PLCζ: a sperm-specific trigger of Ca2+ oscillations in eggs and embryo development

Development ◽  
2002 ◽  
Vol 129 (15) ◽  
pp. 3533-3544 ◽  
Author(s):  
Christopher M. Saunders ◽  
Mark G. Larman ◽  
John Parrington ◽  
Llewellyn J. Cox ◽  
Jillian Royse ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Embryo Development ◽  
Specific Protein ◽  
Normal Embryo ◽  
Egg Activation ◽  
Sperm Factor ◽  
Mammalian Eggs ◽  
Mouse Eggs ◽  
Cytosolic Factor ◽  
Specific Trigger

Upon fertilisation by sperm, mammalian eggs are activated by a series of intracellular Ca2+ oscillations that are essential for embryo development. The mechanism by which sperm induces this complex signalling phenomenon is unknown. One proposal is that the sperm introduces an exclusive cytosolic factor into the egg that elicits serial Ca2+ release. The ‘sperm factor’ hypothesis has not been ratified because a sperm-specific protein that generates repetitive Ca2+ transients and egg activation has not been found. We identify a novel, sperm-specific phospholipase C, PLCζ, that triggers Ca2+ oscillations in mouse eggs indistinguishable from those at fertilisation. PLCζ removal from sperm extracts abolishes Ca2+ release in eggs. Moreover, the PLCζ content of a single sperm was sufficient to produce Ca2+ oscillations as well as normal embryo development to blastocyst. Our results are consistent with sperm PLCζ as the molecular trigger for development of a fertilised egg into an embryo.

scholarly journals Release of phospholipase C ζand [Ca2+]i oscillation-inducing activity during mammalian fertilization

Reproduction ◽  
2007 ◽  
Vol 134 (5) ◽  
pp. 695-704 ◽  
Author(s):  
Sook-Young Yoon ◽  
Rafael A Fissore
Keyword(s):  
Phospholipase C ◽  
Embryo Development ◽  
Intracytoplasmic Sperm Injection ◽  
Egg Activation ◽  
Mouse Sperm ◽  
Mammalian Sperm ◽  
Sperm Entry ◽  
Sperm Factor ◽  
Mammalian Fertilization ◽  
Mammalian Eggs

During fertilization of mammalian eggs a factor from the sperm, the sperm factor (SF), is released into the ooplasm and induces persistent [Ca2+]i oscillations that are required for egg activation and embryo development. A sperm-specific phospholipase C (PLC), PLCz, is thought to be the SF. Here, we investigated whether the SF activity and PLCζare simultaneously and completely released into the ooplasm soon after sperm entry. To accomplish this, we enucleated sperm heads within 90 min of intracytoplasmic sperm injection (ICSI) and monitored the persistence of the [Ca2+]i oscillations in eggs in which the sperm had been withdrawn. We also stained the enucleatedsperm heads to ascertain the presence/absence of PLCζ. Our results show that by 90 min all the SF activity had been released from the sperm, as fertilized enucleated eggs oscillated as fertilized controls, even in cases in which oscillations were prolonged by arresting eggs at metaphase. In addition, we found that the released SF activity became associated with the pronucleus (PN), as induction of PN envelope breakdown evoked comparable [Ca2+]i responses in enucleated and non-manipulated zygotes. Lastly, we found that PLCzlocalized to the equatorial area of bull sperm and to the post-acrosomal region of mouse sperm and that by 90 min after ICSI all the sperm’s PLCζimmunoreactivity was lost in both species. Altogether, our findings show that during fertilization the SF activity and PLCζimmunoreactivity are simultaneously released from the sperm, suggesting that PLCζmay be the only [Ca2+]i oscillation-inducing factor of mammalian sperm.

The sperm phospholipase C-ζ and Ca2+ signalling at fertilization in mammals

2016 ◽  
Vol 44 (1) ◽  
pp. 267-272 ◽  
Author(s):  
Karl Swann ◽  
F. Anthony Lai
Keyword(s):  
Phospholipase C ◽  
Embryo Development ◽  
Early Embryo ◽  
Egg Activation ◽  
Stable Form ◽  
Ph Domain ◽  
Vitro Fertilization ◽  
Sperm Factor ◽  
Internal Sources

A series of intracellular oscillations in the free cytosolic Ca2+ concentration is responsible for activating mammalian eggs at fertilization, thus initiating embryo development. It has been proposed that the sperm causes these Ca2+ oscillations after membrane fusion by delivering a soluble protein into the egg cytoplasm. We previously identified sperm-specific phospholipase C (PLC)-ζ as a protein that can trigger the same pattern of Ca2+ oscillations in eggs seen at fertilization. PLCζ appears to be the elusive sperm factor mediating egg activation in mammals. It has potential therapeutic use in infertility treatments to improve the rate of egg activation and early embryo development after intra-cytoplasmic sperm injection. A stable form of recombinant human PLCζ could be a prototype for use in such in vitro fertilization (IVF) treatments. We do not yet understand exactly how PLCζ causes inositol 1,4,5-trisphosphate (InsP3) production in eggs. Sperm PLCζ is distinct among mammalian PI-specific PLCs in that it is far more potent in triggering Ca2+ oscillations in eggs than other PLCs, but it lacks a PH domain that would otherwise be considered essential for binding to the phosphatidylinositol 4,5-bisphosphate (PIP2) substrate. PLCζ is also unusual in that it does not appear to interact with or hydrolyse plasma membrane PIP2. We consider how other regions of PLCζ may mediate its binding to PIP2 in eggs and how interaction of PLCζ with egg-specific factors could enable the hydrolysis of internal sources of PIP2.

scholarly journals The role of ATP in the differential ability of Sr2+ to trigger Ca2+ oscillations in mouse and human eggs

2021 ◽  
Author(s):  
Anna Storey ◽  
Khalil Elgmati ◽  
Yisu Wang ◽  
Paul Knaggs ◽  
Karl Swann
Keyword(s):  
Phospholipase C ◽  
Egg Activation ◽  
Apparent Difference ◽  
Free Medium ◽  
Inositol 1 ◽  
Atp Levels ◽  
Mature Mouse ◽  
Differential Ability ◽  
Mouse Eggs

Abstract At fertilization in mice and humans, the activation of the egg is caused by a series of repetitive Ca2+ oscillations which are initiated by phospholipase-C(zeta)ζ that generates inositol-1-4-5-trisphophate (InsP3). Ca2+ oscillations and egg activation can be triggered in mature mouse eggs by incubation in Sr2+ containing medium, but this does not appear to be effective in human eggs. Here we have investigated the reason for this apparent difference using mouse eggs, and human eggs that failed to fertilize after IVF or ICSI. Mouse eggs incubated in Ca2+-free, Sr2+-containing medium immediately underwent Ca2+ oscillations but human eggs consistently failed to undergo Ca2+ oscillations in the same Sr2+ medium. We tested the InsP3-receptor (IP3R) sensitivity directly by photo-release of caged InsP3 and found that mouse eggs were about 10 times more sensitive to InsP3 than human eggs. There were no major differences in the Ca2+ store content between mouse and human eggs. However, we found that the ATP concentration was consistently higher in mouse compared to human eggs. When ATP levels were lowered in mouse eggs by incubation in pyruvate-free medium, Sr2+ failed to cause Ca2+ oscillations. When pyruvate was added back to these eggs, the ATP levels increased and Ca2+ oscillations were induced. This suggests that ATP modulates the ability of Sr2+ to stimulate IP3R-induced Ca2+ release in eggs. We suggest that human eggs may be unresponsive to Sr2+ medium because they have a lower level of cytosolic ATP.

scholarly journals Different Ca2+-releasing abilities of sperm extracts compared with tissue extracts and phospholipase C isoforms in sea urchin egg homogenate and mouse eggs

2000 ◽  
Vol 346 (3) ◽  
pp. 743-749 ◽  
Author(s):  
Keith T. JONES ◽  
Miho MATSUDA ◽  
John PARRINGTON ◽  
Matilda KATAN ◽  
Karl SWANN
Keyword(s):  
Phospholipase C ◽  
Sea Urchin ◽  
Tissue Extracts ◽  
Sea Urchin Egg ◽  
Boar Sperm ◽  
Specific Activities ◽  
Mammalian Eggs ◽  
Mouse Eggs

A soluble phospholipase C (PLC) from boar sperm generates InsP3 and hence causes Ca2+ release when added to sea urchin egg homogenate. This PLC activity is associated with the ability of sperm extracts to cause Ca2+ oscillations in mammalian eggs following fractionation. A sperm PLC may, therefore, be responsible for causing the observed Ca2+ oscillations at fertilization. In the present study we have further characterized this boar sperm PLC activity using sea urchin egg homogenate. Consistent with a sperm PLC acting on egg PtdIns(4,5)P2, the ability of sperm extracts to release Ca2+ was blocked by preincubation with the PLC inhibitor U73122 or by the addition of neomycin to the homogenate. The Ca2+-releasing activity was also detectable in sperm from other species and in whole testis extracts. However, activity was not observed in extracts from other tissues. Moreover recombinant PLCβ1, -γ1, -γ2, -∆1, all of which had higher specific activities than boar sperm extracts, were not able to release Ca2+ in the sea urchin egg homogenate. In addition these PLCs were not able to cause Ca2+ oscillations following microinjection into mouse eggs. These results imply that the sperm PLC possesses distinct properties that allow it to hydrolyse PtdIns(4,5)P2 in eggs.

scholarly journals The soluble sperm factor that activates the egg: PLCzeta and beyond

Reproduction ◽  
2020 ◽  
Vol 160 (1) ◽  
pp. V9-V11
Author(s):  
Karl Swann
Keyword(s):  
Egg Activation ◽  
Sperm Factor ◽  
Mouse Eggs

PLCzeta(ζ) initiates Ca2+ oscillations and egg activation at fertilization in mammals, but studies in mouse eggs fertilized by PLCζ knockout (KO) sperm imply that there is another slow acting factor causing Ca2+ release. Here, I propose a hypothesis for how this second sperm factor might cause Ca2+ oscillations in mouse eggs.

scholarly journals Potential role of a sperm-derived phospholipase C in triggering the egg-activating Ca2+ signal at fertilization

Reproduction ◽  
2001 ◽  
pp. 839-846 ◽  
Author(s):  
K Swann ◽  
J Parrington ◽  
KT Jones
Keyword(s):  
Membrane Fusion ◽  
Phospholipase C ◽  
Potential Role ◽  
Egg Activation ◽  
Gamete Fusion ◽  
Inositol 1,4,5 Trisphosphate ◽  
Sperm Factor

An increase in intracellular Ca2+ at fertilization is the trigger for egg activation in all species that have been studied. Exactly how sperm-egg interaction leads to this Ca2+ increase has not been established. There is increasing support for the hypothesis that the spermatozoon introduces a Ca2+-releasing protein into the egg cytoplasm after gamete membrane fusion. This review discusses the merits of this 'sperm factor' hypothesis and presents evidence indicating that the sperm factor, at least in mammals, consists of a phospholipase C with distinctive properties. This evidence leads us to propose that, after gamete fusion, a sperm-derived phospholipase C causes production of inositol 1,4,5- trisphosphate, which then generates Ca2+ waves from within the egg cytoplasm.

scholarly journals Phospholipase C isoforms in mammalian spermatozoa: potential components of the sperm factor that causes Ca2+ release in eggs

Reproduction ◽  
2002 ◽  
pp. 31-39 ◽  
Author(s):  
J Parrington ◽  
ML Jones ◽  
R Tunwell ◽  
C Devader ◽  
M Katan ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Sea Urchin ◽  
Soluble Protein ◽  
Gel Filtration ◽  
Protein Factor ◽  
Sea Urchin Egg ◽  
Inositol 1,4,5 Trisphosphate ◽  
Sperm Factor ◽  
Mammalian Eggs ◽  
Mammalian Spermatozoa

Injection of a soluble protein factor from mammalian spermatozoa triggers Ca2+ oscillations in mammalian eggs similar to those seen at fertilization. This sperm factor also generates inositol 1,4,5-trisphosphate and causes Ca2+ release in sea urchin egg homogenates and frog eggs. Recent studies have indicated that the sperm factor may be an inositol-specific phospholipase C (PLC) activity. This study investigated whether any of the commonly known PLC isoforms are components of the sperm factor. PLCbeta, PLCgamma and PLCdelta isoforms were shown to be present in boar sperm extracts. However, upon column fractionation of sperm extracts, none of the PLC isoforms detected correlated with the ability to cause Ca2+ release in eggs. In addition to our previous work on recombinant PLCs, it was also shown that PLCdelta3, PLCdelta4 and its splice variant PLCdelta4 Alt1 fail to cause Ca2+ release. The recently discovered 255 kDa PLCepsilon isoform also appears unlikely to be a component of the sperm factor, as fractionation of sperm extracts on a gel filtration column demonstrated that the peak of Ca2+-releasing activity was associated with fractions of 30-70 kDa. These findings indicate that the sperm factor that triggers Ca2+ release in eggs does not appear to have a known PLC isoform as one of its components.

scholarly journals Conventional PKCs regulate the temporal pattern of Ca2+ oscillations at fertilization in mouse eggs

2004 ◽  
Vol 164 (7) ◽  
pp. 1033-1044 ◽  
Author(s):  
Guillaume Halet ◽  
Richard Tunwell ◽  
Scott J. Parkinson ◽  
John Carroll
Keyword(s):  
Embryonic Development ◽  
Temporal Pattern ◽  
Physiological Function ◽  
Egg Activation ◽  
Present Evidence ◽  
Downstream Effectors ◽  
Living Mouse ◽  
Egg Membrane ◽  
Mammalian Eggs ◽  
Mouse Eggs

In mammalian eggs, sperm-induced Ca2+ oscillations at fertilization are the primary trigger for egg activation and initiation of embryonic development. Identifying the downstream effectors that decode this unique Ca2+ signal is essential to understand how the transition from egg to embryo is coordinated. Here, we investigated whether conventional PKCs (cPKCs) can decode Ca2+ oscillations at fertilization. By monitoring the dynamics of GFP-labeled PKCα and PKCγ in living mouse eggs, we demonstrate that cPKCs translocate to the egg membrane at fertilization following a pattern that is shaped by the amplitude, duration, and frequency of the Ca2+ transients. In addition, we show that cPKC translocation is driven by the C2 domain when Ca2+ concentration reaches 1–3 μM. Finally, we present evidence that one physiological function of activated cPKCs in fertilized eggs is to sustain long-lasting Ca2+ oscillations, presumably via the regulation of store-operated Ca2+ entry.

scholarly journals Establishment of the mammalian membrane block to polyspermy: evidence for calcium-dependent and -independent regulation

Reproduction ◽  
2007 ◽  
Vol 133 (2) ◽  
pp. 383-393 ◽  
Author(s):  
Allison J Gardner ◽  
Carmen J Williams ◽  
Janice P Evans
Keyword(s):  
Plasma Membrane ◽  
Zona Pellucida ◽  
Egg Activation ◽  
Membrane Function ◽  
Independent Event ◽  
Calcium Dependent ◽  
Normal Sperm ◽  
Egg Membrane ◽  
Mammalian Eggs ◽  
Mouse Eggs

One crucial result of egg activation is the establishment of blocks on the zona pellucida and the egg plasma membrane to prevent fertilization by additional sperm. The mechanism(s) by which a mammalian egg regulates the establishment of the membrane block to polyspermy is largely unknown. Since Ca2+ signaling regulates several egg activation events, this study investigates how sperm-induced Ca2+ transients affect the membrane block to polyspermy, building on our previous work (Biology of Reproduction 67:1342). We demonstrate that mouse eggs that experience only one sperm-induced Ca2+ transient establish a membrane block that is less effective, than in eggs that experience normal sperm-induced Ca2+ transients but that is more effective than in eggs with completely suppressed [Ca2+]cyt increases. Sperm-induced increases in [Ca2+]cyt regulate the timing of membrane block establishment, as this block is established more slowly in eggs that experience one or no sperm-induced Ca2+ transients. Finally, our studies produce the intriguing discovery that there is also a Ca2+-independent event that is associated with fertilization in the pathway leading to membrane block establishment. Taken together, these data indicate that Ca2+ plays a role in facilitating membrane block establishment by regulating the timing with which this change in egg membrane function occurs, and also that the membrane block differs from other post-fertilization egg activation responses as Ca2+ is not the only stimulus. The membrane block to polyspermy in mammalian eggs is likely to be the culmination of multiple post-fertilization events that together modify the egg membrane’s receptivity to sperm.

scholarly journals Ca2+ oscillation-inducing phospholipase C zeta expressed in mouse eggs is accumulated to the pronucleus during egg activation

2004 ◽  
Vol 268 (2) ◽  
pp. 245-257 ◽  
Author(s):  
Ayako Yoda ◽  
Shoji Oda ◽  
Tomohide Shikano ◽  
Zen Kouchi ◽  
Takeo Awaji ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Egg Activation ◽  
Mouse Eggs
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