|
|
Aurora-A je zhrnuta v znovuzahájení meiosy a formaci metafáze I spindlu
Šašková, Adéla ; Šolc, Petr ; Baran, V. ; Kubelka, Michal ; Motlík, Jan
We study the role of Aurora-A during meiotic maturation of mouse oocytes. Total Aurora-A is present in the nucleus in GV-stage oocytes (G2 equivalent). Additionally, active Aurora-A is localized entirely to the centrosome (MTOC) shorly before germinal vesicle breakdown (GVBD). Compared to somatic cells, where active Aurora-A is at the centrosomes and the spindle poles, active Aurora-A is strictly localized on MTOCs at metaphase I in oocytes. We show that activation of centrosomal Aurora-A is independent on PI3K-PKB and CDK1 signaling pathways. This was proved by cultivation of oocytes in presence of roscovitine (CDK1 inhibitor), LY-294002 (PI3K inhibitor) and SH-6 (PKB inhibitor). Treated oocytes show high phosphorylation of Aurora-A on T288 and centrosome amplification despite the presence of intact nuclear envelope. Silencing of Aurora-A by RNA interference induces incorrect spindle assembly. Oocytes are arrested in prometaphase I and unable to reach metaphase II. After microinjection of eGFP-Aurora-A mRNA into GV-stage oocytes, overexpression of Aurora-A leads to distortion of MI spindle organization as well. Our results indicate that Aurora-A is the key centrosomal player in meiotic maturation, essential for proper spindle formation and metaphase I - metaphase II transition.
|
|
|
Aurora-A je zhrnuta v znovuzahájení meiosy a formaci metafáze I spindlu
Šašková, Adéla ; Šolc, Petr ; Baran, V. ; Kubelka, Michal ; Motlík, Jan
We study the role of Aurora-A during meiotic maturation of mouse oocytes. Total Aurora-A is present in the nucleus in GV-stage oocytes (G2 equivalent). Additionally, active Aurora-A is localized entirely to the centrosome (MTOC) shorly before germinal vesicle breakdown (GVBD). Compared to somatic cells, where active Aurora-A is at the centrosomes and the spindle poles, active Aurora-A is strictly localized on MTOCs at metaphase I in oocytes. We show that activation of centrosomal Aurora-A is independent on PI3K-PKB and CDK1 signaling pathways. This was proved by cultivation of oocytes in presence of roscovitine (CDK1 inhibitor), LY-294002 (PI3K inhibitor) and SH-6 (PKB inhibitor). Treated oocytes show high phosphorylation of Aurora-A on T288 and centrosome amplification despite the presence of intact nuclear envelope. Silencing of Aurora-A by RNA interference induces incorrect spindle assembly. Oocytes are arrested in prometaphase I and unable to reach metaphase II. After microinjection of eGFP-Aurora-A mRNA into GV-stage oocytes, overexpression of Aurora-A leads to distortion of MI spindle organization as well. Our results indicate that Aurora-A is the key centrosomal player in meiotic maturation, essential for proper spindle formation and metaphase I - metaphase II transition.
|
|
|
CDC25A je schopna indukovat znovuzahájení meiosy, ale inhibuje metafase I – metafase II přechod
Šolc, Petr ; Šašková, Adéla ; Baran, V. ; Kubelka, Michal ; Motlík, Jan
We have shown that CDC25A protein is expressed in GV-stage oocytes but decreases, in CDK1-dependent manner, during meiotic maturation. As compared with GV-stage only a very low level of CDC25A protein is present at metaphase I (MI) and metaphase II (MII) stages. CDC25A mRNA is stable during entire meiotic maturation. Exogenous CDC25A was sufficient to overcome cAMP-mediated GV-stage block. Using microinjection of GFP-CDC25A and GFP-CDC25B mRNAs constructs we have revealed that CDC25A is exclusively nuclear protein until nuclear envelope break down (NEBD). In contrast CDC25B localizes to cytoplasm at GV-stage oocytes and translocates to nucleus shortly before NEBD. Overexpression of GFP-CDC25A, to interfere with CDC25A degradation during meiotic maturation, resulted in MI block characterized with problems in chromosome congression and spindle formation. This MI block was accompanied with the transient reduction of both CDK1 and MAPK activities. RNAi mediated CDC25A knock-down resulted in a reduced ability to resume meiosis and to reach MII. These data demonstrate that behavior of CDC25A during female meiosis differs significantly from mitosis and CDC25A is involved in both, resumption of meiosis and also in metaphase I spindle formation as a prerequisite for correct MI-MII transition. It is evident that CDC25B is not only important CDC25 phosphatase for meiotic maturation but also CDC25A has its meiotic specific role.
|
guest ::
