TABLE 1.

Comparison of the different genome editing approaches.

Editing approaches	Advantages	Disadvantages
Gene editing	Efficient Permanent All possible modifications: insertion, deletion and substitution	Off-target cleavage Chromosomal instability Target sequence restriction (PAM for CRISPR; 5’-T for TALENs) NHEJ is heterogeneous HDR is inefficient (especially in post-mitotic cells)
Base editing	Permanent No need to induce DSBs Few or no indels	Off-target at both DNA and RNA level Bystander base editing Target sequence restriction (PAM) Efficiency is low Only substitutions are possible
Transcriptional regulation	Physiological expression level Low off-target effects Cell reprogramming	Efficacy depends on the level of gene expression Large genomic areas can be affected Most modifications are not permanent
Epigenetic editing	Long-term modification Cell reprogramming	Lack of information on epigenetic marks for some targeted genes May affect large genomic regions Simultaneous modification of several epigenetic marks may be necessary