1. Salt Lake City Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center; Human Molecular Biology and Genetics Program; and Department of Neurobiology and Anatomy; University of Utah, Salt Lake City, UT 84112, USA.
2. Departments of Pediatrics and Medicine (Neurology), Duke University Medical Center, Durham, NC 27710, USA.
3. Salt Lake City Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center; Human Molecular Biology and Genetics Program; and Division of Human Development and Aging; University of Utah, Salt Lake City, UT 84112, USA.
4. Salk Institute, La Jolla, CA 92307, USA.
5. Departments of Neurobiology and Medicine (Neurology), Duke University Medical Center, Durham, NC 27710, USA
6. Department of Ophthalmology, Yale University, New Haven, CT 06510, USA.
7. Departments of Neurobiology, Medicine (Neurology), and Pharmacology, Duke University Medical Center, Durham, NC 27710, USA, and Department of Medicine (Neurology), Veterans Affairs Medical Center, Durham, NC 27705, USA.