[1] Univ N Carolina, Lineberger Comprehens Canc Ctr, Dept Genet, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Dept Comp Sci, Chapel Hill, NC 27599 USA
[3] Wellcome Trust Sanger Inst, Cambridge CB10 1HH, England
[4] NHGRI, NIH, Bethesda, MD 20892 USA