Enhanced Taq Variant Enables Efficient Genome Editing Testing and Mutation Detection

Detection of genome editing with quantitative polymerase chain reaction (PCR) primarily relies on and is limited by its ability to discriminate genome modification from the wild-type sequence. An enhanced DNA polymerase variant with superior specificity is needed for this application. Here, we perform semi-rational molecular evolution on full-length Taq polymerase to screen high-specific variants that meet the requirements of gene variation detection. We substituted each of the 40 polar amino acids in direct contact with the primer/template duplex and conducted extensive random mutagenesis to generate a Taq mutation library. Screening on a quantitative PCR system with insertion and deletion-containing templates identified a series of improved Taq variants. We demonstrate that the Taq388 variant bearing three amino acid substitutions, S577A, W645R, and I707V, has improved sensitivity to insertion and deletion-derived primer/template mismatch by a ΔCt value of 25-26 and is superior for application in evaluating CRISPR-Cas9 editing efficiency and single-cell clone genotyping. In addition, the Taq variant shows substantial potential for single-nucleotide polymorphism detection by means of allele-specific PCR because of its high sensitivity to mismatches.