Progress of application and off-target effects of CRISPR/Cas9.

The clustered regulatory interspaced short palindromic repeat/Cas9 (CRISPR/Cas9) system mediates genome editing and is revolutionizing genetic researches. Scientists are able to manipulate the gene of interest from any organism with CRISPR/Cas9. Compared with zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) technologies, the CRISPR/Cas9 technology provides an easy and efficient approach to manipulate the genome. In this system, sgRNA (Single guide RNA), a short RNA matching the targeted DNA fragment, guides the CRISPR/Cas9 to interrogate the genome. Because sgRNA can tolerate certain mismatches to the DNA targets and thereby promote undesired off-target mutagenesis, the key limit of this technology is off-target effects. To eliminate the off-target effects, different strategies have been adopted. In this review, we summarize the application of CRISPR/Cas9 and different strategies for addressing off-target effects.