Somatic mitochondrial DNA mutations in single neurons and glia.
ABSTRACT Somatic mitochondrial DNA (mtDNA) point mutations reach high levels in the brain. However, the cell types that accumulate mutations and the patterns of mutations within individual cells are not known. We have quantified somatic mtDNA mutations in 28 single neurons and in 18 single glia from post-mortem human substantia nigra of six control subjects. Both neurons and glia contain mtDNA with somatic mutations. Single neurons harbor a geometric mean (95% CI) of 200.3 (152.9-262.4) somatic mtDNA point mutations per million base pairs, compared to 133.8 (97.5-184.9) for single glia (p=0.0251). If mutations detected multiple times in the same cell are counted only once, the mean mutation level per million base pairs remains elevated in single neurons (146.9; 124.0-174.2) compared to single glia (100.5; 81.5-126.5; p=0.009). Multiple distinct somatic point mutations are present in different cells from the same subject. Most of these mutations are individually present at low levels (less than 10-20% of mtDNA molecules), but with high aggregate mutation levels, particularly in neurons. These mutations may contribute to changes in brain function during normal aging and neurodegenerative disorders.
- SourceAvailable from: Vilhelm A Bohr[Show abstract] [Hide abstract]
ABSTRACT: Brain aging is associated with synaptic decline and synaptic function is highly dependent on mitochondria. Increased levels of oxidative DNA base damage and accumulation of mitochondrial DNA (mtDNA) mutations or deletions lead to mitochondrial dysfunction, playing an important role in the aging process and the pathogenesis of several neurodegenerative diseases. Here we have investigated the repair of oxidative base damage, in synaptosomes of mouse brain during normal aging and in an AD model. During normal aging, a reduction in the base excision repair (BER) capacity was observed in the synaptosomal fraction, which was associated with a decrease in the level of BER proteins. However, we did not observe changes between the synaptosomal BER activities of presymptomatic and symptomatic AD mice harboring mutated amyolid precursor protein (APP), Tau, and presinilin-1 (PS1) (3xTgAD). Our findings suggest that the age-related reduction in BER capacity in the synaptosomal fraction might contribute to mitochondrial and synaptic dysfunction during aging. The development of AD-like pathology in the 3xTgAD mouse model was, however, not associated with deficiencies of the BER mechanisms in the synaptosomal fraction when the whole brain was analyzed.Neurobiology of aging 04/2012; 33(4):694-707. DOI:10.1016/j.neurobiolaging.2010.06.019 · 4.85 Impact Factor
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ABSTRACT: To date, the beta amyloid (Aβ) cascade hypothesis remains the main pathogenetic model of Alzheimer's disease (AD), but its role in the majority of sporadic AD cases is unclear. The “mitochondrial cascade hypothesis” could explain many of the biochemical, genetic, and pathological features of sporadic AD. Somatic mutations in mitochondrial DNA (mtDNA) could cause energy failure, increased oxidative stress, and accumulation of Aβ, which in a vicious cycle reinforce the mtDNA damage and the oxidative stress. Despite the evidence of mitochondrial dysfunction in AD, no causative mutations in the mtDNA have been detected so far. Indeed, results of studies on the role of mtDNA haplogroups in AD are controversial. In this review we discuss the role of the mitochondria, and especially of the mtDNA, in the cascade of events leading to neurodegeneration, dementia, and AD.07/2009; 2009. DOI:10.4061/2009/951548
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ABSTRACT: A critical role of mitochondrial dysfunction and oxidative damage has been implicated in etiopathology of many neurodegenerative disorders, as well as in normal aging. Alzheimer's and Parkinson's diseases are common devastating late-onset neurodegenerative disorders, associated with mitochondrial DNA variations, which are suggested to affect mitochondrial functions. This paper reviews the current knowledge on the inherited and somatic mtDNA variations in both conditions.Acta neurobiologiae experimentalis 02/2006; 66(2):153-76. · 2.24 Impact Factor