1. Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
2. Department of Chemistry & Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
3. Broad Institute of MIT and Harvard, 7 Cambridge Center, Cambridge, MA 02142, USA.
4. Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.