Bioinformatics and Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.|Institute for Genomic Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.|Department of Pediatrics and Rady Childrens Hospital, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.|Department of Pediatrics and Rady Childrens Hospital, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.|Institute for Genomic Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.|Institute for Genomic Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. kafrazer@ucsd.edu.