Off-target genomic DNA sites (HBB-directed) (HBB off-targets)

Off-target genomic DNA sites with partial sequence homology to HBB-directed guide RNAs are unintended locations within the human genome where gene-editing machinery, such as CRISPR-Cas9 or Prime Editors, may bind and induce modifications (PMID: 31634221). These sites possess DNA sequences that closely resemble the target sequence within the Hemoglobin Subunit Beta (HBB) gene, which is the primary target for treating disorders like Sickle Cell Disease and Beta-thalassemia (PMID: 23792610). The interaction occurs when the guide RNA (sgRNA or pegRNA) hybridizes with these homologous sequences, leading to unintended double-strand breaks or base edits (PMID: 32103171). Such off-target activity poses significant safety risks, including the potential for insertional mutagenesis, gene silencing of essential tumor suppressors, or large-scale chromosomal translocations (PMID: 25590175). In therapeutic development, these sites are not desired targets but rather critical safety parameters that must be monitored using advanced sequencing techniques to ensure the precision of the genetic intervention (PMID: 28459458). The frequency of mutations at these sites is influenced by the concentration of the editing complex and the degree of homology between the guide RNA and the off-target DNA (PMID: 23792610). Strategies to mitigate these risks include the use of high-fidelity Cas9 variants and the optimization of pegRNA design to enhance specificity (PMID: 31634221).

Other names

Unintended genomic modificationsCRISPR off-target sitesHBB homologous sequencesNon-specific DNA binding sitesOff-target DNA cleavage

Unintended DNA cleavage or modification via sequence homology-driven binding of CRISPR-Cas complexes.