1. University of Colorado at Boulder, Department of Molecular, Cellular and Developmental Biology, UCB-0347, Boulder, CO 80309, USA
2. University of Zürich, Department of Molecular Life Sciences, Winterthurerstrasse 190, 8057 Zürich, Switzerland
3. University of Texas at Austin, Center for Nonlinear Dynamics and Department of Physics, Austin, TX 78712, USA