Cell cycle arrest and release in starfish oocytes and eggs.

Immature starfish oocytes are arrested at the prophase of meiosis I. Once released from this arrest, meiotic maturation proceeds to the completion of meiosis II in the absence of fertilization, resulting in a second arrest at the female pronucleus stage. This article discusses how Cdc2 kinase is activated in response to the hormone 1-methyladenine at the release from the meiotic prophase arrest, and how MAP kinase is involved in the arrest at the female pronucleus stage. The experimental findings reveal both generality and divergence in the initial Cdc2 kinase activation pathway and in the role of MAP kinase signaling.