CRISPR system is a novel tool for precise gene editing. Currently, the most commonly used system is derived from Streptococcus pyogenes (Sp), which consists of a Cas9 nuclease and a guide RNA. SpCas9 will induce a DNA double-stranded break after recruited to specific site by sgRNA. The subsequent homologous recombination repair will generate a knock-in or point mutation phenotype in the presence of a recombination donor. Thus, the HDR pathway are exploited to facilitate correction of diseased genes, insertion of epitope tags or fluorescent reporters, and overexpression of genes of interest in a site-specific manner.
