Table 1.
Variations of the CRISPR system
| Variations | Features | Effects | Advantages | Disadvantages | Applications in cancer research |
|---|---|---|---|---|---|
| CRISPR/Cas9 | WT Cas9; sgRNA | Double-strand break at the target site | Versatile; effective; stable; easy accessibility | Off-target; PAM limited; different modified alleles | Set up research model; functional gene study; drug target identification |
| CRISPR/Cas9 Nickase | Mutant Cas9 H840A or D10A; sgRNA | Single-strand break | Convenient; efficient; flexible; precise, scalable; robust | PAM limited; 2 sgRNA for KO |
Manipulate epigenetic modifications; Simultaneous activation and repression |
| CRISPRi | dCas9; repressor peptide; sgRNA | Block transcription elongation or knockdown transcripts | Inducible; reversible; low off-target effects; low toxicity |
PAM limited; off-target effects at bidirectional promoters | Genome and transcriptome research; LncRNA knockdown and overexpression |
| CRISPRa | dCas9; activator peptide; sgRNA | Increase transcription | PAM limited; complicated to deliver the multiple components |