1. Laboratory for Organismal Patterning, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
2. Howard Hughes Medical Institute, Department of Developmental Biology and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
3. Department of Experimental Animal Model for Human Disease, Center for Experimental Animals, Tokyo Medical and Dental University, Tokyo 113-8510, Japan