1. Department of Bioscience, Nagahama Institute of Bioscience and Technology, Tamura 1266, Nagahama, Shiga 526-0829, Japan
2. Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan
3. Department of Biology, Graduate School of Science, Kobe University, Rokkodai 1-1, Nada-ku, 657-8501, Japan