1. Center for iPS Cell Research and Application, Kyoto University , 53 Kawahara-cho, Shogoin , Sakyo-ku , Kyoto 606-8507, Japan
2. Graduate School of Medicine, Kyoto University , Yoshida-Konoe-cho, Sakyo-ku , Kyoto 606-8501, Japan
3. Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-8656, Japan