1. a Department of Biology, Nippon Medical School, Musashino, Tokyo, Japan
2. b Department of Molecular Biology, Institute for Advanced Medical Sciences, Nippon Medical School, Kawasaki, Kanagawa, Japan
3. c Section on Molecular Morphogenesis, Cell Regulation and Development Affinity Group, Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, USA