To further characterize SV breakpoint complexity, we employed two alternative approaches that do not rely on low-coverage Illumina read assembly. We first examined 7,804 small deletions for breakpoint complexity using split-read analysis23 (Fig. 3c) and identified 664 (median size 67 bp) exhibiting complexity, 64 of which contained insertions ≥3 bp that may be derived from a nearby template (Supplementary Table 14, Extended Data Fig. 9). We additionally realigned long DNA reads from a single individual (NA12878)22 sequenced by high-coverage PacBio (median read length 3.0 kbp) and Moleculo (median 3.2 kbp) single-molecule WGS around deletions from our release set (Fig. 3d). Out of 766 deletions in NA12878 investigated with this approach, 62 exhibited complexity showing three to six breakpoints (Supplementary Table 12). A deletion of exon 3 of the serine protease inhibitor SPINK14, for example, was accompanied by an inversion of an internal segment of the SV sequence (Fig. 3d, left panel). In contrast to the smaller proportion of deletions showing breakpoint complexity, the majority of inversions assessed in NA12878 (19/28) exhibited multiple breakpoints.
