1. Center
for Systems Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, United States
2. Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, United States
3. Center
for Computational and Integrative Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, United States
4. Dept.
of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
5. Analytic
and Translational Genetics Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, United States
6. Howard Hughes Medical Institute, Cambridge, Massachusetts 02138, United States