1. Center for Demographic Studies, Duke University, 2117 Campus Drive, Box 90408, Durham, NC 27708-0408, USA
2. Division of Neurology, Duke University Medical Center, Durham, NC 27710, USA
3. Division of Pathology, Duke University Medical Center, Durham, NC 27710, USA
4. Division of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
5. Soybean Genomics and Improvement Laboratory, USDA-ARS, Beltsville, MD 20705, USA