1. Department of Life Science, Tokyo Institute of Technology, 4259-B-6 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, and RIKEN Harima Institute, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan