Pig Or Mouse Oocyte Meiotic Maturation Process Of Pkc And Mapk Signaling Pathway Dialogue And ¦Ã-microtubule Protein Localization Studies

Fully grown mammalian oocytes are arrested at the prophase of the first meiotic division within the ovarian follicles. In vivo, meiosis resumption of part of oocytes occurs in response to the preovulatory surge of gonadotropins. Protein kinase C(PKC) and mitogen-activated protein kinase(MAPK)in cumulus cells are involved in FSH-induced meiotic resumption of cumulus-enclosed oocytes(CEOs), but their regulation and crosstalk are unknown. The present experiments were designed to investigate 1) the possible involvement of MAPK cascade in PKC-induced meiotic resumption; 2) the regulation of PKC on MAPK function in FSH-induced oocyte maturation; and 3) the pattern of PKC and MAPK function in induced meiotic resumption of pig cumulus oocyte complexs(COC). In this experiment an induced meiosis model was used to mimic the gonadotropin-triggered resumption of oocytes in vivo, which is inhibited by the inhibitory ovarian follicular environment. PKC activators, phorbol 12-myrestate 13-acetate (PMA) induced the meiotic resumption of CEOs and activation of MAPK in cumulus cells, while this effect could be abolished by PKC inhibitors, calphostin C and chelerythrine, or MEK inhibitor U0126. These results suggest that PKC might induce the meiotic reinitiation of CEOs by activating MAPK in cumulus cells. Both PKC inhibitors and U0126 inhibited the FSH-induced GVBD of oocytes and MAPK activation in cumulus cells, suggesting that PKC and MAPK are involved in FSH-induced GVBD of pig CEOs. Protein synthesis inhibitor cycloheximide inhibited FSH- or PMA-induced oocyte meiotic resumption, but not the MAPK activation in cumulus cells. Thus, when activated by FSH and PKC, MAPK may stimulate the synthesis of specific proteins and then the secretion of certain meiosis-activating substance by cumulus cells. Taken together, we revealed a hypothesized signaling pathway that mediates the FSH-induced meiotic resumption of pig oocytes: after acting on cumulus cells, FSHleads to the activation of MAPK with the mediation of PKG. Activation of MAPK induces the synthesis of certain proteins in cumulus cells, the undefined factor induces the oocytes to resume meiosis.Y -Tubulin, a member of the microtubule superfamily, is a peri-centriolar component which was considered to be essential for microtubule nucleation. At the present research, the dynamics of Y -tubulin during mouse oocyte meiotic maturation, fertilization, and early cleavage as well as the co-localization of Y -tubulin and a -tubulin during the formation of meiotic I spindle were studied by confocal microscopy. We found that Y-tubulin was even distributed in the GV stage oocyte, but it aggregated into some dots during the interphase of early embryos. After GVBD Y -tubulin dots both localized in the cytoplasm and in the vicinity of the condensed chromosomes, and aligned at both poles of the meiotic spindle at prometaphase. At anaphase and telophase, Y -tubulin was detected between the separated chromosomes. The localization of a -tubulin correlated closely to Y -tubulin. It had the same localization in the cytoplasm and radiated fromY-tubulin center close to the chromosomes during the meiotic spindle formation. Our results suggested that Y-tubulin was essential for microtubule nucleation and spindle formation during mouse oocyte meiosis, fertilization, and early embryos, and that its functions might be regulated by some chromosome associated proteins.