1. Department of Biochemistry, Hiroshima University School of Medicine, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8551,1
2. PRESTO, Japan Science and Technology Corporation, Hiroshima,2
3. Crest Project 3 and
4. Department of Life Science (Biology), 4 University of Tokyo, Meguro-ku, Tokyo 153-8902, and
5. Center for Molecular and Developmental Biology, Faculty of Science, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, 5 and
6. Kondoh Differentiation Signaling Project, ERATO, Japan Science and Technology Corporation, Kyoto, 6 Japan