1. Joint Carnegie Mellon University-University of Pittsburgh PhD Program in Computational Biology, Pittsburgh, PA 15213, U.S.A.
2. Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15213, U.S.A.
3. Department of Biological Science, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
4. Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
5. Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, U.S.A.
6. Department of Human Genetics, University of Utah, Utah 84112, U.S.A.