1. Laboratory for Pluripotent Cell Studies, RIKEN Center for Developmental Biology (CDB), 2-2-3 Minatojima-minamimachi, Chu-o-ku, Kobe, Hyogo 650-0047,Japan.
2. Sir William Dunn School of Pathology, University of Oxford, South Parks Road,Oxford OX1 3RE, UK.
3. Laboratory for Development and Regenerative Medicine, Kobe University Graduate, School of Medicine, 7-5-1 Kusunokicho, Chu-o-ku, Kobe, Hyogo 650-0017, Japan.