1. Systems Biology Program; Graduate School of Media and Governance; Keio University; Fujisawa 252-0882 Japan
2. Institute for Advanced Biosciences; Keio University; Kakuganji Tsuruoka 997-0052 Japan
3. Department of Biological Sciences; Graduate School of Science; University of Tokyo; 7-3-1 Hongo, Bunkyo Tokyo 113-0033 Japan