Mitochondrial DNA analysis in Parkinson's disease

The reduced form of nicotinamide adenine dinucleotide coenzyme Q reductase (complex I) activity has recently been shown to be deficient in the substantia nigra of patients dying with Parkinson's disease. This biochemical defect is identical to that produced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which also produces parkinsonism in humans. Complex I comprises 25 polypeptides, seven of which are encoded by mitochondrial DNA. Restriction fragment analysis of substantia nigra DNA from six patients with Parkinson's disease did not show any major deletion. In two cases, there were different novel polymorphisms that were not observed in control brain (n = 6) or blood (n = 34) samples.