Allotopic expression of genes normally found in mitochondrial DNA is a core portion of the Strategies for Engineered Negligible Senescence. It is the process of inserting a copy of vital mitochondrial genes into the cell nucleus, and then figuring out how to get the proteins produced by those genes back to the mitochondria where they are needed. This could eliminate the contribution of mitochondrial DNA damage to aging. A technique for doing all this is now demonstrated in rats: "We obtained a complete and long-term restoration of mitochondrial function in human fibroblasts in which the mitochondrial genes ATP6, ND1, and ND4 were mutated ... ND1 and ND4 are mutated in nearly all cases of Leber hereditary optic neuropathy (LHON). LHON is the most common mitochondrial disorder and is characterized by a loss of vision. ... They introduced the human ND4 gene with the mutation present in the majority of LHON patients into rat eyes. The treatment caused retinal ganglion cells (RGCs) to degenerate significantly when compared to those from control eyes and was associated with decreased visual performance. Importantly, reintroducing normal ND4 led to prevention of RGC loss and visual impairment, effectively rescuing the animals from impending blindness. ... These data represent the 'proof of principle' that optimized allotropic expression is effective in vivo and can be envisaged as a therapeutic approach for mtDNA-related diseases."