1. Department of Molecular Pharmacology, Diabetes and Metabolic Diseases Research Center, University Medical Center, SUNY–Stony Brook, Stony Brook, NY 11794–8651, USA.
2. Department of Biological Sciences, University of Iowa, Iowa City, IA 52242, USA.
3. Howard Hughes Medical Institute, Department of Pharmacology and Center for Developmental Biology, University of Washington School of Medicine, Seattle, WA 98195, USA.
4. Department of Physiology and Biophysics, Diabetes and Metabolic Diseases Research Center, University Medical Center, SUNY–Stony Brook, Stony Brook, NY 11794–8661, USA.