1. Department of Cardiology, Children's Hospital Boston, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
2. Department of Pediatric Oncology, Dana Farber Cancer Institute, Boston, Massachusetts 02115, the Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142, and Harvard Medical School, Boston, Massachusetts 02115
3. Department of Medical Oncology, Dana Farber Cancer Institute, Boston, Massachusetts 02115
4. Cardiovascular Division, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, Massachusetts 02115
5. Department of Medicine, Children's Hospital Boston, Boston, Massachusetts 02115, and Howard Hughes Medical Institute, Chevy Chase, Maryland 20815
6. Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138