1. Department of Molecular Life Science, Tokai University School of Medicine, Isehara, Kanagawa 259–1193, Japan
2. Current address: Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
3. Current address: Department of Genomic Function and Diversity, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan