Cell‐cycle aspects of growth and maturation of mammalian oocytes

Abstract

In this review, recent data concerning growth and maturation of nonmammalian and mammalian female germ cells are compiled with regard to the increased understanding of somatic cells mitotic cycles, from yeast to human tissues. These data allow us to conclude that growing oocytes of nonvertebrates, lower vertebrates, and mammals resemble somatic cells in the G I In mammals, the LH surge induces "de novo" RNA and protein synthesis in granulosa cells. This metabolic change in granulosa cells abolishes their inhibitory activity, and meiosis in fully grown oocytes in preovulatory follicles is then resumed. Resumption of meiosis requires an activation of pre MPF molecules within oocytes. This can be achieved either without (mouse, rat, and rabbit) or with (pig, sheep, and cow) an active protein synthesis by the oocytes. The species specificity is probably dependent on the presence or absence of cyclin-like and/or mos-like molecules in fully grown oocytes. Both major events during GVBD, chromatin condensation, and nuclear envelope disintegration require protein phosphorylation. Experimentally, these two phosphorylation activities can be separated one from another. The active MPF molecules are amplified autocatalytically in amphibian and starfish oocytes. However, an increase of MPF activity in mouse and pig oocytes, similarly as in Rana pipiens and sturgeon oocytes, requires an active protein synthesis.

Calcium and meiotic maturation of the mammalian oocyte

“…ENTRY into M-phase, e.g., is initiated by the binding of cyclin B to ~34"~"', which together constitue M-phase promoting factor (MPF). MPF activity in the mouse oocyte (Bornslaeger et al, 1988;Hashimoto and Kishimoto, 1988;Rime et al, 1989) as well as in other species (reviewed by Hunt, 1989;Motlik and Kubelka, 1990;Nurse, 1990;Minshull, 1993;Pines, 1993) is in turin regulated by a complex sequence of events including protein synthesis and destruction, as well as post-translational phosphorylation and dephosphorylation. In its inactive form, the ~yclin/p34"~"~ complex remains phoeiphorylated on a tyrosine residue, whereas a threonine residue is prevented from becoming phosphorylated by an inactivating type 1 or 2A phosphatase (PP1 or 2A).…”

Selective degradation of maternal and embryonic transcripts in in vitro produced bovine oocytes and embryos using sequence specific double-stranded RNA

“…During oocyte maturation, meiotic resumption is characterised by germinal vesicle breakdown (GVBD), chromosomal condensation, progression to metaphase of the first meiosis release of the first polar body and then arrest at the metaphase of the second meiosis (MII) (Motlik & Kubelka 1990). The meiotic arrest (MII arrest) is maintained by the persistently high activity of cyclin B-p34 cdc2 kinase, also called maturation promotion factor (MPF) (Draetta & Beach 1988, Brizuela et al 1989, Masui 1992, Fan & Sun 2004.…”

Nitric oxide and meiotic competence of porcine oocytes

“…Its degree depends on the size of the oocyte. Pig oocytes up to 100 mm -E-mail: chmelikova@af.czu.cz are completely meiotically incompetent and under in vitro conditions are incapable of breaking through the first meiotic block and exiting from the germinal vesicle stage (GV; Motlik and Kubelka, 1990). Those ranging from 100 to 110 mm in size have only partially developed meiotic competence for the time being.…”