Fig. 2

Basic approaches for replacement of causative for MD genes with the use of allotopic expression or direct mitochondrial transfer. In order to compensate the function of altered mitochondrial gene, the delivery of correct forms of DNA or mRNA is used. The sequence is transferred in the form of plasmid or delivered by AAV, LNP or in. 1. AAV vectors are able to deliver single-stranded (ss)DNA in nucleus where it further replicates to form double-stranded (ds)DNA, template for synthesis of the proper version of mitochondrial protein. To guide this protein into mitochondria coding ssDNA must contain mitochondrial targeting sequence (MTS). 2. AAV-MTS vectors carrying MTS on its surface are able to directly target mitochondria to provide mitochondrial transfer of ssDNA and subsequent synthesis of proper protein with the use of mitochondrial apparatus. 3. dsDNA can be delivered by being packed in lipid nanoparticles (LNP). As the part of LNP dsDNA apparently can be targeted directly into mitochondria or allotopically expressed in the nucleus, 4. The protein’s coding sequence is delivered into the mitochondria in the form of plasmid by hydrodynamic injection