THE COMMON DELETION IS NOT INCREASED IN PARKINSONIAN SUBSTANTIA-NIGRAAS SHOWN BY COMPETITIVE POLYMERASE CHAIN-REACTION

Previous studies have estimated levels of mitochondrial DNA (mtDNA) ca rrying the 4,977-base-pair 'common deletion' in tissues from patients with Parkinson's disease (PD) by using semiquantitative techniques. Th e role of this deleted mtDNA species in the pathogenesis of PD has rem ained controversial. We have applied competitive polymerase chain reac tion to achieve exact quantitation of deleted mtDNA in the substantia nigra and additional brain regions of cases with neuropathologically c onfirmed Lewy-body parkinsonism. In addition, genotyping was carried o ut for CYP2D6(G1,934A) and CYP2D6(C2,938T) alleles and the mitochondri al ND2 (nucleotide 5,460) and transfer RNA for glutamine (nucleotide 4 ,336) sequence variants. Parkinsonian brains showed 1-3% deleted mtDNA in the substantia nigra, that is, deletion levels were not higher tha n in age-matched controls. Our findings suggest that the defect in com plex I of the respiratory chain observed in PD is not primarily due to the 'common deletion.'.