Cas9 targeted nanopore sequencing with enhanced variant calling improves CYP2D6–CYP2D7 hybrid allele genotyping

CYP2D6 is one of the most challenging pharmacogenes to genotype due to the high similarity with its neighboring pseudogenes and the frequent occurrence of CYP2D6-CYP2D7 hybrids. Unfortunately, most current genotyping methods are therefore unable to correctly determine the complete CYP2D6-CYP2D7 sequence. With this in mind, we developed a genotyping assay to generate complete allele-specific consensus sequences of complex regions, by optimising the PCR-free nanopore Cas9-targeted sequencing (nCATS) method combined with adaptive sequencing, and developing a new comprehensive long read genotyping (CoLoRGen) pipeline. In contrast to state-of-the-art variant callers, CoLoRGen first generates consensus sequences of both alleles and subsequently determines both large structural and small variants to ultimately assign the correct star-alleles.

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