REINITIATION OF MEIOSIS IN STARFISH OOCYTES REQUIRES AN INCREASE IN NUCLEAR CA2+

Here we report that an increase in nuclear Ca2+ is hormonally regulate d and is required for reinitiation of meiosis in starfish oocytes. We have shown in Asteria pectirtifera that a Ca2+ transient and a baselin e increase of Ca2+ occur both in the cytoplasm and in the nucleus. The se increases are in response to 1-methyladenine (1-MA), the hormone re sponsible for the induction of meiotic maturation. The Ca2+ transients are not necessary for the reinitiation of meiosis. However, blocking the baseline increase in nuclear Ca2+ blocks both the nuclear envelope breakdown (NEBD) and the continuation Of meiosis. (C) 1994 Academic P ress, Inc.