fig2

Figure 2. Main approaches of mitochondrial DNA editing. The DdCBE is able to catalyze the transition mutation of C•G base pairs to T•A base pairs by deamination of deoxycytidine to deoxyuridine, thus shifting the levels of heteroplasmy. MitoTALEN and mtZFN can expand the recognition sequences for mtDNA mutations, resulting in greater specificity. The mito-CRISPR/Cas9 gene-editing system uses sgRNA for the recognition of mutations. MitoTALEN, mtZFN, and mito-CRISPR/Cas9 systems use their endonuclease activity to induce double-stranded breaks, and linearizing and elimination of mutated mtDNA. DdCBE: Deoxycytidine deamination-derived-derived cytosine base editor; FokI: restriction endonuclease FokI; IMM: inner mitochondrial membrane; mito-CRISPR/Cas9: mitochondrial clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9; MitoTALEN: mitochondrial transcription activator-like effector nuclease; MtZFN: mitochondrially targeted zinc-finger nuclease; mtDNA: mitochondrial DNA; MTS: mitochondrial targeting sequence; OMM: outer mitochondrial membrane; PNPase: polynucleotide phosphorylase; sgRNA: single-guide RNA; TIM: translocase of the inner mitochondrial membrane; TOM: translocase of the outer mitochondrial membrane; UGI: uracil glycosylase inhibitor.