title: Variation in the frequency of complex forms of mitochondrial DNA in different brain regions of senescent mice.
abstract: It was shown previously that the frequency of an aberrant form of mitochondrial DNA (mtDNA), double-sized circular molecules or circular dimers, increased significantly in the brain of senescent mice, to about 2% versus less than 0.1% in the brain of adult mice. To follow up these observations, we isolated total mtDNA from 6 different brain regions of 29-month-old male BALB/c mice and examined it for the occurrence of circular dimers and other complex forms by electron microscopy. There was a statistically highly significant variability in the occurrence of circular dimer mtDNA among the 6 brain regions. The frequencies of circular dimers were: medulla, 3.3%; cortex, 1.7%; midbrain, 1.1%; cerebellum, 0.9%; hippocampus, 0.5%; and striatum, 0.2%. The frequency of catenated (topologically interlinked) molecules varied only slightly, from 4 to 6%. On the basis of the available literature, a correlation appears to exist between age-related tissue pathology of the mouse brain and the increased incidence of circular dimer mtDNA. Although no cause-effect relationships can be established, it is suggested that the frequency of circular dimer mtDNA may be a useful marker in assessing the general physiological condition of the aging brain.
mesh_terms: D000375:Aging; D000818:Animals; D001923:Brain Chemistry; D002531:Cerebellum / Q000032:analysis; D002540:Cerebral Cortex / Q000032:analysis; D003342:Corpus Striatum / Q000032:analysis; D004270:DNA, Circular / Q000032:analysis*; D004272:DNA, Mitochondrial / Q000032:analysis*; D006624:Hippocampus / Q000032:analysis; D008297:Male; D008526:Medulla Oblongata / Q000032:analysis; D008636:Mesencephalon / Q000032:analysis; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron
chemical_list: D004270:DNA, Circular; D004272:DNA, Mitochondrial