CRISPR off-target genomic DNA sites (Off-target sites)

CRISPR off-target genomic DNA sites refer to unintended locations within the genome where a CRISPR-Cas nuclease complex binds and induces double-strand breaks. This phenomenon occurs when the single guide RNA (sgRNA) exhibits partial sequence complementarity to a non-target DNA sequence that is also adjacent to a compatible Protospacer Adjacent Motif (PAM) (Fu et al., 2013, Nature Biotechnology). Although CRISPR-Cas9 is engineered for high precision, the system can tolerate several mismatches, particularly in the distal region of the sgRNA, leading to non-specific cleavage (Zhang et al., 2015, Molecular Therapy). These off-target events are a primary safety concern in gene editing therapies because they can cause permanent mutations, gene disruptions, or large-scale chromosomal rearrangements (Tsai et al., 2015, Nature Biotechnology). In a clinical context, such modifications could potentially lead to oncogenesis if they occur in tumor suppressor genes or activate proto-oncogenes. Consequently, rigorous bioinformatic prediction and experimental validation using methods like GUIDE-seq or CIRCLE-seq are essential for assessing the safety profile of CRISPR-based drugs like exagamglogene autotemcel (FDA, 2023, Casgevy Prescribing Information).

Other names

Off-target effectsNon-specific cleavage sitesUnintended genomic modificationsCRISPR off-targetssgRNA mismatches

Non-specific DNA cleavage via Cas nuclease activity guided by mismatched sgRNA-DNA hybridization at loci containing a compatible Protospacer Adjacent Motif (PAM).