{Reference Type}: English Abstract {Title}: [The Development of SpCas9 Variants with High Specificity and Efficiency Based on the HH Theory]. {Author}: Wang GH;Wang CM;Wu XJ;Chu T;Huang DW;Li J; {Journal}: Mol Biol (Mosk) {Volume}: 58 {Issue}: 1 {Year}: 2024 Jan-Feb 暂无{DOI}: 10.31857/S0026898424010158, EDN: NTCLJI {Abstract}: Streptococcus pyogenes Cas9 (SpCas9) is the most popular tool in gene editing; however, off-target mutagenesis is one of the biggest impediments in its application. In our previous study, we proposed the HH theory, which states that sgRNA/DNA hybrid (hybrid) extrusion-induced enhancement of hydrophobic interactions between the hybrid and REC3/HNH is a key factor in cleavage initiation. Based on the HH theory, we analyzed the interactions between the REC3 domain and hybrid and obtained 8 mutant sites. We designed 8 SpCas9 variants (V1-V8), used digital droplet PCR to assess SpCas9-induced DNA indels in human cells, and developed high-fidelity variants. Thus, the HH theory may be employed to further optimize SpCas9-mediated genome editing systems, and the resultant V3, V6, V7, and V8 SpCas9 variants may be valuable for applications requiring high-precision genome editing.