1. Division of Genetics, Department of Medicine, Howard Hughes Medical Institute, Brigham and Women's Hospital, Boston, MA 02115, USA.
2. Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
3. Program in Systems, Synthetic, and Quantitative Biology, Harvard University, Boston, MA 02115, USA.
4. Division of Pediatric Infectious Diseases, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL 35233, USA.
5. Division of Gastroenterology, Hepatitis, and Nutrition, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL 35233, USA.