SummaryCRISPR genome editing is a promising tool for translational research but can cause undesired editing outcomes, both on-target at the edited locus and off-target at other genomic loci. We investigated the occurrence of deleterious on-target effects in human stem cells after insertion of disease-related mutations by homology-directed repair (HDR). We identified large, mono-allelic genomic deletions and loss-of-heterozygosity that escaped standard quality controls in up to 40% of edited clones. To reliably detect such events, we developed simple, low-cost and universally applicable quantitative genotyping PCR (qgPCR) as well as sequencing-based tools and suggest their usage as additional quality controls after editing. This will help to ensure the integrity of edited loci and increase the reliability of CRISPR editing.
Detection of deleterious on-target effects after HDR-mediated CRISPR editing
