scholarly journals Egg activation in physiological polyspermy

Reproduction ◽  
2012 ◽  
Vol 144 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Yasuhiro Iwao
Keyword(s):  
Citrate Synthase ◽  
Sperm Nucleus ◽  
Embryonic Cell ◽  
Egg Activation ◽  
Cell Cycles ◽  
Close Relationship ◽  
Intracellular Ca ◽  
Sperm Factor ◽  
Necessary And Sufficient ◽  
Dual Functions

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 Ca2+ concentration induced by the fertilizing sperm is both necessary and sufficient for egg activation in polyspermy. Multiple small Ca2+ waves induced by several fertilizing sperm result in a long-lasting Ca2+ 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 Ca2+ waves. Citrate synthase may perform dual functions: as an enzyme in mitochondria and as a Ca2+-inducing factor in egg cytoplasm. We also discuss the close relationship between the mode of fertilization and the Ca2+ rise at egg activation and consider changes in this process through evolution in vertebrates.

scholarly journals The cytosolic sperm factor that triggers Ca2+ oscillations and egg activation in mammals is a novel phospholipase C: PLCζ

Reproduction ◽  
2004 ◽  
Vol 127 (4) ◽  
pp. 431-439 ◽  
Author(s):  
K Swann ◽  
M G Larman ◽  
C M Saunders ◽  
F A Lai
Keyword(s):  
Membrane Fusion ◽  
Phospholipase C ◽  
Potential Role ◽  
Egg Activation ◽  
Specific Factor ◽  
Sperm Protein ◽  
Protein Factor ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Sperm Factor

When sperm activate eggs at fertilization the signal for activation involves increases in the intracellular free Ca2+concentration. In mammals the Ca2+changes at fertilization consist of intracellular Ca2+oscillations that are driven by the generation of inositol 1,4,5-trisphosphate (InsP3). It is not established how sperm trigger the increases in InsP3and Ca2+at fertilization. One theory suggests that sperm initiate signals to activate the egg by introducing a specific factor into the egg cytoplasm after membrane fusion. This theory has been mainly based upon the observation that injecting a cytosolic sperm protein factor into eggs can trigger the same pattern of Ca2+oscillations induced by the sperm. We have recently shown that this soluble sperm factor protein is a novel form of phospholipase C (PLC), and it is referred to as PLCζ(zeta). We describe the evidence that led to the identification of PLCζ and discuss the issues relating to its potential role in fertilization.

scholarly journals A Maternal Smad Protein Regulates Early Embryonic Apoptosis in Xenopus laevis

2002 ◽  
Vol 22 (5) ◽  
pp. 1317-1328 ◽  
Author(s):  
Yuko Miyanaga ◽  
Ingrid Torregroza ◽  
Todd Evans
Keyword(s):  
Functional Analysis ◽  
Cell Survival ◽  
Caspase 3 ◽  
Embryonic Cell ◽  
Early Embryogenesis ◽  
Cell Cycles ◽  
Smad Proteins ◽  
Smad Protein ◽  
Smad Signaling Pathway ◽  
A Cell

ABSTRACT We identified cDNAs encoding the Xenopus Smad proteins most closely related to mammalian Smad8, and we present a functional analysis of this activity (also referred to recently as xSmad11). Misexpression experiments indicate that xSmad8(11) regulates pathways distinct from those regulated by the closely related xSmad1. Embryos that develop from eggs depleted of xSmad8(11) mRNA fail to gastrulate; instead, at the time of gastrulation, they initiate a widespread program of apoptosis, via a CPP32/caspase 3 pathway. Embryos that avoid this fate display gastrulation defects. Activation of apoptosis is rescued by expression of xSmad8(11) but not xSmad1. Our results demonstrate an embryonic requirement for Smad8(11) activity and show that a maternally derived Smad signaling pathway is required for gastrulation and for mediating a cell survival program during early embryogenesis. We suggest that xSmad8(11) functions as part of a maternally derived mechanism shown previously by others to monitor Xenopus early embryonic cell cycles.

scholarly journals PLCζ or PAWP: revisiting the putative mammalian sperm factor that triggers egg activation and embryogenesis

2015 ◽  
Vol 21 (5) ◽  
pp. 383-388 ◽  
Author(s):  
Junaid Kashir ◽  
Michail Nomikos ◽  
Karl Swann ◽  
F. Anthony Lai
Keyword(s):  
Egg Activation ◽  
Mammalian Sperm ◽  
Sperm Factor

scholarly journals Activation of the Inositol (1,4,5)-Triphosphate Calcium Gate Receptor Is Required for HIV-1 Gag Release

2010 ◽  
Vol 84 (13) ◽  
pp. 6438-6451 ◽  
Author(s):  
Lorna S. Ehrlich ◽  
Gisselle N. Medina ◽  
Mahfuz B. Khan ◽  
Michael D. Powell ◽  
Katsuhiko Mikoshiba ◽  
...  
Keyword(s):  
Particle Production ◽  
Receptor Interaction ◽  
Particle Release ◽  
Virus Particles ◽  
Intracellular Ca ◽  
Necessary And Sufficient ◽  
Gag Assembly ◽  
Immature Virus ◽  
Interfering Rna ◽  
Hiv 1

ABSTRACT The structural precursor polyprotein, Gag, encoded by all retroviruses, including the human immunodeficiency virus type 1 (HIV-1), is necessary and sufficient for the assembly and release of particles that morphologically resemble immature virus particles. Previous studies have shown that the addition of Ca2+ to cells expressing Gag enhances virus particle production. However, no specific cellular factor has been implicated as mediator of Ca2+ provision. The inositol (1,4,5)-triphosphate receptor (IP3R) gates intracellular Ca2+ stores. Following activation by binding of its ligand, IP3, it releases Ca2+ from the stores. We demonstrate here that IP3R function is required for efficient release of HIV-1 virus particles. Depletion of IP3R by small interfering RNA, sequestration of its activating ligand by expression of a mutated fragment of IP3R that binds IP3 with very high affinity, or blocking formation of the ligand by inhibiting phospholipase C-mediated hydrolysis of the precursor, phosphatidylinositol-4,5-biphosphate, inhibited Gag particle release. These disruptions, as well as interference with ligand-receptor interaction using antibody targeted to the ligand-binding site on IP3R, blocked plasma membrane accumulation of Gag. These findings identify IP3R as a new determinant in HIV-1 trafficking during Gag assembly and introduce IP3R-regulated Ca2+ signaling as a potential novel cofactor in viral particle release.

scholarly journals Evolution of CDK1 paralog specializations in a lineage with fast developing planktonic embryos

2019 ◽  
Author(s):  
Xiaofei Ma ◽  
Jan Inge Øvrebø ◽  
Eric M Thompson
Keyword(s):  
General Rule ◽  
Embryonic Cell ◽  
Cyclin B ◽  
Gene Duplications ◽  
Structural Elements ◽  
Oikopleura Dioica ◽  
Cell Cycles ◽  
Protein Levels ◽  
Binding Interface ◽  
M Phase

AbstractThe active site of the essential, eukaryotic CDK1 kinase is generated by core structural elements, among which the PSTAIRE motif in the critical αC-helix, is universally conserved in metazoans. The CDK2 kinase, sharing the PSTAIRE, arose early in metazoan evolution and permitted subdivision of tasks along the S-M-phase axis. The marine chordate, Oikopleura dioica, is the only metazoan known to possess more than a single CDK1 ortholog, and all of its 5 paralogs show sequence divergences in the PSTAIRE. Through assessing CDK1 gene duplications in the appendicularian lineage, we show that the CDK1 activation loop substrate binding platform, ATP entrance site, hinge region, and main Cyclin binding interface, have all diversified under positive selection. Three of the 5 CDK1 paralogs are required for embryonic divisions and knockdown phenotypes illustrate further subdivision of functions along the S-M-phase axis. In parallel to CDK1 gene duplications, there has also been amplification in the Cyclin B complement. Among these, the CDK1d:Cyclin Ba pairing is required for oogenic meiosis and early embryogenesis and shows evidence of coevolution of an exclusive interaction. In an intriguing twist on the general rule that Cyclin B oscillations on a background of stable CDK1 levels regulate M-phase MPF activity, it is CDK1d protein levels that oscillate, rather than Cyclin Ba levels, to drive rapid, early embryonic cell cycles. Strikingly, the modified PSTAIRE of odCDK1d shows convergence over great evolutionary distance with plant CDKB, and in both O. dioica, and plants, these variants exhibit increased specialization to M-phase.

Zygotic expression of the pebble locus is required for cytokinesis during the postblastoderm mitoses of Drosophila

Development ◽  
1992 ◽  
Vol 114 (1) ◽  
pp. 165-171 ◽  
Author(s):  
G. Hime ◽  
R. Saint
Keyword(s):  
Drosophila Melanogaster ◽  
Developmental Regulation ◽  
Single Cells ◽  
Embryonic Cell ◽  
Cell Cycles ◽  
Drosophila Embryogenesis ◽  
Zygotic Transcription ◽  
Homozygous Mutant ◽  
Mitotic Figures

Mutations at the pebble locus of Drosophila melanogaster result in embryonic lethality. Examination of homozygous mutant embryos at the end of embryogenesis revealed the presence of fewer and larger cells which contained enlarged nuclei. Characterization of the embryonic cell cycles using DAPI, propidium iodide, anti-tubulin and anti-spectrin staining showed that the first thirteen rapid syncytial nuclear divisions proceeded normally in pebble mutant embryos. Following cellularization, the postblastoderm nuclear divisions occurred (mitoses 14, 15 and 16), but cytokinesis was never observed. Multinucleate cells and duplicate mitotic figures were seen within single cells at the time of the cycle 15 mitoses. We conclude that zygotic expression of the pebble gene is required for cytokinesis following cellularization during Drosophila embryogenesis. We postulate that developmental regulation of zygotic transcription of the pebble gene is a consequence of the transition from syncytial to cellular mitoses during cycle 14 of embryogenesis.

scholarly journals Volume-regulated Cl− current: contributions of distinct Cl− channels and localized Ca2+ signals

2019 ◽  
Vol 317 (3) ◽  
pp. C466-C480 ◽  
Author(s):  
Yani Liu ◽  
Huiran Zhang ◽  
Hongchao Men ◽  
Yuwei Du ◽  
Ziqian Xiao ◽  
...  
Keyword(s):  
Anion Channel ◽  
Fluorescent Imaging ◽  
Hek293 Cells ◽  
Cell Swelling ◽  
Anoctamin 1 ◽  
Component Cell ◽  
Intracellular Ca ◽  
Cl Channels ◽  
A Cell ◽  
Necessary And Sufficient

The swelling-activated chloride current ( ICl,swell) is induced when a cell swells and plays a central role in maintaining cell volume in response to osmotic stress. The major contributor of ICl,swell is the volume-regulated anion channel (VRAC). Leucine-rich repeat containing 8A (LRRC8A; SWELL1) was recently identified as an essential component of VRAC, but the mechanisms of VRAC activation are still largely unknown; moreover, other Cl− channels, such as anoctamin 1 (ANO1), were also suggested to contribute to ICl,swell. In this present study, we investigated the roles of LRRC8A and ANO1 in activation of ICl,swell; we also explored the role of intracellular Ca2+ in ICl,swell activation. We used a CRISPR/Cas9 gene editing approach, electrophysiology, live fluorescent imaging, selective pharmacology, and other approaches to show that both LRRC8A and ANO1 can be activated by cell swelling in HEK293 cells. Yet, both channels contribute biophysically and pharmacologically distinct components to ICl,swell, with LRRC8A being the major component. Cell swelling induced oscillatory Ca2+ transients, and these Ca2+ signals were required to activate both the LRRC8A- and ANO1-dependent components of ICl,swell. Both ICl,swell components required localized rather than global Ca2+ for activation. Interestingly, while intracellular Ca2+ was necessary and sufficient to activate ANO1, it was necessary but not sufficient to activate LRRC8A-mediated currents. Finally, Ca2+ transients linked to the ICl,swell activation were mediated by the G protein-coupled receptor-independent PLC isoforms.

scholarly journals Characterization of a sperm factor for egg activation at fertilization of the newt Cynops pyrrhogaster

2007 ◽  
Vol 306 (2) ◽  
pp. 797-808 ◽  
Author(s):  
Yuichirou Harada ◽  
Tamami Matsumoto ◽  
Shino Hirahara ◽  
Akira Nakashima ◽  
Shuichi Ueno ◽  
...  
Keyword(s):  
Egg Activation ◽  
Cynops Pyrrhogaster ◽  
Sperm Factor

scholarly journals MaternalXenopusCdk2-Cyclin E Complexes Function during Meiotic and Early Embryonic Cell Cycles That Lack a G1Phase

1995 ◽  
Vol 270 (12) ◽  
pp. 6843-6855 ◽  
Author(s):  
Rachel E. Rempel ◽  
Susan B. Sleight ◽  
James L. Maller
Keyword(s):  
Cyclin E ◽  
Embryonic Cell ◽  
Cell Cycles

scholarly journals Are Src family kinases involved in cell cycle resumption in rat eggs?

Reproduction ◽  
2004 ◽  
Vol 127 (4) ◽  
pp. 455-463 ◽  
Author(s):  
A Talmor-Cohen ◽  
R Tomashov-Matar ◽  
E Eliyahu ◽  
R Shapiro ◽  
R Shalgi
Keyword(s):  
Signal Transduction ◽  
Marine Invertebrate ◽  
Src Family Kinases ◽  
Egg Activation ◽  
Signal Transduction Pathways ◽  
Cortical Granules ◽  
Fusion Site ◽  
Intracellular Ca ◽  
Intensive Investigation ◽  
Mammalian Eggs

The earliest visible indications for the transition to embryos in mammalian eggs, known as egg activation, are cortical granules exocytosis (CGE) and resumption of meiosis (RM); these events are triggered by the fertilizing spermatozoon through a series of Ca2+transients. The pathways, within the egg, leading to the intracellular Ca2+release and to the downstream cellular events, are currently under intensive investigation. The involvement of Src family kinases (SFKs) in Ca2+release at fertilization is well supported in marine invertebrate eggs but not in mammalian eggs. In a previous study we have shown the expression and localization of Fyn, the first SFK member demonstrated in the mammalian egg. The purpose of the current study was to identify other common SFKs and resolve their function during activation of mammalian eggs. All three kinases examined: Fyn, c-Src and c-Yes are distributed throughout the egg cytoplasm. However, Fyn and c-Yes tend to concentrate at the egg cortex, though only Fyn is localized to the spindle as well. The different localizations of the various SFKs imply the possibility of their different functions within the egg. To examine whether SFKs participate in the signal transduction pathways during egg activation, we employed selective inhibitors of the SFKs activity ((PP2 and SU6656). The results demonstrate that RM, which is triggered by Ca2+elevation, is an SFK-dependent process, while CGE, triggered by either Ca2+elevation or protein kinase C (PKC), is not. The possible involvement of SFKs in the signal transduction pathways that lead from the sperm–egg fusion site downstream of the Ca2+release remains unclear.

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