Effect of Chromatin Changes in the Germinal Vesicle on the Development of Porcine Embryos In Vitro

다국어 초록 (Multilingual Abstract)

In all the studies of mammalian species, chromatin in the germinal vesicle (GV) is initially decondensed with the nucleolus not surrounded by heterochromatin (the NSN configurations). During oocyte growth, the GV chromatin condenses into perinucleolar rings (the SN configurations) or other corresponding configurations with or without the perinucleolar rings, depending on species. During oocyte maturation, the GV chromatin is synchronized in a less condensed state before germinal vesicle breakdown (GVBD) in species that has been minutely studied. As not all the species show the SN configuration and gene transcription always stops at the late stage of oocyte growth, it is suggested that a thorough condensation of GV chromatin is essential for transcriptional repression. Because the GV chromatin status is highly correlated with oocyte competence, oocytes must end the NSN configuration before they gain the full meiotic competence and they must take on the SN/corresponding configurations and stop gene transcription before they acquire the competence for early embryonic development. In this study, we firstly investigated whether the layer of cumulus cells and size of oocytes could determine chromatin configurations in porcine oocytes. Using Hoechst3342 staining, the GV nucleolus and chromatin of porcine oocytes was classified into SN and NSN configurations. Next, we examined the changes in GV chromatin configurations during growth and maturation of porcine oocytes. In addition, the maturation and parthenogenetic development abilities in vitro were significant different between the SN and NSN configurations oocytes. These results indicated that chromatin changes in GV oocytes affect the development potential of parthenogenetic embryos.