1. Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892–8028, USA.
2. Incyte Genomics, Palo Alto, CA 94304, USA.
3. Department of Mathematical Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
4. National Institutes of Health Intramural Sequencing Center, National Human Genome Research Institute, National Institutes of Health, Department of Health and Human Services, Gaithersburg, MD 20877, USA.
5. Center for Information Technology, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892–5620, USA.