1. Research Center for Stem Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Science City, Japan
2. Laboratory of Genetics, The Salk Institute, La Jolla, CA, USA
3. Present address: Genome Research Laboratories, Wako Pure Chemical Industries, Ltd., Amagasaki, Hyogo, Japan
4. Laboratory of Molecular Neuroscience, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama, Ikoma, Japan