1
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Watabe M, Hiraiwa A, Sakai M, Ueno T, Ueno S, Nakajima K, Yaoita Y, Iwao Y. Sperm MMP-2 is indispensable for fast electrical block to polyspermy at fertilization in Xenopus tropicalis. Mol Reprod Dev 2021; 88:744-757. [PMID: 34618381 DOI: 10.1002/mrd.23540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 09/24/2021] [Indexed: 01/10/2023]
Abstract
Sperm matrix metalloproteinase-2 (MMP-2) is necessary for frog fertilization. Monospermy is ensured by a fast, electrical block to polyspermy mediated by a positive fertilization potential. To determine the role of the MMP-2 hemopexin domain (HPX) in a fast block to polyspermy during fertilization of the frog, Xenopus tropicalis, we prepared mutant frogs deficient in mmp2 gene using the transcription activator-like effector nuclease method. mmp2 ΔHPX (-/-) sperm without MMP-2 protein were able to fertilize wild-type (WT; +/+) eggs. However, polyspermy occurred in some eggs. The mutant sperm generated a normal fertilization potential amounting to 10 mV, and were able to fertilize eggs at 10 mV, at which WT sperm never fertilized. Sensitivity during voltage-dependent fertilization decreased in mutant sperm. This study demonstrates for the first time that the genetic alteration of the MMP-2 molecule in sperm causes polyspermy during fertilization of a monospermic species. Our findings provide reliable evidence that sperm MMP-2 is indispensable for the fast, electrical block to polyspermy during Xenopus fertilization.
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Affiliation(s)
- Mami Watabe
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Azusa Hiraiwa
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Mami Sakai
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Tomoyo Ueno
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Shuichi Ueno
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Keisuke Nakajima
- Division of Embryology, Amphibian Research Center, Hiroshima University, Higashihiroshima, Japan
| | - Yoshio Yaoita
- Division of Embryology, Amphibian Research Center, Hiroshima University, Higashihiroshima, Japan
| | - Yasuhiro Iwao
- Laboratory of Reproductive Developmental Biology and Developmental Cell Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
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2
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Wozniak KL, Carlson AE. Ion channels and signaling pathways used in the fast polyspermy block. Mol Reprod Dev 2020; 87:350-357. [PMID: 31087507 PMCID: PMC6851399 DOI: 10.1002/mrd.23168] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 04/22/2019] [Accepted: 04/24/2019] [Indexed: 01/03/2023]
Abstract
Fertilization of an egg by multiple sperms, polyspermy, is lethal to most sexually reproducing species. To combat the entry of additional sperm into already fertilized eggs, organisms have developed various polyspermy blocks. One such barrier, the fast polyspermy block, uses a fertilization-activated depolarization of the egg membrane to electrically inhibit supernumerary sperm from entering the egg. The fast block is commonly used by eggs of oviparous animals with external fertilization. In this review, we discuss the history of the fast block discovery, as well as general features shared by all organisms that use this polyspermy block. Given the diversity of habitats of external fertilizers, the fine details of the fast block-signaling pathways differ drastically between species, including the identity of the depolarizing ions. We highlight the known molecular mediators of these signaling pathways in amphibians and echinoderms, with a fine focus on ion channels that signal these fertilization-evoked depolarizations. We also discuss the investigation for a fast polyspermy block in mammals and teleost fish, and we outline potential fast block triggers. Since the first electrical recordings made on eggs in the 1950s, the fields of developmental biology and electrophysiology have substantially matured, and yet we are only now beginning to discern the intricate molecular mechanisms regulating the fast block to polyspermy.
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Affiliation(s)
- Katherine L Wozniak
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anne E Carlson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
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3
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Iwao Y, Kimoto C, Fujimoto A, Suda A, Hara Y. Physiological polyspermy: Selection of a sperm nucleus for the development of diploid genomes in amphibians. Mol Reprod Dev 2020; 87:358-369. [DOI: 10.1002/mrd.23235] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 06/23/2019] [Indexed: 01/04/2023]
Affiliation(s)
- Yasuhiro Iwao
- Laboratory of Reproductive Developmental Biology, Division of Earth Sciences, Biology, and Chemistry, Graduate School of Sciences and Technology for InnovationYamaguchi University Yamaguchi Yamaguchi Japan
| | - Chihiro Kimoto
- Laboratory of Reproductive Developmental Biology, Division of Earth Sciences, Biology, and Chemistry, Graduate School of Sciences and Technology for InnovationYamaguchi University Yamaguchi Yamaguchi Japan
| | - Ayaka Fujimoto
- Laboratory of Reproductive Developmental Biology, Division of Earth Sciences, Biology, and Chemistry, Graduate School of Sciences and Technology for InnovationYamaguchi University Yamaguchi Yamaguchi Japan
| | - Asuka Suda
- Laboratory of Reproductive Developmental Biology, Division of Earth Sciences, Biology, and Chemistry, Graduate School of Sciences and Technology for InnovationYamaguchi University Yamaguchi Yamaguchi Japan
| | - Yuki Hara
- Laboratory of Evolutionary Cell Biology, Department of Biology and Chemistry, Faculty of ScienceYamaguchi University Yamaguchi Yamaguchi Japan
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4
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Watabe M, Izaki K, Fujino S, Maruyama M, Kojima C, Hiraiwa A, Ueno S, Iwao Y. The electrical block to polyspermy induced by an intracellular Ca
2+
increase at fertilization of the clawed frogs,
Xenopus laevis
and
Xenopus tropicalis. Mol Reprod Dev 2019; 86:387-403. [DOI: 10.1002/mrd.23115] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/26/2018] [Accepted: 01/09/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Mami Watabe
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Kenta Izaki
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Shohei Fujino
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Mei Maruyama
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Chiho Kojima
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Azusa Hiraiwa
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Shuichi Ueno
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
| | - Yasuhiro Iwao
- Laboratory of Reproductive Developmental BiologyGraduate School of Sciences and Technology for Innovation, Yamaguchi University Yamaguchi Japan
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5
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Okamura Y, Kawanabe A, Kawai T. Voltage-Sensing Phosphatases: Biophysics, Physiology, and Molecular Engineering. Physiol Rev 2019; 98:2097-2131. [PMID: 30067160 DOI: 10.1152/physrev.00056.2017] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Voltage-sensing phosphatase (VSP) contains a voltage sensor domain (VSD) similar to that in voltage-gated ion channels, and a phosphoinositide phosphatase region similar to phosphatase and tensin homolog deleted on chromosome 10 (PTEN). The VSP gene is conserved from unicellular organisms to higher vertebrates. Membrane depolarization induces electrical driven conformational rearrangement in the VSD, which is translated into catalytic enzyme activity. Biophysical and structural characterization has revealed details of the mechanisms underlying the molecular functions of VSP. Coupling between the VSD and the enzyme is tight, such that enzyme activity is tuned in a graded fashion to the membrane voltage. Upon VSP activation, multiple species of phosphoinositides are simultaneously altered, and the profile of enzyme activity depends on the history of the membrane potential. VSPs have been the obvious candidate link between membrane potential and phosphoinositide regulation. However, patterns of voltage change regulating VSP in native cells remain largely unknown. This review addresses the current understanding of the biophysical biochemical properties of VSP and provides new insight into the proposed functions of VSP.
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Affiliation(s)
- Yasushi Okamura
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Akira Kawanabe
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Takafumi Kawai
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
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6
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Universality and Diversity of a Fast, Electrical Block to Polyspermy During Fertilization in Animals. DIVERSITY AND COMMONALITY IN ANIMALS 2018. [DOI: 10.1007/978-4-431-56609-0_24] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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7
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Fertilization 2: Polyspermic Fertilization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1001:105-123. [DOI: 10.1007/978-981-10-3975-1_7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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8
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Iwao Y, Shiga K, Shiroshita A, Yoshikawa T, Sakiie M, Ueno T, Ueno S, Ijiri TW, Sato KI. The need of MMP-2 on the sperm surface for Xenopus fertilization: Its role in a fast electrical block to polyspermy. Mech Dev 2014; 134:80-95. [DOI: 10.1016/j.mod.2014.09.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 09/22/2014] [Accepted: 09/24/2014] [Indexed: 01/31/2023]
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9
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Mitchison T, Wühr M, Nguyen P, Ishihara K, Groen A, Field C. Growth, interaction, and positioning of microtubule asters in extremely large vertebrate embryo cells. Cytoskeleton (Hoboken) 2012; 69:738-50. [PMID: 22786885 PMCID: PMC3690567 DOI: 10.1002/cm.21050] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2012] [Revised: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 01/03/2023]
Abstract
Ray Rappaport spent many years studying microtubule asters, and how they induce cleavage furrows. Here, we review recent progress on aster structure and dynamics in zygotes and early blastomeres of Xenopus laevis and Zebrafish, where cells are extremely large. Mitotic and interphase asters differ markedly in size, and only interphase asters span the cell. Growth of interphase asters occurs by a mechanism that allows microtubule density at the aster periphery to remain approximately constant as radius increases. We discuss models for aster growth, and favor a branching nucleation process. Neighboring asters that grow into each other interact to block further growth at the shared boundary. We compare the morphology of interaction zones formed between pairs of asters that grow out from the poles of the same mitotic spindle (sister asters) and between pairs not related by mitosis (non-sister asters) that meet following polyspermic fertilization. We argue growing asters recognize each other by interaction between antiparallel microtubules at the mutual boundary, and discuss models for molecular organization of interaction zones. Finally, we discuss models for how asters, and the centrosomes within them, are positioned by dynein-mediated pulling forces so as to generate stereotyped cleavage patterns. Studying these problems in extremely large cells is starting to reveal how general principles of cell organization scale with cell size.
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Affiliation(s)
- T.J. Mitchison
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
| | - M. Wühr
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
| | - P Nguyen
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
| | - K. Ishihara
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
| | - A. Groen
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
| | - C.M. Field
- Dept Systems Biology, Harvard Medical School and Marine Biological Laboratory, Woods Hole
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10
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Abstract
Fertilization is indispensable not only for restoring diploid genomes but also for the initiation of early embryonic cell cycles in sexual reproduction. While most animals exhibit monospermy, which is ensured by polyspermy blocks to prevent the entry of extra sperm into the egg at fertilization, several animals exhibit physiological polyspermy, in which the entry of several sperm is permitted but only one sperm nucleus participates in the formation of a zygote nucleus. Polyspermy requires that the sperm transmit the egg activation signal more slowly, thus allowing the egg to accept several sperm. An increase in intracellular Ca(2+) concentration induced by the fertilizing sperm is both necessary and sufficient for egg activation in polyspermy. Multiple small Ca(2+) waves induced by several fertilizing sperm result in a long-lasting Ca(2+) rise, which is a characteristic of polyspermic amphibian eggs. We introduced a novel soluble sperm factor for egg activation, sperm-specific citrate synthase, into polyspermic newt eggs to cause Ca(2+) waves. Citrate synthase may perform dual functions: as an enzyme in mitochondria and as a Ca(2+)-inducing factor in egg cytoplasm. We also discuss the close relationship between the mode of fertilization and the Ca(2+) rise at egg activation and consider changes in this process through evolution in vertebrates.
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Affiliation(s)
- Yasuhiro Iwao
- Laboratory of Molecular Developmental Biology, Department of Applied Molecular Biosciences, Graduate School of Medicine, Yamaguchi University, 753-8512 Yamaguchi, Japan.
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11
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Kushima S, Mammadova G, Mahbub Hasan AKM, Fukami Y, Sato KI. Characterization of Lipovitellin 2 as a Tyrosine-Phosphorylated Protein in Oocytes, Eggs and Early Embryos ofXenopus laevis. Zoolog Sci 2011; 28:550-9. [DOI: 10.2108/zsj.28.550] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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12
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Mable BK, Alexandrou MA, Taylor MI. Genome duplication in amphibians and fish: an extended synthesis. J Zool (1987) 2011. [DOI: 10.1111/j.1469-7998.2011.00829.x] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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13
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The Ca2+ increase by the sperm factor in physiologically polyspermic newt fertilization: its signaling mechanism in egg cytoplasm and the species-specificity. Dev Biol 2011; 351:266-76. [PMID: 21237143 DOI: 10.1016/j.ydbio.2011.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 12/27/2010] [Accepted: 01/05/2011] [Indexed: 11/22/2022]
Abstract
The newt, Cynops pyrrhogaster, exhibits physiological polyspermic fertilization, in which several sperm enter an egg before egg activation. An intracellular Ca(2+) increase occurs as a Ca(2+) wave at each sperm entry site in the polyspermic egg. Some Ca(2+) waves are preceded by a transient spike-like Ca(2+) increase, probably caused by a tryptic protease in the sperm acrosome at the contact of sperm on the egg surface. The following Ca(2+) wave was induced by a sperm factor derived from sperm cytoplasm after sperm-egg membrane fusion. The Ca(2+) increase in the isolated, cell-free cytoplasm indicates that the endoplasmic reticulum is the major Ca(2+) store for the Ca(2+) wave. We previously demonstrated that citrate synthase in the sperm cytoplasm is a major sperm factor for egg activation in newt fertilization. In the present study, we found that the activation by the sperm factor as well as by fertilizing sperm was prevented by an inhibitor of citrate synthase, palmitoyl CoA, and that an injection of acetyl-CoA or oxaloacetate caused egg activation, indicating that the citrate synthase activity is necessary for egg activation at fertilization. In the frog, Xenopus laevis, which exhibits monospermic fertilization, we were unable to activate the eggs with either the homologous sperm extract or the Cynops sperm extract, indicating that Xenopus sperm lack the sperm factor for egg activation and that their eggs are insensitive to the newt sperm factor. The mechanism of egg activation in the monospermy of frog eggs is quite different from that in the physiological polyspermy of newt eggs.
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14
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Nagai K, Ishida T, Hashimoto T, Harada Y, Ueno S, Ueda Y, Kubo H, Iwao Y. The Sperm-surface glycoprotein, SGP, is necessary for fertilization in the frog, Xenopus laevis. Dev Growth Differ 2009; 51:499-510. [PMID: 19469788 DOI: 10.1111/j.1440-169x.2009.01112.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
To identify a molecule involved in sperm-egg plasma membrane binding at fertilization, a monoclonal antibody against a sperm-surface glycoprotein (SGP) was obtained by immunizing mice with a sperm membrane fraction of the frog, Xenopus laevis, followed by screening of the culture supernatants based on their inhibitory activity against fertilization. The fertilization of both jellied and denuded eggs was effectively inhibited by pretreatment of sperm with intact anti-SGP antibody as well as its Fab fragment, indicating that the antibody recognizes a molecule on the sperm's surface that is necessary for fertilization. On Western blots, the anti-SGP antibody recognized large molecules, with molecular masses of 65-150 kDa and minor smaller molecules with masses of 20-28 kDa in the sperm membrane vesicles. SGP was distributed over nearly the entire surface of the sperm, probably as an integral membrane protein in close association with microfilaments. More membrane vesicles containing SGP bound to the surface were found in the animal hemisphere compared with the vegetal hemisphere in unfertilized eggs, but the vesicle-binding was not observed in fertilized eggs. These results indicate that SGP mediates sperm-egg membrane binding and is responsible for the establishment of fertilization in Xenopus.
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Affiliation(s)
- Keita Nagai
- Laboratory of Molecular Developmental Biology, Graduate School of Medicine, Yamaguchi University, Yamaguchi 753-8512, Japan
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15
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Abstract
Fertilization is the union of a single sperm and an egg, an event that results in a diploid embryo. Animals use many mechanisms to achieve this ratio; the most prevalent involves physically blocking the fusion of subsequent sperm. Selective pressures to maintain monospermy have resulted in an elaboration of diverse egg and sperm structures. The processes employed for monospermy are as diverse as the animals that result from this process. Yet, the fundamental molecular requirements for successful monospermic fertilization are similar, implying that animals may have a common ancestral block to polyspermy. Here, we explore this hypothesis, reviewing biochemical, molecular, and genetic discoveries that lend support to a common ancestral mechanism. We also consider the evolution of alternative or radical techniques, including physiological polyspermy, with respect to our ability to describe a parsimonious guide to fertilization.
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Affiliation(s)
- Julian L Wong
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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16
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Glahn D, Nuccitelli R. Voltage-clamp study of the activation currents and fast block to polyspermy in the egg of Xenopus laevis. Dev Growth Differ 2003; 45:187-97. [PMID: 12752506 DOI: 10.1034/j.1600-0854.2004.00684.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Voltage-clamped mature, jelly-intact Xenopus eggs were used to carefully examine the ionic currents crossing the plasma membrane before, during, and after fertilization. The bulk of the fertilization current was transient, of large amplitude, and reversed at the predicted Cl- reversal potential. However, the large amplitude fertilization current was preceded by a small, step-like increase in holding current. This small increase in holding current is referred to in this paper as Ion to acknowledge its qualitative similarity to the Ion current previously described in the sea urchin. It was observed in both fertilized and artificially activated eggs, and was found to be unaffected by 10 mm tetra-ethyl ammonium (TEA), a concentration found to block K+ currents in Rana pipiens. Current-voltage relationships are presented for the large fertilization potential, and show that the fertilization currents have a marked outward rectification and are voltage sensitive. These properties are in contrast to the total lack of rectification and slight voltage sensitivity seen before or after the fertilization currents. The time required for sperm to fertilize the egg was found to be voltage dependent with a relatively more depolarized voltage requiring a longer time for fertilization to occur. The percentage of eggs blocked with varying potential levels was determined and this information was fitted to a modified Boltzmann equation having a midpoint of -9 mV.
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Affiliation(s)
- David Glahn
- Section of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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17
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Iwao Y. Mechanisms of Egg Activation and Polyspermy Block in Amphibians and Comparative Aspects with Fertilization in Other Vertebrates. Zoolog Sci 2000. [DOI: 10.2108/zsj.17.699] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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19
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Iwao Y, Yasumitsu K, Narihira M, Jiang J, Nagahama Y. Changes in microtubule structures during the first cell cycle of physiologically polyspermic newt eggs. Mol Reprod Dev 1997; 47:210-21. [PMID: 9136124 DOI: 10.1002/(sici)1098-2795(199706)47:2<210::aid-mrd13>3.0.co;2-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The unfertilized egg of the newt, Cynops pyrrhogaster, has a second meiotic spindle at the animal pole and numerous cortical cytasters. After physiologically polyspermic fertilization, all sperm nuclei incorporated into the egg develop sperm asters, and the cortical cytasters change into bundles of cortical microtubules. The size of the sperm asters in the animal hemisphere is approximately 5.6-fold larger than that in the vegetal hemisphere. Only one sperm nucleus moves toward the center of the animal hemisphere to form a zygote nucleus with the egg nucleus. This movement is inhibited by nocodazole, but not by cytochalasin B. The centrosome in the zygote nucleus divides into two parts to form a bipolar spindle for the first cleavage synchronously with the nuclear cycle, but centrosomes of accessory sperm nuclei in the vegetal hemisphere remained to form monopolar interphase asters and subsequently degenerate around the first cleavage stage. The size of sperm asters in monospermically fertilized Xenopus eggs was approximately 37-fold larger than those in Cynops eggs. Since sperm asters that formed in polyspermically fertilized Xenopus eggs exclude each other, the formation of a zygote nucleus is inhibited. Cynops sperm nuclei form larger asters in Xenopus eggs, whereas Xenopus sperm nuclei form smaller asters in Cynops eggs compared with those in homologous eggs. Since there was no significant difference in the concentration of monomeric tubulin between those eggs, the size of sperm asters is probably regulated by a component(s) in egg cytoplasm. Smaller asters in physiologically polyspermic newt eggs might be useful for selecting only one sperm nucleus to move toward the egg nucleus.
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Affiliation(s)
- Y Iwao
- Department of Biological Science, Faculty of Science, Yamaguchi University, Japan
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20
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Iwao Y, Miki A, Kobayashi M, Onitake K. Activation of Xenopus Eggs by an Extract of Cynops Sperm. (fertilization/egg-activation/polyspermy block/sperm protease). Dev Growth Differ 1994. [DOI: 10.1111/j.1440-169x.1994.00469.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Abstract
Fertilization potentials in Pelvetia fastigiata, Fucus vesiculosus, and Fucus ceranoides were studied to examine whether eggs of fucoid algae have an electrical block against polyspermy. The resting potential of eggs of all species was about -60 mV, depolarizing, respectively, to -24 +/- 5 mV (SD, n = 9) for 7.5 +/- 2.1 (n = 8) min, -26 +/- 5 (n = 9) mV for 6.4 +/- 2.3 (n = 9) min, and -24 +/- 6 (n = 5) mV for 6.7 +/- 1.9 (n = 4) min. The depolarization was slower, and the fertilization potential was about 10 mV more negative in eggs of both F. vesiculosus and Pelvetia fertilized in 45-mM Na+ ASW; many of these eggs were polyspermic. Steady current was passed through unfertilized eggs of F. vesiculosus prior to insemination to test the potential dependence of fertilization. Eggs (n = 10) bound sperm at all potentials tested (-45 to -23 mV), but fertilization was prevented if eggs were held at potentials more positive than -45 to -37 mV. Eggs underwent a second depolarization if artificially hyperpolarized to potentials more negative than -50 mV immediately after the rise of a normal fertilization potential. Thus, fucoid eggs have an electrical fast block against polyspermy. Only in F. ceranoides does the formation of the cell wall after fertilization appear to be fast enough (i.e., 3-6 min postfertilization versus at 10-15 min in F. vesiculosus and P. fastigiata) to replace the fertilization potential as a polyspermy block. Nonfertilizing fucoid sperm swim away from the egg surface by 1-3 min after rise of the fertilization potential. This suggests that there is another "intermediate block" against polyspermy.
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Affiliation(s)
- S H Brawley
- Department of Biology, Vanderbilt University, Nashville, Tennessee 37235
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22
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Chapter 3 Electrical Characteristics of Oocytes and Eggs. CURRENT TOPICS IN MEMBRANES 1991. [DOI: 10.1016/s0070-2161(08)60801-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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23
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Iwao Y, Jaffe LA. Evidence that the voltage-dependent component in the fertilization process is contributed by the sperm. Dev Biol 1989; 134:446-51. [PMID: 2744242 DOI: 10.1016/0012-1606(89)90117-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To investigate the mechanisms that account for the voltage dependence of fertilization and provide an electrical block to polyspermy, we studied cross-fertilizations between three species of amphibians having different degrees of voltage dependence. Anurans, such as the toad Bufo japonicus, as well as the primitive urodele Hynobius nebulosus, have voltage-dependent fertilization; other urodeles, such as Cynops pyrrhogaster, have voltage-independent fertilization (Y. Iwao, 1989, Dev. Biol. 134, 438-445). Entry of Hynobius sperm into Cynops eggs was blocked by clamping the egg's membrane potential at +40 mV, as is the case for fertilization of Hynobius eggs with Hynobius sperm, but not for fertilization of Cynops eggs with Cynops sperm. Therefore, fertilization was voltage dependent in an experimental condition where only the sperm could be contributing this characteristic. The voltage-dependent properties of fertilization between Bufo eggs and Hynobius sperm were also characteristic of the sperm species; fertilization was blocked at +50 mV as in Hynobius fertilization, but not at +20 mV as in Bufo fertilization. These results support the conclusion that the voltage dependence of fertilization results from a component contributed by the sperm.
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Affiliation(s)
- Y Iwao
- Biological Institute, Faculty of Science, Yamaguchi University, Japan
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