Efficient Mitochondrial Genome Editing by CRISPR/Cas9

Figure 1

FLAG-NLS-Cas9 localizes to mitochondria. (a) Subcellular localization of FLAG-Cas9 assessed in the cytosolic (Cyt), mitochondrial (Mit), and nuclear (Nu) fractions of HEK-293T cells transfected with lentiCRISPR-sgRNA-eGFP#2 and monitored by Western blot. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) served as a cytosolic marker, poly(ADP-ribose) polymerase 1 (PARP1) served as a nuclear marker, and succinate dehydrogenase complex subunit A (SDHA) served as a mitochondrial marker. Ponceau staining of the blotted nitrocellulose membrane was presented in the bottom lane to visualize relative protein loading amounts. (b) Immunofluorescence images of FLAG-NLS-Cas9 demonstrating its localization to nucleus, cytoplasm, and mitochondria. HEK-293T cells were immunostained with mouse antibody to FLAG (green) 24 hours following transient transfection with FLAG-NLS-Cas9 construct. Mitochondria or nucleus was stained with mitotracker Red or DAPI, respectively. (c) Illustration of human mitochondrial DNA (mtDNA). Simplified view of mtDNA is presented to depict regions encoding peptides or tRNA for indicated amino acids. Filled triangles indicate sites targeted by gRNAs against Cox1 or Cox3. Arrows indicate primer annealing sites used for real-time PCR of Cox1 or Cox3 regions. (d) Quantification of copy numbers for Cox1, Cox3, and ND1 regions of mtDNA extracted from HEK-293T cells transiently transfected with lentiCRISPR-sgRNA-Cox1 and lentiCRISPR-sgRNA-Cox3 or lentiCRISPR-sgRNA-eGFP#2 as a control, determined by real-time quantitative PCR using primers listed in Table 2. GAPDH was used as an internal loading control ( per group). Quantified data (d) are expressed as mean ± s.e.m., , unpaired two-tailed Student’s t-test.

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