1. Laboratory for Mammalian Germ Cell Biology, Center for Developmental Biology,RIKEN Kobe Institute, 2-2-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047,Japan.
2. Laboratory of Molecular Cell Biology and Development, Graduate School of Biostudies, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
3. Department of Biosystems Science, Graduate School of Science and Technology,Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan.
4. Cell Resource Center for Biomedical Research, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aoba-ku, Sendai 980-8575,Japan.
5. Department of Genetics and Division of Mammalian Development, National Institute of Genetics, SOKENDAI, 1111 Yata, Mishima, Shizuoka 411-8540,Japan.
6. Department of Cell Biology, Institute for Virus Research, Kyoto University,Shogoin Kawara-cho, Kyoto 606-8507, Japan.
7. Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan.