Xdrop: Targeted sequencing of long DNA molecules from low input samples using droplet sorting.

Madsen EB, Höijer I, Kvist T, Ameur A, Mikkelsen MJ

Hum. Mutat. - (-) - [2020-06-09; online 2020-06-09]

Long-read sequencing can resolve regions of the genome that are inaccessible to short reads, and therefore are ideal for genome-gap closure, solving structural rearrangements and sequencing through repetitive elements. Here we introduce the Xdrop technology: a novel microfluidic-based system that allows for targeted enrichment of long DNA molecules starting from only a few nanograms of DNA. Xdrop is based on isolation of long DNA fragments in millions of droplets, where the droplets containing a target sequence of interest are fluorescently labeled and sorted using flow cytometry. The final product from the Xdrop procedure is an enriched population of long DNA molecules that can be investigated by sequencing. To demonstrate the capability of Xdrop, we performed enrichment of the human papilloma virus (HPV) 18 integrated in the genome of human HeLa cells. Analysis of the sequencing reads resolved three HPV18-chr8 integrations at base pair resolution, and the captured fragments extended up to 30 kb into the human genome at the integration sites. Further, we enriched the complete TP53 locus in a leukemia cell line and could successfully phase co-existing mutations using PacBio sequencing. In summary, our results show that Xdrop is an efficient enrichment technology for studying complex genomic regions. This article is protected by copyright. All rights reserved.

NGI Uppsala (Uppsala Genome Center) [Technology development]

National Genomics Infrastructure [Technology development]

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PubMed 32516842

DOI 10.1002/humu.24063

Crossref 10.1002/humu.24063