Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093 Zürich and Institute of Molecular Life Sciences, University of Zürich, 8057 Zürich, Switzerland.|Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093 Zürich and Institute of Molecular Life Sciences, University of Zürich, 8057 Zürich, Switzerland.|Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093 Zürich and Institute of Molecular Life Sciences, University of Zürich, 8057 Zürich, Switzerland.|Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093 Zürich and Institute of Molecular Life Sciences, University of Zürich, 8057 Zürich, Switzerland.