On cyclins, oocytes, and eggs

Abstract

Oocyte and egg are suitable model systems for studying cell division since meiotic maturation resembles a G2/M transition and early embryonic divisions are precisely timed and occur without zygotic transcription. The analysis of oocytes and eggs from different species provides the opportunity to understand the roles of proteins that are critical to the progression and maintenance of the cell cycle. Among them, cyclins are certainly worthy of investigation. Mitotic cyclins (cyclins A and B) are clearly implicated in meiosis and early embryonic cell cycles. More recent studies have revealed that G1‐type cyclins (cyclins E and D) could also play a role in both processes and cyclin H has been suggested to participate to CAK activity (cdc2‐activating kinase) in oocytes. The study of cyclins in oocytes and eggs clearly offer insights into their roles during the cell cycle. Mol. Reprod. Dev. 48:397–411, 1997. © 1997 Wiley‐Liss, Inc.

Maturation/M-Phase Promoting Factor Regulates Aging of Porcine Oocytes Matured In Vitro

“…These results indicate that the pre-MPF ratio decreased after insemination, as a result of degradation of cyclin B, because the H1k activity also decreased. These results agree well with several reports of cyclin B degradation after oocyte activation (Thibier et al, 1997;Taieb et al, 1997;Winston, 1997) and also with the generally accepted mechanism of cell cycle regulation that escape from the M-phase depends on the degradation of cyclin B (Norbury and Nurse, 1992). In clear contrast to the situation in activated oocytes after sperm penetration, the pre-MPF ratio of aged oocytes increased gradually according to the culture period due to an increase in pre-MPF levels.…”

Inactivation of p34cdc2 kinase by the accumulation of its phosphorylated forms in porcine oocytes matured and aged in vitro

“…In the present study the M band of 48 h matured oocytes decreased after insemination, indicating the degradation of cyclin B because the MPF activity also decreased. This results agrees well with many reports showing the degradation of cyclin B after oocyte activation (Thibier et al, 1997;Taieb et al, 1997;Winston, 1997) and also the generally accepted view of cell cycle regulation, that is, the escape from M-phase depends on the degradation of cyclin B (Norbury & Nurse, 1992). The increase in intensity of U plus M bands at 10 h pi might reflect the resynthesis of cyclin B during the S-phase of the first mitosis and accumulation of pre-MPF.…”

Phylogenetic conservation of cytostatic factor related genes in the ascidian Ciona intestinalis

“…clearly show that a CSF-like activity is present in metaphase-I arrested C. intestinalis oocytes. We also demonstrated that the blocking activity of CSF does not depend on the continuous synthesis and degradation of short lived proteins, as reported for other invertebrates (Taieb et al, 1997). In fact, emetine, a well-known and largely employed protein synthesis inhibitor, did not interfere with CSF arrest.…”