Fig. 3

Representation of the basic strategies allowing for decrease of the mutant mtDNA content. The ratio between mutant and wildtype mtDNA (heteroplasmy) determines the severity of mitochondrial dysfunction. One way (left) for shifting heteroplasmy is based on the introduction of double strand breaks (DSBs). To introduce DSBs the nuclease machineries (TALEN, ZFN or CRISPR/Cas) targeted on mutant loci are used. Since all the linear dsDNA molecules are normally being eliminated, the levels of mutant mtDNA decrease. Another way (right) to shift heteroplasmy is to complicate mtDNA replication and hence decrease its content against wild type mtDNA copies. Peptide nucleic acid oligomers (PNC) and F-/D-hairpins containing RNA (FD-RNA) can directly pair with high affinity to the sequence of interest and interrupt further replication of this region. Both ways lead to shift of heteroplasmy resulting in attenuation of mitochondrial dysfunction