Off-target genomic DNA sites with partial complementarity to the F8-directed guide RNA (F8 gRNA off-targets)

Off-target genomic DNA sites with partial complementarity to the F8-directed guide RNA are unintended sequences in the genome that a CRISPR-Cas9 system may recognize and cleave during gene therapy for Hemophilia A. These sites share high sequence similarity with the intended target sequence in the Coagulation Factor VIII (F8) gene, leading to off-target binding due to the mismatch tolerance of the Cas9-gRNA complex (Zhang et al., 2015). When the Cas9 nuclease induces double-strand breaks at these locations, the cell's repair mechanisms, such as non-homologous end joining (NHEJ), can introduce permanent insertions or deletions (indels) (Fu et al., 2013). Such mutations are a primary safety concern in genome editing because they can disrupt functional genes or regulatory elements, potentially leading to genotoxicity or oncogenesis (Tsai & Joung, 2016). In the context of F8-directed therapies, minimizing these off-target effects is crucial for ensuring that the treatment for Hemophilia A does not inadvertently cause secondary diseases (Park et al., 2015). Researchers utilize advanced sequencing techniques like GUIDE-seq or CIRCLE-seq to identify and quantify these risks during preclinical development (Tsai et al., 2015).

Other names

CRISPR off-target sitesNon-specific genomic cleavage sitesgRNA mismatchesUnintended F8-directed cleavage sites

Unintended DNA double-strand cleavage followed by error-prone repair (NHEJ or HDR)