Conditions for the appearance of maturation promoting factor following germinal vesicle disruption of prophase‐arrested starfish oocytes

Abstract

AbstractIn this paper, we report that so‐called “incompetent” prophase‐arrested oocytes of Marthasterias glacialis and Asterias rubens fail to produce any aster or spindle when their nucleoplasm and cytoplasm are mixed via pressure or microinjection. We also show that the same incompetent oocytes always complete their maturation up to second polar body extrusion and female pronucleus formation following a 30 sec shaking treatment, which results at once in germinal vesicle (GV) disruption and produces the same mixing of their nuclear and cytoplasmic compartments.32P phosphate incorporation into proteins and cell fusion experiments indicates that this mechanical treatment induces an increased protein phosphorylation and triggers the formation of active maturation promoting factor (MPF) molecules which are not produced following a simple nucleoplasm transfer. While bovine serum albumin (BSA) had no effect on this process, the intracellular Ca2+antagonists (2‐[(2‐bist[Carboxymethyl]‐amino‐5‐methylphenoxy)‐methyl]‐6‐methoxy‐8‐bis[carboxy‐methyl]‐aminoquinolinetetrakis‐[acetoxymethyl]ester) (Quin 2‐AM) and 8(N‐N‐diethylamino) octyl‐3,4,5‐trimethoxybenzoate (TMB 8) were found to inhibit both hormone‐induced and shaking‐induced maturations. These results exclude the possibility that shaking might act by releasing arachidonic acid in the external medium. Instead, they suggest that such a mechanical treatment may trigger the same significant changes in Ca2+ concentration or compartmentalization that have been shown to occur following hormone stimulation and that seem to be required for activating resting female centrioles as well as latent MPF precursors and protein kinases.