Characterization of Missing Human Genome Sequences and Copy-number Polymorphic Insertions

The extent of human genomic structural variation suggests that there must be portions of the genome yet to be discovered, annotated and characterized at the sequence level. We present a resource and analysis of 2,363 novel insertion sequences corresponding to 720 genomic loci. We show that a substantial fraction of these sequences are either missing, fragmented or mis-assigned when compared to recent de novo sequence assemblies from short-read next-generation sequence data. We determine that 18–37% of these novel insertions are copy-number polymorphic, including loci that show extensive population stratification among Europeans, Asians and Africans. Complete sequencing of 156 of these insertions identifies novel exons and conserved non-coding sequences not yet represented in the reference genome. We develop a method to accurately genotype these novel insertions by mapping next-generation sequencing datasets to the breakpoint thereby providing a means to characterize copy-number status for regions previously inaccessible to SNP microarrays.