About the Authors
Department of Molecular Medicine, Cornell University, Ithaca, New York, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: SLG QW LJB HS. Performed the experiments: SLG QW LJB. Analyzed the data: SLG QW LJB HS. Wrote the paper: SLG QW LJB HS.