Genomic double-stranded DNA (off-target loci) (DNA (off-target))

Genomic double-stranded DNA at off-target loci refers to unintended genomic sequences that are recognized and modified by gene-editing technologies such as CRISPR-Cas9, TALENs, or ZFNs (Zhang et al., 2015). These sites typically share significant sequence homology with the intended target site, leading the editing machinery to bind and induce double-strand breaks (DSBs) at these incorrect locations (Fu et al., 2013). The repair of these unintended breaks by cellular mechanisms like non-homologous end joining (NHEJ) can result in permanent mutations, including insertions, deletions, or complex chromosomal rearrangements (Tsai et al., 2015). From a therapeutic perspective, off-target DNA is considered an "anti-target" because its modification can lead to severe adverse effects, such as the activation of oncogenes or the silencing of essential tumor suppressor genes (NIH, 2023). Consequently, the identification and minimization of off-target activity are paramount in the development of safe genomic medicines, requiring rigorous bioinformatic prediction and experimental validation using high-throughput sequencing methods. While traditional drugs target proteins, gene-editing agents directly interact with these genomic loci, making their precision a defining factor in clinical efficacy and safety.

Other names

Off-target sitesUnintended genomic lociNon-specific DNA binding sitesOff-target DNAOff-target effects (OTE)

Unintended sequence-specific binding and cleavage of genomic DNA by programmable nucleases or DNA-binding agents at sites other than the intended therapeutic locus (Zhang et al., 2015).