1,721,189 research outputs found
197th ENMC international workshop: Neuromuscular disorders of mitochondrial fusion and fission - OPA1 and MFN2 molecular mechanisms and therapeutic strategies. 26-28 April 2013, Naarden, The Netherlands
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X-Inactivation patterns in females harboring mtDNA mutations that cause Leber hereditary optic neuropathy
No full textLeber hereditary optic neuropathy (LHON) is a common cause of genetically determined blindness in young adults. LHON preferentially affects males and is primarily due to a mutation affecting complex I genes of mitochondrial DNA (mtDNA). While LHON primarily affects men, a number of women are affected. Segregation analysis has implicated an interacting recessive X-chromosomal locus, with skewed X-inactivation as an explanation for visual failure in affected women. Small studies have failed to detect dramatic skewed X-inactivation in women transmitting LHON mutations. However, segregation analyses predicted skewing only in a proportion of women, which would not have been detected in these studies
Genetic variation in the methylenetetrahydrofolate reductase gene, MTHFR, does not alter the risk of visual failure in Leber's hereditary optic neuropathy
No full textFocal neurodegeneration of the optic nerve in Leber hereditary optic neuropathy (LHON) is primarily due to a maternally inherited mitochondrial DNA mutation. However, the markedly reduced penetrance of LHON and segregation pattern of visual failure within families implicates an interacting nuclear genetic locus modulating the phenotype. Folate deficiency is known to cause bilateral optic neuropathy, and defects of folate metabolism have been associated with nonarteritic ischemic optic neuropathy
A critical analysis of the combined usage of protein localization prediction methods: Increasing the number of independent data sets can reduce the accuracy of predicted mitochondrial localization
Full text linkIn the absence of a comprehensive experimentally derived mitochondrial proteome, several bioinformatic approaches have been developed to aid the identification of novel mitochondrial disease genes within mapped nuclear genetic loci. Often, many classifiers are combined to increase the sensitivity and specificity of the predictions. Here we show that the greatest sensitivity and specificity are obtained by using a combination of seven carefully selected classifiers. We also show that increasing the number of independent prediction methods can paradoxically decrease the accuracy of predicting mitochondrial localization. This approach will help to accelerate the identification of new mitochondrial disease genes by providing a principled way for the selection for combination of appropriate prediction methods of mitochondrial localization of proteins
Inherited mtDNA variations are not strong risk factors in human prion disease
No full textAside from variation in the prion protein gene, genetic risk factors for sporadic Creutzfeldt-Jakob disease remain elusive. Given emerging evidence implicating mitochondrial dysfunction in the pathogenesis of the disorders, we studied the role of inherited mitochondrial DNA variation in a 2255 sporadic prion disease cases and 3768 controls. Our analysis indicates that inherited mitochondrial DNA variation does not have a major role in the risk of developing the disorder. (C) 2015 Elsevier Inc. All rights reserved
The bottleneck for maternal transmission of mtDNA is linked to purifying selection by autophagy
No full textMammalian mitochondrial DNA (mtDNA) inheritance differs fundamentally from nuclear inheritance owing to exclusive maternal transmission, high mutation rate, and lack of recombination. Two key mechanisms shape this inheritance: the bottleneck, which drives stochastic transmission of maternal mtDNA variants, and purifying selection, which actively removes mutant mtDNA. Whether these mechanisms interact has been unresolved. To address this question, we generated a series of mouse models with random mtDNA mutations alongside alleles altering mtDNA copy number or decreasing autophagy. We demonstrate that tightening the mtDNA bottleneck increases heteroplasmic variance between individuals, causing lower mutational burden and nonsynonymous-to-synonymous ratios. In contrast, reduced autophagy weakens purifying selection, leading to decreased interoffspring heteroplasmic variance and increased mutational burden with higher nonsynonymous-to-synonymous ratios. These findings provide experimental evidence that the mtDNA bottleneck size modulates the efficacy of purifying selection. Our findings yield fundamental insights into the processes governing mammalian mtDNA transmission with direct implications for the origin and propagation of mtDNA mutations causing human disease.Revealing mechanisms of mtDNA transmission is critical for combating human disease.Mammalian mitochondrial DNA (mtDNA) inheritance differs fundamentally from nuclear inheritance owing to exclusive maternal transmission, high mutation rate, and lack of recombination. Two key mechanisms shape this inheritance: the bottleneck, which drives stochastic transmission of maternal mtDNA variants, and purifying selection, which actively removes mutant mtDNA. Whether these mechanisms interact has been unresolved. To address this question, we generated a series of mouse models with random mtDNA mutations alongside alleles altering mtDNA copy number or decreasing autophagy. We demonstrate that tightening the mtDNA bottleneck increases heteroplasmic variance between individuals, causing lower mutational burden and nonsynonymous-to-synonymous ratios. In contrast, reduced autophagy weakens purifying selection, leading to decreased interoffspring heteroplasmic variance and increased mutational burden with higher nonsynonymous-to-synonymous ratios. These findings provide experimental evidence that the mtDNA bottleneck size modulates the efficacy of purifying selection. Our findings yield fundamental insights into the processes governing mammalian mtDNA transmission with direct implications for the origin and propagation of mtDNA mutations causing human disease.Revealing mechanisms of mtDNA transmission is critical for combating human disease.LifeArc http://dx.doi.org/10.13039/100012357LifeArc http://dx.doi.org/10.13039/100012357Swedish Cancer Foundation http://dx.doi.org/10.13039/100012538Rosetrees Trust http://dx.doi.org/10.13039/501100000833Knut och Alice Wallenbergs Stiftelse http://dx.doi.org/10.13039/501100004063Knut och Alice Wallenbergs Stiftelse http://dx.doi.org/10.13039/501100004063EMBO long-term fellowshipWenner-Gren foundation postdoctoral fellowshipVetenskapsrådet http://dx.doi.org/10.13039/501100004359Wellcome Discovery AwardWellcome Collaborative AwardMedical Research Council Mitochondrial Biology UnitBiological and Biotechnology Research CouncilLifeArc Centre to Treat Mitochondrial DiseasesNIHR Cambridge Biomedical Research CentreEuropean Research Council Advanced GrantSwedish Brain Foundation 501100003792Novo Nordisk Fonden http://dx.doi.org/10.13039/501100009708Region of Stockhol
Disturbed mitochondrial dynamics and neurodegenerative disorders
No full textMitochondria form a highly interconnected tubular network throughout the cell via a dynamic process, with mitochondrial segments fusing and breaking apart continuously. Strong evidence has emerged to implicate disturbed mitochondrial fusion and fission as central pathological components underpinning a number of childhood and adult-onset neurodegenerative disorders. Several proteins that regulate the morphology of the mitochondrial network have been identified, the most widely studied of which are optic atrophy 1 and mitofusin 2. Pathogenic mutations that disrupt these two pro-fusion proteins cause autosomal dominant optic atrophy and axonal Charcot-Marie-Tooth disease type 2A, respectively. These disorders predominantly affect specialized neurons that require precise shuttling of mitochondria over long axonal distances. Considerable insight has also been gained by carefully dissecting the deleterious consequences of imbalances in mitochondrial fusion and fission on respiratory chain function, mitochondrial quality control (mitophagy), and programmed cell death. Interestingly, these cellular processes are also implicated in more-common complex neurodegenerative disorders, such as Alzheimer disease and Parkinson disease, indicating a common pathological thread and a close relationship with mitochondrial structure, function and localization. Understanding how these fundamental processes become disrupted will prove crucial to the development of therapies for the growing number of neurodegenerative disorders linked to disturbed mitochondrial dynamic
Mitochondrial DNA and traumatic brain injury
Full text linkObjective: Traumatic brain injury (TBI) is a multifactorial pathology with great interindividual variability in response to injury and outcome. Mitochondria contain their own DNA (mtDNA) with genomic variants that have different physiological and pathological characteristics, including susceptibility to neurodegeneration. Given the central role of mitochondria in the pathophysiology of neurological injury, we hypothesized that its genomic variants may account for the variability in outcome following TBI.Methods: We undertook an analysis of mitochondrial haplogroups in a large, well-characterized cohort of 1,094 TBI patients. A proportional odds model including age, brain computed tomography characteristics, injury severity, pupillary reactivity, mitochondrial haplogroups, and APOE was applied to Glasgow Outcome Score (GOS) data.Results: mtDNA had a significant association with 6-month GOS (p = 0.008). Haplogroup K was significantly associated with favorable outcome (odds ratio = 1.64, 95% confidence interval = 1.08–2.51, p = 0.02). There was also a significant interaction between mitochondrial genome and age (p = 0.002), with a strong protective effect of both haplogroups T (p = 0.015) and K (p = 0.017) with advancing age. We also found a strong interaction between APOE and mitochondrial haplogroups (p = 0.001), indicating a protective effect of haplogroup K in carriers of the APOE ε4 allele.Interpretation: These findings reveal an interplay between mitochondrial DNA, pathophysiology of TBI, and aging. Haplogroups K and T, which share a common maternal ancestor, are shown as protective in TBI. The data also suggest that the APOE pathways interact with genetically regulated mitochondrial functions in the response to acute injury, as previously reported in Alzheimer disease
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