Project description:Telomerase, the essential enzyme that maintains telomere length, contains two core components, TERT and TR. While early studies in yeast and mouse both indicated that loss of telomerase leads to phenotypes that arise after an increased number of generations, due to telomere shortening, recent studies claim additional roles for telomerase components in transcription and the response to DNA damage. To test these telomere length maintenance-independent roles of telomerase components, we examined first generation mTR-/- and mTERT-/- mice with long telomeres. We used gene expression profiling and found no genes that were expressed at significantly different levels when independent mTR-/- G1 mice were compared to mTERT-/- G1 mice and to wild-type mice. In addition, we compared the response to DNA damage in mTR-/-G1 and mTERT-/- G1 mouse embryonic fibroblasts, and found no increase in the response to DNA damage in the absence of either telomerase components compared to wild-type. We conclude that in the wild-type physiological telomere length setting, neither mTR nor mTERT act as a transcription factor or have a role in the DNA damage response.
Project description:Telomerase, the essential enzyme that maintains telomere length, contains two core components, TERT and TR. While early studies in yeast and mouse both indicated that loss of telomerase leads to phenotypes that arise after an increased number of generations, due to telomere shortening, recent studies claim additional roles for telomerase components in transcription and the response to DNA damage. To test these telomere length maintenance-independent roles of telomerase components, we examined first generation mTR-/- and mTERT-/- mice with long telomeres. We used gene expression profiling and found no genes that were expressed at significantly different levels when independent mTR-/- G1 mice were compared to mTERT-/- G1 mice and to wild-type mice. In addition, we compared the response to DNA damage in mTR-/-G1 and mTERT-/- G1 mouse embryonic fibroblasts, and found no increase in the response to DNA damage in the absence of either telomerase components compared to wild-type. We conclude that in the wild-type physiological telomere length setting, neither mTR nor mTERT act as a transcription factor or have a role in the DNA damage response.
Project description:Recent studies suggest that telomerase promotes cell growth by mechanisms that extend beyond the rescue of critically short telomeres. The in vitro model of mTert overexpressing MEFs recapitulates fundamental aspects of the growth-promoting effects of mTert in vivo. First, in Terc-proficient cells, mTert overexpression favors escape from replicative senescence and enhances anchorage-independent growth in response to oncogenic stress, which fits well with previous data showing that mTert overexpression promotes tumor formation. Second, in Terc-deficient cells, retroviral transduction with mTert results in a delayed onset of immortalization and impairs colony formation in response to oncogenic stress, which is in agreement with the inhibitory effect of mTert overexpression on tumorigenesis in a Terc null mouse background. To unravel the molecular targets of telomerase that impact on cell growth, we compared the transcriptome of MEFs, before and after mTert introduction. We found that ectopic expression of mTert was associated with detectable gene expression changes (greater than 1.5-fold; validated by qRT-PCR) of 26 transcripts. Analysis of the observed transcriptional changes indicates that ectopic expression of mTert suppresses in a coordinated manner functionally related genes with overlapping roles in growth arrest, resistance to transformation, and apoptosis. We show that the majority of the telomerase target genes are growth-inhibitory, transforming growth factor-beta (TGF-beta) -inducible genes and provide functional evidence for the potential of telomerase to abrogate TGF-beta -mediated growth inhibition. Thus, in line with the current view that the diversity of TGF-beta responses is not so much a consequence of the use of different signaling pathways but caused by different ways of reading the output from the same basic pathway, we propose that the telomerase status of a cell creates a gene expression pattern that determines how cells read growth inhibitory signals, among them signals propagated through the TGF-beta pathway.
Project description:Recent studies suggest that telomerase promotes cell growth by mechanisms that extend beyond the rescue of critically short telomeres. The in vitro model of mTert overexpressing MEFs recapitulates fundamental aspects of the growth-promoting effects of mTert in vivo. First, in Terc-proficient cells, mTert overexpression favors escape from replicative senescence and enhances anchorage-independent growth in response to oncogenic stress, which fits well with previous data showing that mTert overexpression promotes tumor formation. Second, in Terc-deficient cells, retroviral transduction with mTert results in a delayed onset of immortalization and impairs colony formation in response to oncogenic stress, which is in agreement with the inhibitory effect of mTert overexpression on tumorigenesis in a Terc null mouse background. To unravel the molecular targets of telomerase that impact on cell growth, we compared the transcriptome of MEFs, before and after mTert introduction. We found that ectopic expression of mTert was associated with detectable gene expression changes (greater than 1.5-fold; validated by qRT-PCR) of 26 transcripts. Analysis of the observed transcriptional changes indicates that ectopic expression of mTert suppresses in a coordinated manner functionally related genes with overlapping roles in growth arrest, resistance to transformation, and apoptosis. We show that the majority of the telomerase target genes are growth-inhibitory, transforming growth factor-beta (TGF-beta) -inducible genes and provide functional evidence for the potential of telomerase to abrogate TGF-beta -mediated growth inhibition. Thus, in line with the current view that the diversity of TGF-beta responses is not so much a consequence of the use of different signaling pathways but caused by different ways of reading the output from the same basic pathway, we propose that the telomerase status of a cell creates a gene expression pattern that determines how cells read growth inhibitory signals, among them signals propagated through the TGF-beta pathway. Keywords: repeat sample
Project description:Pediatric acute lymphoblastic leukemia (ALL) is believed to originate in utero and frequently involves aberrant promoter methylation. Folate is the methyl donor for DNA methylation, suggesting that maternal folate metabolism may contribute to the development of ALL. We previously reported significant associations between single nucleotide polymorphisms (SNPs) in the maternal methionine synthase (MTR) gene and offspring’s risk of ALL. Here, we test the associations of 11 SNPs in MTR with aberrant DNA methylation in offspring with ALL. We recruited 51 ALL case-mother pairs from Texas Children’s Hospital from 2005-2010. We collected maternal saliva samples and diagnostic bone marrow plasma from cases. Bone marrow plasma was obtained from six healthy donors. DNA methylation was determined using MCA-Seq. Pyrosequencing was used to determine maternal MTR genotypes. We identified offspring with high and low promoter methylation and used logistic regression to estimate the effects of maternal genotype on offspring methylation. Twenty-two cases (43%) demonstrated high promoter methylation. Maternal MTR 113A>G was associated with aberrant DNA methylation in offspring (OR 4.59, 95% CI 1.21-17.93). To the best of our knowledge, this is the first report of an association between maternal genotype and offspring methylation in pediatric ALL.
Project description:Obesity is linked to limited adipose tissue (AT) remodeling capacity, leading to hypertrophic adipocytes, senescence, and inflammation. We used a mouse model expressing mTert, or its catalytically inactive form mTertCi, from the Cdkn1a locus to investigate the role of mTERT in obesity-induced metabolic disorders in mice on a high-fat-diet (HFD). We found that mTERT expression attenuates p21 expression, telomere attrition, senescence, and inflammation in the AT of HFD-induced obese mice, thereby reducing associated metabolic disorders. In vivo and in vitro data reveal that mTERT promotes differentiation of adipose stem and progenitor cells into adipocytes in obese mice. Strikingly, single nucleus RNA-seq data show that both mTERT and mTERTCi remodels the landscape of macrophages in AT of obese mice thereby reducing the immune response. These results emphasize involvement of the canonical and non-canonical mTERT functions in ameliorating metabolic disorders and suggest conditional TERT expression as a potential therapeutic option for obesity.
Project description:Obesity is linked to limited adipose tissue (AT) remodeling capacity, leading to hypertrophic adipocytes, senescence, and inflammation. We used a mouse model expressing mTert, or its catalytically inactive form mTertCi, from the Cdkn1a locus to investigate the role of mTERT in obesity-induced metabolic disorders in mice on a high-fat-diet (HFD). We found that mTERT expression attenuates p21 expression, telomere attrition, senescence, and inflammation in the AT of HFD-induced obese mice, thereby reducing associated metabolic disorders. In vivo and in vitro data reveal that mTERT promotes differentiation of adipose stem and progenitor cells into adipocytes in obese mice. Strikingly, single nucleus RNA-seq data show that both mTERT and mTERTCi remodels the landscape of macrophages in AT of obese mice thereby reducing the immune response. These results emphasize involvement of the canonical and non-canonical mTERT functions in ameliorating metabolic disorders and suggest conditional TERT expression as a potential therapeutic option for obesity.
Project description:Lung diseases develop when telomeres are shortened beyond a critical point. We have constructed a mouse model in which the catalytic subunit of telomerase (mTert), or its catalytically inactive form (mTertCI), is expressed from the p21Cdkn1a promoter. We found that this particular expression of mTert reduces senescence of endothelial cells (EC) in lungs of aged mice, as well as emphysema and pulmonary perivascular fibrosis. We also show that mTert counteracts the decline in capillary density in aged mice and promotes the maintenance of high numbers of Cd34+ cells, identified as a subclass of endothelial cells with proliferative capacity. In line with these results, young p21+/Tert mice treated with a VEGF receptor inhibitor combined with hypoxia are also protected against senescence and emphysema induced by this treatment. The catalytic activity of mTert is required for all the effects observed. However, and unexpectedly, we found that both mTert and mTertCI expression significantly reduced p21 levels in the lungs of aged mice. mTert thus protects against age-related and induced loss of capillary vessels and subsequent lung emphysema.