1. Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
2. Center for Human Genetics and Department of Medicine, Duke University Medical Center, DUMC Box 3445, 595 LaSalle Street, Durham, NC 27710, USA.
3. Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
4. Duke University Eye Center and Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA.