1. Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
2. Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
3. ERATO, Japan Science and Technology Agency, Okazaki 444-8585, Japan
4. National Institute for Basic Biology, Okazaki 444-8585, Japan
5. School of Life Science, Graduate University for Advanced Studies, Okazaki 444-8585, Japan