[1] Tokyo Univ Sci, Res Inst Biomed Sci, Noda, Chiba 278, Japan
[2] Univ Tokyo, Inst Med Sci, Ctr Expt Med & Syst Biol, Minato Ku, Tokyo, Japan
[3] Japan Sci & Technol Agcy JST, CREST, Saitama, Japan
[4] Univ Tokyo, Grad Sch Sci, Minato Ku, Tokyo 113, Japan