About the Authors
Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 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: JEL AJM ELFH. Performed the experiments: JEL AJM MT. Analyzed the data: JEL AJM. Contributed reagents/materials/analysis tools: MT. Wrote the paper: JEL ELFH.