The role of germinal vesicle in maturation of Pleurodeles waltlii oocytes induced by steroids

Essential role of germinal vesicle material in the meiotic cell cycle of Xenopus oocytes

“…1, 5, 28-30). Originally, this general view was built on a number of classical, cytological observations that both enucleated amphibian oocytes and anucleate mouse oocyte fragments undergo MPF activation shortly after release from prophase I arrest (8,(19)(20)(21)(22)(23)(24)(25), and that ''mature'' enucleated oocytes (from many amphibian species) show surface changes and a cortical response (to activation stimuli) that are typical of completely mature oocytes arrested at metaphase II (20,22,23,26,27). Looking into the classical studies (on amphibian oocytes), however, it seems clear that most of the previous workers examined only the initial MPF activation in meiosis I, but not MPF reactivation in meiosis II, in enucleated oocytes, probably because they were unaware of the oscillation in MPF activity during maturation, which was found only in 1984 (6); instead, they took the cortical changes (in mature enucleated oocytes) as indication of the completion of ''meiotic'' maturation (see refs.…”

“…1, 5, 28-30). We therefore challenged this view by using enucleated Xenopus oocytes, as previously performed (8,19,22,23) (as a control of this experiment, we used nucleated oocytes that received a small puncture at their equators; see Materials and Methods). First, we measured MPF activity in progesteronetreated, enucleated oocytes by classical cytoplasmic transfer (6,8), i.e., by assaying the activity of cytoplasmic extracts (from enucleated oocytes) to induce GVBD in recipient immature oocytes.…”

“…1,5,[28][29][30]. Despite the numerous cytological studies (8,13,14,(19)(20)(21)(22)(23)(24)(25)(26)(27), however, the progression of the meiotic cell cycle in enucleated vertebrate oocytes has not so far been examined at all at the molecular level.…”

“…Thus, a number of classical studies showed that enucleated amphibian oocytes and anucleate mouse oocyte fragments undergo MPF activation soon after release from prophase I arrest, as semiquantitatively evidenced by their cytoplasmic activities to induce GVBD in recipient immature oocytes (8,(19)(20)(21)(22)(23) or to induce chromosome condensation in anucleate fragments-fused blastomeres (24,25). Moreover, enucleated amphibian oocytes well after prophase I release are long known to show both surface changes (20,22,23) and a cortical response (to activation stimuli) (8,26,27) that are normally indication of the completion of meiotic maturation in amphibian oocytes (1). Hence, for nearly three decades, it has generally been believed that nuclear material is dispensable for MPF activation and the meiotic cell cycle in vertebrate oocytes, particularly amphibian oocytes (see refs.…”

Germinal Vesicle Material Is Essential for Nucleus Remodeling after Nuclear Transfer1

“…Following hormone stimulation, GV breakdown (GVBD) allows the mixing of GV material with cytoplasm and is thought to be necessary for sperm chromatin decondensation and cleavage in fertilized eggs [10,11]. A number of classic studies have shown that enucleated amphibian oocytes and anucleate mouse oocyte fragments undergo maturation promoting factor (MPF) activation soon after release from prophase I arrest, as semiquantitatively indicated by their cytoplasmic activities, to induce GVBD in recipient immature oocytes [12][13][14][15][16]. In a recent study, GV material was essential for MPF reactivation in Xenopus oocytes [17].…”