1. Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94143–0795, USA.
2. Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
3. Division of Endocrinology, Metabolism, and Gerontology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305–5103, USA.
4. Cardiovascular Research Institute and Departments of Physiology and Medicine, University of California, San Francisco, San Francisco, CA 94107, USA.
5. Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
6. Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA.