About the Authors
Department of Pathology, Stanford Medical School, Stanford, California, United States of America
Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America
Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: EY JD. Performed the experiments: EY. Analyzed the data: EY JD. Wrote the paper: EY JD.