PARENT SESSION
MINISYMPOSIUM VIII. IN VITRO PRODUCTION OF MALE AND FEMALE GAMETES FROM STEM CELLS

Tuesday, August 3, 2004
9:00 AM–10:30 AM
Buchanan A100
Chair: Ryuzo Yanagimachi (University of Hawaii School of Medicine, Honolulu, HI)

(MS22) IN VITRO PRODUCTION OF MOUSE OOCYTES FROM FETAL GERM CELLS.

Kono, Tomohiro^{1, 2}, Obata, Yayoi^{1, 2}, Niwa, Katsutoshi^{1, 2}, Hiura, Hitoshi¹, Komiyama, Junichi¹, Ogawa, Hidehiko^{1, 2}, ¹ Tokyo University of Agriculture, Tokyo, Japan² Bio-oriented Technology Research Advancement Institution (BRAIN), Tokyo, Japan

ABSTRACT- In mammals, the ovaries contain thousands or millions of immature oocytes, however only limited number of oocytes can develop to the full size, until when oocytes are not competent to mature and support normal development. To maximize utilizable female gametes incompetent small oocytes have been reared in a particular in vitro culture system. These experiments showed competent oocytes can be produced from new born mice derived oocytes, but the success rate is still low. The main reason for the extremely low ability of in vitro produced oocytes is due to poor quality of the cytoplasm. To conquer this, we developed nuclear transfer technique for GV stage oocytes. The technique shows that all nuclei at metaphase I diplotene stage, even nuclei of non-growing stage oocytes, can be matured when transferred into fully grown GV oocytes. Further, the reconstructed oocytes can fertilize and develop to blastocysts as well as the controls. However, the embryos lack competence to develop after implantation. This is responsible for genomic imprinting, which is epigenetic modification and imposed during oocytes growth. In this minisymposium, we show that nuclei of oocytes produced by in vitro culture commencing from E12.5 fetal ovary are competent, showing progress of epigenetic modification during oocyte growth in vivo and in vitro.

KEY WORDS: in vitro development, genomic imprinting, oocytes, nuclear transfer