The purpose of the present review is to outline the current understanding on the molecular mechanisms governing various stages of oocyte maturation, transition from maternal to embryonic control and the initial steps of pre-embryo development. The cytoplasmic and nuclear maturation of the oocyte during pre-ovulatory development can be viewed as separate entities. Cytoplasmic maturation and the ...

Oocytes of LT/Sv mice have anomalous cytoplasmic and nuclear maturation. Here, we show that in contrast to the oocytes of wild-type mice, a significant fraction of LT/Sv oocytes remains arrested at the metaphase of the first meiotic division and is unable to undergo sperm-induced activation when fertilized 15 hours after the resumption of meiosis. We also show that LT/Sv oocytes experimentally ...

Although maturation/M phase promoting factor (MPF) can activate autonomously in Xenopus egg cytoplasm, indirect evidence suggests that nuclei and centrosomes may focus activation within the cell. We have dissected the contribution of these structures to MPF activation in fertilized eggs and in egg fragments containing different combinations of nuclei, centrosomes, and microtubules by following ...

Vertebrate oocytes proceed through the first and the second meiotic division without an intervening S-phase to become haploid. Although DNA replication does not take place, unfertilized oocytes acquire the competence to replicate DNA one hour after the first meiotic division by accumulating an essential factor of the replicative machinery, Cdc6. Here, we show that the turnover of Cdc6 is precis...

The eggs of most mammals are shed from the ovary with the first polar body formed. The mechanism controlling this stage of maturation has never been investigated in detail. Furthermore, under normal conditions only shed ova are fertilized. Does this indicate tha t the first matura t ion division is an essential prelude to fertilization? Or m a y ovarian eggs in fact be activated before the firs...

Herpes simplex virus (HSV) types 1 and 2 have been inactivated in vitro using low concentrations of methylene blue (MB), light (lambda) plus electricity (E), or hematoporphyrin derivative (HPD) plus lambda. Both techniques introduce single strand interruptions into viral DNA, but do not make double strand ruptions into viral DNA, but do not make double strand breaks. MB, lambda plus E-treated v...

Here, we outline the mechanisms involved in the regulation of cell divisions during oocyte maturation and early cleavages of the mouse embryo. Our interest is focused on the regulation of meiotic M-phases and the first embryonic mitoses that are differently tuned and are characterized by specifically modified mechanisms, some of which have been recently identified. The transitions between the M...

Accurate positioning of spindles is essential for asymmetric mitotic and meiotic cell divisions that are crucial for animal development and oocyte maturation, respectively. The predominant model for spindle positioning, termed "cortical pulling," involves attachment of the microtubule-based motor cytoplasmic dynein to the cortex, where it exerts a pulling force on microtubules that extend from ...

Release from arrest in G2 phase of the cell cycle causes profound changes in rat ether-à-go-go (r-eag) K+ channels heterologously expressed in Xenopus oocytes. The most evident consequence of the onset of maturation is the appearance of rectification in the r-eag current. The trigger for these changes is located downstream of the activation of mitosis-promoting factor (MPF). We demonstrate here...

Mammalian oocyte meiotic maturation is the precondition of early embryo development. Lots of microtubules (MT)-associated proteins participate in oocyte maturation process. Cytoskeleton-associated protein 5 (CKAP5) is a member of the XMAP215 family that regulates microtubule dynamics during mitosis. However, its role in meiosis has not been fully studied. Here, we investigated the function of C...