1. Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305–5174, USA.
2. School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea.
3. Center for Theoretical Biology, Peking University, Beijing, 100871, China.
4. California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94143–2540, USA.
5. Department of Biology, Indiana University, Bloomington, IN 47405, USA.