1. Center for iPS Cell Research and Application, Kyoto University; Department of Life Science Frontiers; 53 Kawahara-cho, Shogoin, Sakyo-ku Kyoto 606-8507 Japan
2. Ecole Normale Supérieure, UMR 8640 CNRS-ENS-UPMC Pasteur; Department of Chemistry; 24 rue Lhomond Paris 75005 France