Abstract 3522: Enzymatic DNA repair enables high quality library preparation and accurate sequencing from highly damaged DNA inputs

High-throughput sequencing is key for clinical diagnostic applications such as disease mutation profiling and identifying pathogens with high taxonomic specificity. Preparation of high quality next-generation sequencing (NGS) libraries is critical for obtaining accurate patient data, but clinical scientists are often limited by input DNA quality. In cancer genomics, formalin-fixed, paraffin-embedded (FFPE) tissue from patient biopsy is a common source of DNA, but the extracted DNA is often poor in both yield and quality due to fixation- and storage-induced damage. Additionally, these damage-induced sequencing artifacts raise the background level of mutations, making it difficult to discern true, low frequency, disease-related variants from noise. Even relatively high-quality DNA inputs contain nicks and gaps limiting library yields and read lengths for long read sequencing platforms including Oxford Nanopore Technologies (ONT) and Pacific Biosciences (PacBio). We developed a second-generation DNA repair enzyme mix (V2) that efficiently repairs the most prevalent damage types found in FFPE DNA and further improves the quality and yield of NGS libraries through efficient nick and gap repair. Illumina library yield and quality were improved when DNA samples were treated with FFPE DNA Repair V2 before library preparation. Target enrichment and whole exome enrichment experiments showed that the V2 repair mix did not alter the overall frequency of variants identified, thus it did not introduce bias, but significantly improved the sequencing accuracy by reducing the number of false variant calls due to damage-induced sequence artifacts. True mutation frequencies were validated using droplet digital PCR (ddPCR). Repaired ONT libraries using DNA inputs of varying quality also showed improved library quality as well as greater read lengths. Therefore, enzymatic DNA repair prior to NGS library preparation is a critical first step for improving the quality and accuracy of short- and long-read sequencing libraries. Citation Format: Margaret R. Heider, Lixin Chen, Chen Song, Luo Sun, Pingfang Liu, Laurence Ettwiller, Lauren Higgins, Eileen Dimalanta, Theodore Davis, Thomas Evans. Enzymatic DNA repair enables high quality library preparation and accurate sequencing from highly damaged DNA inputs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Su