Engineering guide RNA to reduce the off-target effects of CRISPR

As versatile and robust genome editing tools, clustered regularly interspaced short palindromic repeats (CRISPR) technologies have been broadly used in basic research, biotechnology, and therapeutic development. Off-target mutagenesis by CRISPR systems has been demonstrated, and various methods have been developed to markedly increase their specificity. In this review, we highlight the efforts of producing and modifying guide RNA (gRNA) to minimize off-target activities, including sequence and structure design, tuning expression and chemical modification. The modalities of gRNA engineering can be applied across CRISPR systems. In conjunction with CRISPR protein effectors, the engineered gRNA enables efficient and precise genome editing.