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{sl c--erbB_(2)} and {sl c--myb} induce oocyte maturation via activation of mitogen--activated protein kinase and maturation promoting factor

Zheng Yuehui, Zheng Liping, Li Fang, Wu Lei, Dai Yucheng

Department of Physiology,School of Medicine, Nanchang University.Nanchang 330006,Jiangxi；China

Abstract

It is important to study the mechanism of oocyte maturation because oocyte maturation is essential for the female procreation. The present study was designed to observe the effects of protooncogenes c-erbB_(2) and c-myb on oocyte maturation and the upstream and downstream relationship with mitogen-activated protein kinase （MAPK） and maturation promoting factor （MPF）. The investigation was designed as follows： （1） In order to explore the effects of protooncogenes on oocyte maturation, the dose- and time-depondent effects of c-erbB_(2) antisense oligodeoxynucleotide （ASODN） and c-myb ASODN on oocyte maturation were examined, and the effects of oocyte microinjection with recombinant c-erbB_(2) and c-myb proteins on oocyte maturation were investigated; （2） In order to study the upstream and downstream relationship among protooncogenes of c-erbB_(2), c-myb and protein kinases of MAPK and MPF in regulating oocyte maturation, mouse oocytes were cultured in the medium treated with c-erbB_(2) ASODN, c-myb ASODN, PD98059 （the MAPK inhibitor） or roscovitine （the MPF inhibitor） for 8 h, respectively, and the expressions of c-erbB_(2) mRNA, c-myb mRNA, MAPK and MPF were examined. The results showed that both c-erbB_(2) ASODN and c-myb ASODN inhibited the rate of germinal vesicle breakdown （GVBD） and the first polar （PB1） extrusion of denuded oocytes （DOs） in a dose- and time-dependent way, and delayed their maturation time significantly. When recombinant c-erbB_(2) and c-myb proteins were microinjected into cytoplasm of germinal vesicle stage oocyte, we found that the GVBD rate increased by 23.1% （P〈0.05） and 32.2% （P〈0.05）, respectively, for 6-hour culture, and the PB1 extrusion rate increased by 17.3% （P〈0.05） and 23.5% （P〈0.05）, respectively, for 12-hour culture. RT-PCR showed that the mRNA expressions of c-erbB_(2) and c-myb were detected in oocytes; c-erbB_(2) ASODN inhibited c-erbB_(2) mRNA and c-myb mRNA expressions; c-myb ASODN inhibited c-myb mRNA expression but had no effect on c-erbB_(2) mRNA expression. Nonsense tat ODN had no effects on the expressions of c-erbB_(2) mRNA and c-myb mRNA. Neither PD98059 nor roscovitine changed the expressions of c-erbB_(2) mRNA and c-myb mRNA though both of them inhibited recombinant c-erbB_(2) and c-myb proteins-induced oocyte maturation. Furthermore, MAPK phosphorylation and cyclinB1 synthesis in oocytes were inhibited remarkably when oocytes were treated with c-erbB_(2) ASODN, c-myb ASODN, PD98059 and roscovitine. Nonsense tat ODN had no effects on MAPK phosphorylation and cyclinB1 content. The results suggest that protooncogenes c-erbB_(2) and c-myb play an important role in oocyte maturation; the effects of c-erbB_(2) and c-myb depend upon the action of MAPK and MPF, and their activation is the event that occurs downstream of c-erbB_(2) and c-myb in the maturation signal pathway.

Key words: oocyte maturation;Gene;c-erbB_(2);c-myb;mitogen-activated protein kinase;maturation promoting factor

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Zheng Yuehui, Zheng Liping, Li Fang, Wu Lei, Dai Yucheng. {sl c--erbB_(2)} and {sl c--myb} induce oocyte maturation via activation of mitogen--activated protein kinase and maturation promoting factor. Acta Physiol Sin 2008; 60 (1): 97-104 (in Chinese with English abstract).