About the Authors
Department of Cell Biology, Harvard Medical School, Children's Hospital and Immune Disease Institute, Boston, Massachusetts, 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: SS EC TK. Performed the experiments: SS EC. Analyzed the data: SS EC TK. Contributed reagents/materials/analysis tools: SS EC. Wrote the paper: SS EC TK.