Sperm entry into fertilised mouse eggs

Maluchnik, Darek; Borsuk, Ewa

doi:10.1017/s096719940000188x

Cited by 24 publications

(28 citation statements)

References 12 publications

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“…Thus, the precise moment of fertilization was estimated by the time of the first Ca 2C transient. Since a membrane block to polyspermy develops in fertilized oocytes in w1 h (Maluchnik & Borsuk 1994), we assumed that in polyspermic oocytes all spermatozoa fused at the similar time. In all examined oocytes penetrated in prometaphase I by a single spermatozoon (7/7) or several spermatozoa (7/7), Ca 2C oscillations caused by sperm penetration did not visibly affect the increase in Luminescence emitted by the oocytes reflected changes in the expression of cyclin B1-luc.…”

Section: Fertilization Of Maturing Oocytes Does Not Results In Cyclin mentioning

confidence: 99%

Fertilization differently affects the levels of cyclin B1 and M-phase promoting factor activity in maturing and metaphase II mouse oocytes

Ajduk¹,

Ciemerych²,

Nixon³

et al. 2008

Reproduction

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Fertilization affects levels of cyclin B1 and M-phase promoting factor (MPF) activity in maturing and metaphase II mouse oocytes in two distinct ways. In metaphase II oocytes, it leads to a Ca 2C -dependent, continuous degradation of cyclin B1 and inactivation of cyclin dependent kinase (CDC2A)-cyclin B1 complex (MPF). In this paper, we show that neither mono-nor polyspermic fertilization of prometaphase I and metaphase I oocytes triggered degradation of cyclin B1. However, polyspermic fertilization of prometaphase I oocytes led to a transient decrease in MPF activity that lasted for 2 h. The inactivation of MPF in polyspermic prometaphase I oocytes did not depend on the fertilization-induced increase in the cytoplasmic concentration of free Ca 2C ions, but was caused, at least in part, by dephosphorylation of CDC2A at threonine 161 (Thr161). We found that polyspermic fertilization did not affect glutathione levels in prometaphase I oocytes, and concluded that the decrease in MPF activity and dephosphorylation of CDC2A at Thr161 in polyspermic prometaphase I oocytes were not caused by a change in the redox status of the cell induced by an introduction of excessive amount of sperm protamines. Instead, we propose that inactivation of MPF activity in polyspermic maturing oocytes is caused by a change in nucleocytoplasmic ratio that leads to a 'titration' of kinases and phosphatases responsible for keeping MPF in an active state. This idea is supported by the finding that oocytes fused with thymocytes rather than spermatozoa also showed a transient decrease in MPF activity.Reproduction (2008) 136 741-752

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Section: Fertilization Of Maturing Oocytes Does Not Results In Cyclin mentioning

confidence: 99%

Fertilization differently affects the levels of cyclin B1 and M-phase promoting factor activity in maturing and metaphase II mouse oocytes

Ajduk¹,

Ciemerych²,

Nixon³

et al. 2008

Reproduction

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“…Mammalian eggs use both a zona pellucida (ZP) block and a membrane block to prevent polyspermy (Yanagimachi 1994, Abbott & Ducibella 2001. Very little is known about the membrane block, although evidence demonstrating its existence comes from several studies (Austin 1961, Wolf 1978, Zuccotti et al 1991, Horvath et al 1993, Maluchnik & Borsuk 1994, Sengoku et al 1995, McAvey et al 2002, Gardner & Evans 2006. The mechanism by which a mammalian egg membrane decreases its receptivity to sperm is not known.…”

Section: Introductionmentioning

confidence: 99%

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

2007

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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 Ca 2C signaling regulates several egg activation events, this study investigates how sperm-induced Ca 2C transients affect the membrane block to polyspermy, building on our previous work (Biology of ] cyt regulate the timing of membrane block establishment, as this block is established more slowly in eggs that experience one or no sperm-induced Ca 2C transients. Finally, our studies produce the intriguing discovery that there is also a Ca 2C -independent event that is associated with fertilization in the pathway leading to membrane block establishment. Taken together, these data indicate that Ca 2C 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 Ca 2C 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.

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“…This suggests that aged eggs can establish a ZP block to polyspermy, and raises the possibility that the increases in polyspermy in aged eggs may be due more to deficiencies in the membrane block than in the ZP block. The mechanistic basis of the membrane block is poorly understood, although evidence for mammalian eggs using a membrane block to prevent polyspermy comes from numerous studies in several species (Austin, 1961, Gardner and Evans, 2006, Horvath et al, 1993, Maluchnik and Borsuk, 1994, McAvey et al, 2002, Sengoku et al, 1995, Wolf, 1978, Zuccotti et al, 1991. Our recent data indicate that sperminduced Ca 2+ -dependent signaling plays a partial role in membrane block establishment (Gardner et al, 2007a, Gardner et al, cytosolic Ca 2+ concentrations occur in the form of transients, also called oscillations.…”

Section: Membrane Abnormalities In Post-ovulatory Aged Eggsmentioning

confidence: 99%

Ultrastructural analysis of egg membrane abnormalities in post-ovulatory aged eggs

Dalo¹,

McCaffery²,

Evans³

2008

Int. J. Dev. Biol.

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Microscopic analyses of mammalian gamete ultrastructure have provided among the most seminal insights into fertilization. Here we present a summary of ultrastructural studies of mammalian fertilization, together with a review of the effects of post-ovulatory aging in eggs, and our own results using scanning electron microscopy to examine the effects of post-ovulatory aging on the egg membrane topography. Our previous work detected two abnormalities in egg membrane function in aged eggs: aged eggs appeared to be less able to support sperm-egg membrane interaction, thus rendering the eggs less fertilizable, and aged eggs appear to have a reduced ability to prevent polyspermy at the level of the egg membrane, i.e., to establish a membrane block to polyspermy. In the work presented here, we tested the suitability of both environmental (ESEM) and low-vacuum (LVSEM) modes of the FEI Quanta 200 Environmental Scanning Electron Microscope to study mammalian gametes. While ESEM mode was not sufficient under the conditions we used to observe fine cell surface details, the LVSEM mode proved to be an excellent way to view egg membrane topography. Unfertilized aged eggs have an abnormally distended amicrovillar region over the meiotic spindle, and fertilized aged eggs had three different abnormalities detected, from reduced sperm-induced membrane remodeling to abnormal sperm-induced membrane remodeling and membrane blebbing. Combining these insights of egg membrane function and topography with others in the field of post-ovulatory aging, we have expanded insights into why fertilization at increased times after ovulation is associated with poor reproductive outcomes.

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Sperm entry into fertilised mouse eggs

Cited by 24 publications

References 12 publications

Fertilization differently affects the levels of cyclin B1 and M-phase promoting factor activity in maturing and metaphase II mouse oocytes

Fertilization differently affects the levels of cyclin B1 and M-phase promoting factor activity in maturing and metaphase II mouse oocytes

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

Ultrastructural analysis of egg membrane abnormalities in post-ovulatory aged eggs

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