1. Department of Genetics, Stanford University, Stanford, CA 94305, USA.
2. Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
3. Howard Hughes Medical Institute, Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
4. Department of Medical Genetics, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
5. Graduate Program of Genetics, Department of Genetics, Stanford University, Stanford, CA 94305, USA.
6. Glenn Laboratories for the Biology of Aging, Stanford University, Stanford, CA 94305, USA.