phys.org/news/2018-05-mitoc...
In a later paper, these researchers reported that patients with mitochondrial disease who showed considerable neuronal loss in the substantia nigra all had POLG mutations. Considering the fact that in completely normal and healthy people, about half of all the mtDNA found in neurons of their substantia nigra harbors at least one deletion, developing treatments to fix these predictable insults should be a critical focus of the rapidly developing field of mitochondrial medicine