Targeted nanopore sequencing with Cas9-guided adapter ligation.

Point mutations, structural variants and DNA methylation at target loci are assessed by nanopore sequencing. Despite recent improvements in sequencing methods, there remains a need for assays that provide high sequencing depth and comprehensive variant detection. Current methods(1-4) are limited by the loss of native modifications, short read length, high input requirements, low yield or long protocols. In the present study, we describe nanopore Cas9-targeted sequencing (nCATS), an enrichment strategy that uses targeted cleavage of chromosomal DNA with Cas9 to ligate adapters for nanopore sequencing. We show that nCATS can simultaneously assess haplotype-resolved single-nucleotide variants, structural variations and CpG methylation. We apply nCATS to four cell lines, to a cell-line-derived xenograft, and to normal and paired tumor/normal primary human breast tissue. Median sequencing coverage was 675x using a MinION flow cell and 34x using the smaller Flongle flow cell. The nCATS sequencing requires only similar to 3 mu g of genomic DNA and can target a large number of loci in a single reaction. The method will facilitate the use of long-read sequencing in research and in the clinic.