Abstract
The c-mos protooncogene is expressed as a maternal message that is required for oocyte meiosis. The mechanism of action of c-mos was investigated by analysis of mouse eggs injected with antisense c-mos oligonucleotides. In antisense-injected eggs, maturation-promoting factor was not reactivated after the completion of meiosis I, leading to the formation of nuclei containing decondensed chromatin within 2-3 hr after polar body extrusion. This was correlated with a failure of the injected eggs to accumulate newly synthesized cyclin B. The c-mos protooncogene thus appears to affect the pathway that regulates cyclin B stability during meiosis of mouse eggs.