During each reproductive cycle, a preovulatory surge of gonadotropins induces meiotic maturation of the oocyte in the preovulatory follicle followed by ovulation. Although gonadotropins stimulate cAMP production in somatic cells of the follicle, a decrease in intra-oocyte cAMP levels is required for resumption of meiosis in oocytes. Based on the observed compartmentalization of the cAMP-degradi...

During oogenesis, oocytes are arrested in prophase and resume meiosis by activating the kinase Cdk1 upon hormonal stimulation. In all vertebrates, release from prophase arrest relies on protein kinase A (PKA) downregulation and on the dephosphorylation of a long sought but still unidentified substrate. Here we show that ARPP19 is the PKA substrate whose phosphorylation at serine 109 is necessar...

We examined spindle reorganization during the completion of meiosis in fertilized and unfertilized oocytes of Drosophila using indirect immunofluorescence and laser scanning confocal microscopy. The results defined a complex pathway of spindle assembly during resumption of meiosis, and revealed a transient array of microtubules radiating from the equatorial region of the spindle towards discret...

The release of a mature healthy egg for fertilization is the center of the entire reproductive process. From the time of embryonic development till fertilization, the oocyte undergoes several stop-and-go periods. In most animals, oocytes are held in meiotic arrest in prophase I prior to ovulation. The ovulatory luteinizing hormone (LH) surge promotes the resumption of meiosis of the arrested oo...

The aim of our in vitro experiments was to study the role of growth factors and protein kinase A (PKA)-dependent intracellular mechanisms in the control of nuclear maturation of porcine oocytes. Oocytes were cultured with or without growth factors (IGF-I, IGF-II, EGF; 10 ng x mL(-1) medium) and inhibitors of PKA (Rp-cAMPS or KT5720; 100 ng x mL(-1)). Stages of meiosis were determined from the s...

Eggs of most animal species are fertilized by a single sperm and fusion of these two cells is essential for the activation of the developmental program of the zygote. Cases in which multiple sperm fertilize an egg, a condition known as polyspermy, the supernumerary paternal centrioles and chromosomes usually create aberrant cell divisions that result in death. Thus, eggs have evolved mechanisms...

KIF2A, a member of the kinesin-13 family, has been reported to play a role in spindle assembly in mitosis. However, its function in mammalian meiosis remains unknown. In this research, we examined the expression, localization and function of KIF2A during mouse oocyte meiosis. KIF2A was expressed in some key stages in mouse oocyte meiosis. Immunofluorescent staining showed that KIF2A distributed...

Effects of the neutralization of endogenous progesterone with rabbit antiserum to progesterone (anti-progesterone) on germinal vesicle breakdown of ova in follicles of small (less than 125 micrometers), intermediate (125-250 micrometers) and large (greater than 250 micrometers) diameter were examined by a quantitative histological technique. Immature rats were treated with 5 IU pregnant mare's ...

SMC complexes include three major classes: cohesin, condensin and SMC5/6. However, the localization pattern and genetic requirements for the SMC5/6 complex during mammalian oogenesis have not previously been examined. In mouse oocytes, the SMC5/6 complex is enriched at the pericentromeric heterochromatin, and also localizes along chromosome arms during meiosis. The infertility phenotypes of fem...