1. Howard Hughes Medical Institute, Department of Medicine, School of Medicine, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093–0648, USA.
2. Department of Medicine, Division of Endocrinology, School of Medicine, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093–0648, USA.
3. Department of Cellular and Molecular Medicine, School of Medicine, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093–0648, USA.