1. Technology and Development Team for Mammalian Cellular Dynamics; RIKEN BioResource Center; Ibaraki 305-0074 Japan
2. Department of Animal Developmental Genetics, Graduate School of Life and Environmental Sciences; University of Tsukuba; Ibaraki 305-8577 Japan
3. Global Center of Excellence Program; Tokyo Medical and Dental University; 1-5-45 Yushima Bunkyo-ku Tokyo 113-8510 Japan
4. Department of Urology; Yokohama City University Graduate School of Medicine; Yokohama City 236-0004 Japan
5. Bioresource Engineering Division; RIKEN BioResource Center; Ibaraki 305-00074 Japan