Table 1
A comparison of different gene editing tools
| Gene editing tools | ZFNs | TALENs | CRISPR/Cas9 | Base editors |
| Target DNA sequence recognition elements | Zinc-finger protein | TALE protein | Single guide RNA | Single guide RNA |
| The length of recognition elements | 9–18 bp/ZFN | 14–20 bp/TALE | 20 bp gRNA + PAM sequence | 20 bp gRNA + PAM sequence |
| DNA double-strand break element | Fok I endonuclease | Fok I endonuclease | Cas9 protein | − |
| Advantages | Efficient, small size and easy delivery | High efficiency, low off-target rate, low toxicity, and easy to design | Efficient, easy to construct, and edit multiple sites simultaneously | Safe, DSB-free, high efficiency in dividing cells and non-dividing cells |
| Disadvantages | Requires large-scale screening and engineering of large numbers of proteins, time-consuming and costly, off-target effects and toxicity | It is time-consuming and expensive, requires sequencing, and molecular cloning is complex and difficult to perform | May induce large DNA deletion, reversion, translocation, and complex rearrangements; the efficiency of editing can be affected by the sequence context of the targeted locus; may induce a p53-mediated DNA damage response | Undesired bystander mutations, gRNA independent DNA and RNA off target, too large for efficient in vivo delivery by single AAV vectors, the efficiency of editing can be affected by the sequence context of the targeted locus |
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