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.
Loss of Caenorhabditis elegans UNG-1 uracil-DNA glycosylase affects apoptosis in response to DNA damaging agents.
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View SamplesBackground: 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.
Active transcriptomic and proteomic reprogramming in the C. elegans nucleotide excision repair mutant xpa-1.
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View SamplesThe goal of this study was to compare expression profiles of B cells in the presence and absence of transcription factor MAX under normal and premalignant settings Overall design: Each genotype is represented in triplicate (cells isolated from 3 individual mice for each)
<i>Max</i> deletion destabilizes MYC protein and abrogates Eµ-<i>Myc</i> lymphomagenesis.
Specimen part, Subject
View SamplesDuchenne Muscular Dystrophy (DMD) is a fatal muscle wasting disorder caused by dystrophin deficiency. Previous work suggested that increased expression of the dystrophin-related protein utrophin in the mdx mouse model of DMD can prevent dystrophic pathophysiology. Physiological tests showed that the transgenic mouse muscle functioned in a way similar to normal muscle. More recently, it has become possible to analyse disease pathways using microarrays, a sensitive method to evaluate the efficacy of a therapeutic approach. We thus examined the gene expression profile of mdx mouse muscle compared to normal mouse muscle and compared the data with that obtained from the transgenic line expressing utrophin. The data confirm that the expression of utrophin in the mdx mouse muscle results in a gene expression profile virtually identical to that seen for the normal mouse. This study confirms that a strategy to up-regulate utrophin is likely to be effective in preventing the disease.
Microarray analysis of mdx mice expressing high levels of utrophin: therapeutic implications for dystrophin deficiency.
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View SamplesThere is much evidence that T cells may be activated via mechanisms which act independently of direct TCR ligation. Despite this, the question of whether such forms of bystander T cell activation occur during immune responses is hotly debated.
Human CD4+ memory T cells are preferential targets for bystander activation and apoptosis.
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View SamplesReplicating viruses have broad applications in biomedicine, notably in cancer virotherapy and in the design of attenuated vaccines, however uncontrolled virus replication in vulnerable tissues can give pathology and often restricts the use of potent strains. Increased knowledge of tissue-selective microRNA expression now affords the possibility of engineering replicating viruses that are attenuated at the RNA level in sites of potential pathology, but retain wild type replication activity at sites not expressing the relevant microRNA.
MicroRNA controlled adenovirus mediates anti-cancer efficacy without affecting endogenous microRNA activity.
Sex, Age, Specimen part, Treatment
View SamplesOligodendrocyte precursor cells from postnatal day 10 optic nerve remained in a developmentally immature state in LIF-/- mice. Partial recovery of myelin genes is seen in LIF-/- mice by postnatal day 14 in the optic nerve. Very little difference in myelin genes in the optic nerve is seen by postnatal day 35 (adult).
Leukemia inhibitory factor regulates the timing of oligodendrocyte development and myelination in the postnatal optic nerve.
Sex, Specimen part
View SamplesIn the normal mouse the pituitary gonadotrophins determine development, maturation and physiological regulation of the testis with follicle-stimulating hormone (FSH) activating the Sertoli cell and luteinising hormone (LH) the Leydig cell. To look at the potential interaction of cell types within the testis following hormone stimulation we have investigated the effect of rFSH on testicular gene expression in the hypogonadal (hpg) male mouse. Due to a deletion in the gene encoding gonadotrophin-releasing hormone (GnRH), FSH and LH levels are at the lower limit of detection in the circulation and mice remain in a pre-pubertal state throughout life unless given exogenous hormone.
Effects of FSH on testicular mRNA transcript levels in the hypogonadal mouse.
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View SamplesThe number of transcripts where allelic bias is dependent parent-of-origin was predicted at 100-200 until two recent studies applied RNA-Seq to brain regions from reciprocally crossed inbred mouse strains and identified over a thousand novel imprinted loci, including hundreds present in only males or females. Reanalysis revealed that the vast majority of these novel loci are explained by technical and biological variation of the approach, and are not genuine cases of general or sex-specific parent-of-origin allelic expression. Independent replication projects that, at most, a few dozen novel imprinted transcripts are present in the dataset, in line with previous projections of 100-200 total imprinted transcripts. Overall design: Whole brain transcriptome analysis of E17.5 F1 embryos from reciprocally crossed C57BL/6J and CastEi/J parents
Critical evaluation of imprinted gene expression by RNA-Seq: a new perspective.
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View SamplesThe exit of antigen-presenting cells (APC) and lymphocytes from inflamed skin to afferent lymph is vital for the initiation and maintenance of dermal immune responses. How such exit is achieved and how cells transmigrate the distinct endothelium of lymphatic vessels is however unknown. Here we show that inflammatory cytokines trigger activation of dermal lymphatic endothelial cells (LEC) leading to expression of the key leukocyte adhesion receptors ICAM-1, VCAM-1 and E-selectin, as well as a discrete panel of chemokines and other potential regulators of leukocyte transmigration. Furthermore, we show that both ICAM-1 and VCAM-1 are induced in the dermal lymphatic vessels of mice exposed to skin contact hypersensitivity where they mediate lymph node trafficking of DC via afferent lymphatics. Lastly, we show that TNF_-stimulates both DC adhesion and transmigration of dermal LEC monolayers in vitro and that the process is efficiently inhibited by ICAM-1 and VCAM-1 adhesion-blocking mAbs. These results reveal a CAM-mediated mechanism for recruiting leukocytes to the lymph nodes in inflammation and highlight the process of lymphatic transmigration as a potential new target for anti-inflammatory therapy.
An inflammation-induced mechanism for leukocyte transmigration across lymphatic vessel endothelium.
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