1. Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06511, USA
2. Simons Center for Systems Biology, School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540, USA
3. Complex Systems and Statistical Mechanics, Department of Physics and Materials Science, University of Luxembourg, 162a, Avenue de la Faïencerie, 1511 Luxembourg, G. D. Luxembourg