title: Ca2+ release and the development of Ca2+ release mechanisms during oocyte maturation: a prelude to fertilization.
abstract: Oogenesis involves the production of an oocyte that can undergo fertilization and support early development. The stimulus that initiates embryogenesis is an increase in the concentration of intracellular Ca2+ in the cytoplasm of the oocyte at the time of fertilization. The development of the ability of the oocyte to release Ca2+ in response to the fertilizing spermatozoon is an essential step in the process of oogenesis. Mammalian oocytes are particularly useful for studying the development of Ca2+ signalling systems, owing to the series of Ca2+ oscillations generated at fertilization, compared with the monotonic Ca2+ increase seen in nonmammalian species. Recent evidence has revealed that Ca2+ release mechanisms are modified during oogenesis. The maximal sensitivity of Ca2+ release is reached in the final stages of oocyte maturation, just before the optimal time for fertilization. In this review, we consider the mechanism underlying Ca2+ release in mammalian oocytes and discuss how the release mechanisms are modified during oocyte maturation. The tight co-ordination of the differentiation of the Ca2+ signalling system with the development of the oocyte provides a means of ensuring successful activation at the time of fertilization. Finally, we consider the consequences for embryo development in circumstances in which the co-ordination is lost.
authors.affiliation: MRC Experimental Embryology and Teratology Unit, St George's Hospital Medical School, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Carroll
authors.forename: K T
authors.initials: KT
authors.lastname: Jones
authors.forename: D G
authors.initials: DG
authors.lastname: Whittingham
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002453:Cell Cycle; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006801:Humans; D008297:Male; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D002118:Calcium