1. Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Fukuoka 812-8582, Japan
2. CREST, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan
3. Laboratory of Embryonic and Genetic Engineering, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Fukuoka 812-8582, Japan