About the Authors
Departments of Developmental Biology, Genetics, and Bioengineering, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California, United States of America
The authors have declared that no competing interests exist.
DCK, LM, SMB, and MPS conceived and designed the experiments. DCK, LM, HM, and JB performed the experiments. DCK analyzed the data. DCK, LM, SMB, HM, and JB contributed reagents/materials/analysis tools. DCK, LM, and MPS wrote the paper.