Off-target genomic DNA locus (Off-target sites)

Off-target genomic DNA loci are unintended sites within the genome where gene-editing complexes, such as CRISPR-Cas9, bind and induce double-strand breaks or other modifications. This phenomenon occurs because the guide RNA (gRNA) can occasionally hybridize with DNA sequences that are not perfectly complementary but share sufficient similarity to allow the effector enzyme to function (Zhang et al., 2015, Nature Methods). These off-target events are a major concern in the development of genetic medicines, as they can lead to deleterious mutations, large-scale chromosomal rearrangements, or the disruption of essential genes (Fu et al., 2013, Nature Biotechnology). In a clinical context, off-target activity can potentially trigger oncogenesis if it occurs within or near proto-oncogenes or tumor suppressor genes. Consequently, rigorous bioinformatic prediction and empirical validation using sensitive sequencing methods like GUIDE-seq or CIRCLE-seq are required to ensure the safety and specificity of therapeutic gene-editing products (Tsai et al., 2015, Nature Biotechnology). Strategies to mitigate these risks include the use of high-fidelity Cas variants and optimized gRNA design.

Other names

Off-target effectsCRISPR off-targetsUnintended genomic modificationsNon-specific cleavage sites

Unintended binding and enzymatic cleavage of DNA sequences that possess partial homology to a therapeutic guide RNA (gRNA) sequence.