Meiosis-Activating Sterol-Mediated Resumption of Meiosis in Mouse Oocytes In Vitro Is Influenced by Protein Synthesis Inhibition and Cholera Toxin1

Abstract

To explore the possible signaling pathways of meiosis-activating sterol (MAS)-induced oocyte maturation and to elucidate whether the MAS pathway involves transcription or translation, arrested immature mouse oocytes were cultured with either the protein synthesis inhibitor cycloheximide or the heteronuclear RNA inhibitors alpha-amanitin or actinomycin D, respectively. Moreover, the possible involvement of a G protein-coupled receptor mechanism in MAS-mediated oocyte maturation was explored by influencing oocyte maturation with cholera toxin (CT). MAS-induced oocyte maturation was completely blocked by the addition of 50 microg/ml cycloheximide 4 h before the addition of MAS. Simultaneous addition of MAS and the protein synthesis inhibitor also significantly reduced the meiotic resumption compared to that in MAS-treated controls. In contrast, neither of the treatment regimens to inhibit transcription of DNA to RNA was observed to have any effect on the MAS-induced resumption of meiosis. CT was observed to inhibit MAS-induced, but not spontaneous, oocyte maturation in vitro, suggesting a putative involvement of G protein-coupled receptor mechanism in the MAS mode of action. In conclusion, protein synthesis was found to be an essential requirement for maintaining the oocytes' responsiveness to MAS-induced resumption of meiosis, in contrast to transcription.

Regulatory contribution of heterotrimeric G-proteins to oocyte maturation in the sea urchin

“…However, a follicle fluid sterol (called FF-MAS) was identified in a screen for the substances able to induce maturation of mouse follicle-enclosed oocytes (Byskov et al, 1995). Detailed analysis of cell signaling pathways comparing spontaneous and FF-MAS-induced maturation indicated that the pathways differ significantly between these mechanisms (Grondahl et al, 2000;Faerge et al, 2001). It is of interest that starfish oocytes of a number of species exhibit a significant degree of spontaneous maturation when dissected form the ovary, up to 10 -15% GVBD in the first 90 min (Schuetz, 1971).…”

The in vitro growth and maturation of follicles

“…Oocyte maturational competence is linked to follicle size and the follicular microenvironment immediately before nuclear and cytoplasmic maturation. Just as has been recorded for IVG, there is a clear need to optimise IVM culture media (Filali et al 2008) and to test the efficacy of physiologically relevant additives such as human chorionic gonadotrophin (Ge et al 2008); umbilical cord blood (Zhang et al 2007);and FCS (van Wagtendonk-de Leeuw et al 2000); as well as to test the efficacy of physiologically relevant additives such as follicular fluid meiosis activating sterol (Gröndahl et al 2000a(Gröndahl et al , 2000b and fetuin (Schroeder et al 1990, Dell'Aquila et al 1999; and to standardise factors such as priming with FSH, time of aspiration and the time interval to maturation in vitro (Mikkelsen et al 2000). There is evidence that meiotic maturation and fertilisation rates and blastocyst production are compromised when compared with in vivo matured counterparts (Banwell & Thompson 2008).…”

Effect of rescuing donated immature human oocytes derived after FSH/hCG stimulation following in vitro culture with or without Follicular Fluid Meiosis Activating Sterol (FF-MAS)—an embryo chromosomal and morphological analysis

“…Follicular-Fluid Meiosis Activating Sterol (FF-MAS) which is found in high concentrations (around 1.6 µM) in follicular fluid in mammals [8], has been shown to be involved in the control of meiosis [8][9][10]. In mouse oocytes, addition of FF-MAS to the culture medium induce dosedependent resumption of meiosis [10][11], and increase the synchrony of cytoplasmic and nuclear maturation [12][13].…”

“…In mouse oocytes, addition of FF-MAS to the culture medium induce dosedependent resumption of meiosis [10][11], and increase the synchrony of cytoplasmic and nuclear maturation [12][13].…”