1. Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
2. Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3. Department of Biological Chemistry, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, and Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
4. Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
5. Department of Systems Biology, Harvard Medical School, Boston, MA 02114, USA.