PT - JOURNAL ARTICLE AU - Iyer, Vivek AU - Boroviak, Katharina AU - Thomas, Mark AU - Doe, Brendan AU - Ryder, Edward AU - Adams, David TI - No unexpected CRISPR-Cas9 off-target activity revealed by trio sequencing of gene-edited mice AID - 10.1101/263129 DP - 2018 Jan 01 TA - bioRxiv PG - 263129 4099 - http://biorxiv.org/content/early/2018/02/09/263129.short 4100 - http://biorxiv.org/content/early/2018/02/09/263129.full AB - CRISPR-Cas technologies have transformed genome-editing of experimental organisms and have immense therapeutic potential. Despite significant advances in our understanding of the CRISPR-Cas9 system, concerns remain over the potential for off-target effects. Recent studies have addressed these concerns using whole-genome sequencing (WGS) of gene-edited embryos or animals to search for de novo mutations (DNMs), which may represent candidate changes induced by poor editing fidelity. Critically, these studies used strain-matched but not pedigree-matched controls and thus were unable to reliably distinguish generational or colony-related differences from true DNMs. Here we used a trio design and whole genome sequenced 8 parents and 19 embryos, where 10 of the embryos were mutagenised with well-characterised gRNAs targeting the coat colour Tyrosinase (Tyr) locus. Detailed analyses of these whole genome data allowed us to conclude that if CRISPR mutagenesis were causing SNV or indel off-target mutations in treated embryos, then the number of these mutations is not statistically distinguishable from the background rate of DNMs occurring due to other processes.