1. Bioinformatics and Computational Biology Program, Iowa State University , Ames, IA 50011, United States
2. Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , Ames, IA 50011, United States
3. Computational Neurobiology Laboratory, Salk Institute for Biological Studies , La Jolla, CA 92037, United States
4. Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh , Pittsburgh, PA 15232, United States
5. Department of Statistics, Iowa State University , Ames, IA 50011, United States