On-target genomic DNA locus complementary to the sgRNA

The on-target genomic DNA locus complementary to the single guide RNA (sgRNA) is the specific chromosomal sequence targeted for modification by CRISPR-Cas systems (Jinek et al., 2012, Science). This locus is defined by a sequence match to the sgRNA's spacer and the presence of a Protospacer Adjacent Motif (PAM) required for Cas protein binding (Sternberg et al., 2014, Nature). In clinical applications, such as the FDA-approved Exagamglogene autotemcel (Casgevy), the target is often a regulatory element like the BCL11A erythroid-specific enhancer used to treat sickle cell disease (Frangoul et al., 2021, NEJM). The interaction between the sgRNA and this DNA locus facilitates site-specific double-strand breaks or chemical modifications like base editing (Gaudelli et al., 2017, Nature). Precision at this site is vital to avoid off-target mutations at similar genomic sequences, which remains a primary safety concern in gene editing (Fu et al., 2013, Nature Biotechnology). Consequently, this target represents the fundamental site of action for programmable genomic medicines.

Other names

ProtospacerTarget DNA sequenceGenomic target locussgRNA-complementary DNA sequence

The target is recognized by a CRISPR-Cas ribonucleoprotein complex through Watson-Crick base pairing between the sgRNA and the genomic DNA, leading to site-specific cleavage or chemical modification (Jinek et al., 2012, Science).