Unexpected Mutations After CRISPR-Cas9 Editing in vivo. Mus musculus strain:FVB/NJ

CRISPR/Cas9 editing shows promise for correcting disease-causing mutations. For example, in a recent study we could restore sight in blind rd1 mice, by correcting a mutation in the Pde6b gene. However, concerns persist regarding secondary mutations in regions not targeted by the single guide RNA (sgRNA). Algorithms generate likely off-target sites for a given gRNA but miss unexpected mutations. Whole genome sequencing (WGS) has been used to assess the presence of small insertions and deletions, but not to probe for single nucleotide variants (SNV) in a whole organism. We performed WGS on a CRISPR/Cas9 edited mouse to identify all off-target mutations and found an unexpectedly high number of SNVs.