Norio Amizuka1, Sohei Kitazawa2. 1. Developmental Biology of Hard Tissue, Graduate School of Dental Medicine and Faculty of Dental Medicine, Hokkaido University, Sapporo, Hokkaido, 060-8586, Japan. amizuka@den.hokudai.ac.jp. 2. Department of Molecular Pathology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, 791-0295, Japan. kitazawa@m.ehime-u.ac.jp.