1. Department of Physiology Keio University School of Medicine 35 Shinanomachi, Shinjuku‐ku Tokyo 160‐8582 Japan
2. Department of Orthopaedic Surgery Graduate School of Medical Sciences Kyushu University 3‐1‐1 Maidashi, Higashi‐ku Fukuoka 812‐8582 Japan
3. Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Saitama 332‐0012 Japan
4. Department of Orthopaedic Surgery Keio University School of Medicine 35 Shinanomachi, Shinjuku‐ku Tokyo 160‐8582 Japan
5. Subteam for Manipulation of Cell Fate BioResource Center RIKEN TSUKUBA Institute Ibaraki 305‐0074 Japan
6. Department of Pediatrics Stanford University School of Medicine The Bio‐X Program at the James H. Clark Center 318 Campus Drive, E‐150 Stanford CA 94305‐5427