Cryptic mitochondrial DNA mutations coincide with mid-late life and are pathophysiologically informative in single cells across tissues and species
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE284767 | GEO | 2025/02/10
REPOSITORIES: GEO
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Project description:Mitochondrial DNA (mtDNA) mutations may contribute to aging and age-related disorders. Previously, we created mice expressing a proofreading-deficient version of the mtDNA polymerase gamma (Polg) which accumulate age-related mtDNA mutations and display premature aging. Here we performed microarray gene expression profiling to identify mtDNA mutation-responsive genes in the cochlea of aged mitochondrial mutator mice. Age-related accumulation of mtDNA mutations was associated with transcriptional alternations consistent with reduced inner ear function, mitochondrial dysfunction, neurodegeneration, and reduced cell structural modulation. Hearing assessment and histopathological results confirmed that aged PolgD257A/D257A (D257A) mice exhibited moderate hearing loss and severe cochlear degenerations. Age-related accumulation of mtDNA mutations also resulted in alternations in gene expression consistent with induction of apoptosis, proteolysis, stress response, and reduced DNA repair. TUNEL (Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) assay confirmed that the cochleae from aged D257A mice showed significantly more TUNEL positive cells compared to wild-type (WT) mice. The levels of cleaved caspase-3 were also found to increase in the cochleae of aged D257A mice. These observations provide evidence that age-related accumulation of mtDNA mutations is associated with apoptotic cell death in aged cochlea. Our results provide the first global view of molecular events associated with mtDNA mutations in postmitotic tissue, and suggest that apoptosis is the major mechanism of mtDNA mediated cell death in the development of age-related hearing disorder. Experiment Overall Design: To determine the effects of age-related accumulation of mtDNA mutations, each WT sample (n = 5) was compared to each D257A sample (n = 5), generating a total of twenty-five pairwise comparisons. Genes with significantly altered expression levels were sorted into gene ontology biological process categories. Experiment Overall Design: Gene expression change was called statistically significant when at least one gene was called present in a group, the P value was < 0.0500, FC was > 1.1, and FDR was > 30.00 for identification of mtDNA mutations-induced genes. Experiment Overall Design: Affymetrix standard spike controls were used in all experiments (eukaryotic hybridization control kit). Quality control measures were not used. No replicates were done. Dye swap was not used.
2008-11-07 | E-GEOD-4866 | biostudies-arrayexpress
Project description:Mitochondrial DNA (mtDNA) mutations may contribute to aging and age-related disorders. Previously, we created mice expressing a proofreading-deficient version of the mtDNA polymerase gamma (Polg) which accumulate age-related mtDNA mutations and display premature aging. Here we performed microarray gene expression profiling to identify mtDNA mutation-responsive genes in the cochlea of aged mitochondrial mutator mice. Age-related accumulation of mtDNA mutations was associated with transcriptional alternations consistent with reduced inner ear function, mitochondrial dysfunction, neurodegeneration, and reduced cell structural modulation. Hearing assessment and histopathological results confirmed that aged PolgD257A/D257A (D257A) mice exhibited moderate hearing loss and severe cochlear degenerations. Age-related accumulation of mtDNA mutations also resulted in alternations in gene expression consistent with induction of apoptosis, proteolysis, stress response, and reduced DNA repair. TUNEL (Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) assay confirmed that the cochleae from aged D257A mice showed significantly more TUNEL positive cells compared to wild-type (WT) mice. The levels of cleaved caspase-3 were also found to increase in the cochleae of aged D257A mice. These observations provide evidence that age-related accumulation of mtDNA mutations is associated with apoptotic cell death in aged cochlea. Our results provide the first global view of molecular events associated with mtDNA mutations in postmitotic tissue, and suggest that apoptosis is the major mechanism of mtDNA mediated cell death in the development of age-related hearing disorder. Keywords: disease state analysis
2007-05-18 | GSE4866 | GEO
Project description:Somatic mitochondrial DNA (mtDNA) mutations contribute to the pathogenesis of age-related disorders, including myelodysplastic syndromes (MDS). The accumulation of mitochondria harboring mtDNA mutations in patients with these disorders suggests a failure of normal mitochondrial quality-control systems. The mtDNA-mutator mice acquire somatic mtDNA mutations via a targeted defect in the proofreading function of the mtDNA polymerase, PolgA, and develop macrocyticanemia similar to that of patients with MDS. We observed an unexpected defect in clearance of dysfunctional mitochondria at specific stages during erythroid maturation in hematopoietic cells from aged mtDNA-mutator mice. Mechanistically, aberrant activation of mechanistic target of rapamycin signaling and phosphorylation of uncoordinated 51-like kinase (ULK) 1 in mtDNA-mutator mice resulted in proteasome mediated degradation of ULK1 and inhibition of autophagy in erythroid cells. To directly evaluate the consequence of inhibiting autophagy on mitochondrial function in erythroid cells harboring mtDNA mutations in vivo, we deleted Atg7 from erythroid progenitors of wildtype and mtDNA-mutator mice. Genetic disruption of autophagy did not cause anemia in wild-type mice but accelerated the decline in mitochondrial respiration and development of macrocytic anemia in mtDNA-mutator mice. These findings highlight a pathological feedback loop that explains how dysfunctional mitochondria can escape autophagy-mediated degradation and propagate in cells predisposed to somatic mtDNA mutations, leading to disease. We used microarrays to identify expression profiles and pathways that are differentially activated or suppressed in Ter119+ bone marrow cells isolated from phlebotomized wildtype or Polg mutant mice
2015-04-21 | E-GEOD-57761 | biostudies-arrayexpress
Project description:Somatic mitochondrial DNA (mtDNA) mutations contribute to the pathogenesis of age-related disorders, including myelodysplastic syndromes (MDS). The accumulation of mitochondria harboring mtDNA mutations in patients with these disorders suggests a failure of normal mitochondrial quality-control systems. The mtDNA-mutator mice acquire somatic mtDNA mutations via a targeted defect in the proofreading function of the mtDNA polymerase, PolgA, and develop macrocytic anemia similar to that of patients with MDS. We observed an unexpected defect in clearance of dysfunctional mitochondria at specific stages during erythroid maturation in hematopoietic cells from aged mtDNA-mutator mice. Mechanistically, aberrant activation of mechanistic target of rapamycin signaling and phosphorylation of uncoordinated 51-like kinase (ULK) 1 in mtDNA-mutator mice resulted in proteasome mediated degradation of ULK1 and inhibition of autophagy in erythroid cells. To directly evaluate the consequence of inhibiting autophagy on mitochondrial function in erythroid cells harboring mtDNA mutations in vivo, we deleted Atg7 from erythroid progenitors of wildtype and mtDNA-mutator mice. Genetic disruption of autophagy did not cause anemia in wild-type mice but accelerated the decline in mitochondrial respiration and development of macrocytic anemia in mtDNA-mutator mice. These findings highlight a pathological feedback loop that explains how dysfunctional mitochondria can escape autophagy-mediated degradation and propagate in cells predisposed to somatic mtDNA mutations, leading to disease.
2015-04-21 | GSE57761 | GEO
Project description:Decreased telomerase expression, telomere shortening, senescence-associated markers and inflammation have all been independently observed in the ageing brain and associated with disease. However, causality between limited telomerase expression and brain senescence and neuro-inflammation in the natural ageing setting is yet to be established. Here, we address these questions using the zebrafish as an ageing model which, akin to humans, displays premature ageing and death in the absence of telomerase and where telomere shortening is a driver of cellular senescence. Our work shows for the first time that telomerase deficiency (tert-/-) accelerates key hallmarks of ageing identified in the Wild Type (WT) zebrafish brain at transcriptional, cellular, tissue and functional levels. We show that Tert-dependent transcriptomic changes associated with dysregulation of gene expression, stress response and dysregulation of immune genes are accompanied by accelerated accumulation of senescence-associated markers and inflammation in the aged brain. Importantly, In vivo, these changes correlate with increased blood-brain barrier permeability and altered cognitive behaviour. Of note, telomerase-dependent accumulation of senescence-associated markers in the brain occurs not only in the expected proliferative areas but also in non-proliferative ones, where it is unlikely due to telomere-dependent replicative exhaustion, suggesting that non-canonical roles of telomerase may be involved. Together, our work suggests that telomerase has a protective role in the zebrafish brain against the accumulation of senescence and neuro-inflammation and is required for blood brain barrier integrity.
2022-06-09 | GSE205601 | GEO
Project description:Pathogenic mutations in the catalytic DNA polymerase gamma (POLG1) gene result in the accumulation of mtDNA mutations, deletions and/or decrease of mtDNA copy number. These features interfere with proper functioning of the electron transport chain, mostly affecting metabolically active tissues such as the brain, the heart and the liver. So far, mechanisms underlying POLG pathogenesis are not fully understood. To identify general pathways influenced by mutant polymerase gamma, skeletal muscle gene expression profiles of six POLG1 patients and twelve controls were compared. Patient and control subject from three age categories (<10; 11-49; >50) were selected. RNA was extracted from skeletal muscle biopsies and hybridized on Affymetrix microarrays.
2016-07-03 | E-GEOD-18715 | biostudies-arrayexpress
Project description:The breach of proteostasis, leading to the accumulation of protein aggregates, is a hallmark of ageing and age-associated disorders, up to now well-established in neurodegeneration. Few studies have addressed the issue of dysfunctional cell response to protein deposition also for the cardiovascular system. However, the molecular basis of proteostasis decline in vascular cells, as well as its relation to ageing, are not understood. Recent studies have indicated the associations of Nrf2 transcription factor, the critical modulator of cellular stress-response, with ageing and premature senescence. In this report, we outline the significance of protein aggregation in physiological and premature ageing of murine and human endothelial cells (ECs). Our study shows that aged donor-derived and prematurely senescent Nrf2-deficient primary human ECs, but not those overexpressing dominant-negative Nrf2, exhibit increased accumulation of protein aggregates. Such phenotype is also found in the aortas of aged mice and young Nrf2 tKO mice. Ageing-related loss of proteostasis in ECs depends on Keap1, well-known repressor of Nrf2, recently perceived as a key independent regulator of EC function. Ageing-induced deposition of protein aggregates in ECs is associated with impaired autophagy and can be counteracted by Keap1 depletion or rapamycin treatment. Our results show that Keap1:Nrf2 protein balance predominates Nrf2 transcription-dependent mechanisms in governing proteostasis and ageing in ECs.
2020-08-12 | PXD018969 | Pride
Project description:Integrity of mitochondrial DNA (mtDNA), encoding several subunits of the respiratory chain, is essential to maintain mitochondrial fitness. Mitochondria, as a central hub for metabolism, are affected in a wide variety of human diseases but also during normal ageing, where mtDNA integrity is compromised. Mitochondrial quality control mechanisms work at different levels, and mitophagy and its variants are critical to remove dysfunctional mitochondria and mtDNA to maintain cellular homeostasis. Understanding the mechanisms governing a selective turnover of mutation-bearing mtDNA without affecting the entire mitochondrial pool is fundamental to design therapeutic strategies against mtDNA diseases and ageing. Here, we show that mtDNA damage after expressing a dominant negative version of the mitochondrial helicase Twinkle, or by chemical means, leads to an exacerbated mtDNA turnover. mtDNA removal depends on lysosomal function and requires the autophagy protein Atg5 but is independent of canonical mitophagy or autophagy. Using proximity labelling, we demonstrated that the area of influence of mitochondrial nucleoids differs upon mtDNA damage, which induces mitochondrial membrane remodelling and endosomal recruitment in close proximity to mitochondrial nucleoid sub compartments. Targeting of nucleoids is controlled by the mitochondrial transmembrane proteins ATAD3 and SAMM50, which together with the endosomal trafficking protein VPS35, orchestrate endosomal nucleoid engulfment. SAMM50 acts as a gatekeeper to avoid mtDNA release to the cytoplasm and facilitating mtDNA transfer to VPS35. Lastly, we show that stimulation of lysosomal activity by rapamycin selectively removes mtDNA deletions in vivo, without affecting mtDNA copy number. With these results, we unveil the molecular players of a new complex mechanism specifically targeting and removing mutant mtDNA which occurs outside the mitochondrial network, a process with multiple potential benefits to understand human mtDNA related diseases, either inherited, acquired or due to normal ageing.
2022-11-07 | PXD023939 | Pride
Project description:The age-related failure to regenerate lost oligodendrocytes from oligodendrocyte progenitor cells (OPCs) is associated with irreversible neurodegeneration in multiple sclerosis. Consequently, regenerative therapies for chronic demyelinating diseases remain a long sought after but elusive goal. Here we show that adult OPCs lose their inherent differentiation potential with increasing age. Moreover, aged OPCs do not remain responsive to pro-differentiation signals, posing significant constraints on the effectiveness of remyelination therapies based on the enhancement of OPC differentiation. We show that this reduced regenerative capacity is associated with hallmarks of cellular ageing, including reduced metabolic function and increased DNA damage. We find that fasting or treatment with metformin can reverse these changes and restore the regenerative capacity of aged OPCs, improving remyelination in aged animals following white matter injury. Importantly, aged OPCs treated with metformin regain their responsiveness to pro-differentiation factors, suggesting a potential for synergistic effects of rejuvenation and pro-differentiation therapies. Our findings have direct implications for understanding oligodendrocyte regeneration failure with ageing and how it might be reversed therapeutically.
2019-11-01 | GSE134765 | GEO
Project description:Age-associated accumulation of somatic mutations in mitochondrial DNA (mtDNA) has been proposed to be responsible for the age-associated mitochondrial respiration defects found in elderly human subjects. In contrasts, our previous studies proposed that the age-associated respiration defects found in human fibroblasts are caused not by mtDNA mutations. To addressed these controversial issues, we carried out microarray analysis of two young (TIG3S and TIG121) and two elderly (TIG107 and TIG102) fibroblasts.
2015-03-18 | GSE67000 | GEO