title: How do spermatozoa activate oocytes?
abstract: Although the spermatozoon is 500,000 times smaller in volume than the oocyte, it induces rapid and dramatic changes in oocyte physiology that lead to meiosis re-initiation. These oocyte activation events are described here, as is the evidence for a soluble activating factor in the spermatozoon. Since changes in plasma membrane conductance, calcium ion release and maturation-promoting factor inactivation are common to all animal oocytes at activation, it is expected that the sperm-borne trigger is also ubiquitous. One likely candidate, phospholipase C (PLC) zeta 1, induces calcium release in mammalian oocytes; however, work on other deuterostomes suggests that the sperm factor is non-specific and multifactorial, regulating several activation events. Human, sea urchin and ascidian gametes are remarkably similar and comparative studies across the deuterostomes may help in elucidating basic principles in fertilization. Questions to be answered include the identification of PLC zeta 1 in invertebrate spermatozoa and the characterization of other targets in mammalian oocytes, such as the adenosine diphosphate ribose/nitric oxide pathway.
authors.affiliation: CFA-Italia, Naples and Stazione Zoologica, Naples, Italy. brian.dale@virgilio.it
authors.forename: Brian
authors.initials: B
authors.lastname: Dale
authors.forename: Martin
authors.initials: M
authors.lastname: Wilding
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Coppola
authors.forename: Elizabetta
authors.initials: E
authors.lastname: Tosti
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D005306:Fertilization / Q000502:physiology; D006801:Humans; D008297:Male; D008540:Meiosis; D009865:Oocytes / Q000502:physiology; D054801:Phosphoinositide Phospholipase C / Q000502:physiology; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology; D014561:Urochordata
chemical_list: C499235:PLCZ1 protein, human; D054801:Phosphoinositide Phospholipase C; D002118:Calcium