Cell cycle-dependent repetitive Ca(2+ )waves induced by a cytosolic sperm extract in mature ascidian eggs mimic those observed at fertilization. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Cell Science Année : 2000

Cell cycle-dependent repetitive Ca(2+ )waves induced by a cytosolic sperm extract in mature ascidian eggs mimic those observed at fertilization.

Mark Levasseur
  • Fonction : Auteur
Antony J O'Sullivan
  • Fonction : Auteur
Keith T Jones

Résumé

Sperm-triggered Ca(2+) oscillations occur throughout the animal kingdom. The mechanism sperm use to trigger Ca(2+) oscillations at fertilization has not been resolved in any egg. The temporal, spatial and regulatory characteristics of the Ca(2+) oscillations during fertilization in ascidians offer a unique advantage over other systems for determining the mechanism of fertilization. For example, sperm trigger two phases of Ca(2+) oscillations that are all waves in ascidians. The first of these Ca(2+) waves begins at the point of sperm-egg fusion while a second phase of Ca(2+) waves originates at a vegetal protrusion termed the contraction pole. In addition, cyclin B1-dependent kinase activity provides a form of positive feedback, maintaining the second phase of Ca(2+) waves during meiosis and thereby ensuring meiotic exit. We therefore prepared cytosolic ascidian sperm extracts or MonoQ-fractionated ascidian sperm extracts from this urochordate to investigate if a Ca(2+)-releasing sperm-borne factor was responsible for egg activation. Spatially, ascidian sperm extract induced repetitive Ca(2+) waves that mimicked the spatial pattern displayed during fertilization: all the second-phase Ca(2+) waves originated at a vegetal protrusion termed the contraction pole (thus mimicking fertilisation). We also demonstrated that ascidian sperm extract-induced Ca(2+) oscillations were maintained when CDK activity was elevated and MAP kinase activity was low, as found previously for sperm-triggered Ca(2+) oscillations. As would be predicted, large doses of ascidian sperm extract injected into prophase-stage oocytes, lacking CDK activity, failed to induce any Ca(2+) release even though they responded to microinjection of the Ca(2+)-releasing second messenger inositol 1,4,5-trisphosphate. Finally, since the Ca(2+)-releasing activity from Mono-Q fractionated ascidian sperm extract eluted predominantly as one fraction, this may imply that one factor is responsible for the Ca(2+)-releasing activity. These data support a model of egg activation whereby the sperm introduces a Ca(2+)-releasing cytosolic factor into the egg. We demonstrated that ascidian sperm contain a protein factor(s) that is regulated by the egg CDK activity and can trigger all the Ca(2+ )waves observed at fertilization with a spatial pattern that mimics those initiated by sperm.
Fichier principal
Vignette du fichier
2000 JCSc2000.pdf (391.03 Ko) Télécharger le fichier
Origine : Accord explicite pour ce dépôt

Dates et versions

hal-03025761 , version 1 (16-12-2020)

Identifiants

  • HAL Id : hal-03025761 , version 1
  • PUBMED : 10984436

Citer

Alex Mcdougall, Mark Levasseur, Antony J O'Sullivan, Keith T Jones. Cell cycle-dependent repetitive Ca(2+ )waves induced by a cytosolic sperm extract in mature ascidian eggs mimic those observed at fertilization.. Journal of Cell Science, 2000, 113 Pt 19, pp.3453-62. ⟨hal-03025761⟩
28 Consultations
20 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More