1. Genomic Medicine Institute, Medical Research Center, Seoul National University, Seoul 100-799, Korea.
2. Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 100-799, Korea.
3. Department of Biomedical Sciences, Seoul National University Graduate School, Seoul 100-799, Korea.
4. Department of Epidemiology, Graduate School of Public Health and Institute of Health and Environment, Seoul National University, Seoul 151-742, Korea.