Genomic DNA at unintended off-target sites (Off-target DNA)

Genomic DNA at unintended off-target sites refers to regions of the genome that are inadvertently modified by gene-editing tools due to sequence homology with the intended target. This phenomenon is a primary concern for technologies like CRISPR-Cas9, where the guide RNA may tolerate mismatches and direct the Cas9 nuclease to non-target loci (Fu et al., 2013, Nature Biotechnology). Such unintended modifications can result in permanent mutations, including insertions, deletions, or translocations (Zhang et al., 2015, Science). The biological consequence of these events can be severe, potentially leading to the inactivation of tumor suppressor genes or the activation of proto-oncogenes (NIH, 2023). In the context of therapeutic development, these sites are not targets in the sense of desired interaction but are instead critical parameters for safety assessment. Advanced detection methods, such as GUIDE-seq or CIRCLE-seq, are employed to map these sites and evaluate the specificity of genetic medicines (Tsai et al., 2015, Nature Biotechnology). Minimizing activity at these sites is essential to prevent genotoxicity and ensure the long-term safety of patients undergoing gene therapy.

Other names

Off-target sitesNon-specific DNA cleavage sitesOff-target genomic lociUnintended genomic modificationsOff-target effects

Unintended binding and enzymatic modification (cleavage, base editing, or integration) of DNA sequences that share partial homology with the intended therapeutic target sequence.