High-throughput multiplexed tandem repeat genotyping using targeted long-read sequencing

Tandem repeats (TRs) are highly prone to variation in copy numbers due to their repetitive and unstable nature, which makes them a major source of genomic variation between individuals. However, population variation of TRs have not been widely explored due to the limitations of existing tools, which are either low-throughput or restricted to a small subset of TRs. Here, we used SureSelect targeted sequencing approach combined with Nanopore sequencing to overcome these limitations. We achieved an average of 3062-fold target enrichment on a panel of 142 TR loci, generating an average of 97X sequence coverage on 7 samples utilizing 2 MinION flow-cells with 200ng of input DNA per sample. We identified a subset of 110 TR loci with length less than 2kb, and GC content greater than 25% for which we achieved an average genotyping rate of 75% and increasing to 91% for the highest-coverage sample. Alleles estimated from targeted long-read sequencing were concordant with gold standard PCR sizing analysis and moreover highly correlated with alleles estimated from whole genome long-read sequencing. We demonstrate a targeted long-read sequencing approach that enables simultaneous analysis of hundreds of TRs and accuracy is comparable to PCR sizing analysis. Our approach is feasible to scale for more targets and more samples facilitating large-scale analysis of TRs.