Haplotype sequence collection of ABO blood group alleles by long-read sequencing reveals putative A1-diagnostic variants

In the era of blood group genomics, reference collections of complete and fully-resolved blood group gene alleles have gained high importance. For most blood groups, however, such collections are currently lacking, as resolving full-length gene sequences as haplotypes (i.e. separated maternal/paternal origin) remains exceedingly difficult with both Sanger and short-read next-generation sequencing. Using the latest third-generation long-read sequencing, we generated a collection of fully-resolved sequences for all six main ABO allele groups: ABO*A1/A2/B/O.01.01/O.01.02/O.02. We selected 77 samples from an ABO genotype dataset (n=25,200) of serologically-typed Swiss blood donors. The entire ABO gene was amplified in two overlapping long-range PCRs (covering ~23.6 kb) and sequenced by long-read Oxford Nanopore sequencing. For quality validation, two samples per ABO group were re-sequenced using Illumina and PacBio technology. All 154 full-length ABO sequences were resolved as haplotypes. W...