title: Role of cyclic AMP in the maturation of Ciona intestinalis oocytes.
abstract: Immature oocytes are arrested at prophase I of the meiotic process and maturation onset is indicated by oocyte nuclear disassembly (germinal vesicle breakdown or GVBD). Signaling pathways that elevate intracellular cyclic AMP (cAMP) may either prevent or induce oocyte maturation depending on the species. In some marine invertebrates and, in particular, in ascidian oocytes, cAMP triggers GVBD rather than blocking it. In this paper, we tested different cAMP elevators in fully grown oocytes at the germinal vesicle stage (GV) of the ascidian Ciona intestinalis. We demonstrated that through the activation of adenylate cyclase or the inhibition and phosphodiesterases the oocyte remained at the GV stage. This effect was reversible as the GV-arrested oocytes, rinsed and incubated in sea water, are able to undergo spontaneous maturation and extrusion of follicle cells. In addition, oocytes acquire the ability to be fertilized and start early development. However, morphology of follicle cells, embryos and larvae from in vitro matured oocytes showed different morphology from those derived from in vivo mature oocytes. The role and the transduction mechanism of cAMP in the regulation of oocyte maturation were discussed. Finally, we indicated a variation of biological mechanisms present in the ascidian species; moreover, we sustain evidence proving that tunicates share some biological mechanisms with vertebrates. This information provided new hints on the importance of ascidians in the evolution of chordates.
authors.affiliation: Animal Physiology and Evolution Laboratory, Stazione Zoologica Anton Dohrn, Naples, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Silvestre
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gallo
authors.forename: Annunziata
authors.initials: A
authors.lastname: Cuomo
authors.forename: Tiziana
authors.initials: T
authors.lastname: Covino
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Tosti
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002938:Ciona intestinalis / Q000196:embryology* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D009866:Oogenesis; D015398:Signal Transduction
chemical_list: D000242:Cyclic AMP; D000262:Adenylyl Cyclases