Project description:Background: The ability of an organism to repair DNA damage is implicated in carcinogenesis and aging. Interestingly expression profiling of Nucleotide Excision Repair (NER) deficient segmental progeroid mice revealed gene expression changes resembling these observed in aged wild type animals. Our previous transcriptional profiling of NER-deficient C. elegans xpa-1 mutant showed overrepresentation of genes involved in lifespan determination and upregulation of several oxidative stress response genes (Fensgard et al. Aging 2010). However, since an independent study performed by Boyd and coworkers (Boyd et al. Mut Res 2010) showed limited number of changes in xpa-1 mutant. Therefore to independently validate that transcriptome modulation does take place in xpa-1 mutants, we performed another global gene expression profiling based on 5 independent biological replicates allowing more stringent statistical analysis. Results: In agreement with what was observed by Boyd and coworkers (Boyd et al. Mut Res 2010) current transcriptomic analysis detected fewer changes in xpa-1 C. elegans mutant with only a few genes regulated more than 4-fold. Nevertheless, Gene Ontology (GO) enrichment analysis performed on statistically significantly regulated unique protein coding genes revealed overrepresentation of aging gene cluster. Moreover, as before, overexpression of several genes involved in oxidative stress responses was detected. Conclusion: More stringent statistical analysis predictably resulted in a smaller number of regulated genes and thus overrepresented GOs comparing to the earlier paper. However, major conclusions of the previous study can be still regarded as valid, as the most important aging GO is still overrepresented. Background: The ability of an organism to repair DNA damage is implicated in carcinogenesis and aging. Interestingly expression profiling of Nucleotide Excision Repair (NER) deficient segmental progeroid mice revealed gene expression changes resembling these observed in aged wild type animals. Our previous transcriptional profiling of NER-deficient C. elegans xpa-1 mutant showed overrepresentation of genes involved in lifespan determination and upregulation of several oxidative stress response genes (Fensgard et al. Aging 2010). However, since an independent study performed by Boyd and coworkers (Boyd et al. Mut Res 2010) showed limited number of changes in xpa-1 mutant. Therefore to independently validate that transcriptome modulation does take place in xpa-1 mutants, we performed another global gene expression profiling based on 5 independent biological replicates allowing more stringent statistical analysis. Results: In agreement with what was observed by Boyd and coworkers (Boyd et al. Mut Res 2010) current transcriptomic analysis detected fewer changes in xpa-1 C. elegans mutant with only a few genes regulated more than 4-fold. Nevertheless, Gene Ontology (GO) enrichment analysis performed on statistically significantly regulated unique protein coding genes revealed overrepresentation of aging gene cluster. Moreover, as before, overexpression of several genes involved in oxidative stress responses was detected. Conclusion: More stringent statistical analysis predictably resulted in a smaller number of regulated genes and thus overrepresented GOs comparing to the earlier paper. However, major conclusions of the previous study can be still regarded as valid, as the most important aging GO is still overrepresented. Background: The ability of an organism to repair DNA damage is implicated in carcinogenesis and aging. Interestingly expression profiling of Nucleotide Excision Repair (NER) deficient segmental progeroid mice revealed gene expression changes resembling these observed in aged wild type animals. Our previous transcriptional profiling of NER-deficient C. elegans xpa-1 mutant showed overrepresentation of genes involved in lifespan determination and upregulation of several oxidative stress response genes (Fensgard et al. Aging 2010). However, since an independent study performed by Boyd and coworkers (Boyd et al. Mut Res 2010) showed limited number of changes in xpa-1 mutant. Therefore to independently validate that transcriptome modulation does take place in xpa-1 mutants, we performed another global gene expression profiling based on 5 independent biological replicates allowing more stringent statistical analysis. Results: In agreement with what was observed by Boyd and coworkers (Boyd et al. Mut Res 2010) current transcriptomic analysis detected fewer changes in xpa-1 C. elegans mutant with only a few genes regulated more than 4-fold. Nevertheless, Gene Ontology (GO) enrichment analysis performed on statistically significantly regulated unique protein coding genes revealed overrepresentation of aging gene cluster. Moreover, as before, overexpression of several genes involved in oxidative stress responses was detected. Conclusion: More stringent statistical analysis predictably resulted in a smaller number of regulated genes and thus overrepresented GOs comparing to the earlier paper. However, major conclusions of the previous study can be still regarded as valid, as the most important aging GO is still overrepresented. Activation of oxidative stress-responses and downregulation of insulin-like signaling (ILS) is seen in Nucleotide Excision Repair (NER) deficient segmental progeroid mice. Evidence suggests that this is a survival response to persistent transcription-blocking DNA damage, although the relevant lesions have not been identified. Here we provide evidence for transcriptional reprogramming in NER-deficient C. elegans xpa-1 by transcriptomic and proteomic approaches. This reprograming is accompanied by increased intracellular ROS and ATP levels and lifespan shortening in xpa-1 mutant. Moreover we show that Base Excision Repair DNA glycosylase NTH-1 is upstream form the signaling events leading to transcriptomic changes, as its downregulation reverses overexpression of sod-3, gst-4 and aqp-1 genes, reduces intracellular ROS and ATP levels and reverses lifespan shortening observed in xpa-1 mutant. Surprisingly, however, these responses appear to not depend on cyclopurine levels, since these lesions are lower in xpa-1 C. elegans mutant than in the wild type. Finally, we also explore here which other upstream factors are necessary for transcriptional reprograming in xpa-1 mutant. Untreated Caenorhabditis elegans mutant deficient in xpa-1 and the wild type N2 strain were subjected to transcriptome analysis using Affymetrix platform. For each sample group five replicates were analyzed.
Project description:DNA damage comprises a causal factor for aging and aging-associated diseases. Defects in genome maintenance pathways give rise to a variety of human congenital syndromes that are characterized by growth retardation, cancer susceptibility, and accelerated aging. The specific consequences of unrepaired DNA damage in human diseases are particularly apparent in syndromes caused by distinct nucleotide excision repair (NER) defects, however, with yet poorly understood genotype-phenotype correlations and highly complex disease phenotypes. We have established that the equivalent mutations in the simple metazoan Caenorhabditis elegans reflect the distinct outcomes of DNA repair defects and allow investigating the consequences of persistent DNA damage during animal development and aging. Here, we employed proteome, lipidome, and phosphoproteome analysis of NER-deficient animals in response to UV treatment in order to gain comprehensive insights into the full range of physiological adaptations to the presence of unrepaired DNA damage. We derive metabolic changes indicative of a tissue maintenance program and implicate an autophagy-mediated protoestatic response. We assign central roles for the IIS regulator DAF-2 and the EGF-signalling pathway in orchestrating this adaptive response to DNA damage. Our results provide new insights into the DNA damage responses in the organismal context.
Project description:We demonstrate that transcriptomic profiling of the NER mutant ercc-1 offers better understanding of the complex phenotypes of ercc-1 deficiency in C. elegans, as it does in mammalian models. There is a transcriptomic shift in ercc-1 mutants that suggests a stochastic impairment of growth and development, with a shift towards a higher proportion of males in the population. Extensive phenotypic analyses confirm that NER deficiency in C. elegans leads to severe developmental and growth defects and a reduced replicative lifespan, although post-mitotic lifespan is not affected. Results suggest that these defects are caused by an inability to cope with randomly occurring DNA damage, which may interfere with transcription and replication. The study investigates the developmental and aging phenotypes of different NER deficient C. elegans mutants (xpa-1, ercc-1, xpf-1 and xpg-1), where the transcriptomic profile of ercc-1 mutant is presented. We show that loss of NER function does not affect post-mitotic lifespan, but leads to impaired embryogenesis, germ cell and larval development and causes a reduced replicative lifespan. Phenotypes are most pronounced in ercc-1, xpf-1 and xpg-1 mutant animals. We provide evidence that this more pronounced phenotype is likely caused by the fact that these genes are involved in multiple repair pathways besides NER. Furthermore, transcriptional profiling of ercc-1 mutants confirms these observations, showing that growth and developmental pathways are underrepresented but that insulin signaling is not affected. Our analysis suggests that XPA-1, ERCC-1, XPF-1 and XPG-1 protect animals against replicative aging by preventing the accumulation of randomly acquired DNA damage. Eight mixed stage C. elegans samples were run on Affymetrix GeneChip C. elegans Genome Arrays. Four samples belong to ercc-1 mutant group and four to the wild-type, N2.
Project description:Background: The ability of an organism to repair DNA damage is implicated in carcinogenesis and aging. Interestingly expression profiling of Nucleotide Excision Repair (NER) deficient segmental progeroid mice revealed gene expression changes resembling these observed in aged wild type animals. Our previous transcriptional profiling of NER-deficient C. elegans xpa-1 mutant showed overrepresentation of genes involved in lifespan determination and upregulation of several oxidative stress response genes (Fensgard et al. Aging 2010). However, since an independent study performed by Boyd and coworkers (Boyd et al. Mut Res 2010) showed limited number of changes in xpa-1 mutant. Therefore to independently validate that transcriptome modulation does take place in xpa-1 mutants, we performed another global gene expression profiling based on 5 independent biological replicates allowing more stringent statistical analysis. Results: In agreement with what was observed by Boyd and coworkers (Boyd et al. Mut Res 2010) current transcriptomic analysis detected fewer changes in xpa-1 C. elegans mutant with only a few genes regulated more than 4-fold. Nevertheless, Gene Ontology (GO) enrichment analysis performed on statistically significantly regulated unique protein coding genes revealed overrepresentation of aging gene cluster. Moreover, as before, overexpression of several genes involved in oxidative stress responses was detected. Conclusion: More stringent statistical analysis predictably resulted in a smaller number of regulated genes and thus overrepresented GOs comparing to the earlier paper. However, major conclusions of the previous study can be still regarded as valid, as the most important aging GO is still overrepresented. Activation of oxidative stress-responses and downregulation of insulin-like signaling (ILS) is seen in Nucleotide Excision Repair (NER) deficient segmental progeroid mice. Evidence suggests that this is a survival response to persistent transcription-blocking DNA damage, although the relevant lesions have not been identified. Here we provide evidence for transcriptional reprogramming in NER-deficient C. elegans xpa-1 by transcriptomic and proteomic approaches. This reprograming is accompanied by increased intracellular ROS and ATP levels and lifespan shortening in xpa-1 mutant. Moreover we show that Base Excision Repair DNA glycosylase NTH-1 is upstream form the signaling events leading to transcriptomic changes, as its downregulation reverses overexpression of sod-3, gst-4 and aqp-1 genes, reduces intracellular ROS and ATP levels and reverses lifespan shortening observed in xpa-1 mutant. Surprisingly, however, these responses appear to not depend on cyclopurine levels, since these lesions are lower in xpa-1 C. elegans mutant than in the wild type. Finally, we also explore here which other upstream factors are necessary for transcriptional reprograming in xpa-1 mutant.
Project description:We used gene expression profiling to address several specific questions that arose in a study of repair of ultraviolet C radiation in C elegans, as well as to generate hypotheses regarding the possible mechanism(s) of decreased DNA repair observed in old adults in that study. This analysis was performed in order to analyze gene expression in the strain (JK1107) and experimental conditions that we used for our DNA repair studies. The supplementary file GSE4766_Resolver_all_data.txt includes Resolver generated fold-changes and p values based on ratios built in Rosetta Resolver as described in the Rosetta Biosoftware Technical Note (Lee Weng, 2004), Data processing and analysis methods in the Rosetta Resolver system (http://www.rosettabio.com/tech/default.htm). Keywords: C elegans, glp-1, age, nucleotide excision repair, ultraviolet radiation, DNA damage
Project description:We demonstrate that transcriptomic profiling of the NER mutant ercc-1 offers better understanding of the complex phenotypes of ercc-1 deficiency in C. elegans, as it does in mammalian models. There is a transcriptomic shift in ercc-1 mutants that suggests a stochastic impairment of growth and development, with a shift towards a higher proportion of males in the population. Extensive phenotypic analyses confirm that NER deficiency in C. elegans leads to severe developmental and growth defects and a reduced replicative lifespan, although post-mitotic lifespan is not affected. Results suggest that these defects are caused by an inability to cope with randomly occurring DNA damage, which may interfere with transcription and replication. The study investigates the developmental and aging phenotypes of different NER deficient C. elegans mutants (xpa-1, ercc-1, xpf-1 and xpg-1), where the transcriptomic profile of ercc-1 mutant is presented. We show that loss of NER function does not affect post-mitotic lifespan, but leads to impaired embryogenesis, germ cell and larval development and causes a reduced replicative lifespan. Phenotypes are most pronounced in ercc-1, xpf-1 and xpg-1 mutant animals. We provide evidence that this more pronounced phenotype is likely caused by the fact that these genes are involved in multiple repair pathways besides NER. Furthermore, transcriptional profiling of ercc-1 mutants confirms these observations, showing that growth and developmental pathways are underrepresented but that insulin signaling is not affected. Our analysis suggests that XPA-1, ERCC-1, XPF-1 and XPG-1 protect animals against replicative aging by preventing the accumulation of randomly acquired DNA damage.
Project description:The nematode Caenorhabditis elegans has been used extensively to study responses to DNA damage. In contrast, little is known about DNA repair in this organism. C. elegans is unusual in that it encodes few DNA glycosylases and the uracil-DNA glycosylase (UDG) encoded by the ung-1 gene is the only known UDG. C. elegans could therefore become a valuable model organism for studies of the genetic interaction networks involving base excision repair (BER). As a first step towards characterization of BER in C. elegans, we show that the UNG-1 protein is an active uracil-DNA glycosylase. We demonstrate that an ung-1 mutant has reduced ability to repair uracil-containing DNA but that an alternative Ugi-inhibited activity is present in ung-1 nuclear extracts. Finally, we demonstrate that ung-1 mutants show altered levels of apoptotic cell corpses formed in response to DNA damaging agents. Increased apoptosis in the ung-1 mutant in response to ionizing radiation (IR) suggests that UNG-1 contributes to repair of IR-induced DNA base damage in vivo. Following treatment with paraquat however, the apoptotic corpse-formation was reduced. Gene expression profiling suggests that this phenotype is a consequence of compensatory transcriptomic shifts that modulate oxidative stress responses in the mutant and not an effect of reduced DNA damage signaling. C. elegans RNAi mutants deficient in ung-1 and the corresponding wild-type N2, were subjected to Affymetrix whole C. elegans genome microarrays. Triplicates were run for each sample group.
Project description:Ultraviolet C radiation (UVC) damages the nuclear and mitochondrial genomes; this damage is repaired in the nuclear but not mitochondrial genome. Ethidium bromide (EtBr) inhibits mitochondrial DNA replication. We were interested in the transcriptomic response to exposure to UVC, EtBr, and the combination. The UVC exposure protocol results in a high level of mitochondrial DNA damage, and a low level of nuclear DNA damage (because of repair).
Project description:The nematode Caenorhabditis elegans has been used extensively to study responses to DNA damage. In contrast, little is known about DNA repair in this organism. C. elegans is unusual in that it encodes few DNA glycosylases and the uracil-DNA glycosylase (UDG) encoded by the ung-1 gene is the only known UDG. C. elegans could therefore become a valuable model organism for studies of the genetic interaction networks involving base excision repair (BER). As a first step towards characterization of BER in C. elegans, we show that the UNG-1 protein is an active uracil-DNA glycosylase. We demonstrate that an ung-1 mutant has reduced ability to repair uracil-containing DNA but that an alternative Ugi-inhibited activity is present in ung-1 nuclear extracts. Finally, we demonstrate that ung-1 mutants show altered levels of apoptotic cell corpses formed in response to DNA damaging agents. Increased apoptosis in the ung-1 mutant in response to ionizing radiation (IR) suggests that UNG-1 contributes to repair of IR-induced DNA base damage in vivo. Following treatment with paraquat however, the apoptotic corpse-formation was reduced. Gene expression profiling suggests that this phenotype is a consequence of compensatory transcriptomic shifts that modulate oxidative stress responses in the mutant and not an effect of reduced DNA damage signaling.
Project description:Unlike aging somatic cells, which exhibit a decline in molecular fidelity and eventually reach a state of replicative senescence, pluripotent stem cells can indefinitely replenish themselves while retaining full homeostatic capacity. The conferment of beneficial -pluripotency related traits via in vivo partial cellular reprogramming (IVPR) significantly extends lifespan and restores aging phenotypes in mouse models. Although the phases of cellular reprogramming are well characterized, details of the rejuvenation processes are poorly defined. Here we created the first reprogrammable accelerated aging mouse model with a DNA damage repair defect to better understand the effects of reprogramming on a key driver of aging. Using enhanced partial reprogramming by combining small molecules with the Yamanaka factors, we observed potent reversion of DNA damage, significant upregulation of multiple DNA damage repair processes, and restoration of the epigenetic clock is observed. In addition, we present evidence that TGFb inhibition of the ALK5 or ALK2 receptor is able to phenocopy some benefits including epigenetic clock restoration suggesting a role in the mechanism of rejuvenation during partial reprogramming.