Control of epigenetic modification for oocytes genome

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In this study we evaluated epigenetic modification during oocyte growth in mice and pig in relation to in vitro production of oocytes. The results obtained were summarized as follows. 1)Production system for competent oocytes commencing from day 12.5 fetal ovaries has been developed in vitro. The fetal ovary with mesonephroi was cultured in vitro for 8 days, and followed by 10 days culture after removal of mesonephroi. Developed follicles were dissected and collected from the ovaries, and then the follicles were further cultured for 11 days. Finally, oocytes developed over 60μm in diameter were obtained. 2)To evaluate epigenetic status, methylation status of the differentially methylated region of Igf2r, Zac1 and H19 genes were analyzed in the in vitro produced oocytes. The results showed that oocytes acquired appropriate epigenetic modification during their growth period in vitro. Nuclear transfer study revealed that the genome derived from in vitro produced oocytes was competent to support normal development. 3)In pig, significantly small oocytes, which were collected from adult ovary, were applied for in vitro culture and the full size oocytes were successfully obtained. 4)Molecular analysis for parental imprinting, we detected that 27 of imprinted genes are epigenetically modified in the female germ line. Together, the present study show that genomic imprinting in female germ line plays definitive role for supporting normal development.