1. Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
2. Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3. Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
4. Department of Pediatrics, Stanford University, Stanford, CA, USA.
5. Computational and Systems Biology Program, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
6. Howard Hughes Medical Institute.