From: Current strategies employed in the manipulation of gene expression for clinical purposes
 | ZFNs | TALENs | CRISPR/Cas |
---|---|---|---|
Phylogenetic origin | Xanthomonas bacteria [254] | Streptococcus pyogenes [255] | |
DNA binding domain | |||
DNA cleavage | FokI [262] | ||
DNA recognition range | 18–36 bp (3 bp per module) [253] | 22 bp (DNA-RNA base pairing) [261] | |
DNA cut | dsDNA as a dimer [264] | dsDNA as a dimer [265] | dsDNA complex protein-gRNA [259] |
Recognition sequence | 5'-GNNGNNGNN-3’ [256] | ||
Advantages | Small protein size (< 1 Kb), sequence-based module engineering [267] | High specificity, easy selection of target region [268] | Easy to multiplex, simple synthesis of gRNA, easy selection of target region [269] |
Disadvantages | Difficult sequence selection and protein engineering,, expensive and time consuming [267] | Large protein size (> 3 Kb), expensive and time-consuming [269, 270] | Large protein size (> 4 Kb) [269] |
Safety concerns | off-target effects: genome mutagenesis and GCRs [271] | off-target effects: genome mutagenesis and GCRs [270] | off-target effects: genome mutagenesis and GCRs [271] |