Calcium-Independent, Meiotic Spindle-Dependent Metaphase-to-Interphase Transition in Phorbol Ester-Treated Mouse Eggs

Moses, Ruth M.; Kline, Douglas

doi:10.1006/dbio.1995.1264

Cited by 38 publications

(28 citation statements)

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“…This is so because it is well known that if arrested into a metaphase-like stage, fertilized eggs can continue to oscillate for nearly 20 h (Day et al 2000), whereas under natural conditions, the oscillations cease by the approximate time of PN formation (Jones et al 1995). Hence, to extend these findings, we performed that same experimental design but in the presence of 100 ng/ml colcemid, which is known to prevent MII exit (Jones et al 1995, Moses & Kline 1995, Gordo et al 2002. Under these conditions, oscillations in enucleated eggs persisted in excess of 8 h ( Fig.…”

Section: Resultsmentioning

confidence: 99%

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

Yoon

Fissore²

2007

Reproduction

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During fertilization of mammalian eggs a factor from the sperm, the sperm factor (SF), is released into the ooplasm and induces persistent [Ca 2C ] 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 PLCz are 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sperm injection (ICSI) and monitored the persistence of the [Ca 2C ] i oscillations in eggs in which the sperm had been withdrawn. We also stained the enucleated sperm heads to ascertain the presence/absence of PLCz. 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 [Ca 2C ] i responses in enucleated and non-manipulated zygotes. Lastly, we found that PLCz localized 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 PLCz immunoreactivity was lost in both species. Altogether, our findings show that during fertilization the SF activity and PLCz immunoreactivity are simultaneously released from the sperm, suggesting that PLCz may be the only [Ca 2C ] i oscillation-inducing factor of mammalian sperm.

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Section: Resultsmentioning

confidence: 99%

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

Yoon

Fissore²

2007

Reproduction

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“…Evidence also suggests that PKC is involved in regulating sperminduced calcium oscillations by exerting a negative f e e d b a c k e f f e c t o n c a l c i u m r e l e a s e [ 8 0 ] . Furthermore, PKC has been implicated in the resumption of meiosis [81], cortical granule exocytosis [82][83][84] and pronuclear formation [85,86] in artificially activated oocytes. However, other evidence suggests that a different calciumdependent pathway, involving calmodulin and CaMKII, is responsible for the resumption of meiosis at fertilization [87].…”

Section: The Role Of Calcium At Activationmentioning

confidence: 99%

Calcium Release at Fertilization: Artificially Mimicking the Oocyte's Response to Sperm.

Grupen¹,

Nottle²,

Nagashima

2002

Journal of Reproduction and Development

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Abstract. The mechanism of sperm-induced calcium release has been the subject of many studies since the development in the late 1950s of in vitro culture systems that support mammalian fertilization. Despite efforts to elucidate the nature of the signal from the sperm that triggers both the early and late events of oocyte activation, the precise mechanism remains unresolved. Now, with the advent of somatic nuclear transfer technologies, the need to better understand this unique process has been recognised. Nuclear transfer embryos must be induced to commence development artificially because the activating signal from the sperm is absent. The primary activating stimulus is a large increase in the concentration of intracellular-free calcium and numerous physical and chemical treatments have been found to induce calcium changes that initiate the events of oocyte activation. Although live cloned offspring have been produced in a number of species, the overall efficiencies of the nuclear transfer procedures described thus far are unacceptably low and phenotypic anomalies are common. With the aim of improving these efficiencies, researchers are developing artificial activation treatments which induce oocyte responses that mimic those induced by fertilizing sperm. One strategy is to replicate the pattern of calcium change more closely. Another strategy is to couple an activating stimulus with treatments that inhibit maturation (or M-phase) promoting factor (MPF) activity, which regulates meiotic progression in oocytes. This paper reviews what is understood of calcium release at fertilization and describes the treatments that have been used to induce oocyte activation artificially in parthenogenetic and nuclear transfer studies. The relative effectiveness of the strategies employed to mimic the oocyte's response to sperm are discussed. Key words: Oocyte activation, Fertilization, Parthenogenesis, Nuclear transfer (J. Reprod. Dev. 48: 2002) o produce a viable embryo at fertilization, the s p e r m n o t o n l y p r o v i d e s t h e m a l e chromosomal complement, but also the stimulus that initiates development. The mechanism by which the activating signal is transmitted from the sperm to the oocyte is not fully clarified, but it is clear that this signal triggers a large increase in the concentration of intracellular-free calcium. In fertilized sea urchin and Xenopus eggs, the calcium increase takes the form of a propagating wave that originates at the point of sperm attachment and traverses the egg at a velocity of 5 to 10 µm/sec

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“…Treatment of mouse eggs with thimerosal caused repetitive calcium transients and cortical granule exocytosis, but these eggs remained at metaphase because thimerosal also disrupts the spindle [31]. The importance of meiotic spindle assembly for the exit from metaphase induced by PKC activation has also been proposed [32]. Recently it was reported that colcemid-treated eggs that were fertilized or treated with A23187 remained arrested at metaphase, but when the above-treated eggs were further exposed to 6-DMAP, they entered interphase [25].…”

Section: The Relationship Among Protein Kinase Activity Spindle Morpmentioning

confidence: 99%

Calcium-Independent, Egg Age-Dependent Parthenogenic Activation of Mouse Eggs by Staurosporine.

Sun

Liu

Chen

1997

Journal of Reproduction and Development

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Abstract. The effect of protein kinase inhibitors on the activation events of mouse eggs at different ages and the dependence on Ca 2+ were studied. Inhibition of protein kinase(s) by staurosporine with concentration over 2 µM first induced the destruction of meiotic spindle and then the nuclear formation in metaphase II eggs, but did not stimulate the cortical granule exocytosis; staurosporine with concentration below 0.2 µM and protein kinase C inhibitor sphingosine at concentrations of 10-100 µM did not activate mouse eggs. The activation of mouse eggs by staurosporine was egg age-dependent, but calcium-independent. The number of nucleoli in the formed nucleus or naked nucleoli in the ooplasm was dose-and egg age-dependent. To further evaluate the nuclear and cytoplasmic activation by staurosporine, interphase eggs were processed for electron microscopy and it was found that most nucleoli were highly condenced like those in the pronucleus, but vacuolated or ring-shaped ones also appeared, which implied the activation of egg genome. In addition, staurosporine also induced the formation of Golgi complexes around the nucleus. The nuclear formation induced by staurosporine was completely overcome by okadaic acid. These results suggest that inhibition of staurosporine-sensitive protein kinase(s) other than protein kinase A and C is responsible for the transition from metaphase to interphase in an egg age-dependent but calcium-independent manner in mouse eggs. Key words: Protein kinase, Mouse, Egg activation, Egg age, Calcium.(J. Reprod. Dev. 43: [189][190][191][192][193][194][195][196][197] 1997) inactivation of MPF.Research on the parthenogenic activation of eggs is important for understanding the mechanism of fertilization. Studies on the role of protein kinase C (PKC) activation in meiotic resumption and pronuclear formation of mouse and hamster eggs have been conducted in recent years, but, apparently conflicting conclusions were obtained in different species and even in different strains of the same species [1,[5][6][7]. Protein kinase inhibitor 6-dimethylaminopurine (6-DMAP) was reported not to induce the activation of MII mouse eggs in the OF1 strain [8]. On the other hand, this drug activated Kunming mouse eggs effectively (Sun et al., unpublished results). Protein kinase inhibitors lthough it is well established that a transient increase in intracellular free Ca 2+ ([Ca 2+ ]i) occurs after fertilization, the mechanism by which the [Ca 2+ ]i rise leads to the cellular changes that transform the egg into zygote is poorly known [1]. Before fertilization and artificial activation, mammalian eggs are arrested at metaphase II by maturation promoting factor (MPF) which is a protein kinase composed of p34 cdc2 and cyclin B. The activity of MPF is controlled by protein phosphorylation/dephosphorylation induced by other protein kinase(s) and protein phosphatase(s) [2][3][4]. Release of meiotic arrest is accompanied by the A

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Calcium-Independent, Meiotic Spindle-Dependent Metaphase-to-Interphase Transition in Phorbol Ester-Treated Mouse Eggs

Cited by 38 publications

References 0 publications

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

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

Calcium Release at Fertilization: Artificially Mimicking the Oocyte's Response to Sperm.

Calcium-Independent, Egg Age-Dependent Parthenogenic Activation of Mouse Eggs by Staurosporine.

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