Mitochondrial DNA Damage Level Determines Neural Stem Cell Differentiation Fate (original) (raw)
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Stem Cells, 2010
Differentiation of neural stem cells (NSCs) involves the activation of aerobic metabolism, which is dependent on mitochondrial function. Here, we show that the differentiation of NSCs involves robust increases in mitochondrial mass, mitochondrial DNA (mtDNA) copy number, and respiration capacity. The increased respiration activity renders mtDNA vulnerable to oxidative damage, and NSCs defective for the mitochondrial 8-oxoguanine DNA glycosylase (OGG1) function accumulate mtDNA damage during the differentiation. The accumulated mtDNA damages in ogg1−/− cells inhibit the normal maturation of mitochondria that is manifested by reduced cellular levels of mitochondrial encoded complex proteins (complex I [cI], cIII, and cIV) with normal levels of the nuclear encoded cII present. The specific cI activity and inner membrane organization of respiratory complexes are similar in wt and ogg1−/− cells, inferring that mtDNA damage manifests itself as diminished mitochondrial biogenesis rather th...
Scientific reports, 2016
Oxidative stress and mitochondrial dysfunction are implicated in aging-related neurodegenerative disorders. 8-Oxoguanine (8-oxoG), a common oxidised base lesion, is often highly accumulated in brains from patients with neurodegenerative disorders. MTH1 hydrolyses 8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dGTP) to 8-oxo-dGMP and pyrophosphate in nucleotide pools, while OGG1 excises 8-oxoG paired with cytosine in DNA, thereby minimising the accumulation of 8-oxoG in DNA. Mth1/Ogg1-double knockout (TO-DKO) mice are highly susceptible to neurodegeneration under oxidative conditions and show increased accumulation of 8-oxoG in mitochondrial DNA (mtDNA) in neurons, suggesting that 8-oxoG accumulation in mtDNA causes mitochondrial dysfunction. Here, we evaluated the contribution of MTH1 and OGG1 to the prevention of mitochondrial dysfunction during neuritogenesis in vitro. We isolated cortical neurons from adult wild-type and TO-DKO mice and maintained them with or without antioxidan...
Nucleic Acids Research, 2005
Neurodegeneration can occur as a result of endogenous oxidative stress. Primary cerebellar granule cells were used in this study to determine if mitochondrial DNA (mtDNA) repair deficiencies correlate with oxidative stress-induced apoptosis in neuronal cells. Granule cells exhibited a significantly higher intracellular oxidative state compared with primary astrocytes as well as increases in reductants, such as glutathione, and redox sensitive signaling molecules, such as AP endonuclease/redox effector factor-1. Cerebellar granule cultures also exhibited an increased susceptibility to exogenous oxidative stress. Menadione (50 mM) produced twice as many lesions in granule cell mtDNA compared with astrocytes, and granule cell mtDNA repair was significantly less efficient. A decreased capacity to repair oxidative mtDNA damage correlates strongly with mitochondrial initiated apoptosis in these neuronal cultures. Interestingly, the mitochondrial activities of initiators for base excision repair (BER), the bifunctional glycosylase/AP lyases as well as AP endonuclease, were significantly higher in cerebellar granule cells compared with astrocytes. The increased mitochondrial AP endonuclease activity in combination with decreased polymerase g activity may cause an imbalance in oxidative BER leading to an increased production and persistence of mtDNA damage in neurons when treated with menadione. This study provides evidence linking neuronal mtDNA repair capacity with oxidative stress-related neurodegeneration.
Frontiers in Neuroscience
Since the discovery of Neural Stem Cells (NSCs) there are still mechanism to be clarified, such as the role of mitochondrial metabolism in the regulation of endogenous adult neurogenesis and its implication in neurodegeneration. Although stem cells require glycolysis to maintain their stemness, they can perform oxidative phosphorylation and it is becoming more and more evident that mitochondria are central players, not only for ATP production but also for neuronal differentiation’s steps regulation, through their ability to handle cellular redox state, intracellular signaling, epigenetic state of the cell, as well as the gut microbiota-brain axis, upon dietary influences. In this scenario, the 8-oxoguanine DNA glycosylase (OGG1) repair system would link mitochondrial DNA integrity to the modulation of neural differentiation. On the other side, there is an increasing interest in NSCs generation, from induced pluripotent stem cells, as a clinical model for neurodegenerative diseases (...
Neurochemical Research, 2007
Oxidative stress can induce mitochondrial dysfunction, mitochondrial DNA (mtDNA) depletion, and neurodegeneration, although the underlying mechanisms are poorly understood. The major mitochondrial antioxidant system that protects cells consists of manganese superoxide dismutase (MnSOD), glutathione peroxidase (GPx) and glutathione (GSH). To investigate the putative adaptive changes in antioxidant enzyme protein expression and targeting to mitochondria as mtDNA depletion occurs, we progressively depleted U87 astrocytoma cells of mtDNA by chronic treatment with ethidium bromide (EB, 50 ng/ml). Cellular MnSOD protein expression was markedly increased in a time-related manner while that of GPx showed time-related decreases. The mtDNA depletion also altered targeting or subcellular distribution of GPx, suggesting the importance of intact mtDNA in mitochondrial genome-nuclear genome signaling/communication. Cellular NADP +-ICDH activity also showed marked, timerelated increases while their GSH content decreased. Thus, our findings suggest that interventions to elevate MnSOD, GPx, NADP +-ICDH, and GSH levels may protect brain cells from oxidative stress.
Biochemical and Biophysical Research Communications, 2012
Embryonic neural stem cells (NSCs) exhibit self-renewal and multipotency as intrinsic characteristics that are key parameters for proper brain development. When cells are challenged by oxidative stress agents the resulting DNA lesions are repaired by DNA glycosylases through the base excision repair (BER) pathway as a means to maintain the fidelity of the genome, and thus, proper cellular characteristics. The functional roles for DNA glycosylases in NSCs have however remained largely unexplored. Here we demonstrate that RNA knockdown of the DNA glycosylases OGG1 and NEIL3 decreased NSC differentiation ability and resulted in decreased expression of both neuronal and astrocytic genes after mitogen withdrawal, as well as the stem cell marker Musashi-1. Furthermore, while cell survival remained unaffected, NEIL3 deficient cells displayed decreased cell proliferation rates along with an increase in HP1c immunoreactivity, a sign of premature senescence. Our results suggest that DNA glycosylases play multiple roles in governing essential neural stem cell characteristics.
2020
The inability to reliably replicate mitochondrial DNA (mtDNA) by mitochondrial DNA polymerase gamma (POLG) leads to a subset of common mitochondrial diseases associated with neuronal death and depletion of neuronal mtDNA. Defining disease mechanisms remains difficult due to the limited access to human tissue. Astrocytes are highly abundant in the brain, playing a crucial role in the support and modulation of neuronal function. Astrocytes also respond to insults affecting the brain. Following damage to the center neural system, which can be hypoxia, inflammation or neurodegeneration, astrocytes become activated and lose their supportive role and gain toxic functions that induce rapid death of neurons and oligodendrocytes. The role of astrocyte reactivation and the consequences this has for neuronal homeostasis in mitochondrial diseases has not been explored. Here, using patient cells carrying POLG mutations, we generated iPSCs and then differentiated into astrocytes. We demonstrated ...
Human Molecular Genetics
Mitochondrial dysfunction is a common feature of many genetic disorders that target the brain and cognition. However, the exact role these organelles play in the etiology of such disorders is not understood. Here, we show that mitochondrial dysfunction impairs brain development, depletes the adult neural stem cell (NSC) pool and impacts embryonic and adult neurogenesis. Using deletion of the mitochondrial oxidoreductase AIF as a genetic model of mitochondrial and neurodegenerative diseases revealed the importance of mitochondria in multiple steps of the neurogenic process. Developmentally, impaired mitochondrial function causes defects in NSC self-renewal, neural progenitor cell proliferation and cell cycle exit, as well as neuronal differentiation. Sustained mitochondrial dysfunction into adulthood leads to NSC depletion, loss of adult neurogenesis and manifests as a decline in brain function and cognitive impairment. These data demonstrate that mitochondrial dysfunction, as observed in genetic mitochondrial and neurodegenerative diseases, underlies the decline of brain function and cognition due to impaired stem cell maintenance and neurogenesis.
Molecular and Cellular Biology, 2010
Mitochondrial dysfunction underlying changes in neurodegenerative diseases is often associated with apoptosis and a progressive loss of neurons, and damage to the mitochondrial genome is proposed to be involved in such pathologies. In the present study we designed a mouse model that allows us to specifically induce mitochondrial DNA toxicity in the forebrain neurons of adult mice. This is achieved by CaMKII␣regulated inducible expression of a mutated version of the mitochondrial UNG DNA repair enzyme (mutUNG1). This enzyme is capable of removing thymine from the mitochondrial genome. We demonstrate that a continual generation of apyrimidinic sites causes apoptosis and neuronal death. These defects are associated with behavioral alterations characterized by increased locomotor activity, impaired cognitive abilities, and lack of anxietylike responses. In summary, whereas mitochondrial base substitution and deletions previously have been shown to correlate with premature and natural aging, respectively, we show that a high level of apyrimidinic sites lead to mitochondrial DNA cytotoxicity, which causes apoptosis, followed by neurodegeneration.