Detection of genome-edited cells by oligoribonucleotide interference-PCR

Genome editing by engineered sequence-specific nucleases, such as the clustered regularly interspaced short palindromic repeats (CRISPR) system is widely used for analysis of gene functions. Several techniques have been developed for detection of genome-edited cells, but simple, cost-effective, and positive detection methods remain limited. Recently, we developed oligoribonucleotide (ORN) interference-PCR (ORNi-PCR), in which hybridization of an ORN with a complementary DNA sequence inhibits amplification across the sequence. Here, we investigated whether ORNi-PCR can be used to detect genome-edited cells. First, we showed that ORNs that hybridize to a CRISPR target site in the THYN1 locus inhibited amplification across the target site, but no longer inhibited amplification after the target site was edited, resulting in mismatches. Importantly, ORNi-PCR could distinguish even single-nucleotide differences. These features of ORNi-PCR enabled detection of genome-edited cells by positive PCR amplification. In addition, ORNi-PCR was successful in discriminating genome-edited cells from wild-type cells, and multiplex ORNi-PCR simultaneously detected indel mutations at multiple loci. However, endpoint ORNi-PCR may not be able to distinguish between mono- and bi-allelic mutations, which may limit its utility. Taken together, these results demonstrate the potential utility of ORNi-PCR for the screening of genome-edited cells.