title: Calcium and actin in the saga of awakening oocytes.
abstract: The interaction of the spermatozoon with the egg at fertilization remains one of the most fascinating mysteries of life. Much of our scientific knowledge on fertilization comes from studies on sea urchin and starfish, which provide plenty of gametes. Large and transparent, these eggs have served as excellent model systems for studying egg activation and embryo development in seawater, a plain natural medium. Starfish oocytes allow the study of the cortical, cytoplasmic and nuclear changes during the meiotic maturation process, which can also be triggered in vitro by hormonal stimulation. These morphological and biochemical changes ensure successful fertilization of the eggs at the first metaphase. On the other hand, sea urchin eggs are fertilized after the completion of meiosis, and are particularly suitable for the study of sperm-egg interaction, early events of egg activation, and embryonic development, as a large number of mature eggs can be fertilized synchronously. Starfish and sea urchin eggs undergo abrupt changes in the cytoskeleton and ion fluxes in response to the fertilizing spermatozoon. The plasma membrane and cortex of an egg thus represent "excitable media" that quickly respond to the stimulus with the Ca(2+) swings and structural changes. In this article, we review some of the key findings on the rapid dynamic rearrangements of the actin cytoskeleton in the oocyte/egg cortex upon hormonal or sperm stimulation and their roles in the modulation of the Ca(2+) signals and in the control of monospermic fertilization.
authors.affiliation: Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy. Electronic address: santella@szn.it.
authors.forename: Luigia
authors.initials: L
authors.lastname: Santella
authors.affiliation: Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy.
authors.forename: Nunzia
authors.initials: N
authors.lastname: Limatola
authors.affiliation: Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, I-80121, Italy.
authors.forename: Jong T
authors.initials: JT
authors.lastname: Chun
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D049108:Cell Enlargement; D002478:Cells, Cultured; D005260:Female; D009865:Oocytes / Q000502:physiology*; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013215:Starfish
chemical_list: D000199:Actins; D002118:Calcium
keywords: Actin; Calcium; Fertilization; Maturation; Sea urchin; Starfish