Studies on molecular mechanisms and artificial regulation of maturation and aging of mammalian oocytes

Aims of the present study are clarifying the cytoplasmic changes during mammalian oocyte aging at molecular levels and subsequently regulating this process artificially.The present study might contribute to prevent the deterioration of oocyte qualities derived from elongated manipulation period of the in vitro matured mammalian oocytes，used for such as reproductive and developmental technologies.The gradual decrease of maturation promoting factor(MPF)activity during oocyte aging has been reported previously。The present study revealed that the molecular mechanism of the decrease of MPF activity during oocyte aging was completely different from that during oocyte activation Although the decrease of MPF activity at oocyte activation was attributed to the rapid degradation of cyclin B，a regulatory subunit of MPF，the levels of MPF subunits，both p34i D1 and cyclin B，were notory subunit of MPF；More e MPF，so-called pre-MPF，was observed。In order to confirm that this hyperphosphorylation of MPF was the course of the decreased MPF activity in aged oocytes，I treated the fresh and aged oocytes，respectively，with vanadate and caffeine which modulated the phosphorylation states of MPF.These experiments suggested that the change of phosphorylation state of MPF was the main course of the decrease of the activity during oocyte aging and that the MPF activity in aged oocytes could be regulated at lease in part by vanadate and caffeine treatment。These findings might be valuable as the first report showing the possibility of artificial regulation of MPF activity。Furthermore，I revealed that these treatments could change the rates of spontaneous activation and fragmentation of oocytes，both are the parameters of oocyte aging.In summary，the present study showed cytoplasmic changes during mammalian oocyte aging at molecular levels and proposed a simple method for artificial regulation of this process at least partially.Less：Less

Aims of the present study are clarifying the cytoplasmic changes during mammalian oocyte aging at molecular levels and subsequently regulating this process artificially. The present study might contribute to prevent the deterioration of oocyte qualities derived from elongated manipulation period of the in vitro matured mammalian oocytes, used for such as reproductive and developmental technologies.The gradual decrease of maturation promoting factor (MPF) activity during oocyte aging has been reported previously. The present study revealed that the molecular mechanism of the decrease of MPF activity during oocyte aging was completely different from that during oocyte activation Although the decrease of MPF activity at oocyte activation was attributed to the rapid degradation of cyclin B, a regulatory subunit of MPF, the levels of MPF subunits, both p34ィイD1cdc2ィエD1 and cyclin B, were not significant]y changed during oocyte aging but the gradual accumulation of hyperphosphorylated inactiv … More e MPF, so- called pre-MPF, was observed. In order to confirm that this hyperphosphorylation of MPF was the course of the decreased MPF activity in aged oocytes, I treated the fresh and aged oocytes, respectively, with vanadate and caffeine which modulated the phosphorylation states of MPF. These experiments suggested that the change of phosphorylation state of MPF was the main course of the decrease of the activity during oocyte aging and that the MPF activity in aged oocytes could be regulated at lease in part by vanadate and caffeine treatment. These findings might be valuable as the first report showing the possibility of artificial regulation of MPF activity. Furthermore, I revealed that these treatments could change the rates of spontaneous activation and fragmentation of oocytes, both are the parameters of oocyte aging.In summary, the present study showed cytoplasmic changes during mammalian oocyte aging at molecular levels and proposed a simple method for artificial regulation of this process at least partially. Less