About the Authors

Feng Chen

Affiliations Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America, Genomics Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America

Aaron J. Mackey

Current address: Informatics, GlaxoSmithKline, Collegeville, Pennsylvania, United States of America

Affiliations Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America, Genomics Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America

Jeroen K. Vermunt

Affiliation Department of Methodology and Statistics, Tilburg University, The Netherlands

David S. Roos

To whom correspondence should be addressed. E-mail: droos@sas.upenn.edu

Affiliations Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America, Genomics Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: DR FC AM JV. Performed the experiments: FC. Analyzed the data: FC. Wrote the paper: DR FC JV.