1. Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544
2. Banting and Best Department of Medical Research, Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto M5S 3E1, Canada
3. Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455
4. Department of Molecular Genetics, University of Toronto, Toronto M5S 3E1, Canada;