DOCSLIB.ORG

Cellular and Molecular Aspects of Oocyte

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cellular and Molecular Aspects of Oocyte Santella et al. Zoological Letters (2020) 6:5 https://doi.org/10.1186/s40851-020-00157-5 REVIEW Open Access Cellular and molecular aspects of oocyte maturation and fertilization: a perspective from the actin cytoskeleton Luigia Santella1*, Nunzia Limatola1 and Jong Tai Chun2 Abstract Much of the scientific knowledge on oocyte maturation, fertilization, and embryonic development has come from the experiments using gametes of marine organisms that reproduce by external fertilization. In particular, echinoderm eggs have enabled the study of structural and biochemical changes related to meiotic maturation and fertilization owing to the abundant availability of large and transparent oocytes and eggs. Thus, in vitro studies of oocyte maturation and sperm-induced egg activation in starfish are carried out under experimental conditions that resemble those occurring in nature. During the maturation process, immature oocytes of starfish are released from the prophase of the first meiotic division, and acquire the competence to be fertilized through a highly programmed sequence of morphological and physiological changes at the oocyte surface. In addition, the changes in the cortical and nuclear regions are essential for normal and monospermic fertilization. This review summarizes the current state of research on the cortical actin cytoskeleton in mediating structural and physiological changes during oocyte maturation and sperm and egg activation in starfish and sea urchin. The common denominator in these studies with echinoderms is that exquisite rearrangements of the egg cortical actin filaments play pivotal roles in gamete interactions, Ca2+ signaling, exocytosis of cortical granules, and control of monospermic fertilization. In this review, we also compare findings from studies using invertebrate eggs with what is known about the contributions made by the actin cytoskeleton in mammalian eggs. Since the cortical actin cytoskeleton affects microvillar morphology, movement, and positioning of organelles and vesicles, and the topography of the egg surface, these changes have impacts on the fertilization process, as has been suggested by recent morphological studies on starfish oocytes and eggs using scanning electron microscopy. Drawing the parallelism between vitelline layer of echinoderm eggs and the zona pellucida of mammalian eggs, we also discuss the importance of the egg surface in mediating monospermic fertilization. Keywords: Actin, Calcium, Oocyte maturation, Polyspermy, Sea urchin, Starfish, Ageing, Fertilization, Vitelline layer, Zona pellucida * Correspondence: [email protected] 1Department of Research Infrastructures for Marine Biological Resources, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli 80121, Italy Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Santella et al. Zoological Letters (2020) 6:5 Page 2 of 21 Introduction remain blocked at that stage until spawning (Fig. 1). The During gametogenesis, primordial germ-cells, which pro- release from meiotic arrest, i.e. the maturation process, duce either eggs or spermatozoa in sexually-reproducing is triggered by the hormone 1-methyladenine (1-MA), animals, undergo mitosis to increase in number and gen- which is secreted by the follicles cells surrounding the erate oogonia (in females) and spermatogonia (in males). oocytes, while the fully grown immature oocytes are still With the onset of meiosis, these diploid cells are trans- in the ovary [6, 7]. The hormone acts on a yet- formed into primary oocytes and spermatocytes. The unidentified receptor on the cell surface, and thereby in- meiotic (maturation) divisions that follow are markedly duces the breakdown of the envelope of the large nu- different in the two gametes. In male, each primary cleus known as germinal vesicle (GV). The germinal spermatocyte divides to produce four haploid sperma- vesicle breakdown (GVBD) allows the intermixing of the tids, which differentiate into spermatozoa capable of fer- nucleoplasm with the cytoplasm and is followed by for- tilizing the eggs. In female, unequal partition of the mation of the polar bodies (Fig. 1e arrows). The spawned cytoplasm results from two meiotic divisions that are maturing oocytes at sea are at the stage of their GVBD asymmetric in size and lead to the formation of one (Fig. 1c), and are to be fertilized before the extrusion of large haploid oocyte and three polar bodies, the latter the first polar body [8, 9]. At variance with oocytes of of which eventually degenerate. Another striking distinc- other vertebrate species in which a second meiotic arrest tion between oocytes and spermatozoa is that the latter may occur at different cell cycle stages, starfish eggs ma- fertilize the eggs at the end of the meiotic divisions, tured in vitro can complete meiotic divisions without whereas oocytes reach the period of fertilizability at dif- further maturation arrest. ferent stages of the maturation process, depending on Although sperm can penetrate immature oocytes of animal species. Indeed, marine invertebrate oocytes can starfish before GVBD, cortical events that block the be grouped into four different classes based on the mei- entry of supernumerary spermatozoa and ensure normal otic stage at which fertilization takes place. Oocytes of egg activation and cleavage take place within a precise various annelids and molluscs are fertilized at the GV time frame only after 1-MA stimulation. Indeed, it is stage, and the breakdown of the nuclear envelope is a well known that starfish eggs lose their ability to prevent sign that the oocytes have been activated. Eggs of ne- polyspermic fertilization when inseminated after being merteans, ascidians, some annelids, and molluscs are treated with 1-MA for several hours (overripe eggs). blocked at the metaphase of the first meiotic division These results indicate that the competence of the egg until fertilization triggers the completion of meiosis. The cytoplasm to be successfully fertilized is achieved at a eggs of frogs and mammals are arrested and fertilized at precise maturation stage but is lost soon after that. Stud- metaphase II, i.e., after the second maturation spindle ies of oocyte maturation using Patiria pectinifera (a.k.a. has formed and one polar body has been extruded [1–4]. Asterina pectinifera, Pacific Ocean) and Astropecten ara- Thus, as highlighted by Ernest Everett Just, “the fertiliz- nciacus (Mediterranean Sea) have made interesting ob- ability of all animal eggs hangs together with some condi- servations about the time frame and other requirements tion in the cytoplasm of the egg and is independent of its for eggs’ optimal fertilizability and successful develop- nuclear state, as germinal vesicle, as first or second ment [10–12]. maturation-nucleus or as a completely matured nucleus” Recent studies have provided evidence that the cortical ([5], page 185), and may be related to the structural actin cytoskeleton is a key player in the development of organization of the cortex of the female gametes. mature and competent eggs manifesting normal Starfish and sea urchin eggs, which respectively are fertilization responses. It is well established that actin, naturally fertilized before the extrusion of the first polar which is one the most abundant and highly conserved body and at the end of the two meiotic divisions, are proteins in eukaryotic cells, participates in the mainten- useful animal models for the study of in vitro oocyte ance of cell shape, as well as in many cellular functions maturation, fertilization, and embryonic development. such as cell migration, growth, motility, organelle move- This is due to the fact that they offer advantages not ment, polarization, and exocytosis/endocytosis. Together only in size and abundance but also in transparency of with myosin, actin can drive not only muscle contrac- their cytoplasm and extracellular coats. These unique tion, but also regulation of genes in the nucleus [13]. properties of the echinoderm eggs allow us to perform Actin molecules undergo transition between monomeric time-lapse imaging to follow the early structural and globular (G-actin) and filamentous (F-actin) states under ionic events regulating the maturation process, during the control of its own concentration and by the action of which the oocytes acquire the full cytoplasmic compe- numerous actin-binding proteins (ABPs) that affect their tence to be fertilized, as well as egg activation. polymerization
Load more

Recommended publications
  • Induction of Cortical Granule Exocytosis of Pig Oocytes by Spermatozoa During Meiotic Maturation W
    Induction of cortical granule exocytosis of pig oocytes by spermatozoa during meiotic maturation W. H. Wang, M. Hosoe and Y. Shioya Department of Reproduction, National Institute of Animal Industry, Tsukuba Norindanchi, PO Box 5, Ibaraki 305, Japan Pig oocytes were examined to test their ability to undergo cortical granule exocytosis upon penetration by spermatozoa during meiotic maturation. Immature or maturing oocytes (cultured in vitro for 0 h, 26 h and 46 h) were inseminated with ejaculated boar spermatozoa in vitro. Before and after insemination, oocytes were stained with peanut agglutinin labelled with fluorescein isothiocyanate and the cortical granule distributions were examined under the fluorescent microscope and the laser confocal microscope. Before insemination, all the oocytes at the germinal vesicle stage showed a uniform distribution of cortical granules throughout the cortical cytoplasm. The granules migrated centrifugally during maturation and were distributed just beneath the oolemma in the oocytes after germinal vesicle breakdown, forming a monolayer in metaphase I or metaphase II. Cortical granules were still present in all penetrated oocytes at the germinal vesicle stage 18 h after insemination; in contrast, 26% and 84% of the oocytes inseminated at the stages of germinal vesicle breakdown or at metaphase I and II, respectively, completely released their cortical granules. Nuclear activation rates of penetrated oocytes were 0%, 38% and 96% in oocytes cultured for 0 h, 26 h and 46 h, respectively. Of the nuclear-activated oocytes, 67% (oocytes cultured for 26 h) and 88% (oocytes cultured for 46 h) released cortical granules completely. Complete cortical granule exocytosis was not observed in nuclear-inactivated oocytes.
    [Show full text]
  • EE Just's "Independent Irritability"
    ESSAY Molecular Reproduction & Development 76:966–974 (2009) E.E. Just’s ‘‘Independent Irritability’’ Revisited: The Activated Egg as Excitable Soft Matter STUART A. NEWMAN* Department of Cell Biology and Anatomy, New York Medical College, Valhalla, New York SUMMARY Ernest Everett Just’s experimental work on post-fertilization events in invertebrate eggs led him to posit a dynamic and directive role for the zygotic ‘‘ectoplasm’’ (cortical Just was correct in his estimation cytoplasm), in subsequent development. His perspective was neglected during the of the ‘‘informational’’ role of the years that followed his early death not only because of his well-documented margina- ectoplasm’s dynamics. lization as an African-American in U.S. science, but because his ideas were at odds with the growing gene-centrism of developmental biology in the latter half of the 20th century. This essay reviews experimental work that shows that the egg cortex in many animal groups is a chemically and mechanically active medium that sustains both spatiotemporal calcium ion transients and periodic deformations in the time leading up * Corresponding author: to cleavage. These wave phenomena are seen to play regulatory roles in germ plasm Department of Cell Biology and localization and gene expression, and influence the reliability and success of devel- Anatomy opmental outcomes. Just resisted vitalistic explanations for the active processes he New York Medical College Basic Science Building observed and inferred regarding the egg cortical cytoplasm, but recognized that the Valhalla, NY 10595. physics and chemistry of his time were inadequate to account for these phenomena E-mail: [email protected] and anticipated that expansions of these fields would be necessary to explain them.
    [Show full text]
  • Two Pathways Regulate Cortical Granule Translocation to Prevent Polyspermy in Mouse Oocytes
    ARTICLE Received 12 Jun 2016 | Accepted 27 Oct 2016 | Published 19 Dec 2016 DOI: 10.1038/ncomms13726 OPEN Two pathways regulate cortical granule translocation to prevent polyspermy in mouse oocytes Liam P. Cheeseman1,Je´roˆme Boulanger1, Lisa M. Bond1 & Melina Schuh1,2 An egg must be fertilized by a single sperm only. To prevent polyspermy, the zona pellucida, a structure that surrounds mammalian eggs, becomes impermeable upon fertilization, preventing the entry of further sperm. The structural changes in the zona upon fertilization are driven by the exocytosis of cortical granules. These translocate from the oocyte’s centre to the plasma membrane during meiosis. However, very little is known about the mechanism of cortical granule translocation. Here we investigate cortical granule transport and dynamics in live mammalian oocytes by using Rab27a as a marker. We show that two separate mechanisms drive their transport: myosin Va-dependent movement along actin filaments, and an unexpected vesicle hitchhiking mechanism by which cortical granules bind to Rab11a vesicles powered by myosin Vb. Inhibiting cortical granule translocation severely impaired the block to sperm entry, suggesting that translocation defects could contribute to miscarriages that are caused by polyspermy. 1 Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK. 2 Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Go¨ttingen 37077, Germany. Correspondence and requests for materials should be addressed to M.S. (email: [email protected]). NATURE COMMUNICATIONS | 7:13726 | DOI: 10.1038/ncomms13726 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/ncomms13726 viable human embryo can only develop from an egg that established marker for cortical granules21 (Fig.
    [Show full text]
  • Cortical Granules of the Sea Urchin Translocate Early in Oocyte Maturation
    Development 124, 1845-1850 (1997) 1845 Printed in Great Britain © The Company of Biologists Limited 1997 DEV6281 Cortical granules of the sea urchin translocate early in oocyte maturation Linnea K. Berg and Gary M. Wessel* Department of Molecular and Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA *Author for correspondence (e-mail: [email protected]) SUMMARY Cortical granules are secretory vesicles poised at the cortex ically in cortical granules. We found that the translocation of an egg that, upon stimulation by sperm contact at fer- of cortical granules in in vitro-matured oocytes begins with tilization, secrete their contents. These contents modify the the movement of the germinal vesicle to the oocyte cell extracellular environment and block additional sperm surface, and is 50% complete 1 hour after germinal vesicle from reaching the egg. The role of cortical granules in breakdown. In the in vitro-matured egg, 99% of the blocking polyspermy is conserved throughout much of cortical granules are at the cortex, indistinguishable from phylogeny. In the sea urchin, cortical granules accumulate translocation in oocytes that mature in vivo. We have also throughout the cytoplasm during oogenesis, but in mature found that eggs that mature in vitro are functionally eggs the cortical granules are attached to the plasma identical to eggs that mature in vivo by four criteria. membrane, having translocated to the cortex at some (1) The matured cells undergo a selective turnover of earlier time. To study the process of cortical granule mRNA encoding cortical granule contents. (2) The newly translocation to the cell surface we have devised a formed pronucleus begins transcription of histone procedure for maturation of sea urchin oocytes in vitro.
    [Show full text]
  • Reproductionresearch
    REPRODUCTIONRESEARCH Calcium-free vitrification reduces cryoprotectant-induced zona pellucida hardening and increases fertilization rates in mouse oocytes Mark G Larman, Courtney B Sheehan and David K Gardner Colorado Center for Reproductive Medicine, 799 East Hampden Avenue, Suite 520, Englewood, Colorado 80113, USA Correspondence should be addressed to D K Gardner; Email: [email protected] Abstract Despite the success of embryo cyropreservation, routine oocyte freezing has proved elusive with only around 200 children born since the first reported birth in 1986. The reason for the poor efficiency is unclear, but evidence of zona pellucida hardening following oocyte freezing indicates that current protocols affect oocyte physiology. Here we report that two cryoprotectants commonly used in vitrification procedures, dimethyl sulfoxide (DMSO) and ethylene glycol, cause a large transient increase in intracellular calcium concentration in mouse metaphase II (MII) oocytes comparable to the initial increase triggered at fertilization. Removal of extracellular calcium from the medium failed to affect the response exacted by DMSO challenge, but significantly reduced the ethylene glycol-induced calcium increase. These results suggest that the source of the DMSO-induced calcium increase is solely from the internal calcium pool, as opposed to ethylene glycol that causes an influx of calcium across the plasma membrane from the external medium. By carrying out vitrification in calcium-free media, it was found that zona hardening is significantly reduced and subsequent fertilization and development to the two-cell stage significantly increased. Furthermore, such calcium-free treatment appears not to affect the embryo adversely, as shown by development rates to the blastocyst stage and cell number/allocation.
    [Show full text]
  • Regulation of Dynamic Events by Microfilaments During Oocyte Maturation and Fertilization
    REPRODUCTIONREVIEW Regulation of dynamic events by microfilaments during oocyte maturation and fertilization Qing-Yuan Sun1,2 and Heide Schatten2 1State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China and 2Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA Correspondence should be addressed to H Schatten; Email: [email protected] Abstract Actin filaments (microfilaments) regulate various dynamic events during oocyte meiotic maturation and fertilization. In most species, microfilaments are not required for germinal vesicle breakdown and meiotic spindle formation, but they mediate per- ipheral nucleus (chromosome) migration, cortical spindle anchorage, homologous chromosome separation, cortex develop- ment/maintenance, polarity establishment, and first polar body emission during oocyte maturation. Peripheral cortical granule migration is controlled by microfilaments, while mitochondria movement is mediated by microtubules. During fertilization, microfilaments are involved in sperm incorporation, spindle rotation (mouse), cortical granule exocytosis, second polar body emission and cleavage ring formation, but are not required for pronuclear apposition (except for the mouse). Many of the events are driven by the dynamic interactions between myosin and actin filaments whose polymerization is regulated by RhoA, Cdc42, Arp2/3 and other signaling molecules. Studies have also shown that oocyte cortex organization and polarity formation mediated by
    [Show full text]
  • Calreticulin Antibody (Internal Region) Peptide-Affinity Purified Goat Antibody Catalog # Af4081a
    10320 Camino Santa Fe, Suite G San Diego, CA 92121 Tel: 858.875.1900 Fax: 858.622.0609 calreticulin Antibody (internal region) Peptide-affinity purified goat antibody Catalog # AF4081a Specification calreticulin Antibody (internal region) - Product Information Application WB Primary Accession P27797 Other Accession NP_004334.1, 811, 12317 (mouse), 64202 (rat) Reactivity Human Predicted Mouse, Rat, Pig, Dog, Cow Host Goat Clonality Polyclonal Concentration 0.5 mg/ml Isotype IgG Calculated MW 48142 calreticulin Antibody (internal region) - AF4081a (0.01 µg/ml) staining of Human (A) Additional Information and Rat (B) Lung lysates (35 µg protein in RIPA buffer). Primary incubation was 1 hour. Gene ID 811 Detected by chemiluminescence. Other Names Calreticulin, CRP55, Calregulin, Endoplasmic calreticulin Antibody (internal region) - reticulum resident protein 60, ERp60, References HACBP, grp60, CALR, CRTC The polypeptide binding conformation of Format calreticulin facilitates its cell-surface 0.5 mg/ml in Tris saline, 0.02% sodium expression under conditions of endoplasmic azide, pH7.3 with 0.5% bovine serum reticulum stress. Jeffery E, Peters LR, Raghavan albumin M. The Journal of biological chemistry 2011 Jan 286 (4): 2402-15. PMID: 21075854 Storage Maintain refrigerated at 2-8°C for up to 6 months. For long term storage store at -20°C in small aliquots to prevent freeze-thaw cycles. Precautions calreticulin Antibody (internal region) is for research use only and not for use in diagnostic or therapeutic procedures. calreticulin Antibody (internal region) - Protein Information Page 1/3 10320 Camino Santa Fe, Suite G San Diego, CA 92121 Tel: 858.875.1900 Fax: 858.622.0609 Name CALR (HGNC:1455) Synonyms CRTC Function Calcium-binding chaperone that promotes folding, oligomeric assembly and quality control in the endoplasmic reticulum (ER) via the calreticulin/calnexin cycle.
    [Show full text]
  • In Vitro Maturation of Porcine Oocyte
    IN VITRO MATURATION OF PORCINE OOCYTE Effects of lipid manipulation on fertilization, embryo development and cryo-resistance Elsa Cristina da Graça Prates Tese apresentada à Universidade de Évora para obtenção do Grau de Doutor em Ciências Veterinárias ORIENTADOR(ES): Professora Doutora Rosa Maria Lino Neto Pereira Professor Doutor José Luís Tirapicos Nunes CO-ORIENTADOR: Professor Doutor Carlos E. Plancha dos Santos ÉVORA, SETEMBRO DE 2012 INSTITUTO DE INVESTIGAÇÃO E FORMAÇÃO AVANÇADA i ii IN VITRO MATURATION OF PORCINE OOCYTE Effects of lipid manipulation on fertilization, embryo development and cryo-resistance Elsa Cristina da Graça Prates Tese apresentada à Universidade de Évora para obtenção do Grau de Doutor em Ciências Veterinárias ORIENTADOR(ES): Professora Doutora Rosa Maria Lino Neto Pereira Professor Doutor José Luís Tirapicos Nunes CO-ORIENTADOR: Professor Doutor Carlos E. Plancha dos Santos ÉVORA, SETEMBRO DE 2012 INSTITUTO DE INVESTIGAÇÃO E FORMAÇÃO AVANÇADA iii iv AGRADECIMENTOS A presente tese não seria possível sem a contribuição de várias pessoas e Instituições às quais gostaria de expressar um enorme reconhecimento e gratidão. Agradeço ao L-INIA de Santarém – Instituto Nacional de Recursos Biológicos (INRB), particularmente à UNIGRMA - Unidade de Genética, Reprodução e Melhoramento Animal, pelos meios humanos e materiais disponibilizados para a execução do trabalho que originou esta tese. Agradeço igualmente ao Departamento de Medicina Veterinária e Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM) da Universidade de Évora, pela disponibilidade nos recursos materiais e humanos disponibilizados para o desenrolar deste trabalho. À Professora Doutora Rosa Lino Neto Pereira por ter aceitado a orientação científica deste trabalho, pelo auxílio e estímulo para a concretização das várias fases do mesmo, pela dedicação e amizade.
    [Show full text]
  • The Involvement of Protein Kinase C and Actin Filaments in Cortical
    REPRODUCTIONRESEARCH The involvement of protein kinase C and actin filaments in cortical granule exocytosis in the rat E Eliyahu, A Tsaadon, N Shtraizent and R Shalgi Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel Correspondence should be addressed to R Shalgi; Email: [email protected] Abstract Mammalian sperm–egg fusion results in cortical granule exocytosis (CGE) and resumption of meiosis. Studies of various exocy- totic cells suggest that filamentous actin (F-actin) blocks exocytosis by excluding secretory vesicles from the plasma membrane. However, the exact function of these microfilaments, in mammalian egg CGE, is still elusive. In the present study we investi- gated the role of actin in the process of CGE, and the possible interaction between actin and protein kinase C (PKC), by using coimmunoprecipitation, immunohistochemistry and confocal microscopy. We identified an interaction between actin and the PKC alpha isoenzyme in non-activated metaphase II (MII) eggs and in eggs activated by phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA). F-actin was evenly distributed throughout the egg’s cytosol with a marked concentration at the cortex and at the plasma membrane. A decrease in the fluorescence signal of F-actin, which represents its depolymerization/ reorganization, was detected upon fertilization and upon parthenogenetic activation. Exposing the eggs to drugs that cause either polymerization or depolymerization of actin (jasplakinolide (JAS) and cytochalasin D (CD) respectively) did not induce or prevent CGE. However, CD, but not JAS, followed by a low dose of TPA doubled the percentage of eggs undergoing com- plete CGE, as compared with TPA alone.
    [Show full text]
  • Calcium-Free Vitrification Reduces Cryoprotectant-Induced Zona
    REPRODUCTIONRESEARCH Calcium-free vitrification reduces cryoprotectant-induced zona pellucida hardening and increases fertilization rates in mouse oocytes Mark G Larman, Courtney B Sheehan and David K Gardner Colorado Center for Reproductive Medicine, 799 East Hampden Avenue, Suite 520, Englewood, Colorado 80113, USA Correspondence should be addressed to D K Gardner; Email: [email protected] Abstract Despite the success of embryo cyropreservation, routine oocyte freezing has proved elusive with only around 200 children born since the first reported birth in 1986. The reason for the poor efficiency is unclear, but evidence of zona pellucida hardening following oocyte freezing indicates that current protocols affect oocyte physiology. Here we report that two cryoprotectants commonly used in vitrification procedures, dimethyl sulfoxide (DMSO) and ethylene glycol, cause a large transient increase in intracellular calcium concentration in mouse metaphase II (MII) oocytes comparable to the initial increase triggered at fertilization. Removal of extracellular calcium from the medium failed to affect the response exacted by DMSO challenge, but significantly reduced the ethylene glycol-induced calcium increase. These results suggest that the source of the DMSO-induced calcium increase is solely from the internal calcium pool, as opposed to ethylene glycol that causes an influx of calcium across the plasma membrane from the external medium. By carrying out vitrification in calcium-free media, it was found that zona hardening is significantly reduced and subsequent fertilization and development to the two-cell stage significantly increased. Furthermore, such calcium-free treatment appears not to affect the embryo adversely, as shown by development rates to the blastocyst stage and cell number/allocation.
    [Show full text]
  • A Role of Lipid Metabolism During Cumulus-Oocyte Complex Maturation: Impact of Lipid Modulators to Improve Embryo Production
    Hindawi Publishing Corporation Mediators of Inflammation Volume 2014, Article ID 692067, 11 pages http://dx.doi.org/10.1155/2014/692067 Review Article A Role of Lipid Metabolism during Cumulus-Oocyte Complex Maturation: Impact of Lipid Modulators to Improve Embryo Production E. G. Prates,1,2 J. T. Nunes,2 and R. M. Pereira1,3 1 INIAV Instituto Nacional de Investigac¸ao˜ Agraria´ e Veterinaria,´ Unidade de Biotecnologias e Recursos Geneticos-Santar´ em,´ Quinta da Fonte Boa, 2000-048 Vale de Santarem,´ Portugal 2 Instituto de Cienciasˆ Agrarias´ e Ambientais Mediterranicasˆ (ICAAM), Universidade de Evora,´ NucleodaMitra,Ap.94,´ 7002-554 Evora,´ Portugal 3 Escola Universitaria´ Vasco da Gama, Mosteiro de S. Jorge de Milreu,´ 3040-714 Coimbra, Portugal Correspondence should be addressed to R. M. Pereira; [email protected] Received 15 November 2013; Revised 9 January 2014; Accepted 18 January 2014; Published 6 March 2014 Academic Editor: Izabela Woclawek-Potocka Copyright © 2014 E. G. Prates et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Oocyte intracellular lipids are mainly stored in lipid droplets (LD) providing energy for proper growth and development. Lipids are also important signalling molecules involved in the regulatory mechanisms of maturation and hence in oocyte competence acquisition. Recent studies show that LD are highly dynamic organelles. They change their shape, volume, and location within the ooplasm as well as their interaction with other organelles during the maturation process. The droplets high lipid content has been correlated with impaired oocyte developmental competence and low cryosurvival.
    [Show full text]
  • The Molecular Mechanisms Underlying Exocytosis in Sea Urchin Eggs
    THE MOLECULAR MECHANISMS UNDERLYING EXOCYTOSIS IN SEA URCHIN EGGS. Julia Catherine Avery Department of Physiology University College University of London. A Thesis submitted for the degree of Doctor of Philosophy in the University of London. March 1996. ProQuest Number: 10017484 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10017484 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT. Exocytosis is a ubiquitous cellular mechanism for the export of secretory products and the insertion of proteins and lipid into the plasma membrane. The sea urchin egg is an ideal system in which to study exocytosis. Fertilization in the sea urchin egg is characterized by a transient increase in intracellular calcium. This triggers the exocytosis of cortical secretory granules which lie immediately beneath the plasma membrane of unfertilized eggs, producing a structure called the fertilization envelope. Exocytosis can also be studied directly; the exocytotic apparatus, the egg cortex, can be isolated and responds to the physiological trigger - Ca^^ - in vitro. It has been suggested that the molecular mechanisms underlying exocytosis are evolutionarily conserved.
    [Show full text]