent decrease in amounts of ZP1 and ZP2 bands on SDS-PAGE was observed in a single oocyte during activation, a maximum decrease in these bands was detected in oocytes incubated for at least 3.5 h after electrical stimulation. These results show that the method employed, ECL detection of the biotinylated ZP of a single oocyte, is a valuable tool for the analysis of ZP modification resulting from a decrease in amounts of ZP1 and ZP2 glycoproteins in combination with exocytosis of CGs, and that the prolonged period after activation is required for complete ZP modification in porcine oocytes.
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Affiliation(s)
- H Tatemoto
- Department of Bioresources, Hiroshima Prefectural University, Shobara, Japan
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48
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Fissore RA, Longo FJ, Anderson E, Parys JB, Ducibella T. Differential distribution of inositol trisphosphate receptor isoforms in mouse oocytes. Biol Reprod 1999; 60:49-57. [PMID: 9858485 DOI: 10.1095/biolreprod60.1.49] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In mammalian fertilization, inositol 1,4,5-trisphosphate receptor (IP3R)-dependent Ca2+ release is a crucial signaling event that originates from the vicinity of sperm-egg interaction and spreads as a wave throughout the egg cytoplasm. While it is known that Ca2+ is released by the type 1 IP3R in the egg cortex, the potential involvement of other isoform types responsible for the Ca2+ rise in the mouse egg (interior) and their spatial distribution are not known. In addition, the biochemical basis has not been definitively established for the development of increased sensitivity to inositol 1,4,5-trisphosphate (IP3) during meiotic maturation. Using specific antibodies to the type 1, 2, and 3 IP3R, we tested the hypotheses that different IP3R isoforms are responsible for the internal Ca2+ elevation and that they contribute to the maturation-associated acquisition of IP3 sensitivity. In both preovulatory oocytes and ovulated eggs of CF-1 mice, immunofluorescence revealed that types 1 and 2 isoforms were present in the cell cortex and interior. Type 1 was observed throughout the cytoplasm, and Western analysis indicated a 1.9-fold maturation-associated increase. In contrast, the signals detected for the type 2 (high-affinity) isoform and type 3 were present to a lesser extent, with type 2 restricted to isolated islands (similar to aggregates of vesicles detected by electron microscopy), which, in the cortex, may amplify early sperm-egg signaling events. The cortical-to-perinuclear localization of the receptor and cortical vesicle aggregates imply an efficient mechanism for propagating Ca2+ release from the cortex into the interior of the egg to activate development, and the isoform localization analysis indicates a clear spatial and biochemical heterogeneity. Types 1 and 2 isoforms were also present in granulosa cells.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies/pharmacology
- Antibodies, Monoclonal/pharmacology
- Blotting, Western
- Calcium/metabolism
- Calcium Channels/analysis
- Calcium Channels/chemistry
- Calcium Channels/physiology
- Female
- Fluorescent Antibody Technique
- Inositol 1,4,5-Trisphosphate/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors
- Meiosis
- Mice
- Microscopy, Electron
- Molecular Sequence Data
- Oocytes/chemistry
- Oocytes/drug effects
- Oocytes/physiology
- Receptors, Cytoplasmic and Nuclear/analysis
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/physiology
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Affiliation(s)
- R A Fissore
- Department of Obstetrics/Gynecology, Tufts University School of Medicine and New England Medical Center Hospital, Boston, Massachusetts 02111, USA
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Lawrence Y, Ozil JP, Swann K. The effects of a Ca2+ chelator and heavy-metal-ion chelators upon Ca2+ oscillations and activation at fertilization in mouse eggs suggest a role for repetitive Ca2+ increases. Biochem J 1998; 335 ( Pt 2):335-42. [PMID: 9761732 PMCID: PMC1219787 DOI: 10.1042/bj3350335] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During fertilization in mouse eggs, the sperm triggers a series of intracellular Ca2+ oscillations that lead to egg activation, as indicated by pronuclear formation. We show that Ca2+ oscillations in fertilized mouse eggs can be inhibited by addition of either the Ca2+ chelator 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester (BAPTA-AM) or the heavy-metal-ion chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) plus dithiothreitol (DTT). Both treatments inhibited Ca2+ oscillations, but they had different effects upon egg activation. Blocking Ca2+ oscillations with BAPTA-AM after the occurrence of just two Ca2+ spikes resulted in most eggs forming pronuclei. However, we found that BAPTA-AM-treated fertilizing eggs showed a decreased rate of protein synthesis, which by itself can promote egg activation. In contrast, blocking Ca2+ oscillations with TPEN plus DTT was accompanied by the inhibition of egg activation with no significant effect on protein synthesis. In eggs that were fertilized and then treated with TPEN plus DTT, there was a correlation between the number of Ca2+ spikes and the proportion of eggs that formed pronuclei, as well as between the number of Ca2+ spikes and the time taken for pronuclear formation and the first mitosis to occur. The addition of TPEN plus DTT did not block the generation of Ca2+ spikes or pronuclear formation when eggs were artificially stimulated by electroporation pulses. These data suggest that TPEN plus DTT inhibits pronuclear formation in fertilizing eggs via the inhibition of Ca2+ oscillations and that the number of Ca2+ spikes may regulate egg activation.
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Affiliation(s)
- Y Lawrence
- Department of Anatomy and Developmental Biology, University College, Gower Street, London WC1E 6BT, UK
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De Sousa PA, Watson AJ, Schultz RM. Transient expression of a translation initiation factor is conservatively associated with embryonic gene activation in murine and bovine embryos. Biol Reprod 1998; 59:969-77. [PMID: 9746750 DOI: 10.1095/biolreprod59.4.969] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In the present study the abundance of mRNAs for eukaryotic translation initiation factors eIF-1A (formerly known as eIF-4C), -2alpha, -4A, -4E, and -5 was examined in in vivo-derived mouse embryos throughout preimplantation development using a semiquantitative reverse transcription-polymerase chain reaction assay. Although the mRNA profile for each gene is unique, only mRNA for eIF-1A transiently increases during embryonic gene activation (EGA) at the 2-cell stage, and this was confirmed by an independent hybridization-based assay. In in vitro-developed bovine embryos, mRNA for eIF-1A was transiently detected at the 8-cell stage, when the major activation of the genome occurs in this species. As in the mouse, detection in 8-cell bovine embryos was sensitive to the transcriptional inhibitor alpha-amanitin. It was also observed at the same time relative to cleavage in embryos cultured in defined medium under a reduced oxygen environment, and in medium supplemented with serum and somatic cells in 5% CO2 in air. Neither the chronology of early cleavage divisions nor the yield of bovine blastocysts differed in these culture media. Our results suggest that transient expression of eIF-1A in the mouse and cow is a conserved pattern of gene expression associated with EGA in mammals.
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Affiliation(s)
- P A De Sousa
- Departments of Obstetrics and Gynaecology and Physiology, University of Western Ontario, London,Ontario, Canada N6A 5C1
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