Entry into the uterus occurs 4.2 min. after ovulation. Meiosis I and II divisions occur in the uterus. While signals have been identified in several species, the process is currently obscure in C. elegans. As a first step toward identifying a maturation signal, we have shown that sperm act to promote oocyte maturation. In unmated females, oocytes arrest in diakinesis, failing to undergo maturation and ovulation for hours.
Numerous oocytes accumulate, each with an enlarged, distally positioned nucleus lacking a nucleolus.
This phenotype defines an oocyte cell cycle arrest point, and separates the events belonging to oocyte development from those of meiotic maturation. 1 McCarter, et al. We thank Stuart Kim, Simon Tuck, and Iva Greenwald for strains.