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Sample records for abnormally short telomeres

  1. Telomeric noncoding RNA TERRA is induced by telomere shortening to nucleate telomerase molecules at short telomeres.

    PubMed

    Cusanelli, Emilio; Romero, Carmina Angelica Perez; Chartrand, Pascal

    2013-09-26

    Elongation of a short telomere depends on the action of multiple telomerase molecules, which are visible as telomerase RNA foci or clusters associated with telomeres in yeast and mammalian cells. How several telomerase molecules act on a single short telomere is unknown. Herein, we report that the telomeric noncoding RNA TERRA is involved in the nucleation of telomerase molecules into clusters prior to their recruitment at a short telomere. We find that telomere shortening induces TERRA expression, leading to the accumulation of TERRA molecules into a nuclear focus. Simultaneous time-lapse imaging of telomerase RNA and TERRA reveals spontaneous events of telomerase nucleation on TERRA foci in early S phase, generating TERRA-telomerase clusters. This cluster is subsequently recruited to the short telomere from which TERRA transcripts originate during S phase. We propose that telomere shortening induces noncoding RNA expression to coordinate the recruitment and activity of telomerase molecules at short telomeres.

  2. Induced pluripotent stem cells as a model for telomeric abnormalities in ICF type I syndrome.

    PubMed

    Sagie, Shira; Ellran, Erika; Katzir, Hagar; Shaked, Rony; Yehezkel, Shiran; Laevsky, Ilana; Ghanayim, Alaa; Geiger, Dan; Tzukerman, Maty; Selig, Sara

    2014-07-15

    Human telomeric regions are packaged as constitutive heterochromatin, characterized by extensive subtelomeric DNA methylation and specific histone modifications. ICF (immunodeficiency, centromeric instability, facial anomalies) type I patients carry mutations in DNA methyltransferase 3B (DNMT3B) that methylates de novo repetitive sequences during early embryonic development. ICF type I patient fibroblasts display hypomethylated subtelomeres, abnormally short telomeres and premature senescence. In order to study the molecular mechanism by which the failure to de novo methylate subtelomeres results in accelerated telomere shortening, we generated induced pluripotent stem cells (iPSCs) from 3 ICF type I patients. Telomeres were elongated in ICF-iPSCs during reprogramming, and the senescence phenotype was abolished despite sustained subtelomeric hypomethylation and high TERRA levels. Fibroblast-like cells (FLs) isolated from differentiated ICF-iPSCs maintained abnormally high TERRA levels, and telomeres in these cells shortened at an accelerated rate, leading to early senescence, thus recapitulating the telomeric phenotype of the parental fibroblasts. These findings demonstrate that the abnormal telomere phenotype associated with subtelomeric hypomethylation is overridden in cells expressing telomerase, therefore excluding telomerase inhibition by TERRA as a central mechanism responsible for telomere shortening in ICF syndrome. The data in the current study lend support to the use of ICF-iPSCs for modeling of phenotypic and molecular defects in ICF syndrome and for unraveling the mechanism whereby subtelomeric hypomethylation is linked to accelerated telomeric loss in this syndrome.

  3. Short Telomeres in Key Tissues Initiate Local and Systemic Aging in Zebrafish

    PubMed Central

    Carneiro, Madalena C.; Ferreira, Tânia; Carvalho, Tânia; Ferreira, Miguel Godinho

    2016-01-01

    Telomeres shorten with each cell division and telomere dysfunction is a recognized hallmark of aging. Tissue proliferation is expected to dictate the rate at which telomeres shorten. We set out to test whether proliferative tissues age faster than non-proliferative due to telomere shortening during zebrafish aging. We performed a prospective study linking telomere length to tissue pathology and disease. Contrary to expectations, we show that telomeres shorten to critical lengths only in specific tissues and independently of their proliferation rate. Short telomeres accumulate in the gut but not in other highly proliferative tissues such as the blood and gonads. Notably, the muscle, a low proliferative tissue, accumulates short telomeres and DNA damage at the same rate as the gut. Together, our work shows that telomere shortening and DNA damage in key tissues triggers not only local dysfunction but also anticipates the onset of age-associated diseases in other tissues, including cancer. PMID:26789415

  4. Telomeres and marrow failure.

    PubMed

    Calado, Rodrigo T

    2009-01-01

    Telomeres, repeat sequences at the ends of chromosomes, are protective chromosomal structures highly conserved from primitive organisms to humans. Telomeres inevitably shorten with every cell cycle, and telomere attrition has been hypothesized to be fundamental to normal senescence of cells, tissues, and organisms. Molecular mechanisms have evolved to maintain their length and protective function; telomerase (TERT) is a reverse transcriptase enzyme that uses an RNA molecule (TERC) as the template to elongate the 3' ends of telomeres. Shelterin is a collection of DNA-binding proteins that cover and protect telomeres. The recent discovery of inherited mutations in genes that function to repair telomeres as etiologic in a range of human diseases, which have clinical manifestations in diverse tissues, including the hematopoietic tissue, suggests that defects in telomere repair and protection can cause organ failure. Dyskeratosis congenita is the prototype of telomere diseases; it is characterized by bone marrow failure, mucocutaneous abnormalities, pulmonary fibrosis, liver cirrhosis, and increased susceptibility to cancer, including acute myeloid leukemia. Aplastic anemia, acute myeloid leukemia, and idiopathic pulmonary fibrosis also are associated with inherited mutations in telomere repair or protection genes. Additionally, telomere defects associate with predisposition to hematologic malignancy and epithelial tumors. Telomere erosion is abnormally rapid in patients with mutations in telomerase genes but also after hematopoietic stem cell transplant, and telomeres are naturally shorter in older individuals-all conditions associated with higher rates of malignant diseases. In human tissue culture, short telomeres produce end-to-end chromosome fusion, nonreciprocal translocations, and aneuploidy.

  5. At Short Telomeres Tel1 Directs Early Replication and Phosphorylates Rif1

    PubMed Central

    Sridhar, Akila; Kedziora, Sylwia; Donaldson, Anne D.

    2014-01-01

    The replication time of Saccharomyces cerevisiae telomeres responds to TG1–3 repeat length, with telomeres of normal length replicating late during S phase and short telomeres replicating early. Here we show that Tel1 kinase, which is recruited to short telomeres, specifies their early replication, because we find a tel1Δ mutant has short telomeres that nonetheless replicate late. Consistent with a role for Tel1 in driving early telomere replication, initiation at a replication origin close to an induced short telomere was reduced in tel1Δ cells, in an S phase blocked by hydroxyurea. The telomeric chromatin component Rif1 mediates late replication of normal telomeres and is a potential substrate of Tel1 phosphorylation, so we tested whether Tel1 directs early replication of short telomeres by inactivating Rif1. A strain lacking both Rif1 and Tel1 behaves like a rif1Δ mutant by replicating its telomeres early, implying that Tel1 can counteract the delaying effect of Rif1 to control telomere replication time. Proteomic analyses reveals that in yku70Δ cells that have short telomeres, Rif1 is phosphorylated at Tel1 consensus sequences (S/TQ sites), with phosphorylation of Serine-1308 being completely dependent on Tel1. Replication timing analysis of a strain mutated at these phosphorylation sites, however, suggested that Tel1-mediated phosphorylation of Rif1 is not the sole mechanism of replication timing control at telomeres. Overall, our results reveal two new functions of Tel1 at shortened telomeres: phosphorylation of Rif1, and specification of early replication by counteracting the Rif1-mediated delay in initiation at nearby replication origins. PMID:25329891

  6. Preferential extension of short telomeres induced by low extracellular pH

    PubMed Central

    Ge, Yuanlong; Wu, Shu; Xue, Yong; Tao, Jun; Li, Feng; Chen, Yanlian; Liu, Haiying; Ma, Wenbin; Huang, Junjiu; Zhao, Yong

    2016-01-01

    The majority of tumor cells overcome proliferative limit by expressing telomerase. Whether or not telomerase preferentially extends the shortest telomeres is still under debate. When human cancer cells are cultured at neutral pH, telomerase extends telomeres in telomere length-independent manner. However, the microenvironment of tumor is slightly acidic, and it is not yet known how this influences telomerase action. Here, we examine telomere length homeostasis in tumor cells cultured at pHe 6.8. The results indicate that telomerase preferentially extends short telomeres, such that telomere length distribution narrows and telomeres become nearly uniform in size. After growth at pHe 6.8, the expression of telomerase, TRF1, TRF2 and TIN2 decreases, and the abundance of Cajal bodies decreases. Therefore, telomerase are insufficient for extending every telomere and shorter telomeres bearing less shelterin proteins are more accessible for telomerase recruitment. The findings support the ‘protein-counting mechanism’ in which extended and unextended state of telomere is determined by the number of associated shelterin proteins and the abundance of telomerase. Decreased expression of telomerase and preferential extension of short telomeres have important implications for tumor cell viability, and generate a strong rationale for research on telomerase-targeted anti-cancer therapeutics. PMID:27220467

  7. Telomeres, stem cells, and hematology

    PubMed Central

    2008-01-01

    Telomeres are highly dynamic structures that adjust the cellular response to stress and growth stimulation based on previous cell divisions. This critical function is accomplished by progressive telomere shortening and DNA damage responses activated by chromosome ends without sufficient telomere repeats. Repair of critically short telomeres by telomerase or recombination is limited in most somatic cells, and apoptosis or cellular senescence is triggered when too many uncapped telomeres accumulate. The chance of the latter increases as the average telomere length decreases. The average telomere length is set and maintained in cells of the germ line that typically express high levels of telomerase. In somatic cells, the telomere length typically declines with age, posing a barrier to tumor growth but also contributing to loss of cells with age. Loss of (stem) cells via telomere attrition provides strong selection for abnormal cells in which malignant progression is facilitated by genome instability resulting from uncapped telomeres. The critical role of telomeres in cell proliferation and aging is illustrated in patients with 50% of normal telomerase levels resulting from a mutation in one of the telomerase genes. Here, the role of telomeres and telomerase in human biology is reviewed from a personal historical perspective. PMID:18263784

  8. Short telomere length and breast cancer risk: a study in sister sets.

    PubMed

    Shen, Jing; Terry, Mary Beth; Gurvich, Irina; Liao, Yuyan; Senie, Ruby T; Santella, Regina M

    2007-06-01

    Telomeres consist of a tandem repeats of the sequence TTAGGG at the ends of chromosomes and play a key role in the maintenance of chromosomal stability. Previous studies indicated that short telomeres are associated with increased risk for human bladder, head and neck, lung, and renal cell cancer. We investigated the association between white blood cell telomere length and breast cancer risk among 268 family sets (287 breast cancer cases and 350 sister controls). Telomere length was assessed by quantitative PCR. The mean telomere length was shorter in cases (mean, 0.70; range, 0.03-1.95) than in unaffected control sisters (mean, 0.74; range, 0.03-2.29), but no significant difference was observed (P = 0.11). When subjects were categorized according to the median telomere length in controls (0.70), affected sisters had shorter telomeres compared with unaffected sisters after adjusting for age at blood donation and smoking status [odds ratio (OR), 1.3; 95% confidence interval (95% CI), 0.9-1.8], but the association was not statistically significant. The association by quartile of telomere length (Q4 shortest versus Q1 longest) also supported an increase in risk from shorter telomere length, although the association was not statistically significant (OR, 1.6; 95% CI, 0.9-2.7). This association was more pronounced among premenopausal women (OR, 2.1; 95% CI, 0.8-5.5) than postmenopausal women (OR, 1.3; 95% CI, 0.5-3.6 for Q4 versus Q1). If these associations are replicated in larger studies, they provide modest epidemiologic evidence that shortened telomere length may be associated with breast cancer risk.

  9. Short Telomeres Result in Organismal Hypersensitivity to Ionizing Radiation in Mammals

    PubMed Central

    Goytisolo, Fermín A.; Samper, Enrique; Martín-Caballero, Juan; Finnon, Paul; Herrera, Eloísa; Flores, Juana M.; Bouffler, Simon D.; Blasco, María A.

    2000-01-01

    Here we show a correlation between telomere length and organismal sensitivity to ionizing radiation (IR) in mammals. In particular, fifth generation (G5) mouse telomerase RNA (mTR)−/− mice, with telomeres 40% shorter than in wild-type mice, are hypersensitive to cumulative doses of gamma rays. 60% of the irradiated G5 mTR−/− mice die of acute radiation toxicity in the gastrointestinal tract, lymphoid organs, and kidney. The affected G5 mTR−/− mice show higher chromosomal damage and greater apoptosis than similarly irradiated wild-type controls. Furthermore, we show that G5 mTR−/− mice show normal frequencies of sister chromatid exchange and normal V(D)J recombination, suggesting that short telomeres do not significantly affect the efficiency of DNA double strand break repair in mammals. The IR-sensitive phenotype of G5 mTR−/− mice suggests that telomere function is one of the determinants of radiation sensitivity of whole animals. PMID:11104804

  10. Msh2 deficiency leads to chromosomal abnormalities, centrosome amplification, and telomere capping defect

    SciTech Connect

    Wang, Yisong; Liu, Yie

    2006-01-01

    Msh2 is a key mammalian DNA mismatch repair (MMR) gene and mutations or deficiencies in mammalian Msh2 gene result in microsatellite instability (MSI+) and the development of cancer. Here, we report that primary mouse embryonic fibroblasts (MEFs) deficient in the murine MMR gene Msh2 (Msh2-/-) showed a significant increase in chromosome aneuploidy, centrosome amplification, and defective mitotic spindle organization and unequal chromosome segregation. Although Msh2-/- mouse tissues or primary MEFs had no apparent change in telomerase activity, telomere length, or recombination at telomeres, Msh2-/- MEFs showed an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA. These data suggest that MSH2 helps to maintain genomic stability through the regulation of the centrosome and normal telomere capping in vivo and that defects in MMR can contribute to oncogenesis through multiple pathways.

  11. Decreased B16F10 melanoma growth and impaired vascularization in telomerase-deficient mice with critically short telomeres.

    PubMed

    Franco, Sonia; Segura, Inmaculada; Riese, Hans H; Blasco, María A

    2002-01-15

    Endothelial cell function and angiogenesis are modulated by aging. However, the underlying molecular mechanisms are largely unknown. Here we show that in telomerase-deficient mice Terc(-/-), short telomeres result in a sharp decrease in angiogenesis in both Matrigel implants and murine melanoma grafts. In the latter model, decreased microvessel counts in late generation Terc(-/-) mice led to diminished tumor cell proliferation and increased tumor cell apoptosis, resulting in a lower tumor growth rate. Our results indicate that telomere length is a key molecular determinant of angiogenic potential in vivo and that telomere length modifiers and telomerase inhibitors could be useful antiangiogenic agents.

  12. Telomere length alterations unique to invasive lobular carcinoma.

    PubMed

    Heaphy, Christopher M; Asch-Kendrick, Rebecca; Argani, Pedram; Meeker, Alan K; Cimino-Mathews, Ashley

    2015-08-01

    Telomeres are nucleoprotein complexes located at the extreme ends of eukaryotic chromosomes and protect chromosomal ends from degradation and recombination. Dysfunctional telomeres contribute to genomic instability, promote tumorigenesis, and, in breast cancer, have been associated with increased cancer risk and poor prognosis. Short telomere lengths have been previously associated with triple-negative and human epidermal growth factor receptor (Her2)--positive ductal carcinomas. However, these investigations have not specifically assessed invasive lobular carcinomas (ILCs), which accounts for 5% to 15% of all invasive breast cancers. Here, we evaluate telomere lengths within 48 primary ILCs with complete characterization of estrogen receptor (ER), progesterone receptor (PR), and Her2 status, including 32 luminal/Her2- (ER+/PR+/Her2-), 8 luminal/Her2+ (ER+/PR+/Her2+), 3 Her2+ (ER-/PR-/Her2+), and 5 triple-negative (ER-/PR-/Her2-) carcinomas. A telomere-specific fluorescence in situ hybridization assay, which provides single-cell telomere length resolution, was used to evaluate telomere lengths and compare with standard clinicopathological markers. In contrast to breast ductal carcinoma, in which more than 85% of cases display abnormally short telomeres, approximately half (52%) of the ILCs displayed either normal or long telomeres. Short telomere length was associated with older patient age. Interestingly, 3 cases (6%) displayed a unique telomere pattern consisting of 1 or 2 bright telomere spots among the normal telomere signals within each individual cancer cell, a phenotype that has not been previously described. Additional studies are needed to further evaluate the significance of the unique bright telomere spot phenotype and the potential utility of telomere length as a prognostic marker in ILC.

  13. The effect of Ku on telomere replication time is mediated by telomere length but is independent of histone tail acetylation

    PubMed Central

    Lian, Hui-Yong; Robertson, E. Douglas; Hiraga, Shin-ichiro; Alvino, Gina M.; Collingwood, David; McCune, Heather J.; Sridhar, Akila; Brewer, Bonita J.; Raghuraman, M. K.; Donaldson, Anne D.

    2011-01-01

    DNA replication in Saccharomyces cerevisiae proceeds according to a temporal program. We have investigated the role of the telomere-binding Ku complex in specifying late replication of telomere-proximal sequences. Genome-wide analysis shows that regions extending up to 80 kb from telomeres replicate abnormally early in a yku70 mutant. We find that Ku does not appear to regulate replication time by binding replication origins directly, nor is its effect on telomere replication timing mediated by histone tail acetylation. We show that Ku instead regulates replication timing through its effect on telomere length, because deletion of the telomerase regulator Pif1 largely reverses the short telomere defect of a yku70 mutant and simultaneously rescues its replication timing defect. Consistent with this conclusion, deleting the genome integrity component Elg1 partially rescued both length and replication timing of yku70 telomeres. Telomere length–mediated control of replication timing requires the TG1–3 repeat-counting component Rif1, because a rif1 mutant replicates telomeric regions early, despite having extended TG1–3 tracts. Overall, our results suggest that the effect of Ku on telomere replication timing results from its impact on TG1–3 repeat length and support a model in which Rif1 measures telomere repeat length to ensure that telomere replication timing is correctly programmed. PMID:21441303

  14. Complex cytogenetic abnormalities including telomeric associations and MEN1 mutation in a pediatric ependymoma.

    PubMed

    Urioste, M; Martínez-Ramírez, A; Cigudosa, J C; Colmenero, I; Madero, L; Robledo, M; Martínez-Delgado, B; Benítez, J

    2002-10-15

    Ependymomas are neuroectodermal tumors of the brain and spinal cord. Some recurrent cytogenetic aberrations have been reported in these tumors, including alterations involving chromosomes 22, 6, and 11. However, consistent molecular alterations have not been identified in ependymal tumors. We studied a recurrent ependymoma in a 3-year-old patient by standard cytogenetic and molecular analysis of TP53 and MEN1 genes. In the present case, we found many of the cytogenetic features previously described as being recurrent in ependymomas, including unstable telomeric alterations. Furthermore, we detected a novel acquired heterozygous mutation in the MEN1 gene. The chromosomal instability produced by the telomeric alterations and the mutation in the MEN1 gene could be important events in the tumorigenesis of ependymomas.

  15. BRCA1/2 mutations perturb telomere biology: characterization of structural and functional abnormalities in vitro and in vivo

    PubMed Central

    Zuriano, Lital; Naser, Shaden; Beery, Einat; Nordenberg, Jardena; Lubin, Ido; Adel, Yonatan; Shepshelovich, Daniel; Yavin, Hagai; Aharon, Irit Ben; Pery, Shlomit; Rizel, Shulamit; Pasmanik-Chor, Metsada; Frumkin, Dan; Lahav, Meir

    2016-01-01

    BRCA1 mutation is associated with carcinogenesis, especially of breast tissue. Telomere maintenance is crucial for malignant transformation. Being a part of the DNA repair machinery, BRCA1 may be implicated in telomere biology. We explored the role of BRCA1 in telomere maintenance in lymphocytes of BRCA1/2 mutation carriers and in in vitro system by knocking down its expression in non-malignant breast epithelial cells. The results in both systems were similar. BRCA1/2 mutation caused perturbation of telomere homeostasis, shortening of the single stranded telomere overhang and increased the intercellular telomere length variability as well as the number of telomere free chromosomal ends and telomeric circles. These changes resulted in an increased DNA damage status. Telomerase activity, inducibility and expression remained unchanged. BRCA1 mutation resulted also in changes in the binding of shelterin proteins to telomeres. DNMT-1 levels were markedly reduced both in the carriers and in in vitro system. The methylation pattern of the sub-telomeric regions in carriers suggested hypomethylation in chromosome 10. The expression of a distinct set of genes was also changed, some of which may relate to pre-disposition to malignancy. These results show that BRCA gene products have a role in telomere length homeostasis. It is plausible that these perturbations contribute to malignant transformation in BRCA mutants. PMID:26515461

  16. Different chromosome Y abnormalities in a case with short stature

    PubMed Central

    Balkan, Mahmut; Fidanboy, Mehmet; Özbek, M. Nuri; Alp, M. Nail; Budak, Turgay

    2012-01-01

    We report a case with different chromosome Y abnormalities. Case was an 11-year-old boy, who was diagnosed with short stature, referred to laboratory of human medical genetics laboratory for genetic evaluation. Chromosomal analysis of the case was carried out on peripheral blood lymphocyte culture. Classic cytogenetic analysis (G and C banding) was confirmed by using fluorescence in situ hybridization analysis (FISH) technique. Cytogenetic and FISH analysis showed a mosaic 46,X,i(Yq)/45,X/47,X,i(Yq)x2/47,XYY karyotype. Case, which was found interesting due to its rarity, is discussed with its clinical features and cytogenetic results, in the light of relevant source information. This case underlines the importance of karyotyping patients with unexplained short stature. This clinical report also will be helpful in defining the phenotypic range associated with these karyotypes.

  17. Different chromosome Y abnormalities in a case with short stature.

    PubMed

    Balkan, Mahmut; Fidanboy, Mehmet; Özbek, M Nuri; Alp, M Nail; Budak, Turgay

    2012-12-01

    We report a case with different chromosome Y abnormalities. Case was an 11-year-old boy, who was diagnosed with short stature, referred to laboratory of human medical genetics laboratory for genetic evaluation. Chromosomal analysis of the case was carried out on peripheral blood lymphocyte culture. Classic cytogenetic analysis (G and C banding) was confirmed by using fluorescence in situ hybridization analysis (FISH) technique. Cytogenetic and FISH analysis showed a mosaic 46,X,i(Yq)/45,X/47,X,i(Yq)x2/47,XYY karyotype. Case, which was found interesting due to its rarity, is discussed with its clinical features and cytogenetic results, in the light of relevant source information. This case underlines the importance of karyotyping patients with unexplained short stature. This clinical report also will be helpful in defining the phenotypic range associated with these karyotypes. PMID:27625830

  18. Telomeres and telomerase.

    PubMed Central

    Chan, Simon R W L; Blackburn, Elizabeth H

    2004-01-01

    Telomeres are the protective DNA-protein complexes found at the ends of eukaryotic chromosomes. Telomeric DNA consists of tandem repeats of a simple, often G-rich, sequence specified by the action of telomerase, and complete replication of telomeric DNA requires telomerase. Telomerase is a specialized cellular ribonucleoprotein reverse transcriptase. By copying a short template sequence within its intrinsic RNA moiety, telomerase synthesizes the telomeric DNA strand running 5' to 3' towards the distal end of the chromosome, thus extending it. Fusion of a telomere, either with another telomere or with a broken DNA end, generally constitutes a catastrophic event for genomic stability. Telomerase acts to prevent such fusions. The molecular consequences of telomere failure, and the molecular contributors to telomere function, with an emphasis on telomerase, are discussed here. PMID:15065663

  19. The telomerase activator TA-65 elongates short telomeres and increases health span of adult/old mice without increasing cancer incidence

    PubMed Central

    de Jesus, Bruno Bernardes; Schneeberger, Kerstin; Vera, Elsa; Tejera, Agueda; Harley, Calvin B.; Blasco, Maria A.

    2013-01-01

    Here, we show that a small-molecule activator of telomerase (TA-65) purified from the root of Astragalus membranaceus is capable of increasing average telomere length and decreasing the percentage of critically short telomeres and of DNA damage in haploinsufficient mouse embryonic fibroblasts (MEFs) that harbor critically short telomeres and a single copy of the telomerase RNA Terc gene (G3 Terc+/− MEFs). Importantly, TA-65 does not cause telomere elongation or rescues DNA damage in similarly treated telomerase-deficient G3 Terc−/− littermate MEFs. These results indicate that TA-65 treatment results in telomerase-dependent elongation of short telomeres and rescue of associated DNA damage, thus demonstrating that TA-65 mechanism of action is through the telomerase pathway. In addition, we demonstrate that TA-65 is capable of increasing mTERT levels in some mouse tissues and elongating critically short telomeres when supplemented as part of a standard diet in mice. Finally, TA-65 dietary supplementation in female mice leads to an improvement of certain health-span indicators including glucose tolerance, osteoporosis and skin fitness, without significantly increasing global cancer incidence. PMID:21426483

  20. A quantitative telomeric chromatin isolation protocol identifies different telomeric states

    NASA Astrophysics Data System (ADS)

    Grolimund, Larissa; Aeby, Eric; Hamelin, Romain; Armand, Florence; Chiappe, Diego; Moniatte, Marc; Lingner, Joachim

    2013-11-01

    Telomere composition changes during tumourigenesis, aging and in telomere syndromes in a poorly defined manner. Here we develop a quantitative telomeric chromatin isolation protocol (QTIP) for human cells, in which chromatin is cross-linked, immunopurified and analysed by mass spectrometry. QTIP involves stable isotope labelling by amino acids in cell culture (SILAC) to compare and identify quantitative differences in telomere protein composition of cells from various states. With QTIP, we specifically enrich telomeric DNA and all shelterin components. We validate the method characterizing changes at dysfunctional telomeres, and identify and validate known, as well as novel telomere-associated polypeptides including all THO subunits, SMCHD1 and LRIF1. We apply QTIP to long and short telomeres and detect increased density of SMCHD1 and LRIF1 and increased association of the shelterins TRF1, TIN2, TPP1 and POT1 with long telomeres. Our results validate QTIP to study telomeric states during normal development and in disease.

  1. Vanishing honey bees: Is the dying of adult worker bees a consequence of short telomeres and premature aging?

    PubMed

    Stindl, Reinhard; Stindl, Wolfgang

    2010-10-01

    Einstein is often quoted to have said that without the bee, mankind would have but 4years to live. It is highly unlikely that he made this comment, which was even mentioned in a Lancet article on honey bees. However, the current vanishing of the bees can have serious consequences for human health, because 35% of the human diet is thought to benefit from pollination. Colony collapse disorder (CCD) in honey bees is characterized by the rapid decline of the adult bee population, leaving the brood and the queen poorly or completely unattended, with no dead bodies in or around the hive. A large study found no evidence that the presence or amount of any individual pesticide or infectious agent occurred more frequently or abundantly in CCD-affected colonies. The growing consensus is that honey bees are suffering from comprised immune systems, which allow various infectious pathogens to invade. The question remains, what causes immunosuppression in many colonies of Apis mellifera in North America and Europe? Telomeres are protective DNA structures located at eukaryotic chromosome tips that shorten in the somatic tissues of animals with age. Lifelong tissue regeneration takes place in Apis mellifera, and worker bees have been shown to senesce. In humans, a vast amount of literature has accumulated on exhausted telomere reserves causing impaired tissue regeneration and age-associated diseases, specifically cancer and immunosuppression. Therefore, we propose a new causative mechanism for the vanishing of the bees: critically short telomeres in long-lived winter bees. We term this the telomere premature aging syndrome. PMID:20478660

  2. Study of 30 patients with unexplained developmental delay and dysmorphic features or congenital abnormalities using conventional cytogenetics and multiplex FISH telomere (M-TEL) integrity assay.

    PubMed

    Popp, Susanne; Schulze, Birgit; Granzow, Martin; Keller, Monika; Holtgreve-Grez, Heidi; Schoell, Brigitte; Brough, Michaela; Hager, Hans-Dieter; Tariverdian, Gholamali; Brown, Jill; Kearney, Lyndal; Jauch, Anna

    2002-07-01

    Cryptic subtelomeric chromosome rearrangements are a major cause of mild to severe mental retardation pointing out the necessity of sensitive screening techniques to detect such aberrations among affected patients. In this prospective study a group of 30 patients with unexplained developmental retardation and dysmorphic features or congenital abnormalities were analysed using the recently published multiplex FISH telomere (M-TEL) integrity assay in combination with conventional G-banding analysis. The patients were selected by one or more of the following criteria defined by de Vries et al.: (a) family history with two or more affected individuals, (b) prenatal onset growth retardation, (c) postnatal growth abnormalities, (d) facial dysmorphic features, (e) non-facial dysmorphism and congenital abnormalities. In addition, we included two patients who met these criteria and revealed questionable chromosome regions requiring further clarification. In four patients (13.3%) cryptic chromosome aberrations were successfully determined by the M-TEL integrity assay and in two patients with abnormal chromosome regions intrachromosomal aberrations were characterized by targetted FISH experiments. Our results accentuate the requirement of strict selection criteria prior to patient testing with the M-TEL integrity assay. Another essential precondition is high-quality banding analysis to identify structural abnormal chromosomes. The detection of familial balanced translocation carriers in 50% of the cases emphasizes the significance of such an integrated approach for genetic counselling and prenatal diagnosis.

  3. A Common Variant in the Telomerase RNA Component Is Associated with Short Telomere Length

    PubMed Central

    Njajou, Omer T.; Blackburn, Elizabeth H.; Pawlikowska, Ludmila; Mangino, Massimo; Damcott, Coleen M.; Kwok, Pui-Yan; Spector, Timothy D.; Newman, Anne B.; Harris, Tamara B.; Cummings, Steven R.; Cawthon, Richard M.; Shuldiner, Alan R.; Valdes, Ana M.; Hsueh, Wen-Chi

    2010-01-01

    Background Telomeres shorten as cells divide. This shortening is compensated by the enzyme telomerase. We evaluated the effect of common variants in the telomerase RNA component (TERC) gene on telomere length (TL) in the population-based Health Aging and Body Composition (Health ABC) Study and in two replication samples (the TwinsUK Study and the Amish Family Osteoporosis Study, AFOS). Methodology Five variants were identified in the TERC region by sequence analysis and only one SNP was common (rs2293607, G/A). The frequency of the G allele was 0.26 and 0.07 in white and black, respectively. Testing for association between TL and rs2293607 was performed using linear regression models or variance component analysis conditioning on relatedness among subjects. Results The adjusted mean TL was significantly shorter in 665 white carriers of the G allele compared to 887 non-carriers from the Health ABC Study (4.69±0.05 kbp vs. 4.86±0.04 kbp, measured by quantitative PCR, p = 0.005). This association was replicated in another white sample from the TwinsUK Study (6.90±0.03 kbp in 301 carriers compared to 7.06±0.03 kbp in 395 non-carriers, measured by Southern blots, p = 0.009). A similar pattern of association was observed in whites from the family-based AFOS and blacks from the Health ABC cohort, although not statistically significant, possibly due to the lower allele frequency in these populations. Combined analysis using 2,953 white subjects from 3 studies showed a significant association between TL and rs2293607 (β = −0.19±0.04 kbp, p = 0.001). Conclusion Our study shows a significant association between a common variant in TERC and TL in humans, suggesting that TERC may play a role in telomere homeostasis. PMID:20885959

  4. Lead Exposure Induces Telomere Instability in Human Cells

    PubMed Central

    Pottier, Géraldine; Viau, Muriel; Ricoul, Michelle; Shim, Grace; Bellamy, Marion; Cuceu, Corina; Hempel, William M.; Sabatier, Laure

    2013-01-01

    Lead (Pb) is an important environmental contaminant due to its widespread use over many centuries. While it affects primarily every organ system of the body, the most pernicious effects of Pb are on the central nervous system leading to cognitive and behavioral modification. Despite decades of research, the mechanisms responsible for Pb toxicity remain poorly understood. Recent work has suggested that Pb exposure may have consequences on chromosomal integrity as it was shown that Pb exposure leads to the generation of γH2Ax foci, a well-established biomarker for DNA double stranded break (DSB formation). As the chromosomal localization of γH2Ax foci plays an important role in determining the molecular mechanism responsible for their formation, we examined the localization of Pb-induced foci with respect to telomeres. Indeed, short or dysfunctional telomeres (uncapped or damaged telomeres) may be recognized as DSB by the DNA repair machinery, leading to “telomere-Induced Foci” (TIFs). In the current study, we show that while Pb exposure did not increase intra-chromosomal foci, it significantly induced TIFs, leading in some cases, to chromosomal abnormalities including telomere loss. The evidence suggests that these chromosomal abnormalities are likely due to perturbation of telomere replication, in particular on the lagging DNA strand. We propose a mechanism by which Pb exposure leads to the loss of telomere maintenance. As numerous studies have demonstrated a role for telomere maintenance in brain development and tissue homeostasis, our results suggest a possible mechanism for lead-induced neurotoxicity. PMID:23840724

  5. Telomerase gene therapy rescues telomere length, bone marrow aplasia, and survival in mice with aplastic anemia.

    PubMed

    Bär, Christian; Povedano, Juan Manuel; Serrano, Rosa; Benitez-Buelga, Carlos; Popkes, Miriam; Formentini, Ivan; Bobadilla, Maria; Bosch, Fatima; Blasco, Maria A

    2016-04-01

    Aplastic anemia is a fatal bone marrow disorder characterized by peripheral pancytopenia and marrow hypoplasia. The disease can be hereditary or acquired and develops at any stage of life. A subgroup of the inherited form is caused by replicative impairment of hematopoietic stem and progenitor cells due to very short telomeres as a result of mutations in telomerase and other telomere components. Abnormal telomere shortening is also described in cases of acquired aplastic anemia, most likely secondary to increased turnover of bone marrow stem and progenitor cells. Here, we test the therapeutic efficacy of telomerase activation by using adeno-associated virus (AAV)9 gene therapy vectors carrying the telomerase Tert gene in 2 independent mouse models of aplastic anemia due to short telomeres (Trf1- and Tert-deficient mice). We find that a high dose of AAV9-Tert targets the bone marrow compartment, including hematopoietic stem cells. AAV9-Tert treatment after telomere attrition in bone marrow cells rescues aplastic anemia and mouse survival compared with mice treated with the empty vector. Improved survival is associated with a significant increase in telomere length in peripheral blood and bone marrow cells, as well as improved blood counts. These findings indicate that telomerase gene therapy represents a novel therapeutic strategy to treat aplastic anemia provoked or associated with short telomeres.

  6. Sphingolipids regulate telomere clustering by affecting the transcription of genes involved in telomere homeostasis.

    PubMed

    Ikeda, Atsuko; Muneoka, Tetsuya; Murakami, Suguru; Hirota, Ayaka; Yabuki, Yukari; Karashima, Takefumi; Nakazono, Kota; Tsuruno, Masahiro; Pichler, Harald; Shirahige, Katsuhiko; Kodama, Yukiko; Shimamoto, Toshi; Mizuta, Keiko; Funato, Kouichi

    2015-07-15

    In eukaryotic organisms, including mammals, nematodes and yeasts, the ends of chromosomes, telomeres are clustered at the nuclear periphery. Telomere clustering is assumed to be functionally important because proper organization of chromosomes is necessary for proper genome function and stability. However, the mechanisms and physiological roles of telomere clustering remain poorly understood. In this study, we demonstrate a role for sphingolipids in telomere clustering in the budding yeast Saccharomyces cerevisiae. Because abnormal sphingolipid metabolism causes downregulation of expression levels of genes involved in telomere organization, sphingolipids appear to control telomere clustering at the transcriptional level. In addition, the data presented here provide evidence that telomere clustering is required to protect chromosome ends from DNA-damage checkpoint signaling. As sphingolipids are found in all eukaryotes, we speculate that sphingolipid-based regulation of telomere clustering and the protective role of telomere clusters in maintaining genome stability might be conserved in eukaryotes.

  7. Telomere length is inherited with resetting of the telomere set-point.

    PubMed

    Chiang, Y Jeffrey; Calado, Rodrigo T; Hathcock, Karen S; Lansdorp, Peter M; Young, Neal S; Hodes, Richard J

    2010-06-01

    We have studied models of telomerase haploinsufficiency in humans and mice to analyze regulation of telomere length and the significance of "set points" in inheritance of telomere length. In three families with clinical syndromes associated with short telomeres resulting from haploinsufficient mutations in TERT, the gene encoding telomerase reverse transcriptase, we asked whether restoration of normal genotypes in offspring of affected individuals would elongate inherited short telomeres. Telomeres were shorter than normal in some but not all genotypically normal offspring of telomerase-mutant parents or grandparents. Analysis of these findings was complicated by heterogeneity of telomere length among individuals, as well as by the admixing of telomeres inherited from affected parents with those inherited from unaffected ("wild-type" TERT) parents. To understand further the inheritance of telomere length, we established a shortened-telomere mouse model. When Tert(+/-) heterozygous mice were successively cross-bred through 17 generations, telomere length shortened progressively. The late-generation Tert(+/-) mice were intercrossed to produce genotypically wild-type Tert(+/+) mice, for which telomere length was characterized. Strikingly, telomere length in these Tert(+/+) mice was not longer than that of their Tert(+/-) parents. Moreover, when successive crosses were carried out among these short-telomere Tert(+/+) offspring mice, telomere length was stable, with no elongation up to six generations. This breeding strategy therefore has established a mouse strain, B6.ST (short telomeres), with C57BL/6 genotype and stable short telomeres. These findings suggest that the set point of telomere lengths of offspring is determined by the telomere lengths of their parents in the presence of normal expression of telomerase.

  8. Telomeres and longevity: testing an evolutionary hypothesis.

    PubMed

    Haussmann, Mark F; Mauck, Robert A

    2008-01-01

    Identifying mechanisms that underlie variation in adult survivorship provide insight into the evolution of life history strategies and phenotypic variation in longevity. There is accumulating evidence that shortening telomeres, the protective caps at the ends of chromosomes, play an important role in individual variation in longevity. Given that telomeres generally shorten with age, it was surprising to find that in a population of a long-lived seabird, Leach's storm petrel, telomeres appear to lengthen with age. This unique finding suggested that the longest lived individuals are able to elongate telomeres, an interpretation we call the "elongation hypothesis." Alternatively, the "selection hypothesis" states that the longest lived individuals start with the longest telomeres and variation in telomere length decreases with age due to the selective disappearance of individuals with short telomeres. In the same population in which evidence supporting both hypotheses was uncovered, we tested mutually exclusive predictions from the elongation and selection hypotheses by measuring telomere length with the telomere restriction fragment assay in hatchling and old, adult storm petrels. As previously found, adult birds had longer telomeres on average compared with hatchlings. We also found that 3 hatchlings had mean telomere lengths exceeding that of the most extreme old bird, old birds on average had longer initial telomere lengths than hatchlings, and the variance in mean telomere length was significantly greater for hatchlings than for old birds, all predicted by the selection hypothesis. Perhaps more surprisingly, the oldest adults also show little or no accumulation of short telomeres over time, a pattern unknown in other species. Long telomeres are thought to provide a buffer against cellular senescence and be generally indicative of genome stability and overall cell health. In storm petrels, because the progressive accumulation of short telomeres appears negligible

  9. Telomere Length Reprogramming in Embryos and Stem Cells

    PubMed Central

    Robinson, LeRoy G.; Wang, Fang; Liu, Lin; Keefe, David

    2014-01-01

    Telomeres protect and cap linear chromosome ends, yet these genomic buffers erode over an organism's lifespan. Short telomeres have been associated with many age-related conditions in humans, and genetic mutations resulting in short telomeres in humans manifest as syndromes of precocious aging. In women, telomere length limits a fertilized egg's capacity to develop into a healthy embryo. Thus, telomere length must be reset with each subsequent generation. Although telomerase is purportedly responsible for restoring telomere DNA, recent studies have elucidated the role of alternative telomeres lengthening mechanisms in the reprogramming of early embryos and stem cells, which we review here. PMID:24719895

  10. Molecular basis of telomere dysfunction in human genetic diseases.

    PubMed

    Sarek, Grzegorz; Marzec, Paulina; Margalef, Pol; Boulton, Simon J

    2015-11-01

    Mutations in genes encoding proteins required for telomere structure, replication, repair and length maintenance are associated with several debilitating human genetic disorders. These complex telomere biology disorders (TBDs) give rise to critically short telomeres that affect the homeostasis of multiple organs. Furthermore, genome instability is often a hallmark of telomere syndromes, which are associated with increased cancer risk. Here, we summarize the molecular causes and cellular consequences of disease-causing mutations associated with telomere dysfunction.

  11. Telomerase Activity and Telomere Length in Daphnia

    PubMed Central

    Schumpert, Charles; Nelson, Jacob; Kim, Eunsuk; Dudycha, Jeffry L.; Patel, Rekha C.

    2015-01-01

    Telomeres, comprised of short repetitive sequences, are essential for genome stability and have been studied in relation to cellular senescence and aging. Telomerase, the enzyme that adds telomeric repeats to chromosome ends, is essential for maintaining the overall telomere length. A lack of telomerase activity in mammalian somatic cells results in progressive shortening of telomeres with each cellular replication event. Mammals exhibit high rates of cell proliferation during embryonic and juvenile stages but very little somatic cell proliferation occurs during adult and senescent stages. The telomere hypothesis of cellular aging states that telomeres serve as an internal mitotic clock and telomere length erosion leads to cellular senescence and eventual cell death. In this report, we have examined telomerase activity, processivity, and telomere length in Daphnia, an organism that grows continuously throughout its life. Similar to insects, Daphnia telomeric repeat sequence was determined to be TTAGG and telomerase products with five-nucleotide periodicity were generated in the telomerase activity assay. We investigated telomerase function and telomere lengths in two closely related ecotypes of Daphnia with divergent lifespans, short-lived D. pulex and long-lived D. pulicaria. Our results indicate that there is no age-dependent decline in telomere length, telomerase activity, or processivity in short-lived D. pulex. On the contrary, a significant age dependent decline in telomere length, telomerase activity and processivity is observed during life span in long-lived D. pulicaria. While providing the first report on characterization of Daphnia telomeres and telomerase activity, our results also indicate that mechanisms other than telomere shortening may be responsible for the strikingly short life span of D. pulex. PMID:25962144

  12. Telomerase activity and telomere length in Daphnia.

    PubMed

    Schumpert, Charles; Nelson, Jacob; Kim, Eunsuk; Dudycha, Jeffry L; Patel, Rekha C

    2015-01-01

    Telomeres, comprised of short repetitive sequences, are essential for genome stability and have been studied in relation to cellular senescence and aging. Telomerase, the enzyme that adds telomeric repeats to chromosome ends, is essential for maintaining the overall telomere length. A lack of telomerase activity in mammalian somatic cells results in progressive shortening of telomeres with each cellular replication event. Mammals exhibit high rates of cell proliferation during embryonic and juvenile stages but very little somatic cell proliferation occurs during adult and senescent stages. The telomere hypothesis of cellular aging states that telomeres serve as an internal mitotic clock and telomere length erosion leads to cellular senescence and eventual cell death. In this report, we have examined telomerase activity, processivity, and telomere length in Daphnia, an organism that grows continuously throughout its life. Similar to insects, Daphnia telomeric repeat sequence was determined to be TTAGG and telomerase products with five-nucleotide periodicity were generated in the telomerase activity assay. We investigated telomerase function and telomere lengths in two closely related ecotypes of Daphnia with divergent lifespans, short-lived D. pulex and long-lived D. pulicaria. Our results indicate that there is no age-dependent decline in telomere length, telomerase activity, or processivity in short-lived D. pulex. On the contrary, a significant age dependent decline in telomere length, telomerase activity and processivity is observed during life span in long-lived D. pulicaria. While providing the first report on characterization of Daphnia telomeres and telomerase activity, our results also indicate that mechanisms other than telomere shortening may be responsible for the strikingly short life span of D. pulex.

  13. ATM kinase is required for telomere elongation in mouse and human cells

    PubMed Central

    Lee, Stella Suyong; Bohrson, Craig; Pike, Alexandra Mims; Wheelan, Sarah Jo; Greider, Carol Widney

    2015-01-01

    Summary Short telomeres induce a DNA damage response, senescence and apoptosis; thus, maintaining telomere length equilibrium is essential for cell viability. Telomerase addition of telomere repeats is tightly regulated in cells. To probe pathways that regulate telomere addition, we developed the ADDIT assay to measure new telomere addition at a single telomere in vivo. Sequence analysis showed telomerase specific addition of repeats onto a new telomere occurred in just 48 hr. Using the ADDIT assay, we found that ATM is required for addition of new repeats onto telomeres in mouse cells. Evaluation of bulk telomeres, in both human and mouse cells, showed that blocking ATM inhibited telomere elongation. Finally, the activation of ATM through the inhibition of PARP1 resulted in increased telomere elongation, supporting the central role of the ATM pathway in regulating telomere addition. Understanding this role of ATM may yield new areas for possible therapeutic intervention in telomere-mediated disease. PMID:26586427

  14. ATM Kinase Is Required for Telomere Elongation in Mouse and Human Cells.

    PubMed

    Lee, Stella Suyong; Bohrson, Craig; Pike, Alexandra Mims; Wheelan, Sarah Jo; Greider, Carol Widney

    2015-11-24

    Short telomeres induce a DNA damage response, senescence, and apoptosis, thus maintaining telomere length equilibrium is essential for cell viability. Telomerase addition of telomere repeats is tightly regulated in cells. To probe pathways that regulate telomere addition, we developed the ADDIT assay to measure new telomere addition at a single telomere in vivo. Sequence analysis showed telomerase-specific addition of repeats onto a new telomere occurred in just 48 hr. Using the ADDIT assay, we found that ATM is required for addition of new repeats onto telomeres in mouse cells. Evaluation of bulk telomeres, in both human and mouse cells, showed that blocking ATM inhibited telomere elongation. Finally, the activation of ATM through the inhibition of PARP1 resulted in increased telomere elongation, supporting the central role of the ATM pathway in regulating telomere addition. Understanding this role of ATM may yield new areas for possible therapeutic intervention in telomere-mediated disease.

  15. Telomeres and Telomerase in Cardiovascular Diseases

    PubMed Central

    Yeh, Jih-Kai; Wang, Chao-Yung

    2016-01-01

    Telomeres are tandem repeat DNA sequences present at the ends of each eukaryotic chromosome to stabilize the genome structure integrity. Telomere lengths progressively shorten with each cell division. Inflammation and oxidative stress, which are implicated as major mechanisms underlying cardiovascular diseases, increase the rate of telomere shortening and lead to cellular senescence. In clinical studies, cardiovascular risk factors such as smoking, obesity, sedentary lifestyle, and hypertension have been associated with short leukocyte telomere length. In addition, low telomerase activity and short leukocyte telomere length have been observed in atherosclerotic plaque and associated with plaque instability, thus stroke or acute myocardial infarction. The aging myocardium with telomere shortening and accumulation of senescent cells limits the tissue regenerative capacity, contributing to systolic or diastolic heart failure. In addition, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. In this review, we summarize the current understanding of telomeres and telomerase in the aging process and their association with cardiovascular diseases. In addition, we discuss therapeutic interventions targeting the telomere system in cardiovascular disease treatments. PMID:27598203

  16. Telomeres and Telomerase in Cardiovascular Diseases.

    PubMed

    Yeh, Jih-Kai; Wang, Chao-Yung

    2016-01-01

    Telomeres are tandem repeat DNA sequences present at the ends of each eukaryotic chromosome to stabilize the genome structure integrity. Telomere lengths progressively shorten with each cell division. Inflammation and oxidative stress, which are implicated as major mechanisms underlying cardiovascular diseases, increase the rate of telomere shortening and lead to cellular senescence. In clinical studies, cardiovascular risk factors such as smoking, obesity, sedentary lifestyle, and hypertension have been associated with short leukocyte telomere length. In addition, low telomerase activity and short leukocyte telomere length have been observed in atherosclerotic plaque and associated with plaque instability, thus stroke or acute myocardial infarction. The aging myocardium with telomere shortening and accumulation of senescent cells limits the tissue regenerative capacity, contributing to systolic or diastolic heart failure. In addition, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. In this review, we summarize the current understanding of telomeres and telomerase in the aging process and their association with cardiovascular diseases. In addition, we discuss therapeutic interventions targeting the telomere system in cardiovascular disease treatments. PMID:27598203

  17. Telomere length and heredity: Indications of paternal inheritance.

    PubMed

    Nordfjäll, Katarina; Larefalk, Asa; Lindgren, Petter; Holmberg, Dan; Roos, Göran

    2005-11-01

    Cellular telomere length is linked to replicative life span. Telomere repeats are lost in peripheral blood cells in vivo by age, and women show less telomere attrition than men. Previous reports have indicated that telomere length and chromosome-specific telomere-length patterns partly are inherited. The mode of heredity has not been clarified, but a link to the X chromosome was recently suggested. We analyzed peripheral mononuclear cells from 49 unrelated families for telomere length using a real-time PCR method. Short-term cultured Epstein-Barr virus-transformed lymphoblasts from the same individuals (n = 130) were analyzed for ability to maintain telomere length and possible gender-linked inheritance. A statistically significant association between telomere lengths comparing father-son (P = 0.011, n = 20) and father-daughter (P = 0.005, n = 22) pairs was found. However, no correlation was observed between mother-daughter (P = 0.463, n = 23) or mother-son (P = 0.577, n = 18). The father-offspring correlation was highly significant (P < 0.0001), in contrast to mother-offspring (P = 0.361). Epstein-Barr virus cultures demonstrated in most cases telomere preservation inversely related to initial mononuclear cell telomere length with short telomeres displaying the most pronounced elongation. Telomere length is inherited, and evidence for a father-to-offspring heritage of this trait was obtained, whereas in vitro telomere length maintenance was found to be dependent on the initial telomere length.

  18. Telomere position effect: regulation of gene expression with progressive telomere shortening over long distances

    PubMed Central

    Robin, Jérôme D.; Ludlow, Andrew T.; Batten, Kimberly; Magdinier, Frédérique; Stadler, Guido; Wagner, Kathyrin R.; Wright, Woodring E.

    2014-01-01

    While global chromatin conformation studies are emerging, very little is known about the chromatin conformation of human telomeres. Most studies have focused on the role of telomeres as a tumor suppressor mechanism. Here we describe how telomere length regulates gene expression long before telomeres become short enough to produce a DNA damage response (senescence). We directly mapped the interactions adjacent to specific telomere ends using a Hi-C (chromosome capture followed by high-throughput sequencing) technique modified to enrich for specific genomic regions. We demonstrate that chromosome looping brings the telomere close to genes up to 10 Mb away from the telomere when telomeres are long and that the same loci become separated when telomeres are short. Furthermore, expression array analysis reveals that many loci, including noncoding RNAs, may be regulated by telomere length. We report three genes (ISG15 [interferon-stimulated gene 15 kd], DSP [Desmoplakin], and C1S [complement component 1s subcomplement]) located at three different subtelomeric ends (1p, 6p, and 12p) whose expressions are altered with telomere length. Additionally, we confirmed by in situ analysis (3D-FISH [three-dimensional fluorescence in situ hybridization]) that chromosomal looping occurs between the loci of those genes and their respective telomere ends. We term this process TPE-OLD for “telomere position effect over long distances.” Our results suggest a potential novel mechanism for how telomere shortening could contribute to aging and disease initiation/progression in human cells long before the induction of a critical DNA damage response. PMID:25403178

  19. Recombinogenic Telomeres in Diploid Sorex granarius (Soricidae, Eulipotyphla) Fibroblast Cells

    PubMed Central

    Draskovic, I.; Minina, J. M.; Karamysheva, T. V.; Novo, C. L.; Liu, W.-Y.; Porreca, R. M.; Gibaud, A.; Zvereva, M. E.; Skvortsov, D. A.; Rubtsov, N. B.

    2014-01-01

    The telomere structure in the Iberian shrew Sorex granarius is characterized by unique, striking features, with short arms of acrocentric chromosomes carrying extremely long telomeres (up to 300 kb) with interspersed ribosomal DNA (rDNA) repeat blocks. In this work, we investigated the telomere physiology of S. granarius fibroblast cells and found that telomere repeats are transcribed on both strands and that there is no telomere-dependent senescence mechanism. Although telomerase activity is detectable throughout cell culture and appears to act on both short and long telomeres, we also discovered that signatures of a recombinogenic activity are omnipresent, including telomere-sister chromatid exchanges, formation of alternative lengthening of telomeres (ALT)-associated PML-like bodies, production of telomere circles, and a high frequency of telomeres carrying marks of a DNA damage response. Our results suggest that recombination participates in the maintenance of the very long telomeres in normal S. granarius fibroblasts. We discuss the possible interplay between the interspersed telomere and rDNA repeats in the stabilization of the very long telomeres in this organism. PMID:24842907

  20. Telomere shortening and telomere position effect in mild ring 17 syndrome

    PubMed Central

    2014-01-01

    Background Ring chromosome 17 syndrome is a rare disease that arises from the breakage and reunion of the short and long arms of chromosome 17. Usually this abnormality results in deletion of genetic material, which explains the clinical features of the syndrome. Moreover, similar phenotypic features have been observed in cases with complete or partial loss of the telomeric repeats and conservation of the euchromatic regions. We studied two different cases of ring 17 syndrome, firstly, to clarify, by analyzing gene expression analysis using real-time qPCR, the role of the telomere absence in relationship with the clinical symptoms, and secondly, to look for a new model of the mechanism of ring chromosome transmission in a rare case of familial mosaicism, through cytomolecular and quantitative fluorescence in-situ hybridization (Q-FISH) investigations. Results The results for the first case showed that the expression levels of genes selected, which were located close to the p and q ends of chromosome 17, were significantly downregulated in comparison with controls. Moreover, for the second case, we demonstrated that the telomeres were conserved, but were significantly shorter than those of age-matched controls; data from segregation analysis showed that the ring chromosome was transmitted only to the affected subjects of the family. Conclusions Subtelomeric gene regulation is responsible for the phenotypic aspects of ring 17 syndrome; telomere shortening influences the phenotypic spectrum of this disease and strongly contributes to the familial transmission of the mosaic ring. Together, these results provide new insights into the genotype-phenotype relationships in mild ring 17 syndrome. PMID:24393457

  1. Telomere Maintenance Mechanisms in Cancer: Clinical Implications

    PubMed Central

    Reddel, Roger R

    2014-01-01

    The presence of immortal cell populations with an up-regulated telomere maintenance mechanism (TMM) is an almost univer-sal characteristic of cancers, whereas normal somatic cells are unable to prevent proliferation-associated telomere shortening and have a limited proliferative potential. TMMs and related aspects of telomere structure and function therefore appear to be ideal targets for the development of anticancer therapeutics. Such treatments would be targeted to a specific cancer-related molecular abnormality, and also be broad-spectrum in that they would be expected to be potentially applicable to most cancers. However, the telomere biology of normal and malignant human cells is a relatively young research field with large numbers of unanswered questions, so the optimal design of TMM-targeted therapeutic approaches remains unclear. This review outlines the opportunities and challenges presented by telomeres and TMMs for clinical management of cancer. PMID:24975603

  2. Do telomeres adapt to physiological stress? Exploring the effect of exercise on telomere length and telomere-related proteins.

    PubMed

    Ludlow, Andrew T; Ludlow, Lindsay W; Roth, Stephen M

    2013-01-01

    Aging is associated with a tissue degeneration phenotype marked by a loss of tissue regenerative capacity. Regenerative capacity is dictated by environmental and genetic factors that govern the balance between damage and repair. The age-associated changes in the ability of tissues to replace lost or damaged cells is partly the cause of many age-related diseases such as Alzheimer's disease, cardiovascular disease, type II diabetes, and sarcopenia. A well-established marker of the aging process is the length of the protective cap at the ends of chromosomes, called telomeres. Telomeres shorten with each cell division and with increasing chronological age and short telomeres have been associated with a range of age-related diseases. Several studies have shown that chronic exposure to exercise (i.e., exercise training) is associated with telomere length maintenance; however, recent evidence points out several controversial issues concerning tissue-specific telomere length responses. The goals of the review are to familiarize the reader with the current telomere dogma, review the literature exploring the interactions of exercise with telomere phenotypes, discuss the mechanistic research relating telomere dynamics to exercise stimuli, and finally propose future directions for work related to telomeres and physiological stress.

  3. Smoking and perceived stress in relation to short salivary telomere length among caregivers of children with disabilities

    PubMed Central

    Chen, Xiaoli; Velez, Juan Carlos; Barbosa, Clarita; Pepper, Micah; Andrade, Asterio; Stoner, Lee; De Vivo, Immaculata; Gelaye, Bizu; Williams, Michelle A.

    2014-01-01

    Telomere length (TL), the length of repeated DNA sequence that forms protective caps at the end of chromosomes, has emerged as a novel biomarker of cell aging and oxidative stress. There is increasing research exploring the associations of smoking and perceived stress with TL, and the results are inconsistent. This study aimed to examine whether smoking and perceived stress were associated with shortened salivary TL among primary caregivers of children with disabilities. Using a quantitative polymerase chain reaction method, salivary TL was assessed among 89 caregivers aged 19–69 years (87% were women) who took care of disabled children in the Patagonia Region, Chile. Interviewer-administered questionnaires were used to collect information on sociodemographic and lifestyle behaviors. The 14-item Perceived Stress Scale was used to assess perceived stress. Mean relative TL was 0.92 (standard error=0.03). Smokers had age-adjusted mean TL that was 0.07 units lower (beta=−0.07, standard error=0.03; p=0.012) than non-smokers. Smokers were 2.17 times more likely to have shorter TL (<0.73, the lowest quartile of TL) than non-smokers (odds ratio =3.17; 95% confidence interval=1.05–9.52) with adjustment for age and perceived stress. Caregivers with higher perceived stress were 2.13 times more likely to have shorter TL (odds ratio=3.13; 95% confidence interval=1.03–9.55) than caregivers with lower perceived stress after adjustment for age and smoking. This study provides the first evidence of strong associations between smoking and perceived stress and shortened salivary TL among caregivers of children with disabilities. Larger studies with detailed information on smoking status are warranted to confirm our findings. PMID:25256607

  4. Smoking and perceived stress in relation to short salivary telomere length among caregivers of children with disabilities.

    PubMed

    Chen, Xiaoli; Velez, Juan Carlos; Barbosa, Clarita; Pepper, Micah; Andrade, Asterio; Stoner, Lee; De Vivo, Immaculata; Gelaye, Bizu; Williams, Michelle A

    2015-01-01

    Telomere length (TL), the length of repeated DNA sequence that forms protective caps at the end of chromosomes, has emerged as a novel biomarker of cell aging and oxidative stress. There is increasing research exploring the associations of smoking and perceived stress with TL, and the results are inconsistent. This study aimed to examine whether smoking and perceived stress were associated with shortened salivary TL among primary caregivers of children with disabilities. Using a quantitative polymerase chain reaction method, salivary TL was assessed among 89 caregivers aged 19-69 years (87% were women) who took care of disabled children in the Patagonia Region, Chile. Interviewer-administered questionnaires were used to collect information on sociodemographic and lifestyle factors. The 14-item Perceived Stress Scale was used to assess perceived stress. Mean relative TL was 0.92 (standard error = 0.03). Smokers had age-adjusted mean TL that was 0.07 units lower (β = -0.07, standard error = 0.03; p = 0.012) than non-smokers. Smokers were 2.17 times more likely to have shorter TL ( < 0.73, the lowest quartile of TL) than non-smokers (odds ratio = 3.17; 95% confidence interval = 1.05-9.52) with adjustment for age and perceived stress. Caregivers with higher perceived stress were 2.13 times more likely to have shorter TL (odds ratio = 3.13; 95% confidence interval = 1.03-9.55) than caregivers with lower perceived stress after adjustment for age and smoking. This study provides the first evidence of strong associations between smoking and perceived stress and shortened salivary TL among caregivers of children with disabilities. Larger studies with detailed information on smoking status are warranted to confirm our findings.

  5. Extreme Telomere Length Dimorphism in the Tasmanian Devil and Related Marsupials Suggests Parental Control of Telomere Length

    PubMed Central

    Bender, Hannah S.; Murchison, Elizabeth P.; Pickett, Hilda A.; Deakin, Janine E.; Strong, Margaret A.; Conlan, Carly; McMillan, Daniel A.; Neumann, Axel A.; Greider, Carol W.; Hannon, Gregory J.; Reddel, Roger R.; Graves, Jennifer A. Marshall.

    2012-01-01

    Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii) are of particular interest in light of the emergence of devil facial tumour disease (DFTD), a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago. PMID:23049977

  6. Telomere Shortening and Associated Chromosomal Instability in Peripheral Blood Lymphocytes of Patients With Hodgkin's Lymphoma Prior to Any Treatment Are Predictive of Second Cancers

    SciTech Connect

    M'kacher, Radhia . E-mail: mkacher@igr.fr; Bennaceur-Griscelli, Annelise; Girinsky, Theodore; Koscielny, Serge; Delhommeau, Francois; Dossou, Julien; Violot, Dominique; Leclercq, Evelyne; Courtier, Marie Helene; Beron-Gaillard, Nadine; Assaf, Elias; Ribrag, Vincent; Carde, Patrice; Bourhis, Jean |; Feneux, Daniele; Bernheim, Alain; Parmentier, Claude

    2007-06-01

    Purpose: To investigate a potential link between telomere length, chromosomal instability, and the advent of a second cancer (SC) in patients with Hodgkin's lymphoma (HL), who are known to be at risk for SCs. This study was premised on the finding that telomere dysfunction and DNA repair pathways were related to many pathologic conditions. Methods and Materials: Three cohorts of patients with HL were studied: 73 who were prospectively followed >5 years after diagnosis (prospective HL cohort), 28 who developed a SC (SC HL cohort), and 18 long-term survivors with no evidence of disease or complication since their initial treatment (NED HL cohort). Telomere length was analyzed by a telomeric restriction fragment assay in peripheral blood lymphocytes. Thirty healthy donors and 70 patients with a newly diagnosed solid tumor were the control population. Results: Compared with controls, patients from the prospective HL cohort, before any treatment, showed age-independent shorter telomeres (mean, 8.3 vs. 11.7 kb in healthy donors; <6 kb in 18% in HL patients), increased spontaneous chromosomal abnormalities, and increased in vitro radiation sensitivity (p < 10{sup -4} each). After treatment, telomere shortening was associated with cytogenetic profiles characterized by the persistence of complex chromosomal rearrangement and clonal aberrations. Moreover, the two cases of SC in the prospective HL patients had short telomeres and CCR initially. In addition, the SC HL cohort was characterized by markedly short telomeres (6.6 vs. 9.7 kb in the NED HL cohort), the presence of complex chromosome rearrangements, and increased in vitro radiation sensitivity. Conclusions: An intimate relationship between pre-treatment telomere shortening, chromosomal instability, radiation sensitivity and occurrence of SC was found in HL patients.

  7. An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

    SciTech Connect

    Wang, Yisong; Giannone, Richard J; Wu, Jun; Gomez, Marla V; Liu, Yie

    2005-01-01

    Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient (mTert -/-) splenocytes and ES cells. Because telomerase deficiency leads to gradual loss of telomeric DNA in mTert -/- splenocytes and ES cells and eventually to chromosomes with telomere signal-free ends (SFEs), we examined these cell types for evidence of sister chromatid exchange at telomeres, and observed an increase in T-SCEs only in a subset of mTert -/- splenocytes or ES cells that possessed multiple SFEs. Furthermore, T-SCEs were more often detected in ES cells than in splenocytes that harbored a similar frequency of SFEs. In mTert heterozygous (mTert +/-) ES cells or splenocytes, which are known to exhibit a decrease in average telomere length but no SFEs, no increase in T-SCE was observed. In addition to T-SCE, other genomic rearrangements (i.e., SCE) were also significantly increased in mTert -/- ES cells possessing critically short telomeres, but not in splenocytes. Our results suggest that animals and cell culture differ in their ability to carry out genomic rearrangements as a means of maintaining telomere integrity when telomeres become critically shortened.

  8. Telomere length and the risk of lung cancer.

    PubMed

    Jang, Jin Sung; Choi, Yi Young; Lee, Won Kee; Choi, Jin Eun; Cha, Sung Ick; Kim, Yeon Jae; Kim, Chang Ho; Kam, Sin; Jung, Tae Hoon; Park, Jae Yong

    2008-07-01

    Telomeres play a key role in the maintenance of chromosome integrity and stability. There is growing evidence that short telomeres induce chromosome instability and thereby promote the development of cancer. We investigated the association of telomere length and the risk of lung cancer. Relative telomere length in peripheral blood lymphocytes was measured by quantitative polymerase chain reaction in 243 lung cancer patients and 243 healthy controls that were frequency-matched for age, sex and smoking status. Telomere length was significantly shorter in lung cancer patients than in controls (mean +/- standard deviation: 1.59 +/- 0.75 versus 2.16 +/- 1.10, P < 0.0001). When the subjects were categorized into quartiles based on telomere length, the risk of lung cancer was found to increase as telomere length shortened (P(trend) < 0.0001). In addition, when the median of telomere length was used as the cutoff between long and short telomeres, individuals with short telomeres were at a significantly higher risk of lung cancer than those with long telomeres (adjusted odds ratio = 3.15, 95% confidence interval = 2.12-4.67, P < 0.0001). When the cases were categorized by tumor histology, the effect of short telomere length on the risk of lung cancer was more pronounced in patients with small cell carcinoma than in those with squamous cell carcinoma and adenocarcinoma (P = 0.001, test for homogeneity). These findings suggest that shortening of the telomeres may be a risk factor for lung cancer, and therefore, the presence of shortened telomeres may be used as a marker for susceptibility to lung cancer.

  9. Mre11 and Blm-Dependent Formation of ALT-Like Telomeres in Ku-Deficient Ustilago maydis.

    PubMed

    Yu, Eun Young; Pérez-Martín, José; Holloman, William K; Lue, Neal F

    2015-10-01

    A subset of human cancer cells uses a specialized, aberrant recombination pathway known as ALT to maintain telomeres, which in these cells are characterized by complex aberrations including length heterogeneity, high levels of unpaired C-strand, and accumulation of extra-chromosomal telomere repeats (ECTR). These phenotypes have not been recapitulated in any standard budding or fission yeast mutant. We found that eliminating Ku70 or Ku80 in the yeast-like fungus Ustilago maydis results initially in all the characteristic telomere aberrations of ALT cancer cells, including C-circles, a highly specific marker of ALT. Subsequently the ku mutants experience permanent G2 cell cycle arrest, accompanied by loss of telomere repeats from chromosome ends and even more drastic accumulation of very short ECTRs (vsECTRs). The deletion of atr1 or chk1 rescued the lethality of the ku mutant, and "trapped" the telomere aberrations in the early ALT-like stage. Telomere abnormalities are telomerase-independent, but dramatically suppressed by deletion of mre11 or blm, suggesting major roles for these factors in the induction of the ALT pathway. In contrast, removal of other DNA damage response and repair factors such as Rad51 has disparate effects on the ALT phenotypes, suggesting that these factors process ALT intermediates or products. Notably, the antagonism of Ku and Mre11 in the induction of ALT is reminiscent of their roles in DSB resection, in which Blm is also known to play a key role. We suggest that an aberrant resection reaction may constitute an early trigger for ALT telomeres, and that the outcomes of ALT are distinct from DSB because of the unique telomere nucleoprotein structure.

  10. Normal telomere lengths found in cloned cattle.

    PubMed

    Tian, X C; Xu, J; Yang, X

    2000-11-01

    Success of cloning using adult somatic cells has been reported in sheep, mice and cattle. The report that 'Dolly' the sheep, the first clone from an adult mammal, inherited shortened telomeres from her cell donor and that her telomeres were further shortened by the brief culture of donor cells has raised serious scientific and public concerns about the 'genetic age' and potential developmental problems of cloned animals. This observation was challenged by a recent report that showed calves cloned from fetal cells have longer telomeres than their age-matched controls. The question remains whether Dolly's short telomeres were an exception or a general fact, which would differ from the telomeres of fetal-derived clones. PMID:11062462

  11. Telomere dysfunction causes alveolar stem cell failure.

    PubMed

    Alder, Jonathan K; Barkauskas, Christina E; Limjunyawong, Nathachit; Stanley, Susan E; Kembou, Frant; Tuder, Rubin M; Hogan, Brigid L M; Mitzner, Wayne; Armanios, Mary

    2015-04-21

    Telomere syndromes have their most common manifestation in lung disease that is recognized as idiopathic pulmonary fibrosis and emphysema. In both conditions, there is loss of alveolar integrity, but the underlying mechanisms are not known. We tested the capacity of alveolar epithelial and stromal cells from mice with short telomeres to support alveolar organoid colony formation and found that type 2 alveolar epithelial cells (AEC2s), the stem cell-containing population, were limiting. When telomere dysfunction was induced in adult AEC2s by conditional deletion of the shelterin component telomeric repeat-binding factor 2, cells survived but remained dormant and showed all the hallmarks of cellular senescence. Telomere dysfunction in AEC2s triggered an immune response, and this was associated with AEC2-derived up-regulation of cytokine signaling pathways that are known to provoke inflammation in the lung. Mice uniformly died after challenge with bleomycin, underscoring an essential role for telomere function in AEC2s for alveolar repair. Our data show that alveoloar progenitor senescence is sufficient to recapitulate the regenerative defects, inflammatory responses, and susceptibility to injury that are characteristic of telomere-mediated lung disease. They suggest alveolar stem cell failure is a driver of telomere-mediated lung disease and that efforts to reverse it may be clinically beneficial. PMID:25840590

  12. Structural and functional association of androgen receptor with telomeres in prostate cancer cells

    PubMed Central

    Zhou, Junying; Richardson, Michelle; Reddy, Vidyavathi; Menon, Mani; Barrack, Evelyn R.; Reddy, G. Prem-Veer; Kim, Sahn-Ho

    2013-01-01

    Telomeres protect the ends of linear chromosomes from being recognized as damaged DNA, and telomere stability is required for genome stability. Here we demonstrate that telomere stability in androgen receptor (AR)-positive LNCaP human prostate cancer cells is dependent on AR and androgen, as AR inactivation by AR antagonist bicalutamide (Casodex), AR-knockdown, or androgen-depletion caused telomere dysfunction, and the effect of androgen-depletion or Casodex was blocked by the addition of androgen. Notably, neither actinomycin D nor cycloheximide blocked the DNA damage response to Casodex, indicating that the role of AR in telomere stability is independent of its role in transcription. We also demonstrate that AR is a component of telomeres, as AR-bound chromatin contains telomeric DNA, and telomeric chromatin contains AR. Importantly, AR inactivation by Casodex caused telomere aberrations, including multiple abnormal telomere signals, remindful of a fragile telomere phenotype that has been described previously to result from defective telomere DNA replication. We suggest that AR plays an important role in telomere stability and replication of telomere DNA in prostate cancer cells, and that AR inactivation-mediated telomere dysfunction may contribute to genomic instability and progression of prostate cancer cells. PMID:23363843

  13. Telomeric transcriptome from Chironomus riparius (Diptera), a species with noncanonical telomeres.

    PubMed

    Martínez-Guitarte, J L; de la Fuente, M; Morcillo, G

    2014-06-01

    Although there are alternative telomere structures, most telomeres contain DNA arrays of short repeats (6-26 bp) maintained by telomerase. Like other diptera, Chironomus riparius has noncanonical telomeres and three subfamilies, TsA, TsB and TsC, of longer sequences (176 bp) are found at their chromosomal ends. Reverse transcription PCR was used to show that different RNAs are transcribed from these sequences. Only one strand from TsA sequences seems to render a noncoding RNA (named CriTER-A); transcripts from both TsB strands were found (CriTER-B and αCriTER-B) but no TsC transcripts were detected. Interestingly, these sequences showed a differential transcriptional response upon heat shock, and they were also differentially affected by inhibitors of RNA polymerase II and RNA polymerase III. A computer search for transcription factor binding sites revealed putative regulatory cis-elements within the transcribed sequence, reinforcing the experimental evidence which suggests that the telomeric repeat might function as a promoter. This work describes the telomeric transcriptome of an insect with non-telomerase telomeres, confirming the evolutionary conservation of telomere transcription. Our data reveal differences in the regulation of telomeric transcripts between control and stressful environmental conditions, supporting the idea that telomeric RNAs could have a relevant role in cellular metabolism in insect cells.

  14. Ciliary abnormalities due to defects in the retrograde transport protein DYNC2H1 in short-rib polydactyly syndrome.

    PubMed

    Merrill, Amy E; Merriman, Barry; Farrington-Rock, Claire; Camacho, Natalia; Sebald, Eiman T; Funari, Vincent A; Schibler, Matthew J; Firestein, Marc H; Cohn, Zachary A; Priore, Mary Ann; Thompson, Alicia K; Rimoin, David L; Nelson, Stanley F; Cohn, Daniel H; Krakow, Deborah

    2009-04-01

    The short-rib polydactyly (SRP) syndromes are a heterogeneous group of perinatal lethal skeletal disorders with polydactyly and multisystem organ abnormalities. Homozygosity by descent mapping in a consanguineous SRP family identified a genomic region that contained DYNC2H1, a cytoplasmic dynein involved in retrograde transport in the cilium. Affected individuals in the family were homozygous for an exon 12 missense mutation that predicted the amino acid substitution R587C. Compound heterozygosity for one missense and one null mutation was identified in two additional nonconsanguineous SRP families. Cultured chondrocytes from affected individuals showed morphologically abnormal, shortened cilia. In addition, the chondrocytes showed abnormal cytoskeletal microtubule architecture, implicating an altered microtubule network as part of the disease process. These findings establish SRP as a cilia disorder and demonstrate that DYNC2H1 is essential for skeletogenesis and growth.

  15. The asymmetry of telomere replication contributes to replicative senescence heterogeneity.

    PubMed

    Bourgeron, Thibault; Xu, Zhou; Doumic, Marie; Teixeira, Maria Teresa

    2015-10-15

    In eukaryotes, the absence of telomerase results in telomere shortening, eventually leading to replicative senescence, an arrested state that prevents further cell divisions. While replicative senescence is mainly controlled by telomere length, the heterogeneity of its onset is not well understood. This study proposes a mathematical model based on the molecular mechanisms of telomere replication and shortening to decipher the causes of this heterogeneity. Using simulations fitted on experimental data obtained from individual lineages of senescent Saccharomyces cerevisiae cells, we decompose the sources of senescence heterogeneity into interclonal and intraclonal components, and show that the latter is based on the asymmetry of the telomere replication mechanism. We also evidence telomere rank-switching events with distinct frequencies in short-lived versus long-lived lineages, revealing that telomere shortening dynamics display important variations. Thus, the intrinsic heterogeneity of replicative senescence and its consequences find their roots in the asymmetric structure of telomeres.

  16. XAV939 promotes apoptosis in a neuroblastoma cell line via telomere shortening.

    PubMed

    Tian, Xiaohong; Hou, Weijian; Bai, Shuling; Fan, Jun; Tong, Hao; Bai, Yu

    2014-11-01

    Telomeres, telomerase and tankyrase (TNKS) have an extremely important and special association with human cell aging and cancer. Telomerase activity is abnormally high in cancer cells and is accompanied by the overexpression of tankyrase 1 (TNKS1). TNKS1 is a positive regulator of telomerase activation and telomere extension in the human body, indicating that TNKS1 may be a possible therapeutic target for cancer. XAV939 is a small-molecule inhibitor of TNKS1. The objective of the present study was to investigate the apoptotic effect of XAV939 on the neuroblastoma (NB) SH-SY5Y cell line, as well as the change in telomere length and telomerase activity and elucidate the mechanism from this perspective. In the present study, we initially treated SH-SY5Y cells with XAV939 and RNA interference (RNAi)-TNKS1, and subsequently chose the optimal sequence for RNAi-TNKS1. We then measured the telomere length using quantitative real-time polymerase chain reaction (qPCR) assay, detected the telomerase activity using the ELISA kit, observed apoptotic morphology by transmission electron microscopy, and detected the percentages of apoptotic cells using flow cytometry and Hoechst 33342 staining. We also determined the invasive ability by a cell invasion assay. The results showed that short hairpin RNA-2 (shRNA-2) was the optimal sequence for RNAi-TNKS1. Treatment with both XAV939 and RNAi-TNKS1 shortened the telomere length, promoted apoptosis and reduced the invasive ability of the SH-SY5Y cells, yet had no effect on telomerase activity. XAV939 promoted apoptosis and reduced the invasiveness of SH-SY5Y cells dependent on telomere shortening, and further research should be conducted to clarify the exact mechanisms. This research may contribute to the cure of malignant NB using multi-targeted therapy with small-molecule agents.

  17. Telomere uncapping by the G-quadruplex ligand RHPS4 inhibits clonogenic tumour cell growth in vitro and in vivo consistent with a cancer stem cell targeting mechanism

    PubMed Central

    Phatak, P; Cookson, J C; Dai, F; Smith, V; Gartenhaus, R B; Stevens, M F G; Burger, A M

    2007-01-01

    The pentacyclic acridinium methosulfate salt RHPS4 induces the 3′single-stranded guanine-rich telomeric overhang to fold into a G-quadruplex structure. Stabilisation of the latter is incompatible with an attachment of telomerase to the telomere and thus G-quadruplex ligands can effectively inhibit both the catalytic and capping functions of telomerase. In this study, we examined mechanisms underlying telomere uncapping by RHPS4 in uterus carcinoma cells (UXF1138L) with short telomeres and compared the susceptibility of bulk and clonogenic cancer cells to the G-quadruplex ligand. We show that treatment of UXF1138L cells with RHPS4 leads to the displacement of the telomerase catalytic subunit (hTERT) from the nucleus, induction of telomere-initiated DNA-damage signalling and chromosome fusions. We further report that RHPS4 is more potent against cancer cells that grow as colonies in soft agar than cells growing as monolayers. Human cord blood and HEK293T embryonic kidney cell colony forming units, however, were more resistant to RHPS4. RHPS4-treated UXF1138L xenografts had a decreased clonogenicity, showed loss of nuclear hTERT expression and an induction of mitotic abnormalities compared with controls. Although single-agent RHPS4 had limited in vivo efficacy, a combination of RHPS4 with the mitotic spindle poison Taxol caused tumour remissions and further enhancement of telomere dysfunction. PMID:17406367

  18. Transcription and activation under environmental stress of the complex telomeric repeats of Chironomus thummi.

    PubMed

    Martínez-Guitarte, J L; Díez, J L; Morcillo, G

    2008-01-01

    In contrast to their traditional role, telomeres seem to behave as transcriptionally active regions. RNAs complementary to the short DNA repeats characteristic of telomerase-maintained telomeres have recently been identified in various mammalian cell lines, representing a new and unexpected element in telomere architecture. Here, we report the existence of transcripts complementary to telomeric sequences characteristic of Chironomus thummi telomeres. As in other Diptera, the non-canonical telomeres of chironomids lack the simple telomerase repeats and have instead more complex repetitive sequences. Northern blots of total RNA hybridized with telomere probes and RT-PCR with telomere-specific tailed primers confirm the existence of small non-coding RNAs of around 200 bp, the size of the DNA repeated telomeric unit. Telomere transcripts are heterogeneous in length, and they appear as a ladder pattern that probably corresponds to multimers of the repeat. Moreover, telomeres are activated under conditions of environmental stress, such as heat shock, appearing highly decondensed and densely labelled with acetylated H4 histone, as well as with RNA polymerase II antibodies, both marks of transcriptional activity. Changes in the expression levels of telomeric RNA were detected after heat shock. These findings provide evidence that transcriptional activity of the repetitive telomere sequences is an evolutionarily conserved feature, not limited to telomerase telomeres. The functional significance of this non-coding RNA as a new additional element in the context of telomere biology remains to be explained.

  19. Identification of Neuroblastoma Subgroups Based on Three-Dimensional Telomere Organization.

    PubMed

    Kuzyk, Alexandra; Gartner, John; Mai, Sabine

    2016-08-01

    Using 3D telomere quantitative fluorescence in situ hybridization, we determined the 3D telomere organization of 74 neuroblastoma tissue samples. Hierarchical cluster analysis of the measured telomere parameters identified three subgroups from our patient cohort. These subgroups have unique telomere profiles based on telomere length and nuclear architecture. Subgroups with higher levels of telomere dysfunction were comprised of tumors with greater numbers of telomeres, telomeric aggregates, and short telomeres (P<.0001). Tumors with greater telomere dysfunction were associated with unfavorable tumor characteristics (greater age at diagnosis, unfavorable histology, higher stage of disease, MYCN amplification, and higher MYCN expression) and poor prognostic risk (P<.001). Subgroups with greater telomere dysfunction also had higher intratumor heterogeneity. MYCN overexpression in two neuroblastoma cell lines with constitutively low MYCN expression induced changes in their telomere profile that were consistent with increased telomere dysfunction; this illustrates a functional relationship between MYCN and 3D telomere organization. This study demonstrates the ability to classify neuroblastomas based on the level of telomere dysfunction, which is a novel approach for this cancer. PMID:27567959

  20. Segregating YKU80 and TLC1 alleles underlying natural variation in telomere properties in wild yeast.

    PubMed

    Liti, Gianni; Haricharan, Svasti; Cubillos, Francisco A; Tierney, Anna L; Sharp, Sarah; Bertuch, Alison A; Parts, Leopold; Bailes, Elizabeth; Louis, Edward J

    2009-09-01

    In yeast, as in humans, telomere length varies among individuals and is controlled by multiple loci. In a quest to define the extent of variation in telomere length, we screened 112 wild-type Saccharomyces sensu stricto isolates. We found extensive telomere length variation in S. paradoxus isolates. This phenotype correlated with their geographic origin: European strains were observed to have extremely short telomeres (<150 bp), whereas American isolates had telomeres approximately three times as long (>400 bp). Insertions of a URA3 gene near telomeres allowed accurate analysis of individual telomere lengths and telomere position effect (TPE). Crossing the American and European strains resulted in F1 spores with a continuum of telomere lengths consistent with what would be predicted if many quantitative trait loci (QTLs) were involved in length maintenance. Variation in TPE is similarly quantitative but only weakly correlated with telomere length. Genotyping F1 segregants indicated several QTLs associated with telomere length and silencing variation. These QTLs include likely candidate genes but also map to regions where there are no known genes involved in telomeric properties. We detected transgressive segregation for both phenotypes. We validated by reciprocal hemizygosity that YKU80 and TLC1 are telomere-length QTLs in the two S. paradoxus subpopulations. Furthermore, we propose that sequence divergence within the Ku heterodimer generates negative epistasis within one of the allelic combinations (American-YKU70 and European-YKU80) resulting in very short telomeres. PMID:19763176

  1. Telomere shortening associated with increased genomic complexity in chronic lymphocytic leukemia.

    PubMed

    Dos Santos, Patricia; Panero, Julieta; Palau Nagore, Virginia; Stanganelli, Carmen; Bezares, Raimundo F; Slavutsky, Irma

    2015-11-01

    Telomeric dysfunction has been proposed as an emerging prognostic factor in chronic lymphocytic leukemia (CLL). We have explored the relationship between telomere length (TL) and chromosome alterations studied by fluorescence in situ hybridization (FISH) and conventional cytogenetics in 107 newly diagnosed CLL patients; 61 normal controls were also evaluated. Results were correlated with clinical parameters and outcome. Absolute TL measurement was carried out on DNA samples by real-time quantitative PCR. A significant telomere shortening in patients compared to controls was observed (p = 0.0001). The analysis taking into account FISH risk groups showed shorter TLs in cases with del11q/17p compared to patients with 13q14 deletion as a single alteration (p = 0.0037), no alterations (NA) (p = 0.028), and cases with abnormal karyotypes (p = 0.014). In addition, a significant TL reduction in cases with two or more anomalies with respect to those with NA (p = 0.033) and with one alteration (p = 0.045), and no differences compared to cases with deletions 11q/17p were observed. Patients with only one anomaly did not show statistical differences with respect to controls; meanwhile, a significant TL reduction in cases with two or more aberrations was observed (p = 0.025). The shortest telomeres were associated to 11q/17p deletion with significant differences compared to the remaining groups (p ≤ 0.045). Significantly shorter treatment free survival in patients with two or more alterations compared to those with NA plus one abnormality was observed (p = 0.0006). Our findings support the association between short TL and chromosome alterations in CLL and indicate the importance of telomere dysfunction in driving genomic instability in this pathology.

  2. Telomere length variations in aging and age-related diseases.

    PubMed

    Rizvi, Saliha; Raza, Syed Tasleem; Mahdi, Farzana

    2014-01-01

    Telomeres are gene sequences present at chromosomal ends and are responsible for maintaining genome integrity. Telomere length is maximum at birth and decreases progressively with advancing age and thus is considered as a biomarker of chronological aging. This age associated decrease in the length of telomere is linked to various ageing associated diseases like diabetes, hypertension, Alzheimer's disease, cancer etc. and their associated complications. Telomere length is a result of combined effect of oxidative stress, inflammation and repeated cell replication on it, and thus forming an association between telomere length and chronological aging and related diseases. Thus, decrease in telomere length was found to be important in determining both, the variations in longevity and age-related diseases in an individual. Ongoing and progressive research in the field of telomere length dynamics has proved that aging and age-related diseases apart from having a synergistic effect on telomere length were also found to effect telomere length independently also. Here a short description about telomere length variations and its association with human aging and age-related diseases is reviewed.

  3. PML is required for telomere stability in non-neoplastic human cells.

    PubMed

    Marchesini, M; Matocci, R; Tasselli, L; Cambiaghi, V; Orleth, A; Furia, L; Marinelli, C; Lombardi, S; Sammarelli, G; Aversa, F; Minucci, S; Faretta, M; Pelicci, P G; Grignani, F

    2016-04-01

    Telomeres interact with numerous proteins, including components of the shelterin complex, whose alteration, similarly to proliferation-induced telomere shortening, initiates cellular senescence. In tumors, telomere length is maintained by Telomerase activity or by the Alternative Lengthening of Telomeres mechanism, whose hallmark is the telomeric localization of the promyelocytic leukemia (PML) protein. Whether PML contributes to telomeres maintenance in normal cells is unknown. We show that in normal human fibroblasts the PML protein associates with few telomeres, preferentially when they are damaged. Proliferation-induced telomere attrition or their damage due to alteration of the shelterin complex enhances the telomeric localization of PML, which is increased in human T-lymphocytes derived from patients genetically deficient in telomerase. In normal fibroblasts, PML depletion induces telomere damage, nuclear and chromosomal abnormalities, and senescence. Expression of the leukemia protein PML/RARα in hematopoietic progenitors displaces PML from telomeres and induces telomere shortening in the bone marrow of pre-leukemic mice. Our work provides a novel view of the physiologic function of PML, which participates in telomeres surveillance in normal cells. Our data further imply that a diminished PML function may contribute to cell senescence, genomic instability, and tumorigenesis.

  4. Telomere Length as a Quantitative Trait: Genome-Wide Survey and Genetic Mapping of Telomere Length-Control Genes in Yeast

    PubMed Central

    Gatbonton, Tonibelle; Imbesi, Maria; Nelson, Melisa; Akey, Joshua M; Ruderfer, Douglas M; Kruglyak, Leonid; Simon, Julian A; Bedalov, Antonio

    2006-01-01

    Telomere length-variation in deletion strains of Saccharomyces cerevisiae was used to identify genes and pathways that regulate telomere length. We found 72 genes that when deleted confer short telomeres, and 80 genes that confer long telomeres relative to those of wild-type yeast. Among identified genes, 88 have not been previously implicated in telomere length control. Genes that regulate telomere length span a variety of functions that can be broadly separated into telomerase-dependent and telomerase-independent pathways. We also found 39 genes that have an important role in telomere maintenance or cell proliferation in the absence of telomerase, including genes that participate in deoxyribonucleotide biosynthesis, sister chromatid cohesion, and vacuolar protein sorting. Given the large number of loci identified, we investigated telomere lengths in 13 wild yeast strains and found substantial natural variation in telomere length among the isolates. Furthermore, we crossed a wild isolate to a laboratory strain and analyzed telomere length in 122 progeny. Genome-wide linkage analysis among these segregants revealed two loci that account for 30%–35% of telomere length-variation between the strains. These findings support a general model of telomere length-variation in outbred populations that results from polymorphisms at a large number of loci. Furthermore, our results laid the foundation for studying genetic determinants of telomere length-variation and their roles in human disease. PMID:16552446

  5. Short antisense-locked nucleic acids (all-LNAs) correct alternative splicing abnormalities in myotonic dystrophy

    PubMed Central

    Wojtkowiak-Szlachcic, Agnieszka; Taylor, Katarzyna; Stepniak-Konieczna, Ewa; Sznajder, Lukasz J.; Mykowska, Agnieszka; Sroka, Joanna; Thornton, Charles A.; Sobczak, Krzysztof

    2015-01-01

    Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by expansion of CTG triplet repeats in 3′-untranslated region of DMPK gene. The pathomechanism of DM1 is driven by accumulation of toxic transcripts containing expanded CUG repeats (CUGexp) in nuclear foci which sequester several factors regulating RNA metabolism, such as Muscleblind-like proteins (MBNLs). In this work, we utilized very short chemically modified antisense oligonucleotides composed exclusively of locked nucleic acids (all-LNAs) complementary to CUG repeats, as potential therapeutic agents against DM1. Our in vitro data demonstrated that very short, 8- or 10-unit all-LNAs effectively bound the CUG repeat RNA and prevented the formation of CUGexp/MBNL complexes. In proliferating DM1 cells as well as in skeletal muscles of DM1 mouse model the all-LNAs induced the reduction of the number and size of CUGexp foci and corrected MBNL-sensitive alternative splicing defects with high efficacy and specificity. The all-LNAs had low impact on the cellular level of CUGexp-containing transcripts and did not affect the expression of other transcripts with short CUG repeats. Our data strongly indicate that short all-LNAs complementary to CUG repeats are a promising therapeutic tool against DM1. PMID:25753670

  6. Microstructural Abnormalities of Short-Distance White Matter Tracts in Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Shukla, Dinesh K.; Keehn, Brandon; Smylie, Daren M.; Muller, Ralph-Axel

    2011-01-01

    Recent functional connectivity magnetic resonance imaging and diffusion tensor imaging (DTI) studies have suggested atypical functional connectivity and reduced integrity of long-distance white matter fibers in autism spectrum disorder (ASD). However, evidence for short-distance white matter fibers is still limited, despite some speculation of…

  7. Telomeric RNAs are essential to maintain telomeres

    PubMed Central

    Montero, Juan José; López de Silanes, Isabel; Graña, Osvaldo; Blasco, Maria A.

    2016-01-01

    Telomeres are transcribed generating long non-coding RNAs known as TERRA. Deciphering the role of TERRA has been one of the unsolved issues of telomere biology in the past decade. This has been, in part, due to lack of knowledge on the TERRA loci, thus preventing functional genetic studies. Here, we describe that long non-coding RNAs with TERRA features are transcribed from the human 20q and Xp subtelomeres. Deletion of the 20q locus by using the CRISPR-Cas9 technology causes a dramatic decrease in TERRA levels, while deletion of the Xp locus does not result in decreased TERRA levels. Strikingly, 20q-TERRA ablation leads to dramatic loss of telomere sequences and the induction of a massive DNA damage response. These findings identify chromosome 20q as a main TERRA locus in human cells and represent the first demonstration in any organism of the essential role of TERRA in the maintenance of telomeres. PMID:27531349

  8. Plant telomeres and telomerases. A review.

    PubMed

    McKnight, T D; Fitzgerald, M S; Shippen, D E

    1997-11-01

    Barbara McClintock began investigating plant telomeres during the 1930s, but little additional work was done in this area until a telomeric DNA sequence was isolated and characterized from Arabidopsis thaliana in 1988. This sequence, a simple repeat of the heptanucleotide 5'-TTTAGGG-3', has been found in telomeres of almost all plants analyzed. Telomere length in plants, which can be a long as 75 kb or as short as 2 kb, is controlled by both genetic and developmental factors. The major mechanism for synthesis of telomeres is telomerase, a ribonucleoprotein with reverse transcriptase activity. Telomerase expression is highly regulated in both plants and animals. For example, there is little or no detectable expression of telomerase in most vegetative tissues of plants nor in most somatic tissues of animals. In contrast to animals, plants do not specify a germ line until late in development, but telomerase is reactivated during flowering, possibly to ensure that gametes and embryos arising from them inherit fully functional chromosomes. Telomerase is also highly expressed in plant tissue culture cells, as might be expected for cells with an unlimited capacity for proliferation. Despite recent progress in investigating plant telomeres and telomerase at the molecular level, there is still much more to learn, especially concerning the developmental control of telomerase activity. PMID:9467846

  9. Plant telomeres and telomerases. A review.

    PubMed

    McKnight, T D; Fitzgerald, M S; Shippen, D E

    1997-11-01

    Barbara McClintock began investigating plant telomeres during the 1930s, but little additional work was done in this area until a telomeric DNA sequence was isolated and characterized from Arabidopsis thaliana in 1988. This sequence, a simple repeat of the heptanucleotide 5'-TTTAGGG-3', has been found in telomeres of almost all plants analyzed. Telomere length in plants, which can be a long as 75 kb or as short as 2 kb, is controlled by both genetic and developmental factors. The major mechanism for synthesis of telomeres is telomerase, a ribonucleoprotein with reverse transcriptase activity. Telomerase expression is highly regulated in both plants and animals. For example, there is little or no detectable expression of telomerase in most vegetative tissues of plants nor in most somatic tissues of animals. In contrast to animals, plants do not specify a germ line until late in development, but telomerase is reactivated during flowering, possibly to ensure that gametes and embryos arising from them inherit fully functional chromosomes. Telomerase is also highly expressed in plant tissue culture cells, as might be expected for cells with an unlimited capacity for proliferation. Despite recent progress in investigating plant telomeres and telomerase at the molecular level, there is still much more to learn, especially concerning the developmental control of telomerase activity.

  10. Telomere dysfunction and chromothripsis.

    PubMed

    Ernst, Aurélie; Jones, David T W; Maass, Kendra K; Rode, Agata; Deeg, Katharina I; Jebaraj, Billy Michael Chelliah; Korshunov, Andrey; Hovestadt, Volker; Tainsky, Michael A; Pajtler, Kristian W; Bender, Sebastian; Brabetz, Sebastian; Gröbner, Susanne; Kool, Marcel; Devens, Frauke; Edelmann, Jennifer; Zhang, Cindy; Castelo-Branco, Pedro; Tabori, Uri; Malkin, David; Rippe, Karsten; Stilgenbauer, Stephan; Pfister, Stefan M; Zapatka, Marc; Lichter, Peter

    2016-06-15

    Chromothripsis is a recently discovered form of genomic instability, characterized by tens to hundreds of clustered DNA rearrangements resulting from a single dramatic event. Telomere dysfunction has been suggested to play a role in the initiation of this phenomenon, which occurs in a large number of tumor entities. Here, we show that telomere attrition can indeed lead to catastrophic genomic events, and that telomere patterns differ between cells analyzed before and after such genomic catastrophes. Telomere length and telomere stabilization mechanisms diverge between samples with and without chromothripsis in a given tumor subtype. Longitudinal analyses of the evolution of chromothriptic patterns identify either stable patterns between matched primary and relapsed tumors, or loss of the chromothriptic clone in the relapsed specimen. The absence of additional chromothriptic events occurring between the initial tumor and the relapsed tumor sample points to telomere stabilization after the initial chromothriptic event which prevents further shattering of the genome. PMID:26856307

  11. Decreasing initial telomere length in humans intergenerationally understates age-associated telomere shortening.

    PubMed

    Holohan, Brody; De Meyer, Tim; Batten, Kimberly; Mangino, Massimo; Hunt, Steven C; Bekaert, Sofie; De Buyzere, Marc L; Rietzschel, Ernst R; Spector, Tim D; Wright, Woodring E; Shay, Jerry W

    2015-08-01

    Telomere length shortens with aging, and short telomeres have been linked to a wide variety of pathologies. Previous studies suggested a discrepancy in age-associated telomere shortening rate estimated by cross-sectional studies versus the rate measured in longitudinal studies, indicating a potential bias in cross-sectional estimates. Intergenerational changes in initial telomere length, such as that predicted by the previously described effect of a father's age at birth of his offspring (FAB), could explain the discrepancy in shortening rate measurements. We evaluated whether changes occur in initial telomere length over multiple generations in three large datasets and identified paternal birth year (PBY) as a variable that reconciles the difference between longitudinal and cross-sectional measurements. We also clarify the association between FAB and offspring telomere length, demonstrating that this effect is substantially larger than reported in the past. These results indicate the presence of a downward secular trend in telomere length at birth over generational time with potential public health implications.

  12. Decreasing initial telomere length in humans intergenerationally understates age-associated telomere shortening

    PubMed Central

    Holohan, Brody; De Meyer, Tim; Batten, Kimberly; Mangino, Massimo; Hunt, Steven C; Bekaert, Sofie; De Buyzere, Marc L; Rietzschel, Ernst R; Spector, Tim D; Wright, Woodring E; Shay, Jerry W

    2015-01-01

    Telomere length shortens with aging, and short telomeres have been linked to a wide variety of pathologies. Previous studies suggested a discrepancy in age-associated telomere shortening rate estimated by cross-sectional studies versus the rate measured in longitudinal studies, indicating a potential bias in cross-sectional estimates. Intergenerational changes in initial telomere length, such as that predicted by the previously described effect of a father’s age at birth of his offspring (FAB), could explain the discrepancy in shortening rate measurements. We evaluated whether changes occur in initial telomere length over multiple generations in three large datasets and identified paternal birth year (PBY) as a variable that reconciles the difference between longitudinal and cross-sectional measurements. We also clarify the association between FAB and offspring telomere length, demonstrating that this effect is substantially larger than reported in the past. These results indicate the presence of a downward secular trend in telomere length at birth over generational time with potential public health implications. PMID:25952108

  13. Unraveling the pathogenesis of Hoyeraal-Hreidarsson syndrome, a complex telomere biology disorder.

    PubMed

    Glousker, Galina; Touzot, Fabien; Revy, Patrick; Tzfati, Yehuda; Savage, Sharon A

    2015-08-01

    Hoyeraal-Hreidarsson (HH) syndrome is a multisystem genetic disorder characterized by very short telomeres and considered a clinically severe variant of dyskeratosis congenita. The main cause of mortality, usually in early childhood, is bone marrow failure. Mutations in several telomere biology genes have been reported to cause HH in about 60% of the HH patients, but the genetic defects in the rest of the patients are still unknown. Understanding the aetiology of HH and its diverse manifestations is challenging because of the complexity of telomere biology and the multiple telomeric and non-telomeric functions played by telomere-associated proteins in processes such as telomere replication, telomere protection, DNA damage response and ribosome and spliceosome assembly. Here we review the known clinical complications, molecular defects and germline mutations associated with HH, and elucidate possible mechanistic explanations and remaining questions in our understanding of the disease.

  14. Quantification of telomere length by FISH and laser scanning cytometry

    NASA Astrophysics Data System (ADS)

    Mahoney, John E.; Sahin, Ergun; Jaskelioff, Mariela; Chin, Lynda; DePinho, Ronald A.; Protopopov, Alexei I.

    2008-02-01

    Telomeres play a critical role in the maintenance of chromosomal stability. Telomere erosion, coupled with loss of DNA damage checkpoint function, results in genomic instability that promotes the development of cancer. The critical role of telomere dynamics in cancer has motivated the development of technologies designed to monitor telomere reserves in a highly quantitative and high-throughput manner in humans and model organisms. To this end, we have adapted and modified two established technologies, telomere-FISH and laser scanning cytometry. Specifically, we have produced a number of enhancements to the iCys LSC (CompuCyte) package including software updates, use of 60X dry objectives, and increased spatial resolution by 0.2 um size of stage steps. In addition, the 633 nm HeNe laser was replaced with a 532 nm green diode laser to better match the viewing options. Utilization of telomere-deficient mouse cells with short dysfunctional telomeres and matched telomerase reconstituted cultures demonstrated significantly higher mean integral specific fluorescence values for mTR transfectants relative to empty vector controls: 4.485M vs. 1.362M (p<0.0001). Histograms of average telomere intensities for individual cells were obtained and demonstrated intercellular heterogeneity in telomere lengths. The validation of the approach derives from a strong correlation between iCys LSC values and Southern blotting. This validated method greatly increases our experimental throughput and objectivity.

  15. Telomere loss: mitotic clock or genetic time bomb?

    PubMed

    Harley, C B

    1991-01-01

    The Holy Grail of gerontologists investigating cellular senescence is the mechanism responsible for the finite proliferative capacity of somatic cells. In 1973, Olovnikov proposed that cells lose a small amount of DNA following each round of replication due to the inability of DNA polymerase to fully replicate chromosome ends (telomeres) and that eventually a critical deletion causes cell death. Recent observations showing that telomeres of human somatic cells act as a mitotic clock, shortening with age both in vitro and in vivo in a replication dependent manner, support this theory's premise. In addition, since telomeres stabilize chromosome ends against recombination, their loss could explain the increased frequency of dicentric chromosomes observed in late passage (senescent) fibroblasts and provide a checkpoint for regulated cell cycle exit. Sperm telomeres are longer than somatic telomeres and are maintained with age, suggesting that germ line cells may express telomerase, the ribonucleoprotein enzyme known to maintain telomere length in immortal unicellular eukaryotes. As predicted, telomerase activity has been found in immortal, transformed human cells and tumour cell lines, but not in normal somatic cells. Telomerase activation may be a late, obligate event in immortalization since many transformed cells and tumour tissues have critically short telomeres. Thus, telomere length and telomerase activity appear to be markers of the replicative history and proliferative potential of cells; the intriguing possibility remains that telomere loss is a genetic time bomb and hence causally involved in cell senescence and immortalization.

  16. Robust algorithmic detection of the developed cardiac pathologies and emerging or transient abnormalities from short periods of RR data

    NASA Astrophysics Data System (ADS)

    Gavrishchaka, Valeriy V.; Senyukova, Olga

    2011-06-01

    Numerous research efforts and clinical testing have confirmed validity of heart rate variability (HRV) analysis as one of the cardiac diagnostics modalities. The majority of HRV analysis tools currently used in practice are based on linear indicators. Methods from nonlinear dynamics (NLD) provide more natural modeling framework for adaptive biological systems with multiple feedback loops. Compared to linear indicators, many NLD-based measures are much less sensitive to data artifacts and non-stationarity. However, majority of NLD measures require long time series for stable calculation. Similar restrictions also apply for linear indicators. Such requirements could drastically limit practical usability of HRV analysis in many applications, including express diagnostics, early indication of subtle directional changes during personalization of medical treatment, and robust detection of emerging or transient abnormalities. Recently we have illustrated that these challenges could be overcome by using classification framework based on boosting-like ensemble learning techniques that are capable of discovering robust meta-indicators from existing HRV measures and other incomplete empirical knowledge. In this paper we demonstrate universality of such meta-indicators and discuss operational details of their practical usage. Using such pathology examples as congestive heart failure (CHF) and arrhythmias, we show that classifiers trained on short RR segments (down to several minutes) could achieve reasonable classification accuracy (˜80-85% and higher). These indicators calculated from longer RR segments could be applicable for accurate diagnostics with classification accuracy approaching 100%. In addition, it is feasible to discover single "normal-abnormal" meta-classifier capable of detecting multiple abnormalities.

  17. Telomere biology: Rationale for diagnostics and therapeutics in cancer.

    PubMed

    Rousseau, Philippe; Autexier, Chantal

    2015-01-01

    The key step of carcinogenesis is the malignant transformation which is fundamentally a telomere biology dysfunction permitting cells to bypass the Hayflick limit and to divide indefinitely and uncontrollably. Thus all partners and structures involved in normal and abnormal telomere maintenance, protection and lengthening can be considered as potential anti-cancer therapeutic targets. In this Point of View we discuss, highlight and provide new perspectives from the current knowledge and understanding to position the different aspects of telomere biology and dysfunction as diagnostic, preventive and curative tools in the field of cancer.

  18. Short-Term Treatment with Bisphenol-A Leads to Metabolic Abnormalities in Adult Male Mice

    PubMed Central

    Batista, Thiago M.; Alonso-Magdalena, Paloma; Vieira, Elaine; Amaral, Maria Esmeria C.; Cederroth, Christopher R.; Nef, Serge; Quesada, Ivan; Carneiro, Everardo M.; Nadal, Angel

    2012-01-01

    Bisphenol-A (BPA) is one of the most widespread endocrine disrupting chemicals (EDC) used as the base compound in the manufacture of polycarbonate plastics. Although evidence points to consider exposure to BPA as a risk factor for insulin resistance, its actions on whole body metabolism and on insulin-sensitive tissues are still unclear. The aim of the present work was to study the effects of low doses of BPA in insulin-sensitive peripheral tissues and whole body metabolism in adult mice. Adult mice were treated with subcutaneous injection of 100 µg/kg BPA or vehicle for 8 days. Whole body energy homeostasis was assessed with in vivo indirect calorimetry. Insulin signaling assays were conducted by western blot analysis. Mice treated with BPA were insulin resistant and had increased glucose-stimulated insulin release. BPA-treated mice had decreased food intake, lower body temperature and locomotor activity compared to control. In skeletal muscle, insulin-stimulated tyrosine phosphorylation of the insulin receptor β subunit was impaired in BPA-treated mice. This impairment was associated with a reduced insulin-stimulated Akt phosphorylation in the Thr308 residue. Both skeletal muscle and liver displayed an upregulation of IRS-1 protein by BPA. The mitogen-activated protein kinase (MAPK) signaling pathway was also impaired in the skeletal muscle from BPA-treated mice. In the liver, BPA effects were of lesser intensity with decreased insulin-stimulated tyrosine phosphorylation of the insulin receptor β subunit. In conclusion, short-term treatment with low doses of BPA slows down whole body energy metabolism and disrupts insulin signaling in peripheral tissues. Thus, our findings support the notion that BPA can be considered a risk factor for the development of type 2 diabetes. PMID:22470480

  19. Telomere Length and the Cancer-Atherosclerosis Trade-Off.

    PubMed

    Stone, Rivka C; Horvath, Kent; Kark, Jeremy D; Susser, Ezra; Tishkoff, Sarah A; Aviv, Abraham

    2016-07-01

    Modern humans, the longest-living terrestrial mammals, display short telomeres and repressed telomerase activity in somatic tissues compared with most short-living small mammals. The dual trait of short telomeres and repressed telomerase might render humans relatively resistant to cancer compared with short-living small mammals. However, the trade-off for cancer resistance is ostensibly increased age-related degenerative diseases, principally in the form of atherosclerosis. In this communication, we discuss (a) the genetics of human telomere length, a highly heritable complex trait that is influenced by genetic ancestry, sex, and paternal age at conception, (b) how cancer might have played a role in the evolution of telomere biology across mammals, (c) evidence that in modern humans telomere length is a determinant (rather than only a biomarker) of cancer and atherosclerosis, and (d) the potential influence of relatively recent evolutionary forces in fashioning the variation in telomere length across and within populations, and their likely lasting impact on major diseases in humans. Finally, we propose venues for future research on human telomere genetics in the context of its potential role in shaping the modern human lifespan. PMID:27386863

  20. Telomere Length and the Cancer–Atherosclerosis Trade-Off

    PubMed Central

    Stone, Rivka C.; Horvath, Kent; Kark, Jeremy D.; Susser, Ezra; Tishkoff, Sarah A.; Aviv, Abraham

    2016-01-01

    Modern humans, the longest-living terrestrial mammals, display short telomeres and repressed telomerase activity in somatic tissues compared with most short-living small mammals. The dual trait of short telomeres and repressed telomerase might render humans relatively resistant to cancer compared with short-living small mammals. However, the trade-off for cancer resistance is ostensibly increased age-related degenerative diseases, principally in the form of atherosclerosis. In this communication, we discuss (a) the genetics of human telomere length, a highly heritable complex trait that is influenced by genetic ancestry, sex, and paternal age at conception, (b) how cancer might have played a role in the evolution of telomere biology across mammals, (c) evidence that in modern humans telomere length is a determinant (rather than only a biomarker) of cancer and atherosclerosis, and (d) the potential influence of relatively recent evolutionary forces in fashioning the variation in telomere length across and within populations, and their likely lasting impact on major diseases in humans. Finally, we propose venues for future research on human telomere genetics in the context of its potential role in shaping the modern human lifespan. PMID:27386863

  1. Hoyeraal-Hreidarsson syndrome caused by a germline mutation in the TEL patch of the telomere protein TPP1

    PubMed Central

    Kocak, Hande; Ballew, Bari J.; Bisht, Kamlesh; Eggebeen, Rebecca; Hicks, Belynda D.; Suman, Shalabh; O’Neil, Adri; Giri, Neelam; Maillard, Ivan; Alter, Blanche P.; Keegan, Catherine E.; Nandakumar, Jayakrishnan

    2014-01-01

    Germline mutations in telomere biology genes cause dyskeratosis congenita (DC), an inherited bone marrow failure and cancer predisposition syndrome. DC is a clinically heterogeneous disorder diagnosed by the triad of dysplastic nails, abnormal skin pigmentation, and oral leukoplakia; Hoyeraal-Hreidarsson syndrome (HH), a clinically severe variant of DC, also includes cerebellar hypoplasia, immunodeficiency, and intrauterine growth retardation. Approximately 70% of DC cases are associated with a germline mutation in one of nine genes, the products of which are all involved in telomere biology. Using exome sequencing, we identified mutations in Adrenocortical Dysplasia Homolog (ACD) (encoding TPP1), a component of the telomeric shelterin complex, in one family affected by HH. The proband inherited a deletion from his father and a missense mutation from his mother, resulting in extremely short telomeres and a severe clinical phenotype. Characterization of the mutations revealed that the single-amino-acid deletion affecting the TEL patch surface of the TPP1 protein significantly compromises both telomerase recruitment and processivity, while the missense mutation in the TIN2-binding region of TPP1 is not as clearly deleterious to TPP1 function. Our results emphasize the critical roles of the TEL patch in proper stem cell function and demonstrate that TPP1 is the second shelterin component (in addition to TIN2) to be implicated in DC. PMID:25233904

  2. Sde2: A novel nuclear protein essential for telomeric silencing and genomic stability in Schizosaccharomyces pombe

    SciTech Connect

    Sugioka-Sugiyama, Rie; Sugiyama, Tomoyasu

    2011-03-18

    Research highlights: {yields} Sde2 is essential for telomere silencing. {yields} Sde2 is involved in the maintenance of genomic stability. {yields} Sde2 promotes the recruitment of SHREC, a histone deacetylase complex, to telomeres. -- Abstract: Telomeres, specialized domains assembled at the ends of linear chromosomes, are essential for genomic stability in eukaryotes. The formation and maintenance of telomeres are governed by numerous factors such as telomeric repeats, telomere-binding proteins, heterochromatin proteins, and telomerase. Here, we report Sde2, a novel nuclear protein essential for telomeric silencing and genomic stability in the fission yeast Schizosaccharomyces pombe. A deficiency in sde2 results in the derepression of the ura4{sup +} gene inserted near telomeric repeats, and the noncoding transcripts from telomeric regions accumulate in sde2{Delta} cells. The loss of Sde2 function compromises transcriptional silencing at telomeres, and this silencing defect is accompanied by increased levels of acetylated histone H3K14 and RNA polymerase II occupancy at telomeres as well as reduced recruitment of the SNF2 ATPase/histone deacetylase-containing complex SHREC to telomeres. Deletion of sde2 also leads to a higher frequency of mitotic minichromosome loss, and sde2{Delta} cells often form asci that contain spores in abnormal numbers, shapes, or both. In addition, sde2{Delta} cells are highly sensitive to several stresses, including high/low temperatures, bleomycin, which induces DNA damage, and thiabendazole, a microtubule-destabilizing agent. Furthermore, Sde2 genetically interacts with the telomere regulators Taz1, Pof3, and Ccq1. These findings demonstrate that Sde2 cooperates with other telomere regulators to maintain functional telomeres, thereby preventing genomic instability.

  3. Telomere biology: cancer firewall or aging clock?

    PubMed

    Mitteldorf, J J

    2013-09-01

    It has been a decade since the first surprising discovery that longer telomeres in humans are statistically associated with longer life expectancies. Since then, it has been firmly established that telomere shortening imposes an individual fitness cost in a number of mammalian species, including humans. But telomere shortening is easily avoided by application of telomerase, an enzyme which is coded into nearly every eukaryotic genome, but whose expression is suppressed most of the time. This raises the question how the sequestration of telomerase might have evolved. The predominant assumption is that in higher organisms, shortening telomeres provide a firewall against tumor growth. A more straightforward interpretation is that telomere attrition provides an aging clock, reliably programming lifespans. The latter hypothesis is routinely rejected by most biologists because the benefit of programmed lifespan applies only to the community, and in fact the individual pays a substantial fitness cost. There is a long-standing skepticism that the concept of fitness can be applied on a communal level, and of group selection in general. But the cancer hypothesis is problematic as well. Animal studies indicate that there is a net fitness cost in sequestration of telomerase, even when cancer risk is lowered. The hypothesis of protection against cancer has never been tested in animals that actually limit telomerase expression, but only in mice, whose lifespans are not telomerase-limited. And human medical evidence suggests a net aggravation of cancer risk from the sequestration of telomerase, because cells with short telomeres are at high risk of neoplastic transformation, and they also secrete cytokines that exacerbate inflammation globally. The aging clock hypothesis fits well with what is known about ancestral origins of telomerase sequestration, and the prejudices concerning group selection are without merit. If telomeres are an aging clock, then telomerase makes an

  4. Telomere regulation during ageing and tumorigenesis of the grey mouse lemur.

    PubMed

    Trochet, Delphine; Mergui, Xénia; Ivkovic, Ivana; Porreca, Rosa Maria; Gerbault-Seureau, Michèle; Sidibe, Assitan; Richard, Florence; Londono-Vallejo, Arturo; Perret, Martine; Aujard, Fabienne; Riou, Jean-François

    2015-06-01

    Telomere erosion leading to replicative senescence has been well documented in human and anthropoid primates, and provides a clue against tumorigenesis. In contrast, other mammals, such as laboratory mice, with short lifespan and low body weight mass have different telomere biology without replicative senescence. We analyzed telomere biology in the grey mouse lemur, a small prosimian model with a relative long lifespan currently used in ageing research. We report an average telomere length by telomere restriction fragment (TRF) among the longest reported so far for a primate species (25-30 kb), but without detectable overall telomere shortening with ageing on blood samples. However, we demonstrate using universal STELA (Single Telomere Length Amplification) the existence of short telomeres, the increase of which, while correlating with ageing might be related to another mechanism than replicative senescence. We also found a low stringency of telomerase restriction in tissues and an ease to immortalize fibroblasts in vitro upon spontaneous telomerase activation. Finally, we describe the first grey mouse lemur cancer cell line showing a dramatic telomere shortening and high telomerase activity associated with polyploidy. Our overall results suggest that telomere biology in grey mouse lemur is an exception among primates, with at best a physiologically limited replicative telomere ageing and closest to that observed in small rodents.

  5. Computel: computation of mean telomere length from whole-genome next-generation sequencing data.

    PubMed

    Nersisyan, Lilit; Arakelyan, Arsen

    2015-01-01

    Telomeres are the ends of eukaryotic chromosomes, consisting of consecutive short repeats that protect chromosome ends from degradation. Telomeres shorten with each cell division, leading to replicative cell senescence. Deregulation of telomere length homeostasis is associated with the development of various age-related diseases and cancers. A number of experimental techniques exist for telomere length measurement; however, until recently, the absence of tools for extracting telomere lengths from high-throughput sequencing data has significantly obscured the association of telomere length with molecular processes in normal and diseased conditions. We have developed Computel, a program in R for computing mean telomere length from whole-genome next-generation sequencing data. Computel is open source, and is freely available at https://github.com/lilit-nersisyan/computel. It utilizes a short-read alignment-based approach and integrates various popular tools for sequencing data analysis. We validated it with synthetic and experimental data, and compared its performance with the previously available software. The results have shown that Computel outperforms existing software in accuracy, independence of results from sequencing conditions, stability against inherent sequencing errors, and better ability to distinguish pure telomeric sequences from interstitial telomeric repeats. By providing a highly reliable methodology for determining telomere lengths from whole-genome sequencing data, Computel should help to elucidate the role of telomeres in cellular health and disease.

  6. Telomere regulation during ageing and tumorigenesis of the grey mouse lemur.

    PubMed

    Trochet, Delphine; Mergui, Xénia; Ivkovic, Ivana; Porreca, Rosa Maria; Gerbault-Seureau, Michèle; Sidibe, Assitan; Richard, Florence; Londono-Vallejo, Arturo; Perret, Martine; Aujard, Fabienne; Riou, Jean-François

    2015-06-01

    Telomere erosion leading to replicative senescence has been well documented in human and anthropoid primates, and provides a clue against tumorigenesis. In contrast, other mammals, such as laboratory mice, with short lifespan and low body weight mass have different telomere biology without replicative senescence. We analyzed telomere biology in the grey mouse lemur, a small prosimian model with a relative long lifespan currently used in ageing research. We report an average telomere length by telomere restriction fragment (TRF) among the longest reported so far for a primate species (25-30 kb), but without detectable overall telomere shortening with ageing on blood samples. However, we demonstrate using universal STELA (Single Telomere Length Amplification) the existence of short telomeres, the increase of which, while correlating with ageing might be related to another mechanism than replicative senescence. We also found a low stringency of telomerase restriction in tissues and an ease to immortalize fibroblasts in vitro upon spontaneous telomerase activation. Finally, we describe the first grey mouse lemur cancer cell line showing a dramatic telomere shortening and high telomerase activity associated with polyploidy. Our overall results suggest that telomere biology in grey mouse lemur is an exception among primates, with at best a physiologically limited replicative telomere ageing and closest to that observed in small rodents. PMID:25882681

  7. Telomeres in aging and disease: lessons from zebrafish

    PubMed Central

    Carneiro, Madalena C.; de Castro, Inês Pimenta

    2016-01-01

    ABSTRACT Age is the highest risk factor for some of the most prevalent human diseases, including cancer. Telomere shortening is thought to play a central role in the aging process in humans. The link between telomeres and aging is highlighted by the fact that genetic diseases causing telomerase deficiency are associated with premature aging and increased risk of cancer. For the last two decades, this link has been mostly investigated using mice that have long telomeres. However, zebrafish has recently emerged as a powerful and complementary model system to study telomere biology. Zebrafish possess human-like short telomeres that progressively decline with age, reaching lengths in old age that are observed when telomerase is mutated. The extensive characterization of its well-conserved molecular and cellular physiology makes this vertebrate an excellent model to unravel the underlying relationship between telomere shortening, tissue regeneration, aging and disease. In this Review, we explore the advantages of using zebrafish in telomere research and discuss the primary discoveries made in this model that have contributed to expanding our knowledge of how telomere attrition contributes to cellular senescence, organ dysfunction and disease. PMID:27482813

  8. Bone marrow skeletal stem/progenitor cell defects in dyskeratosis congenita and telomere biology disorders

    PubMed Central

    Balakumaran, Arun; Mishra, Prasun J.; Pawelczyk, Edyta; Yoshizawa, Sayuri; Sworder, Brian J.; Cherman, Natasha; Kuznetsov, Sergei A.; Bianco, Paolo; Giri, Neelam; Savage, Sharon A.; Merlino, Glenn; Dumitriu, Bogdan; Dunbar, Cynthia E.; Young, Neal S.; Alter, Blanche P.

    2015-01-01

    Dyskeratosis congenita (DC) is an inherited multisystem disorder, characterized by oral leukoplakia, nail dystrophy, and abnormal skin pigmentation, as well as high rates of bone marrow (BM) failure, solid tumors, and other medical problems such as osteopenia. DC and telomere biology disorders (collectively referred to as TBD here) are caused by germline mutations in telomere biology genes leading to very short telomeres and limited proliferative potential of hematopoietic stem cells. We found that skeletal stem cells (SSCs) within the BM stromal cell population (BMSCs, also known as BM–derived mesenchymal stem cells), may contribute to the hematologic phenotype. TBD-BMSCs exhibited reduced clonogenicity, spontaneous differentiation into adipocytes and fibrotic cells, and increased senescence in vitro. Upon in vivo transplantation into mice, TBD-BMSCs failed to form bone or support hematopoiesis, unlike normal BMSCs. TERC reduction (a TBD-associated gene) in normal BMSCs by small interfering TERC-RNA (siTERC-RNA) recapitulated the TBD-BMSC phenotype by reducing proliferation and secondary colony-forming efficiency, and by accelerating senescence in vitro. Microarray profiles of control and siTERC-BMSCs showed decreased hematopoietic factors at the messenger RNA level and decreased secretion of factors at the protein level. These findings are consistent with defects in SSCs/BMSCs contributing to BM failure in TBD. PMID:25499762

  9. Chromatin Structure in Telomere Dynamics

    PubMed Central

    Galati, Alessandra; Micheli, Emanuela; Cacchione, Stefano

    2013-01-01

    The establishment of a specific nucleoprotein structure, the telomere, is required to ensure the protection of chromosome ends from being recognized as DNA damage sites. Telomere shortening below a critical length triggers a DNA damage response that leads to replicative senescence. In normal human somatic cells, characterized by telomere shortening with each cell division, telomere uncapping is a regulated process associated with cell turnover. Nevertheless, telomere dysfunction has also been associated with genomic instability, cell transformation, and cancer. Despite the essential role telomeres play in chromosome protection and in tumorigenesis, our knowledge of the chromatin structure involved in telomere maintenance is still limited. Here we review the recent findings on chromatin modifications associated with the dynamic changes of telomeres from protected to deprotected state and their role in telomere functions. PMID:23471416

  10. Telomerase RNA stem terminus element affects template boundary element function, telomere sequence, and shelterin binding.

    PubMed

    Webb, Christopher J; Zakian, Virginia A

    2015-09-01

    The stem terminus element (STE), which was discovered 13 y ago in human telomerase RNA, is required for telomerase activity, yet its mode of action is unknown. We report that the Schizosaccharomyces pombe telomerase RNA, TER1 (telomerase RNA 1), also contains a STE, which is essential for telomere maintenance. Cells expressing a partial loss-of-function TER1 STE allele maintained short stable telomeres by a recombination-independent mechanism. Remarkably, the mutant telomere sequence was different from that of wild-type cells. Generation of the altered sequence is explained by reverse transcription into the template boundary element, demonstrating that the STE helps maintain template boundary element function. The altered telomeres bound less Pot1 (protection of telomeres 1) and Taz1 (telomere-associated in Schizosaccharomyces pombe 1) in vivo. Thus, the S. pombe STE, although distant from the template, ensures proper telomere sequence, which in turn promotes proper assembly of the shelterin complex.

  11. The role of telomeres and telomerase complex in haematological neoplasia: the length of telomeres as a marker of carcinogenesis and prognosis of disease.

    PubMed

    Gancarcíková, M; Zemanová, Z; Brezinová, J; Berková, A; Vcelíková, S; Smigová, J; Michalová, K

    2010-01-01

    Human telomeres (discovery of telomere structure and function has been recently awarded The Nobel Prize) consist of approximately 5-12 kb of tandem repeated sequences (TTAGGG)n and associated proteins capping chromosome ends which prevent degradation, loss of genetic information, end-to-end fusion, senescence and apoptosis. Due to the end-replication problem, telomere repeats are lost with each cell division, eventually leading to genetic instability and cellular senescence when telomeres become critically short. Stabilization of the telomeric DNA through telomerase activation, unique reverse transcriptase, or activation of the alternative mechanism of telomere maintenance is essential if the cells are to survive and proliferate indefinitely. Telomerase is expressed during early development and remains fully active in specific germline cells, but is undetectable in most normal somatic cells. High level of telomerase activity is detected in almost 90% of human tumours and immortalized cell lines. The hematopoietic compartment may develop genetic instability as a consequence of telomere erosion, resulting in aplastic anaemia (AA) and increased risk of myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML). Genetic instability associated with telomere dysfunction (i.e. short telomeres) is an early event in carcinogenesis. The molecular cytogenetic method telomere/centromere fluorescence in situ hybridization (T/C-FISH) can be used to characterize the telomere length of hematopoietic cells. This review describes recent advances in the molecular characterization of telomere system, the regulation of telomerase activity in cancer pathogenesis and shows that the telomeric length could be a potential clinical marker of hematologic neoplasia and prognosis of disease.

  12. E-type cyclins modulate telomere integrity in mammalian male meiosis.

    PubMed

    Manterola, Marcia; Sicinski, Piotr; Wolgemuth, Debra J

    2016-06-01

    We have shown that E-type cyclins are key regulators of mammalian male meiosis. Depletion of cyclin E2 reduced fertility in male mice due to meiotic defects, involving abnormal pairing and synapsis, unrepaired DNA, and loss of telomere structure. These defects were exacerbated by additional loss of cyclin E1, and complete absence of both E-type cyclins produces a meiotic catastrophe. Here, we investigated the involvement of E-type cyclins in maintaining telomere integrity in male meiosis. Spermatocytes lacking cyclin E2 and one E1 allele (E1+/-E2-/-) displayed a high rate of telomere abnormalities but can progress to pachytene and diplotene stages. We show that their telomeres exhibited an aberrant DNA damage repair response during pachynema and that the shelterin complex proteins TRF2 and RAP2 were significantly decreased in the proximal telomeres. Moreover, the insufficient level of these proteins correlated with an increase of γ-H2AX foci in the affected telomeres and resulted in telomere associations involving TRF1 and telomere detachment in later prophase-I stages. These results suggest that E-type cyclins are key modulators of telomere integrity during meiosis by, at least in part, maintaining the balance of shelterin complex proteins, and uncover a novel role of E-type cyclins in regulating chromosome structure during male meiosis.

  13. Telomere sister chromatid exchange in telomerase deficient murine cells

    SciTech Connect

    Wang, Yisong; Giannone, Richard J; Liu, Yie

    2005-01-01

    We have recently demonstrated that several types of genomic rearrangements (i.e., telomere sister chromatid exchange (T-SCE), genomic-SCE, or end-to-end fusions) were more often detected in long-term cultured murine telomerase deficient embryonic stem (ES) cells than in freshly prepared murine splenocytes, even through they possessed similar frequencies of critically short telomeres. The high rate of genomic rearrangements in telomerase deficient ES cells, when compared to murine splenocytes, may reflect the cultured cells' gained ability to protect chromosome ends with eroded telomeres allowing them to escape 'end crisis'. However, the possibility that ES cells were more permissive to genomic rearrangements than other cell types or that differences in the microenvironment or genetic background of the animals might consequentially determine the rate of T-SCEs or other genomic rearrangements at critically short telomeres could not be ruled out.

  14. Dynamics of rye telomeres in a wheat background during early meiosis.

    PubMed

    Naranjo, Tomás

    2014-01-01

    Migration of the telomere of the short arm of rye chromosome 5R (5RS) during bouquet organization is dependent on the conformation that this chromosome adopts in its intact, submetacentric, or truncated, metacentric, form. In order to establish whether the telomere migration dependence on chromosome conformation is a common feature of all rye chromosomes, the behavior of the telomeres of 2 other rye chromosomes, 1R and 6R, with apparent differences in the arm ratio, has been studied at the bouquet stage and compared with that of 5R. The presence of subtelomeric heterochromatic chromomeres in both arms of 1R and 6R, which were visualized by FISH, revealed the position of the adjacent telomeres in the bouquet. While the end of the long arms of both chromosomes was, with some exceptions, always included in the telomere cluster, the end of the short arms failed to migrate to the telomere pole. Disturbed telomere migration was more often observed in the short arm of the submetacentric chromosome 6R than in the short arm of the almost metacentric chromosome 1R. Thus, the chromosomal conformation effect on telomere mobility is a common feature of all rye chromosomes. Incomplete telomere clustering is followed by failure of synapsis and chiasma formation in chromosomes 5R and 6R. Chromosome arm 1RS, which carries the NOR, completes synapsis earlier than 5RS or 6RS, facilitated by the nucleolar fusion that occurs during early zygotene. PMID:24969495

  15. Telomere Rapid Deletion Regulates Telomere Length in Arabidopsis thaliana▿

    PubMed Central

    Watson, J. Matthew; Shippen, Dorothy E.

    2007-01-01

    Telomere length is maintained in species-specific equilibrium primarily through a competition between telomerase-mediated elongation and the loss of terminal DNA through the end-replication problem. Recombinational activities are also capable of both lengthening and shortening telomeres. Here we demonstrate that elongated telomeres in Arabidopsis Ku70 mutants reach a new length set point after three generations. Restoration of wild-type Ku70 in these mutants leads to discrete telomere-shortening events consistent with telomere rapid deletion (TRD). These findings imply that the longer telomere length set point is achieved through competition between overactive telomerase and TRD. Surprisingly, in the absence of telomerase, a subset of elongated telomeres was further lengthened, suggesting that in this background a mechanism of telomerase-independent lengthening of telomeres operates. Unexpectedly, we also found that plants possessing wild-type-length telomeres exhibit TRD when telomerase is inactivated. TRD is stochastic, and all chromosome ends appear to be equally susceptible. The frequency of TRD decreases as telomeres shorten; telomeres less than 2 kb in length are rarely subject to TRD. We conclude that TRD functions as a potent force to regulate telomere length in Arabidopsis. PMID:17189431

  16. Strong association between long and heterogeneous telomere length in blood lymphocytes and bladder cancer risk in Egyptian.

    PubMed

    Wang, Hongkun; Wang, Ying; Kota, Krishna K; Kallakury, Bhaskar; Mikhail, Nabiel N; Sayed, Douaa; Mokhtar, Ahmed; Maximous, Doaa; Yassin, Etemad H; Gouda, Iman; Sobitan, Adebiyi; Sun, Bing; Loffredo, Christopher A; Zheng, Yun-Ling

    2015-11-01

    Although it is widely recognized that telomere dysfunction plays an important role in cancer, the relationship between telomere function and bladder cancer risk is not well defined. In a case-control study of bladder cancer in Egypt, we examined relationships between two telomere features and bladder cancer risk. Telomere fluorescent in situ hybridization was used to measure telomere features using short-term cultured blood lymphocytes. Logistic regression was used to estimate the strength of association between telomere features and the risk of urothelial carcinoma of the bladder. High telomere length variation (TLV) across all chromosomal ends was significantly associated with an increased risk of bladder cancer [adjusted odds ratios (OR) = 2.22, 95% confidence interval (CI) = 1.48-3.35], as was long average telomere length (OR = 3.19, 95% CI = 2.07, 4.91). Further, TLV and average telomere length jointly affected bladder cancer risk: when comparing individuals with long telomere length and high TLV to those with short telomere length and low TLV, the adjusted OR was 14.68 (95% CI: 6.74-31.98). These associations were stronger among individuals who are 60 years of age or younger. In summary, long and heterogeneous telomere length in blood lymphocytes was strongly associated with an increased bladder cancer risk in Egyptian and the association was modulated by age.

  17. Breast cancer survival is associated with telomere length in peripheral blood cells.

    PubMed

    Svenson, Ulrika; Nordfjäll, Katarina; Stegmayr, Birgitta; Manjer, Jonas; Nilsson, Peter; Tavelin, Björn; Henriksson, Roger; Lenner, Per; Roos, Göran

    2008-05-15

    Telomeres are essential for maintaining chromosomal stability. Previous studies have indicated that individuals with shorter blood telomeres may be at higher risk of developing various types of cancer, such as in lung, bladder, and kidney. We have analyzed relative telomere length (RTL) of peripheral blood cells in relation to breast cancer incidence and prognosis. The study included 265 newly diagnosed breast cancer patients and 446 female controls. RTL was measured by real-time PCR, and our results show that the patient group displayed significantly longer telomeres compared with controls (P < 0.001). Age-adjusted odds ratios (OR) for breast cancer risk increased with increasing telomere length, with a maximal OR of 5.17 [95% confidence interval (95% CI), 3.09-8.64] for the quartile with the longest telomeres. Furthermore, RTL carried prognostic information for patients with advanced disease. Node positive (N+) patients with short telomeres (telomeres (P = 0.001). For patients with ages <50 years with tumors >16 mm (median tumor diameter), short telomeres were associated with a significantly better outcome than longer telomeres (P = 0.006). Cox regression analysis showed that long RTL was a significant independent negative prognostic factor (hazards ratio, 2.92; 95% CI, 1.33-6.39; P = 0.007). Our results indicate that blood RTL may serve as a prognostic indicator in breast cancer patients with advanced disease.

  18. Telomeres in cancer and ageing

    PubMed Central

    Donate, Luis E.; Blasco, Maria A.

    2011-01-01

    Telomeres protect the chromosome ends from unscheduled DNA repair and degradation. Telomeres are heterochromatic domains composed of repetitive DNA (TTAGGG repeats) bound to an array of specialized proteins. The length of telomere repeats and the integrity of telomere-binding proteins are both important for telomere protection. Furthermore, telomere length and integrity are regulated by a number of epigenetic modifications, thus pointing to higher order control of telomere function. In this regard, we have recently discovered that telomeres are transcribed generating long, non-coding RNAs, which remain associated with the telomeric chromatin and are likely to have important roles in telomere regulation. In the past, we showed that telomere length and the catalytic component of telomerase, Tert, are critical determinants for the mobilization of stem cells. These effects of telomerase and telomere length on stem cell behaviour anticipate the premature ageing and cancer phenotypes of telomerase mutant mice. Recently, we have demonstrated the anti-ageing activity of telomerase by forcing telomerase expression in mice with augmented cancer resistance. Shelterin is the major protein complex bound to mammalian telomeres; however, its potential relevance for cancer and ageing remained unaddressed to date. To this end, we have generated mice conditionally deleted for the shelterin proteins TRF1, TPP1 and Rap1. The study of these mice demonstrates that telomere dysfunction, even if telomeres are of a normal length, is sufficient to produce premature tissue degeneration, acquisition of chromosomal aberrations and initiation of neoplastic lesions. These new mouse models, together with the telomerase-deficient mouse model, are valuable tools for understanding human pathologies produced by telomere dysfunction. PMID:21115533

  19. Telomere Restriction Fragment (TRF) Analysis

    PubMed Central

    Mender, Ilgen; Shay, Jerry W.

    2016-01-01

    While telomerase is expressed in ~90% of primary human tumors, most somatic tissue cells except transiently proliferating stem-like cells do not have detectable telomerase activity (Shay and Wright, 1996; Shay and Wright, 2001). Telomeres progressively shorten with each cell division in normal cells, including proliferating stem-like cells, due to the end replication (lagging strand synthesis) problem and other causes such as oxidative damage, therefore all somatic cells have limited cell proliferation capacity (Hayflick limit) (Hayflick and Moorhead, 1961; Olovnikov, 1973). The progressive telomere shortening eventually leads to growth arrest in normal cells, which is known as replicative senescence (Shay et al., 1991). Once telomerase is activated in cancer cells, telomere length is stabilized by the addition of TTAGGG repeats to the end of chromosomes, thus enabling the limitless continuation of cell division (Shay and Wright, 1996; Shay and Wright, 2001). Therefore, the link between aging and cancer can be partially explained by telomere biology. There are many rapid and convenient methods to study telomere biology such as Telomere Restriction Fragment (TRF), Telomere Repeat Amplification Protocol (TRAP) (Mender and Shay, 2015b) and Telomere dysfunction Induced Foci (TIF) analysis (Mender and Shay, 2015a). In this protocol paper we describe Telomere Restriction Fragment (TRF) analysis to determine average telomeric length of cells. Telomeric length can be indirectly measured by a technique called Telomere Restriction Fragment analysis (TRF). This technique is a modified Southern blot, which measures the heterogeneous range of telomere lengths in a cell population using the length distribution of the terminal restriction fragments (Harley et al., 1990; Ouellette et al., 2000). This method can be used in eukaryotic cells. The description below focuses on the measurement of human cancer cells telomere length. The principle of this method relies on the lack of

  20. Ticking Telomeres/Telltale Telomerase.

    ERIC Educational Resources Information Center

    Biermann, Carol A.

    1997-01-01

    Discusses telomeres, complexes of DNA and protein that form the chromatin at the ends of chromosomes. Highlights telomeres as controllers of chromosome integrity, expendable telomeres, DNA replication requirements and their consequences, protection of structural genes, telomerase as indicators of immortality, cancer cells and other immortals, and…

  1. Association of Donor and Recipient Telomere Length with Clinical Outcomes following Lung Transplantation

    PubMed Central

    Courtwright, Andrew M.; Fried, Sabrina; Villalba, Julian A.; Moniodis, Anna; Guleria, Indira; Wood, Isabelle; Milford, Edgar; Mallidi, Hari H.; Hunninghake, Gary M.; Raby, Benjamin A.; Agarwal, Suneet; Camp, Philip C.; Rosas, Ivan O.; Goldberg, Hilary J.; El-Chemaly, Souheil

    2016-01-01

    Background Patients with short telomere syndromes and pulmonary fibrosis have increased complications after lung transplant. However, the more general impact of donor and recipient telomere length in lung transplant has not been well characterized. Methods This was an observational cohort study of patients who received lung transplant at a single center between January 1st 2012 and January 31st 2015. Relative donor lymphocyte telomere length was measured and classified into long (third tertile) and short (other tertiles). Relative recipient lung telomere length was measured and classified into short (first tertile) and long (other tertiles). Outcome data included survival, need for modification of immunosuppression, liver or kidney injury, cytomegalovirus reactivation, and acute rejection. Results Recipient lung tissue telomere lengths were measured for 54 of the 79 patients (68.3%) who underwent transplant during the study period. Donor lymphocyte telomeres were measured for 45 (83.3%) of these recipients. Neither long donor telomere length (hazard ratio [HR] = 0.58, 95% confidence interval [CI], 0.12–2.85, p = 0.50) nor short recipient telomere length (HR = 1.01, 95% CI = 0.50–2.05, p = 0.96) were associated with adjusted survival following lung transplant. Recipients with short telomeres were less likely to have acute cellular rejection (23.5% vs. 58.8%, p = 0.02) but were not more likely to have other organ dysfunction. Conclusions In this small cohort, neither long donor lymphocyte telomeres nor short recipient lung tissue telomeres were associated with adjusted survival after lung transplantation. Larger studies are needed to confirm these findings. PMID:27589328

  2. Telomere length and variation in telomere biology genes in individuals with osteosarcoma.

    PubMed

    Mirabello, Lisa; Richards, Elliott G; Duong, Linh M; Yu, Kai; Wang, Zhaoming; Cawthon, Richard; Berndt, Sonja I; Burdett, Laurie; Chowdhury, Salma; Teshome, Kedest; Douglass, Chester; Savage, Sharon A

    2011-01-01

    Osteosarcoma, the most common primary bone tumor, occurs most frequently in adolescents. Chromosomal aneuploidy is common in osteosarcoma cells, suggesting underlying chromosomal instability. Telomeres, located at chromosome ends, are essential for genomic stability; several studies have suggested that germline telomere length (TL) is associated with cancer risk. We hypothesized that TL and/or common genetic variation in telomere biology genes may be associated with risk of osteosarcoma. We investigated TL in peripheral blood DNA and 713 single nucleotide polymorphisms (SNPs) from 39 telomere biology genes in 98 osteosarcoma cases and 69 orthopedic controls. For the genotyping component, we added 1363 controls from the Prostate, Lung, Colorectal, and Ovarian Cancer ScreeningTrial. Short TL was not associated with osteosarcoma risk overall (OR 1.39, P=0.67), although there was a statistically significant association in females (OR 4.35, 95% Cl 1.20-15.74, P=0.03). Genotype analyses identified seven SNPs in TERF1 significantly associated with osteosarcoma risk after Bonferroni correction by gene. These SNPs were highly linked and associated with a reduced risk of osteosarcoma (OR 0.48-0.53, P=0.0001-0.0006). We also investigated associations between TL and telomere gene SNPs in osteosarcoma cases and orthopedic controls. Several SNPs were associated with TL prior to Bonferroni correction; one SNP in NOLA2 and one in MEN1 were marginally non-significant after correction (P(adj)=0.057 and 0.066, respectively). This pilot-study suggests that females with short telomeres may be at increased risk of osteosarcoma, and that SNPs in TERF1 are inversely associated with osteosarcoma risk.

  3. Telomere Attrition Due to Infection

    PubMed Central

    Ilmonen, Petteri; Kotrschal, Alexander; Penn, Dustin J.

    2008-01-01

    Background Telomeres–the terminal caps of chromosomes–become shorter as individuals age, and there is much interest in determining what causes telomere attrition since this process may play a role in biological aging. The leading hypothesis is that telomere attrition is due to inflammation, exposure to infectious agents, and other types of oxidative stress, which damage telomeres and impair their repair mechanisms. Several lines of evidence support this hypothesis, including observational findings that people exposed to infectious diseases have shorter telomeres. Experimental tests are still needed, however, to distinguish whether infectious diseases actually cause telomere attrition or whether telomere attrition increases susceptibility to infection. Experiments are also needed to determine whether telomere erosion reduces longevity. Methodology/Principal Findings We experimentally tested whether repeated exposure to an infectious agent, Salmonella enterica, causes telomere attrition in wild-derived house mice (Mus musculus musculus). We repeatedly infected mice with a genetically diverse cocktail of five different S. enterica strains over seven months, and compared changes in telomere length with sham-infected sibling controls. We measured changes in telomere length of white blood cells (WBC) after five infections using a real-time PCR method. Our results show that repeated Salmonella infections cause telomere attrition in WBCs, and particularly for males, which appeared less disease resistant than females. Interestingly, we also found that individuals having long WBC telomeres at early age were relatively disease resistant during later life. Finally, we found evidence that more rapid telomere attrition increases mortality risk, although this trend was not significant. Conclusions/Significance Our results indicate that infectious diseases can cause telomere attrition, and support the idea that telomere length could provide a molecular biomarker for assessing

  4. Centrosome aberrations in human mammary epithelial cells driven by cooperative interactions between p16INK4a deficiency and telomere-dependent genotoxic stress

    PubMed Central

    Domínguez, Daniel; Feijoo, Purificación; Bernal, Aina; Ercilla, Amaia; Agell, Neus; Genescà, Anna; Tusell, Laura

    2015-01-01

    Virtually all human cancers display chromosome instability (CIN), a condition in which chromosomes are gained or lost at a high rate. CIN occurs early in cancer development where it may undermine the advance of the neoplastic disease. With the aim of establishing the mechanisms underlying CIN in cancer, we investigated possible links between telomere-dysfunction and centrosome defects, which were seen to coincide in early in breast carcinogenesis using human mammary epithelial cells (HMECs). In this study, we show that TP53 proficient vHMECs cells develop centrosome aberrations when telomere-dysfunction genotoxic stress is produced in the presence of a defective p16INK4a setting and in parallel with an activation of the DNA damage checkpoint response. These aberrations consist of the accumulation of centrosomes in polyploid vHMECs, plus centriole overduplication in both diploid and polyploid cells, thus reflecting that distinct mechanisms underlie the generation of centrosome aberrations in vHMECs. Transduction of vHMEC with hTERT, which rescued the telomere dysfunction phenotype and consequently reduced DNA damage checkpoint activation, led to a progressive reduction of centrosome aberrations with cell culture, both in diploid and in polyploid vHMECs. Radiation-induced DNA damage also raised centrosome aberrations in vHMEC-hTERT. Collectively, our results, using vHMECs define a model where p16INK4a deficiency along with short dysfunctional telomeres cooperatively engenders centrosome abnormalities before p53 function is compromised. PMID:26318587

  5. Formation of extrachromosomal circles from telomeric DNA in Xenopus laevis.

    PubMed

    Cohen, Sarit; Méchali, Marcel

    2002-12-01

    Instability and plasticity of telomeric DNA, which includes extrachromosomal DNA, are usually correlated with the absence of telomerase and with abnormal growth of mammalian cells. Here, we show the formation of extrachromosomal circular DNA of telomeric repeats (tel-eccDNA) during the development of Xenopus laevis. Tel-eccDNA is double-stranded relaxed circles composed of the vertebrate consensus telomeric repeats [TTAGGG](n). Its size varies from <2 to >20 kb and it comprises up to 10% of the total cellular telomere content of the early embryo (pre-MBT stage). The amount of tel-eccDNA is reduced in later developmental stages and in adult tissues. Using a cell-free system derived from Xenopus egg extracts, we show that tel-eccDNA can be formed de novo from the telomere chromosomal tracts of sperm nuclei and naked DNA in a replication-independent manner. These results reveal an unusual plasticity of telomeric DNA during normal development of Xenopus. PMID:12446568

  6. PML body meets telomere

    PubMed Central

    Chung, Inn; Osterwald, Sarah; Deeg, Katharina I.; Rippe, Karsten

    2012-01-01

    The unlimited proliferation potential of cancer cells requires the maintenance of their telomeres. This is frequently accomplished by reactivation of telomerase. However, in a significant fraction of tumors an alternative lengthening of telomeres (ALT) mechanism is active. The molecular mechanism of the ALT pathway remains elusive. In particular, the role of characteristic complexes of promyelocytic leukemia nuclear bodies (PML-NBs) with telomeres, the ALT-associated PML-NBs (APBs), is currently under investigation. Here, we review recent findings on the assembly, structure and functions of APBs. It is discussed how genomic aberrations in ALT-positive cancer cells could result in the formation of APBs and in ALT activity. We conclude that they are important functional intermediates in what is considered the canonical ALT pathway and discuss deregulations of cellular pathways that contribute to the emergence of the ALT phenotype. PMID:22572954

  7. Repetitive telomeric sequences in chromosomal translocations involving chromosome 21

    SciTech Connect

    Qu, J.; Dallaire, L.; Fetni, R.

    1994-09-01

    Telomeres perform key functions in maintaining chromosome integrity. In some structural rearrangements the structure and polymorphism in human telomeres may play a significant role. However, of all the telomeric and subtelomeric sequences, only the terminal TTAGGG repeats are believed essential for telomere function. During the course of a study on the role of telomere structure and polymorphism in chromosomal rearrangements observed in families referred for prenatal diagnosis, we studied three cases in which chromosome 21 was involved. Repetitive TTAGGG sequences for all human chromosomes were used as probes (Oncor). Case 1, a de novo cryptic translocation (2;21) was initially identified as monosomy 21 in a child with psychomotor delay and mild dysmorphism. Using a cosmid probe specific for region 21q22.3 and whole chromosome 21 specific painting probe, the long arm of 21 was found on the short arm of chromosome 2 with an interstitial telomere at the breakpoint junction. All the cells were monosomic for 21pter{yields}q21. Case 2 is a familial (19;21) translocation. GTG-banding and FISH with a satellite probe showed no apparent loss of material at the end of either 19q or 21q, with an interstitial telomere at the fusion site of the two intact chromosomes. In case 3, a four generation reciprocal (20;21) translocation, there was no interstitial telomere. The persistence of an interstitial telomere is a relatively rare event which can now be observed with in situ hybridization. Its study may lead to a better understanding of the dynamics of translocations and of chromosome imbalance.

  8. Cytogenetic telomere and telomerase studies in lumbo-sacral chordoma

    SciTech Connect

    Schwartz, H.S.; Dahir, G.A.; Miller, L.K.

    1994-09-01

    Lumbo-sacral chordomas are rare skeletal sarcomas that originate from the remnant notochord. There are approximately 35 lumbo-sacral chordomas reported annually in the U.S.A. The understanding of this rare human cancer is limited to observations of its clinical behavior and embryonic link. We performed chromosome and molecular analyses from five surgically harvested chordomas in an effort to document genetic abnormalities and to further understand its tumor biology. Cytogenetically, four of five patients had entirely normal chromosomes. One patient had several abnormalities seen in one of 100 cells including a translocation with breakpoints at bands 5q13 and 7q22, loss of one X chromosome and an extra chromosome 14. There was no evidence of monosomy X or trisomy 14 seen with interphase in situ hybridization using biotin-labeled alpha satellite chromosome specific probes for chromosome 14/22 and X. Telomere integrity is required to protect termini from illegitimate recombination. Typically telomeric reduction occurs in senescent fibroblasts in vivo aging and several human solid tumors. A telomeric probe (TTAGGG){sub 50} was hybridized to genomic DNA isolated from chordoma cells and digested with Hinf I which allows the telomeric DNA to remain intact. The tumor DNA was paired with leukocyte DNA from age-matched controls and revealed telomere elongation in all four patients studied with molecular genetic techniques. Telomerase activity is required to maintain telomere integrity and is not present in normal somatic cells. It is determined by visualizing the sizes of the electrophoresis gel-separated radioactive telomeric fragments assembled during incubation of cytoplasmic extracts containing telomerase. Telomerase activity was detected when compared with HeLa cells, a positive control. In addition, no telomerase activity was detected from the chordoma patient`s fibroblasts.

  9. The role of telomeres and telomerase in hematologic malignancies and hematopoietic stem cell transplantation

    PubMed Central

    2014-01-01

    Telomeres are specific nucleoprotein structures at the ends of eukaryotic chromosomes. Telomeres and telomere-associated proteins maintain genome stability by protecting the ends of chromosomes from fusion and degradation. In normal somatic cells, the length of the telomeres gradually becomes shortened with cell division. In tumor cells, the shortening of telomeres length is accelerated under the increased proliferation pressure. However, it will be maintained at an extremely short length as the result of activation of telomerase. Significantly shortened telomeres, activation of telomerase, and altered expression of telomere-associated proteins are common features of various hematologic malignancies and are related with progression or chemotherapy resistance in these diseases. In patients who have received hematopoietic stem cell transplantation (HSCT), the telomere length and the telomerase activity of the engrafted donor cells have a significant influence on HSCT outcomes. Transplantation-related factors should be taken into consideration because of their impacts on telomere homeostasis. As activation of telomerase is widespread in tumor cells, it has been employed as a target point in the treatment of neoplastic hematologic disorders. In this review, the characteristics and roles of telomeres and telomerase both in hematologic malignancies and in HSCT will be summarized. The current status of telomerase-targeted therapies utilized in the treatment of hematologic malignancies will also be reviewed. PMID:25139287

  10. Generation of mice with longer and better preserved telomeres in the absence of genetic manipulations

    PubMed Central

    Varela, Elisa; Muñoz-Lorente, Miguel A.; Tejera, Agueda M.; Ortega, Sagrario; Blasco, Maria A.

    2016-01-01

    Although telomere length is genetically determined, mouse embryonic stem (ES) cells with telomeres of twice the normal size have been generated. Here, we use such ES cells with ‘hyper-long' telomeres, which also express green fluorescent protein (GFP), to generate chimaeric mice containing cells with both hyper-long and normal telomeres. We show that chimaeric mice contain GFP-positive cells in all mouse tissues, display normal tissue histology and normal survival. Both hyper-long and normal telomeres shorten with age, but GFP-positive cells retain longer telomeres as mice age. Chimaeric mice with hyper-long telomeres also accumulate fewer cells with short telomeres and less DNA damage with age, and express lower levels of p53. In highly renewing compartments, such as the blood, cells with hyper-long telomeres are longitudinally maintained or enriched with age. We further show that wound-healing rates in the skin are increased in chimaeric mice. Our work demonstrates that mice with functional, longer and better preserved telomeres can be generated without the need for genetic manipulations, such as TERT overexpression. PMID:27252083

  11. The relationship between telomere length and mortality in chronic obstructive pulmonary disease (COPD).

    PubMed

    Lee, Jee; Sandford, Andrew J; Connett, John E; Yan, Jin; Mui, Tammy; Li, Yuexin; Daley, Denise; Anthonisen, Nicholas R; Brooks-Wilson, Angela; Man, S F Paul; Sin, Don D

    2012-01-01

    Some have suggested that chronic obstructive pulmonary disease (COPD) is a disease of accelerated aging. Aging is characterized by shortening of telomeres. The relationship of telomere length to important clinical outcomes such as mortality, disease progression and cancer in COPD is unknown. Using quantitative polymerase chain reaction (qPCR), we measured telomere length of peripheral leukocytes in 4,271 subjects with mild to moderate COPD who participated in the Lung Health Study (LHS). The subjects were followed for approximately 7.5 years during which time their vital status, FEV(1) and smoking status were ascertained. Using multiple regression methods, we determined the relationship of telomere length to cancer and total mortality in these subjects. We also measured telomere length in healthy "mid-life" volunteers and patients with more severe COPD. The LHS subjects had significantly shorter telomeres than those of healthy "mid-life" volunteers (p<.001). Compared to individuals in the 4(th) quartile of relative telomere length (i.e. longest telomere group), the remaining participants had significantly higher risk of cancer mortality (Hazard ratio, HR, 1.48; p = 0.0324) and total mortality (HR, 1.29; p = 0.0425). Smoking status did not make a significant difference in peripheral blood cells telomere length. In conclusion, COPD patients have short leukocyte telomeres, which are in turn associated increased risk of total and cancer mortality. Accelerated aging is of particular relevance to cancer mortality in COPD.

  12. Generation of mice with longer and better preserved telomeres in the absence of genetic manipulations.

    PubMed

    Varela, Elisa; Muñoz-Lorente, Miguel A; Tejera, Agueda M; Ortega, Sagrario; Blasco, Maria A

    2016-01-01

    Although telomere length is genetically determined, mouse embryonic stem (ES) cells with telomeres of twice the normal size have been generated. Here, we use such ES cells with 'hyper-long' telomeres, which also express green fluorescent protein (GFP), to generate chimaeric mice containing cells with both hyper-long and normal telomeres. We show that chimaeric mice contain GFP-positive cells in all mouse tissues, display normal tissue histology and normal survival. Both hyper-long and normal telomeres shorten with age, but GFP-positive cells retain longer telomeres as mice age. Chimaeric mice with hyper-long telomeres also accumulate fewer cells with short telomeres and less DNA damage with age, and express lower levels of p53. In highly renewing compartments, such as the blood, cells with hyper-long telomeres are longitudinally maintained or enriched with age. We further show that wound-healing rates in the skin are increased in chimaeric mice. Our work demonstrates that mice with functional, longer and better preserved telomeres can be generated without the need for genetic manipulations, such as TERT overexpression. PMID:27252083

  13. Interstitial telomeric sites and Robertsonian translocations in species of Ipheion and Nothoscordum (Amaryllidaceae).

    PubMed

    Souza, Gustavo; Vanzela, Andre L L; Crosa, Orfeo; Guerra, Marcelo

    2016-04-01

    The genera Nothoscordum and Ipheion (Allioideae, Amaryllidaceae) are cytologically characterized by a dysploid series with variable numbers of metacentric and acrocentric chromosomes typical of karyotypes rearranged by Robertsonian translocations (RT). Since they have large chromosomes, low diploid numbers, and possess two telomeric motifs [the vertebrate-type (TTAGGG) n and the Arabidopsis-type (TTTAGGG) n ] they are suitable for investigating the occurrence and possible role of interstitial telomeric sites (ITS) associated with RT. We analyzed the distributions of telomeric sites in 12 species of Nothoscordum and Ipheion and found that both telomeric probes colocalized in all chromosome termini. Cloning and sequencing PCR products obtained using both telomeric primers simultaneously revealed long stretches of (TTAGGG) n and (TTTAGGG) n sequences together with degenerated telomeric sequences. Most acrocentric chromosomes have a 45S rDNA site at the terminal region of the short arms adjacent to the most distal telomeric sites. Telomeric signals were found at all chromosome ends, but ITS were also detected in a few proximal and subterminal regions in some Nothoscordum species. Although RT are common in this group of plants, our findings suggest that proximal positioning of telomeric motifs are not necessarily related to that kind of rearrangement. Rather, transposition of telomeric sequences followed by amplification, could better explain the presence of (TTAGGG) n and (TTTAGGG) n repeats at those sites. Furthermore, a few small interstitial sites found in some Nothoscordum species indicate that dispersion of these sequences was not restricted to the proximal region.

  14. Mild cognitive impairment identified in older individuals with Down syndrome by reduced telomere signal numbers and shorter telomeres measured in microns.

    PubMed

    Jenkins, Edmund C; Ye, Lingling; Velinov, Milen; Krinsky-McHale, Sharon J; Zigman, Warren B; Schupf, Nicole; Silverman, Wayne P

    2012-07-01

    Previously, we established that short-term T lymphocyte cultures from people with Down syndrome (DS) and dementia (Alzheimer's disease) had shorter telomeres than did those from age- and sex-matched people with DS only, quantified as significantly reduced numbers of signals of peptide nucleic acid (PNA) telomere probes in whole metaphases [Jenkins et al. (2008); Neurosci Lett 440:340-343] as well as reduced telomere probe light intensity values in interphases [Jenkins et al. (2010); Neurobiol Aging 31:765-771]. We now describe shorter telomere length in adults with DS and mild cognitive impairment (MCI) compared to age- and sex-matched individuals with DS without MCI. Telomere length is quantified by reduced telomere signal numbers and shorter chromosome 1 telomeres measured in micrometers (microns). These findings were in agreement with quantitative light intensity measurements of chromosome 1 and chromosome 21 PNA telomere probes with and without the use of a "normalizing ratio" involving the fluorescence exhibited by a PNA probe for centromere 2, and with the use of light intensity measurements of interphase preparations. Most importantly, the distributions of chromosome 1 telomere lengths (in microns) were completely non-overlapping for adults with and without MCI, indicating that this measure has great promise as a biomarker for MCI as well as dementia in this population. PMID:22592955

  15. Brh2 and Rad51 promote telomere maintenance in Ustilago maydis, a new model system of DNA repair proteins at telomeres.

    PubMed

    Yu, Eun Young; Kojic, Milorad; Holloman, William K; Lue, Neal F

    2013-07-01

    Recent studies implicate a number of DNA repair proteins in mammalian telomere maintenance. However, because several key repair proteins in mammals are missing from the well-studied budding and fission yeast, their roles at telomeres cannot be modeled in standard fungi. In this report, we explored the dimorphic fungus Ustilago maydis as an alternative model for telomere research. This fungus, which belongs to the phylum Basidiomycota, has a telomere repeat unit that is identical to the mammalian repeat, as well as a constellation of DNA repair proteins that more closely mimic the mammalian collection. We showed that the two core components of homology-directed repair (HDR) in U. maydis, namely Brh2 and Rad51, both promote telomere maintenance in telomerase positive cells, just like in mammals. In addition, we found that Brh2 is localized to telomeres in vivo, suggesting that it acts directly at chromosome ends. We surveyed a series of mutants with DNA repair defects, and found many of them to have short telomeres. Our results indicate that factors involved in DNA repair are probably also needed for optimal telomere maintenance in U. maydis, and that this fungus is a useful alternative model system for telomere research.

  16. Nuclear organization in DNA end processing: Telomeres vs double-strand breaks.

    PubMed

    Marcomini, Isabella; Gasser, Susan M

    2015-08-01

    Many proteins ligands are shared between double-strand breaks and natural chromosomal ends or telomeres. The structural similarity of the 3' overhang, and the efficiency of cellular DNA end degradation machineries, highlight the need for mechanisms that resect selectively to promote or restrict recombination events. Here we examine the means used by eukaryotic cells to suppress resection at telomeres, target telomerase to short telomeres, and process broken ends for appropriate repair. Not only molecular ligands, but the spatial sequestration of telomeres and damage likely ensure that these two very similar structures have very distinct outcomes with respect to the DNA damage response and repair.

  17. Pathways connecting telomeres and p53 in senescence, apoptosis, and cancer

    SciTech Connect

    Artandi, Steven E. . E-mail: sartandi@stanford.edu; Attardi, Laura D. . E-mail: attardi@stanford.edu

    2005-06-10

    The ends of eukaryotic chromosomes are protected by specialized structures termed telomeres that serve in part to prevent the chromosome end from activating a DNA damage response. However, this important function for telomeres in chromosome end protection can be lost as telomeres shorten with cell division in culture or in self-renewing tissues with advancing age. Impaired telomere function leads to induction of a DNA damage response and activation of the tumor suppressor protein p53. p53 serves a critical role in enforcing both senescence and apoptotic responses to dysfunctional telomeres. Loss of p53 creates a permissive environment in which critically short telomeres are inappropriately joined to generate chromosomal end-to-end fusions. These fused chromosomes result in cycles of chromosome fusion-bridge-breakage, which can fuel cancer initiation, especially in epithelial tissues, by facilitating changes in gene copy number.

  18. Telomeres and telomerase as therapeutic targets to prevent and treat age-related diseases

    PubMed Central

    Bär, Christian; Blasco, Maria A.

    2016-01-01

    Telomeres, the protective ends of linear chromosomes, shorten throughout an individual’s lifetime. Telomere shortening is a hallmark of molecular aging and is associated with premature appearance of diseases associated with aging. Here, we discuss the role of telomere shortening as a direct cause for aging and age-related diseases. In particular, we draw attention to the fact that telomere length influences longevity. Furthermore, we discuss intrinsic and environmental factors that can impact on human telomere erosion. Finally, we highlight recent advances in telomerase-based therapeutic strategies for the treatment of diseases associated with extremely short telomeres owing to mutations in telomerase, as well as age-related diseases, and ultimately aging itself. PMID:27081482

  19. Opposing impacts on healthspan and longevity by limiting dietary selenium in Telomere Dysfunctional mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium (Se) is an essential trace element essential for optimal health. We investigated the role of Se in longevity and healthspan in a mouse model of healthy aging in humans with short telomeres. Telomere shortening is associated with aging, mortality and aging-related diseases. We found that whi...

  20. Donor Telomere Length SAA

    Cancer.gov

    A new NCI study has found that, among patients with severe aplastic anemia who received a hematopoietic cell transplant from an unrelated donor, those whose donor white blood cells had longer telomeres had higher survival rates five-years after transplant

  1. Anatomical relationship between traditional acupuncture point ST 36 and Omura's ST 36 (True ST 36) with their therapeutic effects: 1) inhibition of cancer cell division by markedly lowering cancer cell telomere while increasing normal cell telomere, 2) improving circulatory disturbances, with reduction of abnormal increase in high triglyceride, L-homocystein, CRP, or cardiac troponin I & T in blood by the stimulation of Omura's ST 36--Part 1.

    PubMed

    Omura, Yoshiaki; Chen, Yemeng; Lu, Dominic P; Shimotsura, Yasuhiro; Ohki, Motomu; Duvvi, Harsha

    2007-01-01

    Using Bi-Digital O-Ring Test Resonance Phenomena between 2 identical substances, Omura, Y. succeeded in making the image of the outline of internal organs without use of standard imaging devices since 1982. When he imaged the outline of the stomach on the abdominal wall, a number of the lines came out from upper and lower parts of stomach wall. When the lines were followed, they were very close to the well-known stomach meridians. Subsequently, he found a method of localizing meridians and their corresponding acupuncture points as well as shapes and diameters accurately. At the anatomical location of ST 36 described in traditional textbooks, Omura, Y. found there is no acupuncture point. However, in the close vicinity, there is an acupuncture point which he named as true ST 36 in the mid 1980s, but it is generally known as Omura's ST 36. When the effects of the acupuncture on these 2 locations were compared, Omura's ST 36 (true ST 36) produced very significant well-known acupuncture beneficial effects including improved circulation and blood chemistry, while in the traditional ST 36, the effects were small. In this article, the anatomical relationship between these two acupuncture points, with a short distance of 0.6 approximately 1.5 cm between the centers of these locations, was described. In early 2000, Omura, Y. found Press Needle Stimulation of Omura's ST 36, using "Press-Release" procedure repeated 200 times, 4 times a day to cancer patients reduced high cancer cell telomere of 600-1500ng and high Oncogen C-fos Ab2 and Integrin alpha5beta1 of 100-700ng BDORT units to close to lyg (= 10(-24) g) BDORT units. In addition there was a significant reduction of Asbestos and Hg from cancer cells, while markedly reduced normal cell telomere of lyg was increased to optimally high amounts of 500-530ng BDORTunits. Thus, cancer cells can no longer divide and cancer activity is inhibited. The authors have successfully applied this method for a variety of cancers as well as

  2. Telomere length in Hepatitis C.

    PubMed

    Kitay-Cohen, Y; Goldberg-Bittman, L; Hadary, R; Fejgin, M D; Amiel, A

    2008-11-01

    Telomeres are nucleoprotein structures located at the termini of chromosomes that protect the chromosomes from fusion and degradation. Hepatocyte cell-cycle turnover may be a primary mechanism of telomere shortening in hepatitis C virus (HCV) infection, inducing fibrosis and cellular senescence. HCV infection has been recognized as potential cause of B-cell lymphoma and hepatocellular carcinoma. The present study sought to assess relative telomere length in leukocytes from patients with chronic HCV infection, patients after eradication of HCV infection (in remission), and healthy controls. A novel method of manual evaluation was applied. Leukocytes derived from 22 patients with chronic HCV infection and age- and sex-matched patients in remission and healthy control subjects were subjected to a fluorescence-in-situ protocol (DAKO) to determine telomere fluorescence intensity and number. The relative, manual, analysis of telomere length was validated against findings on applied spectral imaging (ASI) in a random sample of study and control subjects. Leukocytes from patients with chronic HCV infection had shorter telomeres than leukocytes from patients in remission and healthy controls. On statistical analysis, more cells with low signal intensity on telomere FISH had shorter telomeres whereas more cells with high signal intensity had longer telomeres. The findings were corroborated by the ASI telomere software. Telomere shortening in leukocytes from patients with active HCV infection is probably due to the lower overall telomere level rather than higher cell cycle turnover. Manual evaluation is an accurate and valid method of assessing relative telomere length between patients with chronic HCV infection and healthy subjects. PMID:18992639

  3. Population mixture model for nonlinear telomere dynamics

    NASA Astrophysics Data System (ADS)

    Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

    2008-12-01

    Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

  4. Change in Leukocyte Telomere Length Predicts Mortality in Patients with Stable Coronary Heart Disease from the Heart and Soul Study

    PubMed Central

    Goglin, Sarah E.; Farzaneh-Far, Ramin; Epel, Elissa S.; Lin, Jue; Blackburn, Elizabeth H.

    2016-01-01

    Background Short telomere length independently predicts mortality in patients with coronary heart disease. Whether 5-year change in telomere length predicts subsequent mortality in patients with coronary heart disease has not been evaluated. Methods In a prospective cohort study of 608 individuals with stable coronary artery disease, we measured leukocyte telomere length at baseline and after five years of follow-up. We divided the sample into tertiles of telomere change: shortened, maintained or lengthened. We used Cox survival models to evaluate 5-year change in telomere length as a predictor of mortality. Results During an average of 4.2 years follow-up, there were 149 deaths. Change in telomere length was inversely predictive of all-cause mortality. Using the continuous variable of telomere length change, each standard deviation (325 base pair) greater increase in telomere length was associated with a 24% reduction in mortality (HR 0.76, 95% CI 0.61–0.94; p = 0.01), adjusted for age, sex, waist to hip ratio, exercise capacity, LV ejection fraction, serum creatinine, and year 5 telomere length. Mortality occurred in 39% (79/203) of patients who experienced telomere shortening, 22% (45/203) of patients whose telomere length was maintained, and 12% (25/202) of patients who experienced telomere lengthening (p<0.001). As compared with patients whose telomere length was maintained, those who experienced telomere lengthening were 56% less likely to die (HR 0.44, 95% CI, 0.23–0.87). Conclusions In patients with coronary heart disease, an increase in leukocyte telomere length over 5 years is associated with decreased mortality. PMID:27783614

  5. Telomere dynamics during aging in polygenic left ventricular hypertrophy.

    PubMed

    Marques, Francine Z; Booth, Scott A; Prestes, Priscilla R; Curl, Claire L; Delbridge, Lea M D; Lewandowski, Paul; Harrap, Stephen B; Charchar, Fadi J

    2016-01-01

    Short telomeres are associated with increased risk of cardiovascular disease. Here we studied cardiomyocyte telomere length at key ages during the ontogeny of cardiac hypertrophy and failure in the hypertrophic heart rat (HHR) and compared these with the normal heart rat (NHR) control strain. Key ages corresponded with the pathophysiological sequence beginning with fewer cardiomyocytes (2 days), leading to left ventricular hypertrophy (LVH) (13 wk) and subsequently progression to heart failure (38 wk). We measured telomere length, tissue activity of telomerase, mRNA levels of telomerase reverse transcriptase (Tert) and telomerase RNA component (Terc), and expression of the telomeric regulator microRNA miR-34a. Cardiac telomere length was longer in the HHR compared with the control strain at 2 days and 38 wk, but shorter at 13 wk. Neonatal HHR had higher cardiac telomerase activity and expression of Tert and miR-34a. Telomerase activity was not different at 13 or 38 wk. Tert mRNA and Terc RNA were overexpressed at 38 wk, while miR-34a was overexpressed at 13 wk but downregulated at 38 wk. Circulating leukocytes were strongly correlated with cardiac telomere length in the HHR only. The longer neonatal telomeres in HHR are likely to reflect fewer fetal and early postnatal cardiomyocyte cell divisions and explain the reduced total cardiomyocyte complement that predisposes to later hypertrophy and failure. Although shorter telomeres were a feature of cardiac hypertrophy at 13 wk, they were not present at the progression to heart failure at 38 wk.

  6. Telomere elongation chooses TERRA ALTernatives.

    PubMed

    Arora, Rajika; Azzalin, Claus M

    2015-01-01

    Alternative Lengthening of Telomeres (ALT) mechanisms allow telomerase-negative immortal cells to buffer replicative telomere shortening. ALT is naturally active in a number of human cancers and might be selected upon telomerase inactivation. ALT is thought to operate through homologous recombination (HR) occurring between telomeric repeats from independent chromosome ends. Indeed, suppression of a number of HR factors impairs ALT cell proliferation. Yet, how HR is initiated at ALT telomeres remains elusive. Mounting evidence suggests that the long noncoding telomeric RNA TERRA renders ALT telomeres recombinogenic by forming RNA:DNA hybrids with the telomeric C-rich strand. TERRA and telomeric hybrids act in concert with a number of other factors, including the RNA endoribonuclease RNaseH1 and the single stranded DNA binding protein RPA. The functional interaction network built upon these different players seems indispensable for ALT telomere maintenance, and digging into the molecular details of this previously unappreciated network might open the way to novel avenues for cancer treatments.

  7. Chromosomal mapping of chicken mega-telomere arrays to GGA9, 16, 28 and W using a cytogenomic approach.

    PubMed

    Delany, M E; Gessaro, T M; Rodrigue, K L; Daniels, L M

    2007-01-01

    Four mega-telomere loci were mapped to chicken chromosomes 9, 16, 28, and the W sex chromosome by dual-color fluorescence in situ hybridization using a telomeric sequence probe and BAC clones previously assigned to chicken chromosomes. The in-common features of the mega-telomere chromosomes are that microchromosomes are involved rather than macrochromosomes; in three cases (9, 16, 28) acrocentrics are involved with the mega-telomeres mapping to the p arms. Three of the four chromosomes (9, 16, W) encode tandem repeats which in two cases (9 and 16) involve the ribosomal DNA arrays (the 5S and 18S-5.8S-28S gene repeats, respectively). All involved chromosomes have a typical-sized telomere on the opposite terminus. Intra- and interindividual variation for mega-telomere distribution are discussed in terms of karyotype abnormalities and the potential for mitotic instability of some telomeres. The diversity and distribution of telomere array quantity in the chicken genome should be useful in contributing to research related to telomere length regulation - how and by what mechanism genomes and individual chromosomes establish and maintain distinct sets of telomere array sizes, as well as for future studies related to stability of the chicken genome affecting development, growth, cellular lifespan and disease. An additional impact of this study includes the listing of BAC clones (26 autosomal and six W BACs tested) that were cytogenetically verified; this set of BACs provide a useful tool for future cytogenetic analyses of the microchromosomes. PMID:17675845

  8. Telomere DNA Deficiency Is Associated with Development of Human Embryonic Aneuploidy

    PubMed Central

    Treff, Nathan R.; Su, Jing; Taylor, Deanne; Scott, Richard T.

    2011-01-01

    Aneuploidy represents the most prevalent form of genetic instability found in human embryos and is the leading genetic cause of miscarriage and developmental delay in newborns. Telomere DNA deficiency is associated with genomic instability in somatic cells and may play a role in development of aneuploidy commonly found in female germ cells and human embryos. To test this hypothesis, we developed a method capable of quantifying telomere DNA in parallel with 24-chromosome aneuploidy screening from the same oocyte or embryo biopsy. Aneuploid human polar bodies possessed significantly less telomere DNA than euploid polar bodies from sibling oocytes (−3.07 fold, P = 0.016). This indicates that oocytes with telomere DNA deficiency are prone to aneuploidy development during meiosis. Aneuploid embryonic cells also possessed significantly less telomere DNA than euploid embryonic cells at the cleavage stage (−2.60 fold, P = 0.002) but not at the blastocyst stage (−1.18 fold, P = 0.340). The lack of a significant difference at the blastocyst stage was found to be due to telomere DNA normalization between the cleavage and blastocyst stage of embryogenesis and not due to developmental arrest of embryos with short telomeres. Heterogeneity in telomere length within oocytes may provide an opportunity to improve the treatment of infertility through telomere-based selection of oocytes and embryos with reproductive competence. PMID:21738493

  9. Presence of a fragile site and interstitial telomere repeat sequences in a(Y;13) translocation

    SciTech Connect

    Lemieux, N.; Fetni, R.; Boutouil, M.

    1994-09-01

    It has been proposed that the telomere repeat sequences (TTAGGG)n, when present at interstitial chromosomal locations, might promote site-specific fragility and recombinational activity. Nevertheless, in mammalians, only a few indications of such involvement of telomeric sequences have been observed. In this study, we show direct cytological evidence that a de novo interstitial telomere can cause the formation of a novel fragile site. Molecular cytogenetic studies of a de novo (Y;13) translocation, using centromeric and telomeric probes, have revealed the presence of two centromeres and interstitial telomere sequences. A fragile site was also found near the interstitial telomere loci. In this case, high-resolution cytogenetics was complemented by two-color FISH to give accurate information. Furthermore, an analysis with short arm Y chromosome DNA probes was carried out to detect possible deletion in this region, including the ZFY gene which is involved in human spermatogenesis. The Y chromosome appeared to be intact upon cytogenetic and in situ hybridization studies even for the telomeric region. Also, we observed two cells showing a normal karyotype without the Y;13 translocation suggesting the instability of this translocation. This finding shows the importance of telomere repeat sequences in translocations and other chromosome rearrangements. We are currently analyzing additional cases with similar analogies to obtain further insight on the role of telomeres and the dynamics of translocations.

  10. Epigenetic maintenance of telomere identity in Drosophila: buckle up for the sperm ride.

    PubMed

    Dubruille, Raphaëlle; Loppin, Benjamin

    2011-04-01

    A critical function of telomeres is to prevent the ligation of chromosome ends by DNA repair enzymes. In most eukaryotes, telomeric DNA consists in large arrays of G-rich tandem repeats that are recognized by DNA binding capping proteins. Drosophila telomeres are unusual as they lack short tandem repeats. However, Drosophila capping proteins can bind chromosome extremities in a DNA sequence-independent manner. This epigenetic protection of fly telomeres has been essentially studied in somatic cells where capping proteins such as HOAP or HP1 are essential in preventing chromosome end-to-end fusions. HipHop and K81 are two recently identified paralogous capping proteins with complementary expression patterns. While HipHop is involved in telomere capping in somatic cells, K81 has specialized in the protection of telomeres in post-meiotic male germ cells. Remarkably, K81 is required for the stabilization of HOAP and HP1 at telomeres during the massive paternal chromatin remodeling that occurs during spermiogenesis and at fertilization. We thus propose that the maintenance of capping proteins at Drosophila sperm telomeres is crucial for the transmission of telomere identity to the diploid zygote. : PMID:21386659

  11. Telomerase suppresses formation of ALT-associated single-stranded telomeric C-circles.

    PubMed

    Plantinga, Matthew J; Pascarelli, Kara M; Merkel, Anna S; Lazar, Alexander J; von Mehren, Margaret; Lev, Dina; Broccoli, Dominique

    2013-06-01

    Telomere maintenance is an essential characteristic of cancer cells, most commonly achieved by activation of telomerase. Telomeres can also be maintained by a recombination-based mechanism, alternative lengthening of telomeres (ALT). Cells using ALT are characterized by the presence of ALT-associated promyelocytic leukemia (PML) bodies (APB), long, heterogeneously sized telomeres, extrachromosomal telomeric circular DNA, and elevated telomeric recombination. Consistent with other reports, we found that liposarcomas containing APBs, but lacking telomerase expression, always contained C-rich circles (C-circles), and these C-circles were never present in the absence of APBs, indicating a tight link between these features in ALT cells. However, a rare subgroup of tumors showing evidence of telomere maintenance by both telomerase and ALT did not contain C-circles. To test the hypothesis that telomerase expression disrupts the tight link between APBs and C-circles, we used ALT cell lines that were engineered to express telomerase. Introduction of telomerase activity in these ALT cells resulted in, on average, shorter telomeres with retention of APBs. However, at high passage, the level of C-circles was significantly reduced, which was paralleled by a switch from C-strand overhangs to G-strand overhangs. We propose that by extending critically short telomeres in these cells, telomerase is disrupting a key step in the ALT pathway necessary for production and/or maintenance of C-circles.

  12. Epigenetic maintenance of telomere identity in Drosophila: buckle up for the sperm ride.

    PubMed

    Dubruille, Raphaëlle; Loppin, Benjamin

    2011-04-01

    A critical function of telomeres is to prevent the ligation of chromosome ends by DNA repair enzymes. In most eukaryotes, telomeric DNA consists in large arrays of G-rich tandem repeats that are recognized by DNA binding capping proteins. Drosophila telomeres are unusual as they lack short tandem repeats. However, Drosophila capping proteins can bind chromosome extremities in a DNA sequence-independent manner. This epigenetic protection of fly telomeres has been essentially studied in somatic cells where capping proteins such as HOAP or HP1 are essential in preventing chromosome end-to-end fusions. HipHop and K81 are two recently identified paralogous capping proteins with complementary expression patterns. While HipHop is involved in telomere capping in somatic cells, K81 has specialized in the protection of telomeres in post-meiotic male germ cells. Remarkably, K81 is required for the stabilization of HOAP and HP1 at telomeres during the massive paternal chromatin remodeling that occurs during spermiogenesis and at fertilization. We thus propose that the maintenance of capping proteins at Drosophila sperm telomeres is crucial for the transmission of telomere identity to the diploid zygote. :

  13. Telomere length, current perceived stress, and urinary stress hormones in women.

    PubMed

    Parks, Christine G; Miller, Diane B; McCanlies, Erin C; Cawthon, Richard M; Andrew, Michael E; DeRoo, Lisa A; Sandler, Dale P

    2009-02-01

    Telomeres are repetitive DNA sequences that cap and protect the ends of chromosomes; critically short telomeres may lead to cellular senescence or carcinogenic transformation. Previous findings suggest a link between psychosocial stress, shorter telomeres, and chronic disease risk. This cross-sectional study examined relative telomere length in relation to perceived stress and urinary stress hormones in a sample of participants (n = 647) in the National Institute of Environmental Health Sciences Sister Study, a cohort of women ages 35 to 74 years who have a sister with breast cancer. Average leukocyte telomere length was determined by quantitative PCR. Current stress was assessed using the Perceived Stress Scale and creatinine-adjusted neuroendocrine hormones in first morning urines. Linear regression models estimated differences in telomere length base pairs (bp) associated with stress measures adjusted for age, race, smoking, and obesity. Women with higher perceived stress had somewhat shorter telomeres [adjusted difference of -129bp for being at or above moderate stress levels; 95% confidence interval (CI), -292 to 33], but telomere length did not decrease monotonically with higher stress levels. Shorter telomeres were independently associated with increasing age (-27bp/year), obesity, and current smoking. Significant stress-related differences in telomere length were seen in women ages 55 years and older (-289bp; 95% CI, -519 to -59), those with recent major losses (-420bp; 95% CI, -814 to -27), and those with above-average urinary catecholamines (e.g., epinephrine: -484bp; 95% CI, -709 to -259). Although current perceived stress was only modestly associated with shorter telomeres in this broad sample of women, our findings suggest the effect of stress on telomere length may vary depending on neuroendocrine responsiveness, external stressors, and age.

  14. Diet-related telomere shortening and chromosome stability.

    PubMed

    Marcon, Francesca; Siniscalchi, Ester; Crebelli, Riccardo; Saieva, Calogero; Sera, Francesco; Fortini, Paola; Simonelli, Valeria; Palli, Domenico

    2012-01-01

    Recent evidences have highlighted an influence of micronutrients in the maintenance of telomere length (TL). In order to explore whether diet-related telomere shortening had any physiological relevance and was accompanied by significant damage in the genome, in the present study, TL was assessed by terminal restriction fragment (TRF) analysis in peripheral blood lymphocytes of 56 healthy subjects for which detailed information on dietary habits was available and data were compared \\with the incidence of nucleoplasmic bridges (NPBs), a marker of chromosomal instability related to telomere dysfunction visualised with the cytokinesis-blocked micronucleus assay. To increase the capability to detect even slight impairment of telomere function, the incidence of NPBs was also evaluated on cells exposed in vitro to ionising radiation. Care was taken to control for potential confounding factors that might influence TL, viz. age, hTERT genotype and smoking status. Data showed that higher consumption of vegetables was related with significantly higher mean TL (P = 0.013); in particular, the analysis of the association between micronutrients and mean TL highlighted a significant role of antioxidant intake, especially beta-carotene, on telomere maintenance (P = 0.004). However, the diet-related telomere shortening did not result in associated increased spontaneous or radiation-induced NPBs. The distribution of TRFs was also analysed and a slight prevalence of radiation-induced NPBs (P = 0.03) was observed in subjects with higher amount of very short TRFs (<2 kb). The relative incidence of very short TRFs was positively associate with ageing (P = 0.008) but unrelated to vegetables consumption and daily intake of micronutrients, suggesting that the degree of telomere erosion related with low dietary intake of antioxidants observed in this study was not so extensive to lead to chromosome instability.

  15. Predictors of telomere content in dragon lizards

    NASA Astrophysics Data System (ADS)

    Ballen, Cissy; Healey, Mo; Wilson, Mark; Tobler, Michael; Olsson, Mats

    2012-08-01

    Telomeres shorten as a consequence of DNA replication, in particular in cells with low production of telomerase and perhaps in response to physiological stress from exposure to reactive oxygen species, such as superoxide. This process of telomere attrition is countered by innate antioxidation, such as via the production of superoxide dismutase. We studied the inheritance of telomere length in the Australian painted dragon lizard ( Ctenophorus pictus) and the extent to which telomere length covaries with mass-corrected maternal reproductive investment, which reflects the level of circulating yolk precursor and antioxidant, vitellogenin. Our predictors of offspring telomere length explained 72 % of telomere variation (including interstitial telomeres if such are present). Maternal telomere length and reproductive investment were positively influencing offspring telomere length in our analyses, whereas flow cytometry-estimated superoxide level was negatively impacting offspring telomere length. We suggest that the effects of superoxide on hatchling telomere shortening may be partly balanced by transgenerational effects of vitellogenin antioxidation.

  16. Salivary Telomere Length and Lung Function in Adolescents Born Very Preterm: A Prospective Multicenter Study

    PubMed Central

    Hadchouel, Alice; Marchand-Martin, Laetitia; Franco-Montoya, Marie-Laure; Peaudecerf, Laetitia; Ancel, Pierre-Yves; Delacourt, Christophe

    2015-01-01

    Preterm birth is associated with abnormal respiratory functions throughout life. The mechanisms underlying these long-term consequences are still unclear. Shortening of telomeres was associated with many conditions, such as chronic obstructive pulmonary disease. We aimed to search for an association between telomere length and lung function in adolescents born preterm. Lung function and telomere length were measured in 236 adolescents born preterm and 38 born full-term from the longitudinal EPIPAGE cohort. Associations between telomere length and spirometric indices were tested in univariate and multivariate models accounting for confounding factors in the study population. Airflows were significantly lower in adolescents born preterm than controls; forced expiratory volume in one second was 12% lower in the extremely preterm born group than controls (p<0.001). Lower birth weight, bronchopulmonary dysplasia and postnatal sepsis were significantly associated with lower airflow values. Gender was the only factor that was significantly associated with telomere length. Telomere length correlated with forced expiratory flow 25–75 in the extremely preterm adolescent group in univariate and multivariate analyses (p = 0.01 and p = 0.02, respectively). We evidenced an association between telomere length and abnormal airflow in a population of adolescents born extremely preterm. There was no evident association with perinatal events. This suggests other involved factors, such as a continuing airway oxidative stress leading to persistent inflammation and altered lung function, ultimately increasing susceptibility to chronic obstructive pulmonary disease. PMID:26355460

  17. Telomeric repeat silencing in germ cells is essential for early development in Drosophila.

    PubMed

    Morgunova, Valeriya; Akulenko, Natalia; Radion, Elizaveta; Olovnikov, Ivan; Abramov, Yuri; Olenina, Ludmila V; Shpiz, Sergey; Kopytova, Daria V; Georgieva, Sofia G; Kalmykova, Alla

    2015-10-15

    The germline-specific role of telomeres consists of chromosome end elongation and proper chromosome segregation during early developmental stages. Despite the crucial role of telomeres in germ cells, little is known about telomere biology in the germline. We analyzed telomere homeostasis in the Drosophila female germline and early embryos. A novel germline-specific function of deadenylase complex Ccr4-Not in the telomeric transcript surveillance mechanism is reported. Depletion of Ccr4-Not complex components causes strong derepression of the telomeric retroelement HeT-A in the germ cells, accompanied by elongation of the HeT-A poly(A) tail. Dysfunction of transcription factors Woc and Trf2, as well as RNA-binding protein Ars2, also results in the accumulation of excessively polyadenylated HeT-A transcripts in ovaries. Germline knockdowns of Ccr4-Not components, Woc, Trf2 and Ars2, lead to abnormal mitosis in early embryos, characterized by chromosome missegregation, centrosome dysfunction and spindle multipolarity. Moreover, the observed phenotype is accompanied by the accumulation of HeT-A transcripts around the centrosomes in early embryos, suggesting the putative relationship between overexpression of telomeric transcripts and mitotic defects. Our data demonstrate that Ccr4-Not, Woc, Trf2 and Ars2, components of different regulatory pathways, are required for telomere protection in the germline in order to guarantee normal development.

  18. Molecular characterisation of a mosaicism with a complex chromosome rearrangement: evidence for coincident chromosome healing by telomere capture and neo‐telomere formation

    PubMed Central

    Chabchoub, Elyes; Rodríguez, Laura; Galán, Enrique; Mansilla, Elena; Martínez‐Fernandez, Maria Luisa; Martínez‐Frías, Maria Luisa; Fryns, Jean‐Pierre; Vermeesch, Joris Robert

    2007-01-01

    Background Broken chromosomes must acquire new telomeric “caps” to be structurally stable. Chromosome healing can be mediated either by telomerase through neo‐telomere synthesis or by telomere capture. Aim To unravel the mechanism(s) generating complex chromosomal mosaicisms and healing broken chromosomes. Methods G banding, array comparative genomic hybridization (aCGH), fluorescence in‐situ hybridisation (FISH) and short tandem repeat analysis (STR) was performed on a girl presenting with mental retardation, facial dysmorphism, urogenital malformations and limb anomalies carrying a complex chromosomal mosaicism. Results & discussion The karyotype showed a de novo chromosome rearrangement with two cell lines: one cell line with a deletion 9pter and one cell line carrying an inverted duplication 9p and a non‐reciprocal translocation 5pter fragment. aCGH, FISH and STR analysis enabled the deduction of the most likely sequence of events generating this complex mosaic. During embryogenesis, a double‐strand break occurred on the paternal chromosome 9. Following mitotic separation of both broken sister chromatids, one acquired a telomere vianeo‐telomere formation, while the other generated a dicentric chromosome which underwent breakage during anaphase, giving rise to the del inv dup(9) that was subsequently healed by chromosome 5 telomere capture. Conclusion Broken chromosomes can coincidently be rescued by both telomere capture and neo‐telomere synthesis. PMID:17172463

  19. Human RECQL1 participates in telomere maintenance.

    PubMed

    Popuri, Venkateswarlu; Hsu, Joseph; Khadka, Prabhat; Horvath, Kent; Liu, Yie; Croteau, Deborah L; Bohr, Vilhelm A

    2014-05-01

    A variety of human tumors employ alternative and recombination-mediated lengthening for telomere maintenance (ALT). Human RecQ helicases, such as BLM and WRN, can efficiently unwind alternate/secondary structures during telomere replication and/or recombination. Here, we report a novel role for RECQL1, the most abundant human RecQ helicase but functionally least studied, in telomere maintenance. RECQL1 associates with telomeres in ALT cells and actively resolves telomeric D-loops and Holliday junction substrates. RECQL1 physically and functionally interacts with telomere repeat-binding factor 2 that in turn regulates its helicase activity on telomeric substrates. The telomeric single-stranded binding protein, protection of telomeres 1 efficiently stimulates RECQL1 on telomeric substrates containing thymine glycol, a replicative blocking lesion. Loss of RECQL1 results in dysfunctional telomeres, telomere loss and telomere shortening, elevation of telomere sister-chromatid exchanges and increased aphidicolin-induced telomere fragility, indicating a role for RECQL1 in telomere maintenance. Further, our results indicate that RECQL1 may participate in the same pathway as WRN, probably in telomere replication.

  20. Telomere dysfunction in alveolar epithelial cells causes lung remodeling and fibrosis

    PubMed Central

    Naikawadi, Ram P.; Disayabutr, Supparerk; Mallavia, Benat; Donne, Matthew L.; Green, Gary; La, Janet L.; Rock, Jason R.; Looney, Mark R.; Wolters, Paul J.

    2016-01-01

    Telomeres are short in type II alveolar epithelial cells (AECs) of patients with idiopathic pulmonary fibrosis (IPF). Whether dysfunctional telomeres contribute directly to development of lung fibrosis remains unknown. The objective of this study was to investigate whether telomere dysfunction in type II AECs, mediated by deletion of the telomere shelterin protein TRF1, leads to pulmonary fibrosis in mice (SPC-Cre TRF1fl/fl mice). Deletion of TRF1 in type II AECs for 2 weeks increased γH2AX DNA damage foci, but not histopathologic changes in the lung. Deletion of TRF1 in type II AECs for up to 9 months resulted in short telomeres and lung remodeling characterized by increased numbers of type II AECs, α-smooth muscle actin+ mesenchymal cells, collagen deposition, and accumulation of senescence-associated β-galactosidase+ lung epithelial cells. Deletion of TRF1 in collagen-expressing cells caused pulmonary edema, but not fibrosis. These results demonstrate that prolonged telomere dysfunction in type II AECs, but not collagen-expressing cells, leads to age-dependent lung remodeling and fibrosis. We conclude that telomere dysfunction in type II AECs is sufficient to cause lung fibrosis, and may be a dominant molecular defect causing IPF. SPC-Cre TRF1fl/fl mice will be useful for assessing cellular and molecular mechanisms of lung fibrosis mediated by telomere dysfunction. PMID:27699234

  1. Telomere length reflects phenotypic quality and costs of reproduction in a long-lived seabird.

    PubMed

    Bauch, Christina; Becker, Peter H; Verhulst, Simon

    2013-02-01

    Telomere length is associated with cellular senescence, lifestyle and ageing. Short telomeres indicate poor health in humans and reduced life expectancy in several bird species, but little is known about telomeres in relation to phenotypic quality in wild animals. We investigated telomere lengths in erythrocytes of known-age common terns (Sterna hirundo), a migratory seabird, in relation to arrival date and reproductive performance. Cross-sectional data revealed that, independent of age, individuals with short telomeres performed better: they arrived and reproduced earlier in the season and had more chicks in the nest. The latter effect was stronger the older the brood and stronger in males, which do most of the chick provisioning. Longitudinal data confirmed this pattern: compared with birds that lost their brood, birds that raised chicks beyond the 10th nestling day experienced higher telomere attrition from one year to the next. However, more detailed analysis revealed that the least and most successful individuals lost the fewest base pairs compared with birds with intermediate success. Our results suggest that reproductive success is achieved at the expense of telomeres, but that individual heterogeneity in susceptibility to such detrimental effects is important, as indicated by low telomere loss in the most successful birds.

  2. Telomere dysfunction in alveolar epithelial cells causes lung remodeling and fibrosis

    PubMed Central

    Naikawadi, Ram P.; Disayabutr, Supparerk; Mallavia, Benat; Donne, Matthew L.; Green, Gary; La, Janet L.; Rock, Jason R.; Looney, Mark R.; Wolters, Paul J.

    2016-01-01

    Telomeres are short in type II alveolar epithelial cells (AECs) of patients with idiopathic pulmonary fibrosis (IPF). Whether dysfunctional telomeres contribute directly to development of lung fibrosis remains unknown. The objective of this study was to investigate whether telomere dysfunction in type II AECs, mediated by deletion of the telomere shelterin protein TRF1, leads to pulmonary fibrosis in mice (SPC-Cre TRF1fl/fl mice). Deletion of TRF1 in type II AECs for 2 weeks increased γH2AX DNA damage foci, but not histopathologic changes in the lung. Deletion of TRF1 in type II AECs for up to 9 months resulted in short telomeres and lung remodeling characterized by increased numbers of type II AECs, α-smooth muscle actin+ mesenchymal cells, collagen deposition, and accumulation of senescence-associated β-galactosidase+ lung epithelial cells. Deletion of TRF1 in collagen-expressing cells caused pulmonary edema, but not fibrosis. These results demonstrate that prolonged telomere dysfunction in type II AECs, but not collagen-expressing cells, leads to age-dependent lung remodeling and fibrosis. We conclude that telomere dysfunction in type II AECs is sufficient to cause lung fibrosis, and may be a dominant molecular defect causing IPF. SPC-Cre TRF1fl/fl mice will be useful for assessing cellular and molecular mechanisms of lung fibrosis mediated by telomere dysfunction.

  3. Dysfunctional telomeres promote genomic instability and metastasis in the absence of telomerase activity in oncogene induced mammary cancer.

    PubMed

    Bojovic, Bojana; Crowe, David L

    2013-02-01

    Telomerase is a ribonucleoprotein that maintains the ends of chromosomes (telomeres). In normal cells lacking telomerase activity, telomeres shorten with each cell division because of the inability to completely synthesize the lagging strand. Critically shortened telomeres elicit DNA damage responses and limit cellular division and lifespan, providing an important tumor suppressor function. Most human cancer cells express telomerase which contributes significantly to the tumor phenotype. In human breast cancer, telomerase expression is predictive of clinical outcomes such as lymph node metastasis and survival. In mouse models of mammary cancer, telomerase expression is also upregulated. Telomerase overexpression resulted in spontaneous mammary tumor development in aged female mice. Increased mammary cancer also was observed when telomerase deficient mice were crossed with p53 null mutant animals. However, the effects of telomerase and telomere length on oncogene driven mammary cancer have not been completely characterized. To address these issues we characterized neu proto-oncogene driven mammary tumor formation in G1 Terc-/- (telomerase deficient with long telomeres), G3 Terc-/- (telomerase deficient with short telomeres), and Terc+/+ mice. Telomerase deficiency reduced the number of mammary tumors and increased tumor latency regardless of telomere length. Decreased tumor formation correlated with increased apoptosis in Terc deficient tumors. Short telomeres dramatically increased lung metastasis which correlated with increased genomic instability, and specific alterations in DNA copy number and gene expression. We concluded that short telomeres promote metastasis in the absence of telomerase activity in neu oncogene driven mammary tumors.

  4. Does the cryogenic freezing process cause shorter telomeres?

    PubMed

    Jenkins, Edmund C; Ye, Lingling; Silverman, Wayne P

    2012-08-01

    We have observed evidence of increased telomere shortening in short-term T-lymphocyte cultures following freezing and thawing of the original inoculum obtained by ficoll-paque gradient centrifugation, compared to T-lymphocytes that were cultured immediately without freezing and thawing from the same blood sample from 3 female and 3 male adults. Because freezing may have similar effects on other cell types, and because telomere shortening may only manifest its effects after many years or decades, we suggest there is a pressing need for evaluation of the effects of freezing on any cells envisioned for clinical applications, including embryo implantation. PMID:22465657

  5. Telomere Biology in Metazoa

    PubMed Central

    Gomes, Nuno M.V.; Shay, Jerry W.; Wright, Woodring E.

    2010-01-01

    In this review we present critical overview of some of the available literature on the fundamental biology of telomeres and telomerase in Metazoan. With the exception of Nematodes and Arthropods, the (TTAGGG)n sequence is conserved in most Metazoa. Available data shows that telomerase-based end maintenance is a very ancient mechanism in unicellular and multicellular organisms. In invertebrates, fish, amphibian, and reptiles persistent telomerase activity in somatic tissues might allow the maintenance of the extensive regenerative potentials of these species. Telomerase repression among birds and many mammals suggests that, as humans, they may use replicative aging as a tumor protection mechanism. PMID:20655915

  6. Telomere length, genetic variants and gastric cancer risk in a Chinese population.

    PubMed

    Du, Jiangbo; Zhu, Xun; Xie, Cuiwei; Dai, Ningbin; Gu, Yayun; Zhu, Meng; Wang, Cheng; Gao, Yong; Pan, Feng; Ren, Chuanli; Ji, Yong; Dai, Juncheng; Ma, Hongxia; Jiang, Yue; Chen, Jiaping; Yi, Honggang; Zhao, Yang; Hu, Zhibin; Shen, Hongbing; Jin, Guangfu

    2015-09-01

    Telomeres maintain chromosomal stability and integrity and are crucial in carcinogenesis. Telomere length is implicated in multiple cancer risk, but the results are conflicting. Genome-wide association studies have identified several genetic loci associated with telomere length in Caucasians. However, the roles of telomere length and related variants on gastric cancer development are largely unknown. We conducted a case-control study including 1136 gastric cancer cases and 1012 controls to evaluate the associations between telomere length, eight telomere length-related variants identified in Caucasians and gastric cancer risk in Chinese population. We observed an obvious U-shaped association between telomere length and gastric cancer risk (P < 0.001), with odds ratios (95% confidence intervals) being 3.81 (2.82-5.13), 1.65 (1.21-2.26), 1.28 (0.93-1.77) and 1.78 (1.30-2.44) for individuals in the first (the shortest), second, third and fifth (the longest) quintile as compared with those in the fourth quintile as reference group. The weighted genetic score (WGS) of eight variants was significantly associated with telomere length (P < 0.001), and in particular, the G allele of rs2736100 in TERT at 5p15.33 exhibited a significant association with long telomeres (P = 0.047). However, we did not observe significant associations between these genetic variants and gastric cancer risk for both single-variant and WGS analyses. These findings suggest that either short or extreme long telomeres may be risk factor for gastric cancer. Genetic variants identified in Caucasians may also contribute to the variation of telomere length in Chinese but seems not to gastric cancer susceptibility.

  7. TP53-dependent chromosome instability is associated with transient reductions in telomere length in immortal telomerase-positive cell lines

    NASA Technical Reports Server (NTRS)

    Schwartz, J. L.; Jordan, R.; Liber, H.; Murnane, J. P.; Evans, H. H.

    2001-01-01

    Telomere shortening in telomerase-negative somatic cells leads to the activation of the TP53 protein and the elimination of potentially unstable cells. We examined the effect of TP53 gene expression on both telomere metabolism and chromosome stability in immortal, telomerase-positive cell lines. Telomere length, telomerase activity, and chromosome instability were measured in multiple clones isolated from three related human B-lymphoblast cell lines that vary in TP53 expression; TK6 cells express wild-type TP53, WTK1 cells overexpress a mutant form of TP53, and NH32 cells express no TP53 protein. Clonal variations in both telomere length and chromosome stability were observed, and shorter telomeres were associated with higher levels of chromosome instability. The shortest telomeres were found in WTK1- and NH32-derived cells, and these cells had 5- to 10-fold higher levels of chromosome instability. The primary marker of instability was the presence of dicentric chromosomes. Aneuploidy and other stable chromosome alterations were also found in clones showing high levels of dicentrics. Polyploidy was found only in WTK1-derived cells. Both telomere length and chromosome instability fluctuated in the different cell populations with time in culture, presumably as unstable cells and cells with short telomeres were eliminated from the growing population. Our results suggest that transient reductions in telomere lengths may be common in immortal cell lines and that these alterations in telomere metabolism can have a profound effect on chromosome stability. Copyright 2000 Wiley-Liss, Inc.

  8. Parallel telomere shortening in multiple body tissues owing to malaria infection.

    PubMed

    Asghar, Muhammad; Palinauskas, Vaidas; Zaghdoudi-Allan, Nadège; Valkiūnas, Gediminas; Mukhin, Andrey; Platonova, Elena; Färnert, Anna; Bensch, Staffan; Hasselquist, Dennis

    2016-08-17

    Several studies have shown associations between shorter telomere length in blood and weakened immune function, susceptibility to infections, and increased risk of morbidity and mortality. Recently, we have shown that malaria accelerates telomere attrition in blood cells and shortens lifespan in birds. However, the impact of infections on telomere attrition in different body tissues within an individual is unknown. Here, we tested whether malarial infection leads to parallel telomere shortening in blood and tissue samples from different organs. We experimentally infected siskins (Spinus spinus) with the avian malaria parasite Plasmodium ashfordi, and used real-time quantitative polymerase chain reaction (PCR) to measure telomere length in control and experimentally infected siskins. We found that experimentally infected birds showed faster telomere attrition in blood over the course of infection compared with control individuals (repeatedly measured over 105 days post-infection (DPI)). Shorter telomeres were also found in the tissue of all six major organs investigated (liver, lungs, spleen, heart, kidney, and brain) in infected birds compared with controls at 105 DPI. To the best of our knowledge, this is the first study showing that an infectious disease results in synchronous telomere shortening in the blood and tissue cells of internal organs within individuals, implying that the infection induces systemic stress. Our results have far-reaching implications for understanding how the short-term effects of an infection can translate into long-term costs, such as organ dysfunction, degenerative diseases, and ageing. PMID:27488651

  9. The human telomere

    SciTech Connect

    Moyzis, R.K.

    1989-01-01

    An ultimate goal of human genetics is the generation of a complete physical and ''functional'' map of the human genome. Twenty-five percent of human DNA, however, consists of repetitive DNA sequences. These repetitive DNA sequences are thought to arise by many mechanisms, from direct sequence amplification by the unequal recombination of homologous DNA regions to the reverse flow of genetic information. A general outline of the chromosomal organization of these repetitive sequences will be discussed. Our working hypothesis is that certain classes of human repetitive DNA sequences ''encode'' the information necessary for defining long-range genomic structure. Evidence will be presented that the first goal of this research, the identification and cloning of the human telomere, has been achieved. A human repetitive DNA library was constructed from randomly sheared, reassociated, and oligo(G/center dot/C)-tailed DNA, a method that minimizes the potential loss of sequences devoid of a given restriction enzyme site. Sequences too large to clone efficiently in cosmid or /lambda/ vectors, such as centromeric repeats, or telomeric sequences with an end incompatible for cloning, should be present in this library. In order to isolate highly conserved repetitive DNA sequences, this library was screened with radiolabeled hamster Cot50 repetitive DNA. Two clones, containing tandem arrays of the sequence (TTAGGG), were isolated by this method. 30 refs., 1 fig., 2 tabs.

  10. Shorter telomere length in peripheral blood leukocytes is associated with childhood autism

    PubMed Central

    Li, Zongchang; Tang, Jinsong; Li, Hong; Chen, Shan; He, Ying; Liao, Yanhui; Wei, Zhen; Wan, Guobin; Xiang, Xi; Xia, Kun; Chen, Xiaogang

    2014-01-01

    Telomeres are protective chromosomal structures that play a key role in preserving genomic stability. Epidemiologic studies have shown that the abnormal telomere length in leukocytes is associated with some mental disorders and age-related diseases. However, the association between leukocyte telomere length and autism has not been investigated. Here we investigated the possible association between relative telomere length (RTL) in peripheral blood leukocytes and childhood autism by using an established real-time polymerase chain reaction method. We observed significantly shorter RTL in patients with childhood autism than in controls (p = 0.006). Individuals with shorter RTL had a significantly increased presence of childhood autism compared with those who had long RTL. In patients, we found that family training interventions have a significant effect on telomere length (P = 0.012), but no correlations between RTL and clinical features (paternal age, maternal age, age of onset, illness of duration, CARS score and ABC score) were observed in this study. These results provided the first evidence that shorter leukocytes telomere length is significantly associated with childhood autism. The molecular mechanism underlying telomere length may be implicated in the development of autism. PMID:25399515

  11. Genetic Inactivation of ATRX Leads to a Decrease in the Amount of Telomeric Cohesin and Level of Telomere Transcription in Human Glioma Cells

    PubMed Central

    Eid, Rita; Demattei, Marie-Véronique; Episkopou, Harikleia; Augé-Gouillou, Corinne; Decottignies, Anabelle; Grandin, Nathalie

    2015-01-01

    Mutations in ATRX (alpha thalassemia/mental retardation syndrome X-linked), a chromatin-remodeling protein, are associated with the telomerase-independent ALT (alternative lengthening of telomeres) pathway of telomere maintenance in several types of cancer, including human gliomas. In telomerase-positive glioma cells, we found by immunofluorescence that ATRX localized not far from the chromosome ends but not exactly at the telomere termini. Chromatin immunoprecipitation (ChIP) experiments confirmed a subtelomeric localization for ATRX, yet short hairpin RNA (shRNA)-mediated genetic inactivation of ATRX failed to trigger the ALT pathway. Cohesin has been recently shown to be part of telomeric chromatin. Here, using ChIP, we showed that genetic inactivation of ATRX provoked diminution in the amount of cohesin in subtelomeric regions of telomerase-positive glioma cells. Inactivation of ATRX also led to diminution in the amount of TERRAs, noncoding RNAs resulting from transcription of telomeric DNA, as well as to a decrease in RNA polymerase II (RNAP II) levels at the telomeres. Our data suggest that ATRX might establish functional interactions with cohesin on telomeric chromatin in order to control TERRA levels and that one or the other or both of these events might be relevant to the triggering of the ALT pathway in cancer cells that exhibit genetic inactivation of ATRX. PMID:26055325

  12. A role for Separase in telomere protection.

    PubMed

    Cipressa, Francesca; Morciano, Patrizia; Bosso, Giuseppe; Mannini, Linda; Galati, Alessandra; Raffa, Grazia Daniela; Cacchione, Stefano; Musio, Antonio; Cenci, Giovanni

    2016-01-18

    Drosophila telomeres are elongated by transposition of specialized retroelements rather than telomerase activity and are assembled independently of the sequence. Fly telomeres are protected by the terminin complex that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. We show that mutations in the Drosophila Separase encoding gene Sse lead not only to endoreduplication but also telomeric fusions (TFs), suggesting a role for Sse in telomere capping. We demonstrate that Separase binds terminin proteins and HP1, and that it is enriched at telomeres. Furthermore, we show that loss of Sse strongly reduces HP1 levels, and that HP1 overexpression in Sse mutants suppresses TFs, suggesting that TFs are caused by a HP1 diminution. Finally, we find that siRNA-induced depletion of ESPL1, the Sse human orthologue, causes telomere dysfunction and HP1 level reduction in primary fibroblasts, highlighting a conserved role of Separase in telomere protection.

  13. Telomere biology and telomere diseases: implications for practice and research.

    PubMed

    Young, Neal S

    2010-01-01

    The recent recognition of genetic defects in telomeres and telomere repair in multiple human diseases has practical implications for hematologists and oncologists and their patients; consequences for future clinical research in hematology and other subspecialties; and even importance in the interpretation of animal experiments involving cell propagation. Telomere diseases include constitutional marrow failure as dyskeratosis congenita, some apparently acquired aplastic anemia, myelodysplasia and acute myeloid leukemia; pulmonary fibrosis; and hepatic nodular regenerative hyperplasia and cirrhosis. Accelerated telomere attrition is a likely pathophysiology of cancer arising from chronic inflammation. Telomerase can be modulated by sex hormones, which may explain the activity of androgens in marrow failure. Measurement of telomere length of peripheral blood leukocytes is a simple screening clinical assay. Detection of a mutation in a patient has implications for therapy, prognosis, monitoring, and genetic counseling. For research in hematology and oncology, telomere biology could be assessed as a risk for secondary malignancies and in graft-versus-host disease, for progression in a variety of blood cancers, and as potentially modifiable by hormone replacement strategies.

  14. Reconstructing the in vivo dynamics of hematopoietic stem cells from telomere length distributions.

    PubMed

    Werner, Benjamin; Beier, Fabian; Hummel, Sebastian; Balabanov, Stefan; Lassay, Lisa; Orlikowsky, Thorsten; Dingli, David; Brümmendorf, Tim H; Traulsen, Arne

    2015-10-15

    We investigate the in vivo patterns of stem cell divisions in the human hematopoietic system throughout life. In particular, we analyze the shape of telomere length distributions underlying stem cell behavior within individuals. Our mathematical model shows that these distributions contain a fingerprint of the progressive telomere loss and the fraction of symmetric cell proliferations. Our predictions are tested against measured telomere length distributions in humans across all ages, collected from lymphocyte and granulocyte sorted telomere length data of 356 healthy individuals, including 47 cord blood and 28 bone marrow samples. We find an increasing stem cell pool during childhood and adolescence and an approximately maintained stem cell population in adults. Furthermore, our method is able to detect individual differences from a single tissue sample, i.e. a single snapshot. Prospectively, this allows us to compare cell proliferation between individuals and identify abnormal stem cell dynamics, which affects the risk of stem cell related diseases.

  15. Telomeres: protecting chromosomes against genome instability

    PubMed Central

    O’Sullivan, Roderick J.; Karlseder, Jan

    2010-01-01

    Preface The natural ends of linear chromosomes require unique genetic and structural adaptations to facilitate the protection of genetic material. This is achieved by the sequestration of the telomeric sequence into a protective nucleoprotein cap that masks the ends from constitutive exposure to the DNA damage response (DDR). When telomeres are unmasked, genome instability arises. Balancing capping requirements with telomere replication and the enzymatic processing steps obligatory for telomere function is a complex problem. Telomeric proteins and their interacting factors create an environment at chromosome ends that inhibits DNA repair there, however, the repair machinery is essential for proper telomere function. PMID:20125188

  16. Genetics and molecular biology of telomeres

    SciTech Connect

    Biessmann, H. ); Mason, J.M. )

    1992-01-01

    For simplicity, we define telomeres as complex structures at the ends of linear chromosomes that perform several cellular functions. Among the functions proposed for telomeres at least two are vital: protection of the chromosome end from degradation and fusion (termed capping) and complete replication of DNA sequences at chromosome ends. Telomeres are also involved in associations with other telomeres and structures within the nucleus, but the functions of these associations are not clearly understood. Although the concept of the telomere was developed, and the term was coined, more than 50 years ago (Muller, 1938), the structure of the telomere and its functions are still not fully understood. 317 refs., 4 figs.

  17. Tired telomeres: Poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women.

    PubMed

    Prather, Aric A; Gurfein, Blake; Moran, Patricia; Daubenmier, Jennifer; Acree, Michael; Bacchetti, Peter; Sinclair, Elizabeth; Lin, Jue; Blackburn, Elizabeth; Hecht, Frederick M; Epel, Elissa S

    2015-07-01

    Poor sleep quality and short sleep duration are associated with increased incidence and progression of a number of chronic health conditions observed at greater frequency among the obese and those experiencing high levels of stress. Accelerated cellular aging, as indexed by telomere attrition in immune cells, is a plausible pathway linking sleep and disease risk. Prior studies linking sleep and telomere length are mixed. One factor may be reliance on leukocytes, which are composed of varied immune cell types, as the sole measure of telomere length. To better clarify these associations, we investigated the relationships of global sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and diary-reported sleep duration with telomere length in different immune cell subsets, including granulocytes, peripheral blood mononuclear cells (PBMCs), CD8+ and CD4+ T lymphocytes, and B lymphocytes in a sample of 87 obese men and women (BMI mean=35.4, SD=3.6; 81.6% women; 62.8% Caucasian). Multiple linear regression analyses were performed adjusting for age, gender, race, education, BMI, sleep apnea risk, and perceived stress. Poorer PSQI global sleep quality was associated with statistically significantly shorter telomere length in lymphocytes but not granulocytes and in particular CD8+ T cells (b=-56.8 base pairs per one point increase in PSQI, SE=20.4, p=0.007) and CD4+ T cells (b=-37.2, SE=15.9, p=0.022). Among separate aspects of global sleep quality, low perceived sleep quality and decrements in daytime function were most related to shorter telomeres. In addition, perceived stress moderated the sleep-CD8+ telomere association. Poorer global sleep quality predicted shorter telomere length in CD8+ T cells among those with high perceived stress but not in low stress participants. These findings provide preliminary evidence that poorer global sleep quality is related to telomere length in several immune cell types, which may serve as a pathway linking sleep and

  18. Tired telomeres: Poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women.

    PubMed

    Prather, Aric A; Gurfein, Blake; Moran, Patricia; Daubenmier, Jennifer; Acree, Michael; Bacchetti, Peter; Sinclair, Elizabeth; Lin, Jue; Blackburn, Elizabeth; Hecht, Frederick M; Epel, Elissa S

    2015-07-01

    Poor sleep quality and short sleep duration are associated with increased incidence and progression of a number of chronic health conditions observed at greater frequency among the obese and those experiencing high levels of stress. Accelerated cellular aging, as indexed by telomere attrition in immune cells, is a plausible pathway linking sleep and disease risk. Prior studies linking sleep and telomere length are mixed. One factor may be reliance on leukocytes, which are composed of varied immune cell types, as the sole measure of telomere length. To better clarify these associations, we investigated the relationships of global sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and diary-reported sleep duration with telomere length in different immune cell subsets, including granulocytes, peripheral blood mononuclear cells (PBMCs), CD8+ and CD4+ T lymphocytes, and B lymphocytes in a sample of 87 obese men and women (BMI mean=35.4, SD=3.6; 81.6% women; 62.8% Caucasian). Multiple linear regression analyses were performed adjusting for age, gender, race, education, BMI, sleep apnea risk, and perceived stress. Poorer PSQI global sleep quality was associated with statistically significantly shorter telomere length in lymphocytes but not granulocytes and in particular CD8+ T cells (b=-56.8 base pairs per one point increase in PSQI, SE=20.4, p=0.007) and CD4+ T cells (b=-37.2, SE=15.9, p=0.022). Among separate aspects of global sleep quality, low perceived sleep quality and decrements in daytime function were most related to shorter telomeres. In addition, perceived stress moderated the sleep-CD8+ telomere association. Poorer global sleep quality predicted shorter telomere length in CD8+ T cells among those with high perceived stress but not in low stress participants. These findings provide preliminary evidence that poorer global sleep quality is related to telomere length in several immune cell types, which may serve as a pathway linking sleep and

  19. Tired Telomeres: poor global sleep quality, perceived stress, and telomere length in immune cell subsets in obese men and women

    PubMed Central

    Prather, Aric A.; Gurfein, Blake; Moran, Patricia; Daubenmier, Jennifer; Acree, Michael; Bacchetti, Peter; Sinclair, Elizabeth; Lin, Jue; Blackburn, Elizabeth; Hecht, Frederick M.; Epel, Elissa S.

    2014-01-01

    Poor sleep quality and short sleep duration are associated with increased incidence and progression of a number of chronic health conditions observed at greater frequency among the obese and those experiencing high levels of stress. Accelerated cellular aging, as indexed by telomere attrition in immune cells, is a plausible pathway linking sleep and disease risk. Prior studies linking sleep and telomere length are mixed. One factor may be reliance on leukocytes, which are composed of varied immune cell types, as the sole measure of telomere length. To better clarify these associations, we investigated the relationships of global sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and diary-reported sleep duration with telomere length in different immune cell subsets, including granulocytes, peripheral blood mononuclear cells (PBMCs), CD8+ and CD4+ T lymphocytes, and B lymphocytes in a sample of 87 obese men and women (BMI mean = 35.4, SD = 3.6; 81.6% women; 62.8% Caucasian). Multiple linear regression analyses were performed adjusting for age, gender, race, education, BMI, sleep apnea risk, and perceived stress. Poorer PSQI global sleep quality was associated with statistically significantly shorter telomere length in lymphocytes but not granulocytes and in particular CD8+ T cells (b = −56.8 base pairs per one point increase in PSQI, SE = 20.4, p=0.007) and CD4+ T cells (b = −37.2, SE = 15.9, p = 0.022). Among separate aspects of global sleep quality, low perceived sleep quality and decrements in daytime function were most related to shorter telomeres. In addition, perceived stress moderated the sleep-CD8+ telomere association. Poorer global sleep quality predicted shorter telomere length in CD8+ T cells among those with high perceived stress but not in low stress participants. These findings provide preliminary evidence that poorer global sleep quality is related to telomere length in several immune cell types, which may serve as a pathway

  20. Is telomere erosion a mechanism of species extinction?

    PubMed

    Stindl, Reinhard

    2004-03-15

    According to the fossil record, 99.9% of all species that have ever lived on Earth have disappeared. However, only about 4% died out during the five mass extinction events, whereas it seems that the majority of species vanished without any signs of significant earthbound or extraterrestrial physical threats. Clearly, biological extinction mechanisms are by far the most important, but they are subject to serious limitations concerning the worldwide disappearance of species. In view of that, species-inherent mechanisms, which could lead to the worldwide destabilization of a population, might be worth reconsideration. Telomeres, the protective caps of chromosome ends, and the enzyme telomerase have been well preserved in plants and animals during evolution. In the absence of telomerase activity, telomeric DNA has been shown to shorten every time a cell divides. The concept of a mitotic clock based on the gradual erosion of telomeres is now generally accepted and has been confirmed in numerous plants and animals. Chromosomal rearrangements are the hallmarks of two completely different biological phenomena, cancer and speciation. In premalignant cells, gradual telomere erosion beyond a critical threshold is a well-known inducer of chromosomal instability. The species clock hypothesis, as presented here, is based on the idea of a tiny loss of mean telomere length per generation. This mechanism would not rapidly endanger the survival of a particular species. Yet, after many thousands of generations, critically short telomeres could lead to the weakening and even the extinction of old species and would simultaneously create the unstable chromosomal environment that might result in the origination of new species.

  1. Mammalian telomeres and their partnership with lamins

    PubMed Central

    Burla, Romina; La Torre, Mattia; Saggio, Isabella

    2016-01-01

    ABSTRACT Chromosome ends are complex structures, which require a panel of factors for their elongation, replication, and protection. We describe here the mechanics of mammalian telomeres, dynamics and maintainance in relation to lamins. Multiple biochemical connections, including association of telomeres to the nuclear envelope and matrix, of telomeric proteins to lamins, and of lamin-associated proteins to chromosome ends, underline the interplay between lamins and telomeres. Paths toward senescence, such as defective telomere replication, altered heterochromatin organization, and impaired DNA repair, are common to lamins' and telomeres' dysfunction. The convergence of phenotypes can be interpreted through a model of dynamic, lamin-controlled functional platforms dedicated to the function of telomeres as fragile sites. The features of telomeropathies and laminopathies, and of animal models underline further overlapping aspects, including the alteration of stem cell compartments. We expect that future studies of basic biology and on aging will benefit from the analysis of this telomere-lamina interplay. PMID:27116558

  2. Stress Responsive Biochemical Anabolic/Catabolic Ratio and Telomere Length in Older Adults

    PubMed Central

    Vasunilashorn, Sarinnapha; Cohen, Alan A.

    2014-01-01

    It has been hypothesized that chronic psychological stress is associated with shorter telomere length; however, the mechanisms that link stress and telomere length are not well understood. To examine the interplay between biochemical factors related to stress arousal and cellular aging, we investigate the association between anabolic/catabolic (A/C) imbalance and leukocyte telomere length (LTL) in the Social Environment and Biomarkers of Aging Study (SEBAS) in Taiwan (N=925). SEBAS participants age 54 and older (mean age 68.3) with values for two anabolic hormones (serum dehydroepiandrosterone sulfate [DHEAS] and insulin growth factor [IGF]-1), four catabolic hormones (cortisol, epinephrine, norepinephrine, and interleukin-6 [IL-6]), and leukocyte telomere length were examined. We found that high IL-6 was associated with short LTL (≤0.88 T/S ratio; odds ratio [OR] 1.41, 95% confidence interval [CI] 1.04–1.92). Neither DHEAS/cortisol nor IGF-1/cortisol ratio was associated with telomere length; however, a high A/C imbalance summary score was associated with a greater odds of having a short LTL relative to long LTL (OR 1.19, 95% CI 1.05–1.35). These results indicate that our A/C imbalance score, defined by several anabolic and catabolic biochemical factors, may be one mechanism through which psychological stress is associated with short leukocyte telomere length and possibly cellular senescence. PMID:25343365

  3. Telomere Dysfunction Triggers Palindrome Formation Independently of Double-Strand Break Repair Mechanisms

    PubMed Central

    Raykov, Vasil; Marvin, Marcus E.; Louis, Edward J.; Maringele, Laura

    2016-01-01

    Inverted chromosome duplications or palindromes are linked with genetic disorders and malignant transformation. They are considered by-products of DNA double-strand break (DSB) repair: the homologous recombination (HR) and the nonhomologous end joining (NHEJ). Palindromes near chromosome ends are often triggered by telomere losses. An important question is to what extent their formation depends upon DSB repair mechanisms. Here we addressed this question using yeast genetics and comparative genomic hybridization. We induced palindrome formation by passaging cells lacking any form of telomere maintenance (telomerase and telomere recombination). Surprisingly, we found that DNA ligase 4, essential for NHEJ, did not make a significant contribution to palindrome formation induced by telomere losses. Moreover RAD51, important for certain HR-derived mechanisms, had little effect. Furthermore RAD52, which is essential for HR in yeast, appeared to decrease the number of palindromes in cells proliferating without telomeres. This study also uncovered an important role for Rev3 and Rev7 (but not for Pol32) subunits of polymerase ζ in the survival of cells undergoing telomere losses and forming palindromes. We propose a model called short-inverted repeat-induced synthesis in which DNA synthesis, rather than DSB repair, drives the inverted duplication triggered by telomere dysfunction. PMID:27334270

  4. The effect of chemotherapeutic agents on telomere length maintenance in breast cancer cell lines.

    PubMed

    Motevalli, Azadeh; Yasaei, Hemad; Virmouni, Sara Anjomani; Slijepcevic, Predrag; Roberts, Terry

    2014-06-01

    Mammalian telomeric DNA consists of tandem repeats of the sequence TTAGGG associated with a specialized set of proteins, known collectively as Shelterin. These telosomal proteins protect the ends of chromosomes against end-to-end fusion and degradation. Short telomeres in breast cancer cells confer telomere dysfunction and this can be related to Shelterin proteins and their level of expression in breast cancer cell lines. This study investigates whether expression of Shelterin and Shelterin-associated proteins are altered, and influence the protection and maintenance of telomeres, in breast cancer cells. 5-aza-2'-deoxycytidine (5-aza-CdR) and trichostatin A (TSA) were used in an attempt to reactivate the expression of silenced genes. Our studies have shown that Shelterin and Shelterin-associated genes were down-regulated in breast cancer cell lines; this may be due to epigenetic modification of DNA as the promoter region of POT1 was found to be partially methylated. Shelterin genes expression was up-regulated upon treatment of 21NT breast cancer cells with 5-aza-CdR and TSA. The telomere length of treated 21NT cells was measured by q-PCR showed an increase in telomere length at different time points. Our studies have shown that down-regulation of Shelterin genes is partially due to methylation in some epithelial breast cancer cell lines. Removal of epigenetic silencing results in up-regulation of Shelterin and Shelterin-associated genes which can then lead to telomere length elongation and stability. PMID:24807106

  5. Lifespan adversity and later adulthood telomere length in the nationally representative US Health and Retirement Study

    PubMed Central

    Gemmill, Alison; Weir, David; Adler, Nancy E.; Prather, Aric A.

    2016-01-01

    Stress over the lifespan is thought to promote accelerated aging and early disease. Telomere length is a marker of cell aging that appears to be one mediator of this relationship. Telomere length is associated with early adversity and with chronic stressors in adulthood in many studies. Although cumulative lifespan adversity should have bigger impacts than single events, it is also possible that adversity in childhood has larger effects on later life health than adult stressors, as suggested by models of biological embedding in early life. No studies have examined the individual vs. cumulative effects of childhood and adulthood adversities on adult telomere length. Here, we examined the relationship between cumulative childhood and adulthood adversity, adding up a range of severe financial, traumatic, and social exposures, as well as comparing them to each other, in relation to salivary telomere length. We examined 4,598 men and women from the US Health and Retirement Study. Single adversities tended to have nonsignificant relations with telomere length. In adjusted models, lifetime cumulative adversity predicted 6% greater odds of shorter telomere length. This result was mainly due to childhood adversity. In adjusted models for cumulative childhood adversity, the occurrence of each additional childhood event predicted 11% increased odds of having short telomeres. This result appeared mainly because of social/traumatic exposures rather than financial exposures. This study suggests that the shadow of childhood adversity may reach far into later adulthood in part through cellular aging. PMID:27698131

  6. Human CST has independent functions during telomere duplex replication and C-strand fill-in

    PubMed Central

    Wang, Feng; Stewart, Jason A.; Kasbek, Christopher; Zhao, Yong; Wright, Woodring E.; Price, Carolyn M.

    2012-01-01

    Summary Human CST (CTC1-STN1-TEN1) is an RPA-like complex that is needed for efficient replication through the telomere duplex and genome-wide replication restart after fork stalling. Here we show that STN1/CST has a second function in telomere replication during G-overhang maturation. Analysis of overhang structure after STN1 depletion revealed normal kinetics for telomerase-mediated extension in S-phase but a delay in subsequent overhang shortening. This delay resulted from a defect in C-strand fill-in. Short telomeres exhibited the fill-in defect but normal telomere duplex replication, indicating that STN1/CST functions independently in these processes. Our work also indicates that the requirement for STN1/CST in telomere duplex replication correlates with increasing telomere length and replication stress. Our results provide the first direct evidence that STN1/CST participates in C-strand fill-in. They also demonstrate that STN1/CST participates in two mechanistically separate steps during telomere replication and identify CST as a novel replication factor that solves diverse replication-associated problems. PMID:23142664

  7. Tel1 and Rad51 are involved in the maintenance of telomeres with capping deficiency.

    PubMed

    Di Domenico, Enea Gino; Mattarocci, Stefano; Cimino-Reale, Graziella; Parisi, Paola; Cifani, Noemi; D'Ambrosio, Ettore; Zakian, Virginia A; Ascenzioni, Fiorentina

    2013-07-01

    Vertebrate-like T2AG3 telomeres in tlc1-h yeast consist of short double-stranded regions and long single-stranded overhang (G-tails) and, although based on Tbf1-capping activity, they are capping deficient. Consistent with this idea, we observe Y' amplification because of homologous recombination, even in the presence of an active telomerase. In these cells, Y' amplification occurs by different pathways: in Tel1(+) tlc1h cells, it is Rad51-dependent, whereas in the absence of Tel1, it depends on Rad50. Generation of telomeric G-tail, which is cell cycle regulated, depends on the MRX (Mre11-Rad50-Xrs2) complex in tlc1h cells or is MRX-independent in tlc1h tel1Δ mutants. Unexpectedly, we observe telomere elongation in tlc1h lacking Rad51 that seems to act as a telomerase competitor for binding to telomeric G-tails. Overall, our results show that Tel1 and Rad51 have multiple roles in the maintenance of vertebrate-like telomeres in yeast, supporting the idea that they may participate to evolutionary conserved telomere protection mechanism/s acting at uncapped telomeres.

  8. Spermatozoa telomeres determine telomere length in early embryos and offspring.

    PubMed

    de Frutos, C; López-Cardona, A P; Fonseca Balvís, N; Laguna-Barraza, R; Rizos, D; Gutierrez-Adán, A; Bermejo-Álvarez, P

    2016-01-01

    Offspring telomere length (TL) has been correlated with paternal TL, but the mechanism for this parent of origin-specific inheritance remains unclear. The objective of this study has been to determine the role of spermatozoa TL in embryonic telomere lengthening by using two mouse models showing dimorphism in their spermatozoa TL: Mus musculus vs Mus spretus and old vs young Mus musculus. Mus spretus spermatozoa displayed a shorter TL than Mus musculus. Hybrid offspring exhibited lower TL compared with Mus musculus starting at the two-cell stage, before the onset of telomerase expression. To analyze the role of spermatozoa telomeres in early telomere lengthening, we compared the TL in oocytes, zygotes, two-cell embryos and blastocysts produced by parthenogenesis or by fertilization with Mus musculus or Mus spretus spermatozoa. TL was significantly higher in spermatozoa compared with oocytes, and it increased significantly from the oocyte to the zygote stage in those embryos fertilized with Mus musculus spermatozoa, but not in those fertilized with Mus spretus spermatozoa or produced by parthenogenesis. A further increase was noted from the zygote to the two-cell stage in fertilized Mus musculus embryos, whereas hybrid embryos maintained the oocyte TL. Spermatozoa TL shortened with age in Mus musculus and the offspring from young males showed a significantly higher TL compared with that fathered by old males. These significant differences were already noticeable at the two-cell stage. These results suggest that spermatozoa telomeres act as a guide for telomerase-independent telomere lengthening resulting in differences in TL that persist after birth.

  9. Spermatozoa telomeres determine telomere length in early embryos and offspring.

    PubMed

    de Frutos, C; López-Cardona, A P; Fonseca Balvís, N; Laguna-Barraza, R; Rizos, D; Gutierrez-Adán, A; Bermejo-Álvarez, P

    2016-01-01

    Offspring telomere length (TL) has been correlated with paternal TL, but the mechanism for this parent of origin-specific inheritance remains unclear. The objective of this study has been to determine the role of spermatozoa TL in embryonic telomere lengthening by using two mouse models showing dimorphism in their spermatozoa TL: Mus musculus vs Mus spretus and old vs young Mus musculus. Mus spretus spermatozoa displayed a shorter TL than Mus musculus. Hybrid offspring exhibited lower TL compared with Mus musculus starting at the two-cell stage, before the onset of telomerase expression. To analyze the role of spermatozoa telomeres in early telomere lengthening, we compared the TL in oocytes, zygotes, two-cell embryos and blastocysts produced by parthenogenesis or by fertilization with Mus musculus or Mus spretus spermatozoa. TL was significantly higher in spermatozoa compared with oocytes, and it increased significantly from the oocyte to the zygote stage in those embryos fertilized with Mus musculus spermatozoa, but not in those fertilized with Mus spretus spermatozoa or produced by parthenogenesis. A further increase was noted from the zygote to the two-cell stage in fertilized Mus musculus embryos, whereas hybrid embryos maintained the oocyte TL. Spermatozoa TL shortened with age in Mus musculus and the offspring from young males showed a significantly higher TL compared with that fathered by old males. These significant differences were already noticeable at the two-cell stage. These results suggest that spermatozoa telomeres act as a guide for telomerase-independent telomere lengthening resulting in differences in TL that persist after birth. PMID:26475708

  10. Variation of the 3' telomeric overhang lengths in human cells.

    PubMed

    Lee, Myung Eun; Rha, Sun Young; Jeung, Hei-Cheul; Kim, Tae Soo; Chung, Hyun Cheol; Oh, Bong-Kyeong

    2008-06-01

    The telomeric G-rich 3' overhang is important for the maintenance of chromosomal integrity by stabilizing T-loop structure in which the 3' overhang invades the double-stranded telomeric DNA. However, the 3' overhang length has not been examined in different human cell lines, and its regulatory mechanism has not been revealed. In this study, we examined overhang length in 56 human cancerous cell lines and five normal cell lines, originated from various tissues. In cancer cells, relative overhang length existed in a wide range from 23% to 308% and showed no significant association with tissue types although short overhang was noted in brain, cervix, and colorectal cells. Normal cells exhibited overhangs in the range from 92% to 202%, which were relatively longer than those seen in cancer cells (p = 0.002). The overhang length was positively correlated with telomere length (p < 0.001), and showed no correlation with mRNA levels of hTERT, a catalytic protein of telomerase, POT1, an overhang binding protein and TPP1, a POT1 interacting protein. This study demonstrates a broad distribution of overhang length in human cells, suggesting a dynamic regulation of 3' overhang length. The overhang length seems to be closely associated with telomere length and might be regulated by multiple mechanisms.

  11. Cell death during crisis is mediated by mitotic telomere deprotection.

    PubMed

    Hayashi, Makoto T; Cesare, Anthony J; Rivera, Teresa; Karlseder, Jan

    2015-06-25

    Tumour formation is blocked by two barriers: replicative senescence and crisis. Senescence is triggered by short telomeres and is bypassed by disruption of tumour-suppressive pathways. After senescence bypass, cells undergo crisis, during which almost all of the cells in the population die. Cells that escape crisis harbour unstable genomes and other parameters of transformation. The mechanism of cell death during crisis remains unexplained. Here we show that human cells in crisis undergo spontaneous mitotic arrest, resulting in death during mitosis or in the following cell cycle. This phenotype is induced by loss of p53 function, and is suppressed by telomerase overexpression. Telomere fusions triggered mitotic arrest in p53-compromised non-crisis cells, indicating that such fusions are the underlying cause of cell death. Exacerbation of mitotic telomere deprotection by partial TRF2 (also known as TERF2) knockdown increased the ratio of cells that died during mitotic arrest and sensitized cancer cells to mitotic poisons. We propose a crisis pathway wherein chromosome fusions induce mitotic arrest, resulting in mitotic telomere deprotection and cell death, thereby eliminating precancerous cells from the population.

  12. Shortened telomere length in white matter oligodendrocytes in major depression: potential role of oxidative stress.

    PubMed

    Szebeni, Attila; Szebeni, Katalin; DiPeri, Timothy; Chandley, Michelle J; Crawford, Jessica D; Stockmeier, Craig A; Ordway, Gregory A

    2014-10-01

    Telomere shortening is observed in peripheral mononuclear cells from patients with major depressive disorder (MDD). Whether this finding and its biological causes impact the health of the brain in MDD is unknown. Brain cells have differing vulnerabilities to biological mechanisms known to play a role in accelerating telomere shortening. Here, two glia cell populations (oligodendrocytes and astrocytes) known to have different vulnerabilities to a key mediator of telomere shortening, oxidative stress, were studied. The two cell populations were separately collected by laser capture micro-dissection of two white matter regions shown previously to demonstrate pathology in MDD patients. Cells were collected from brain donors with MDD at the time of death and age-matched psychiatrically normal control donors (N = 12 donor pairs). Relative telomere lengths in white matter oligodendrocytes, but not astrocytes, from both brain regions were significantly shorter for MDD donors as compared to matched control donors. Gene expression levels of telomerase reverse transcriptase were significantly lower in white matter oligodendrocytes from MDD as compared to control donors. Likewise, the gene expression of oxidative defence enzymes superoxide dismutases (SOD1 and SOD2), catalase (CAT) and glutathione peroxidase (GPX1) were significantly lower in oligodendrocytes from MDD as compared to control donors. No such gene expression changes were observed in astrocytes from MDD donors. These findings suggest that attenuated oxidative stress defence and deficient telomerase contribute to telomere shortening in oligodendrocytes in MDD, and suggest an aetiological link between telomere shortening and white matter abnormalities previously described in MDD.

  13. Murine Pif1 interacts with telomerase and is dispensable for telomere function in vivo.

    PubMed

    Snow, Bryan E; Mateyak, Maria; Paderova, Jana; Wakeham, Andrew; Iorio, Caterina; Zakian, Virginia; Squire, Jeremy; Harrington, Lea

    2007-02-01

    Pif1 is a 5'-to-3' DNA helicase critical to DNA replication and telomere length maintenance in the budding yeast Saccharomyces cerevisiae. ScPif1 is a negative regulator of telomeric repeat synthesis by telomerase, and recombinant ScPif1 promotes the dissociation of the telomerase RNA template from telomeric DNA in vitro. In order to dissect the role of mPif1 in mammals, we cloned and disrupted the mPif1 gene. In wild-type animals, mPif1 expression was detected only in embryonic and hematopoietic lineages. mPif1(-/-) mice were viable at expected frequencies, displayed no visible abnormalities, and showed no reproducible alteration in telomere length in two different null backgrounds, even after several generations. Spectral karyotyping of mPif1(-/-) fibroblasts and splenocytes revealed no significant change in chromosomal rearrangements. Furthermore, induction of apoptosis or DNA damage revealed no differences in cell viability compared to what was found for wild-type fibroblasts and splenocytes. Despite a novel association of mPif1 with telomerase, mPif1 did not affect the elongation activity of telomerase in vitro. Thus, in contrast to what occurs with ScPif1, murine telomere homeostasis or genetic stability does not depend on mPif1, perhaps due to fundamental differences in the regulation of telomerase and/or telomere length between mice and yeast or due to genetic redundancy with other DNA helicases.

  14. Antioxidants safeguard telomeres in bold chicks

    PubMed Central

    Kim, Sin-Yeon; Velando, Alberto

    2015-01-01

    Telomeres are sensitive to damage induced by oxidative stress, and thus it is expected that dietary antioxidants may support the maintenance of telomere length in animals, particularly those with a fast rate of life (e.g. fast metabolism, activity and growth). We tested experimentally the effect of antioxidant supplements on telomere length during early development in wild gull chicks with natural individual variations in behaviour pattern and growth rate. Proactive chicks had shorter telomeres than reactive chicks, but the penalty for the bold behaviour pattern was reduced by antioxidant supplementation. Chicks growing faster had longer telomeres during early growth, suggesting that inherited quality supports a fast life history. PMID:25948570

  15. Analysis of the epigenetic status of telomeres by using ChIP-seq data

    PubMed Central

    Vaquero-Sedas, María I.; Luo, Chongyuan; Vega-Palas, Miguel A.

    2012-01-01

    The chromatin structure of eukaryotic telomeres plays an essential role in telomere functions. However, their study might be impaired by the presence of interstitial telomeric sequences (ITSs), which have a widespread distribution in different model systems. We have developed a simple approach to study the chromatin structure of Arabidopsis telomeres independently of ITSs by analyzing ChIP-seq data. This approach could be used to study the chromatin structure of telomeres in some other eukaryotes. The analysis of ChIP-seq experiments revealed that Arabidopsis telomeres have higher density of histone H3 than centromeres, which might reflects their short nucleosomal organization. These experiments also revealed that Arabidopsis telomeres have lower levels of heterochromatic marks than centromeres (H3K9Me2 and H3K27Me), higher levels of some euchromatic marks (H3K4Me2 and H3K9Ac) and similar or lower levels of other euchromatic marks (H3K4Me3, H3K36Me2, H3K36Me3 and H3K18Ac). Interestingly, the ChIP-seq experiments also revealed that Arabidopsis telomeres exhibit high levels of H3K27Me3, a repressive mark that associates with many euchromatic genes. The epigenetic profile of Arabidopsis telomeres is closely related to the previously defined chromatin state 2. This chromatin state is found in 23% of Arabidopsis genes, many of which are repressed or lowly expressed. At least, in part, this scenario is similar in rice. PMID:22855559

  16. Telomeric repeat-containing RNA (TERRA) and telomerase are components of telomeres during mammalian gametogenesis.

    PubMed

    Reig-Viader, Rita; Vila-Cejudo, Marta; Vitelli, Valerio; Buscà, Rafael; Sabaté, Montserrat; Giulotto, Elena; Caldés, Montserrat Garcia; Ruiz-Herrera, Aurora

    2014-05-01

    Telomeres are ribonucleoprotein structures at the end of chromosomes composed of telomeric DNA, specific-binding proteins, and noncoding RNA (TERRA). Despite their importance in preventing chromosome instability, little is known about the cross talk between these three elements during the formation of the germ line. Here, we provide evidence that both TERRA and the telomerase enzymatic subunit (TERT) are components of telomeres in mammalian germ cells. We found that TERRA colocalizes with telomeres during mammalian meiosis and that its expression progressively increases during spermatogenesis until the beginning of spermiogenesis. While both TERRA levels and distribution would be regulated in a gender-specific manner, telomere-TERT colocalization appears to be regulated based on species-specific characteristics of the telomeric structure. Moreover, we found that TERT localization at telomeres is maintained throughout spermatogenesis as a structural component without affecting telomere elongation. Our results represent the first evidence of colocalization between telomerase and telomeres during mammalian gametogenesis.

  17. Telomere attrition and candidate gene mutations preceding monosomy 7 in aplastic anemia.

    PubMed

    Dumitriu, Bogdan; Feng, Xingmin; Townsley, Danielle M; Ueda, Yasutaka; Yoshizato, Tetsuichi; Calado, Rodrigo T; Yang, Yanqin; Wakabayashi, Yoshiyuki; Kajigaya, Sachiko; Ogawa, Seishi; Zhu, Jun; Young, Neal S

    2015-01-22

    The pathophysiology of severe aplastic anemia (SAA) is immune-mediated destruction of hematopoietic stem and progenitor cells (HSPCs). Most patients respond to immunosuppressive therapies, but a minority transform to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), frequently associated with monosomy 7 (-7). Thirteen SAA patients were analyzed for acquired mutations in myeloid cells at the time of evolution to -7, and all had a dominant HSPC clone bearing specific acquired mutations. However, mutations in genes associated with MDS/AML were present in only 4 cases. Patients who evolved to MDS and AML showed marked progressive telomere attrition before the emergence of -7. Single telomere length analysis confirmed accumulation of short telomere fragments of individual chromosomes. Our results indicate that accelerated telomere attrition in the setting of a decreased HSPC pool is characteristic of early myeloid oncogenesis, specifically chromosome 7 loss, in MDS/AML after SAA, and provides a possible mechanism for development of aneuploidy.

  18. Telomere functions grounding on TERRA firma.

    PubMed

    Azzalin, Claus M; Lingner, Joachim

    2015-01-01

    Long noncoding telomeric repeat-containing RNAs - TERRAs - are transcribed in a regulated manner from telomeres throughout eukaryotes. TERRA molecules consist of chromosome end-specific subtelomeric sequences and telomeric repeats at their 3' ends. Recent work suggests that TERRA sustains several important functions at chromosome ends. TERRA can regulate telomere length through modulation of exonuclease 1 and telomerase, it may promote recruitment of chromatin modifiers to damaged telomeres and thereby enable DNA end-processing, and it may promote telomere protein composition changes during cell cycle progression. Furthermore, telomere transcription regulates chromosome-end mobility within the nucleus. We review how TERRA, by regulated expression and by providing a molecular scaffold for various protein enzymes, can support a large variety of vital functions.

  19. Telomere Length in Aged Mayak PA Nuclear Workers Chronically Exposed to Internal Alpha and External Gamma Radiation.

    PubMed

    Scherthan, Harry; Sotnik, Natalia; Peper, Michel; Schrock, Gerrit; Azizova, Tamara; Abend, Michael

    2016-06-01

    Telomeres consist of GC-rich DNA repeats and the "shelterin" protein complex that together protect chromosome ends from fusion and degradation. Telomeres shorten with age due to incomplete end replication and upon exposure to environmental and intrinsic stressors. Exposure to ionizing radiation is known to modulate telomere length. However, the response of telomere length in humans chronically exposed to radiation is poorly understood. Here, we studied relative telomere length (RTL) by IQ-FISH to leukocyte nuclei in a group of 100 workers from the plutonium production facility at the Mayak Production Association (PA) who were chronically exposed to alpha-emitting ((239)Pu) radiation and/or gamma (photon) radiation, and 51 local residents serving as controls, with a similar mean age of about 80 years. We applied generalized linear statistical models adjusted for age at biosampling and the second exposure type on a linear scale and observed an age-dependent telomere length reduction. In those individuals with the lowest exposure, a significant reduction of about 20% RTL was observed, both for external gamma radiation (≤1 Gy) and internal alpha radiation (≤0.05-0.1 Gy to the red bone marrow). In highly exposed individuals (>0.1 Gy alpha, 1-1.5 Gy gamma), the RTL was similar to control. Stratification by gender revealed a significant (∼30%) telomere reduction in low-dose-exposed males, which was absent in females. While the gender differences in RTL may reflect different working conditions, lifestyle and/or telomere biology, absence of a dose response in the highly exposed individuals may reflect selection against cells with short telomeres or induction of telomere-protective effects. Our observations suggest that chronic systemic exposure to radiation leads to variable dose-dependent effects on telomere length. PMID:27340887

  20. Age-Related Declines and Disease-Associated Variation in Immune Cell Telomere Length in a Wild Mammal

    PubMed Central

    Beirne, Christopher; Delahay, Richard; Hares, Michelle; Young, Andrew

    2014-01-01

    Immunosenescence, the deterioration of immune system capability with age, may play a key role in mediating age-related declines in whole-organism performance, but the mechanisms that underpin immunosenescence are poorly understood. Biomedical research on humans and laboratory models has documented age and disease related declines in the telomere lengths of leukocytes (‘immune cells’), stimulating interest their having a potentially general role in the emergence of immunosenescent phenotypes. However, it is unknown whether such observations generalise to the immune cell populations of wild vertebrates living under ecologically realistic conditions. Here we examine longitudinal changes in the mean telomere lengths of immune cells in wild European badgers (Meles meles). Our findings provide the first evidence of within-individual age-related declines in immune cell telomere lengths in a wild vertebrate. That the rate of age-related decline in telomere length appears to be steeper within individuals than at the overall population level raises the possibility that individuals with short immune cell telomeres and/or higher rates of immune cell telomere attrition may be selectively lost from this population. We also report evidence suggestive of associations between immune cell telomere length and bovine tuberculosis infection status, with individuals detected at the most advanced stage of infection tending to have shorter immune cell telomeres than disease positive individuals. While male European badgers are larger and show higher rates of annual mortality than females, we found no evidence of a sex difference in either mean telomere length or the average rate of within-individual telomere attrition with age. Our findings lend support to the view that age-related declines in the telomere lengths of immune cells may provide one potentially general mechanism underpinning age-related declines in immunocompetence in natural populations. PMID:25268841

  1. Age-related declines and disease-associated variation in immune cell telomere length in a wild mammal.

    PubMed

    Beirne, Christopher; Delahay, Richard; Hares, Michelle; Young, Andrew

    2014-01-01

    Immunosenescence, the deterioration of immune system capability with age, may play a key role in mediating age-related declines in whole-organism performance, but the mechanisms that underpin immunosenescence are poorly understood. Biomedical research on humans and laboratory models has documented age and disease related declines in the telomere lengths of leukocytes ('immune cells'), stimulating interest their having a potentially general role in the emergence of immunosenescent phenotypes. However, it is unknown whether such observations generalise to the immune cell populations of wild vertebrates living under ecologically realistic conditions. Here we examine longitudinal changes in the mean telomere lengths of immune cells in wild European badgers (Meles meles). Our findings provide the first evidence of within-individual age-related declines in immune cell telomere lengths in a wild vertebrate. That the rate of age-related decline in telomere length appears to be steeper within individuals than at the overall population level raises the possibility that individuals with short immune cell telomeres and/or higher rates of immune cell telomere attrition may be selectively lost from this population. We also report evidence suggestive of associations between immune cell telomere length and bovine tuberculosis infection status, with individuals detected at the most advanced stage of infection tending to have shorter immune cell telomeres than disease positive individuals. While male European badgers are larger and show higher rates of annual mortality than females, we found no evidence of a sex difference in either mean telomere length or the average rate of within-individual telomere attrition with age. Our findings lend support to the view that age-related declines in the telomere lengths of immune cells may provide one potentially general mechanism underpinning age-related declines in immunocompetence in natural populations. PMID:25268841

  2. Telomere Length in Aged Mayak PA Nuclear Workers Chronically Exposed to Internal Alpha and External Gamma Radiation.

    PubMed

    Scherthan, Harry; Sotnik, Natalia; Peper, Michel; Schrock, Gerrit; Azizova, Tamara; Abend, Michael

    2016-06-01

    Telomeres consist of GC-rich DNA repeats and the "shelterin" protein complex that together protect chromosome ends from fusion and degradation. Telomeres shorten with age due to incomplete end replication and upon exposure to environmental and intrinsic stressors. Exposure to ionizing radiation is known to modulate telomere length. However, the response of telomere length in humans chronically exposed to radiation is poorly understood. Here, we studied relative telomere length (RTL) by IQ-FISH to leukocyte nuclei in a group of 100 workers from the plutonium production facility at the Mayak Production Association (PA) who were chronically exposed to alpha-emitting ((239)Pu) radiation and/or gamma (photon) radiation, and 51 local residents serving as controls, with a similar mean age of about 80 years. We applied generalized linear statistical models adjusted for age at biosampling and the second exposure type on a linear scale and observed an age-dependent telomere length reduction. In those individuals with the lowest exposure, a significant reduction of about 20% RTL was observed, both for external gamma radiation (≤1 Gy) and internal alpha radiation (≤0.05-0.1 Gy to the red bone marrow). In highly exposed individuals (>0.1 Gy alpha, 1-1.5 Gy gamma), the RTL was similar to control. Stratification by gender revealed a significant (∼30%) telomere reduction in low-dose-exposed males, which was absent in females. While the gender differences in RTL may reflect different working conditions, lifestyle and/or telomere biology, absence of a dose response in the highly exposed individuals may reflect selection against cells with short telomeres or induction of telomere-protective effects. Our observations suggest that chronic systemic exposure to radiation leads to variable dose-dependent effects on telomere length.

  3. Telomerase inhibitor imetelstat has preclinical activity across the spectrum of non-small cell lung cancer oncogenotypes in a telomere length dependent manner.

    PubMed

    Frink, Robin E; Peyton, Michael; Schiller, Joan H; Gazdar, Adi F; Shay, Jerry W; Minna, John D

    2016-05-31

    Telomerase was evaluated as a therapeutic oncotarget by studying the efficacy of the telomerase inhibitor imetelstat in non-small cell lung cancer (NSCLC) cell lines to determine the range of response phenotypes and identify potential biomarkers of response. A panel of 63 NSCLC cell lines was studied for telomere length and imetelstat efficacy in inhibiting colony formation and no correlation was found with patient characteristics, tumor histology, and oncogenotypes. While there was no overall correlation between imetelstat efficacy with initial telomere length (ranging from 1.5 to 20 kb), the quartile of NSCLC lines with the shortest telomeres was more sensitive than the quartile with the longest telomeres. Continuous long-term treatment with imetelstat resulted in sustained telomerase inhibition, progressive telomere shortening and eventual growth inhibition in a telomere-length dependent manner. Cessation of imetelstat therapy before growth inhibition was followed by telomere regrowth. Likewise, in vivo imetelstat treatment caused tumor xenograft growth inhibition in a telomere-length dependent manner. We conclude from these preclinical studies of telomerase as an oncotarget tested by imetelstat response that imetelstat has efficacy across the entire oncogenotype spectrum of NSCLC, continuous therapy is necessary to prevent telomere regrowth, and short telomeres appears to be the best treatment biomarker.

  4. Telomeres thrown for a loop.

    PubMed

    Haber, James E

    2004-11-19

    A remarkable paper from the de Lange lab (Wang et al., 2004) in a recent issue of Cell reveals that homologous recombination can result in the abrupt shortening of telomeres in a process that appears to involve reciprocal crossing over within the t-loop structure that protects chromosome ends.

  5. Nestling telomere shortening, but not telomere length, reflects developmental stress and predicts survival in wild birds.

    PubMed

    Boonekamp, Jelle J; Mulder, G A; Salomons, H Martijn; Dijkstra, Cor; Verhulst, Simon

    2014-06-22

    Developmental stressors often have long-term fitness consequences, but linking offspring traits to fitness prospects has remained a challenge. Telomere length predicts mortality in adult birds, and may provide a link between developmental conditions and fitness prospects. Here, we examine the effects of manipulated brood size on growth, telomere dynamics and post-fledging survival in free-living jackdaws. Nestlings in enlarged broods achieved lower mass and lost 21% more telomere repeats relative to nestlings in reduced broods, showing that developmental stress accelerates telomere shortening. Adult telomere length was positively correlated with their telomere length as nestling (r = 0.83). Thus, an advantage of long telomeres in nestlings is carried through to adulthood. Nestling telomere shortening predicted post-fledging survival and recruitment independent of manipulation and fledgling mass. This effect was strong, with a threefold difference in recruitment probability over the telomere shortening range. By contrast, absolute telomere length was neither affected by brood size manipulation nor related to survival. We conclude that telomere loss, but not absolute telomere length, links developmental conditions to subsequent survival and suggest that telomere shortening may provide a key to unravelling the physiological causes of developmental effects on fitness.

  6. Role of TERRA in the Regulation of Telomere Length

    PubMed Central

    Wang, Caiqin; Zhao, Li; Lu, Shiming

    2015-01-01

    Telomere dysfunction is closely associated with human diseases such as cancer and ageing. Inappropriate changes in telomere length and/or structure result in telomere dysfunction. Telomeres have been considered to be transcriptionally silent, but it was recently demonstrated that mammalian telomeres are transcribed into telomeric repeat-containing RNA (TERRA). TERRA, a long non-coding RNA, participates in the regulation of telomere length, telomerase activity and heterochromatinization. The correct regulation of telomere length may be crucial to telomeric homeostasis and functions. Here, we summarize recent advances in our understanding of the crucial role of TERRA in the maintenance of telomere length, with focus on the variety of mechanisms by which TERRA is involved in the regulation of telomere length. This review aims to enable further understanding of how TERRA-targeted drugs can target telomere-related diseases. PMID:25678850

  7. Role of TERRA in the regulation of telomere length.

    PubMed

    Wang, Caiqin; Zhao, Li; Lu, Shiming

    2015-01-01

    Telomere dysfunction is closely associated with human diseases such as cancer and ageing. Inappropriate changes in telomere length and/or structure result in telomere dysfunction. Telomeres have been considered to be transcriptionally silent, but it was recently demonstrated that mammalian telomeres are transcribed into telomeric repeat-containing RNA (TERRA). TERRA, a long non-coding RNA, participates in the regulation of telomere length, telomerase activity and heterochromatinization. The correct regulation of telomere length may be crucial to telomeric homeostasis and functions. Here, we summarize recent advances in our understanding of the crucial role of TERRA in the maintenance of telomere length, with focus on the variety of mechanisms by which TERRA is involved in the regulation of telomere length. This review aims to enable further understanding of how TERRA-targeted drugs can target telomere-related diseases.

  8. Telomere shortening leads to an acceleration of synucleinopathy and impaired microglia response in a genetic mouse model.

    PubMed

    Scheffold, Annika; Holtman, Inge R; Dieni, Sandra; Brouwer, Nieske; Katz, Sarah-Fee; Jebaraj, Billy Michael Chelliah; Kahle, Philipp J; Hengerer, Bastian; Lechel, André; Stilgenbauer, Stephan; Boddeke, Erik W G M; Eggen, Bart J L; Rudolph, Karl-Lenhard; Biber, Knut

    2016-01-01

    Parkinson's disease is one of the most common neurodegenerative disorders of the elderly and ageing hence described to be a major risk factor. Telomere shortening as a result of the inability to fully replicate the ends of linear chromosomes is one of the hallmarks of ageing. The role of telomere dysfunction in neurological diseases and the ageing brain is not clarified and there is an ongoing discussion whether telomere shortening is linked to Parkinson's disease. Here we studied a mouse model of Parkinson's disease (Thy-1 [A30P] α-synuclein transgenic mouse model) in the background of telomere shortening (Terc knockout mouse model). α-synuclein transgenic mice with short telomeres (αSYN(tg/tg) G3Terc(-/-)) developed an accelerated disease with significantly decreased survival. This accelerated phenotype of mice with short telomeres was characterized by a declined motor performance and an increased formation of α-synuclein aggregates. Immunohistochemical analysis and mRNA expression studies revealed that the disease end-stage brain stem microglia showed an impaired response in αSYN(tg/tg) G3Terc(-/-) microglia animals. These results provide the first experimental data that telomere shortening accelerates α-synuclein pathology that is linked to limited microglia function in the brainstem. PMID:27550225

  9. Moderate stem-cell telomere shortening rate postpones cancer onset in a stochastic model

    NASA Astrophysics Data System (ADS)

    Holbek, Simon; Bendtsen, Kristian Moss; Juul, Jeppe

    2013-10-01

    Mammalian cells are restricted from proliferating indefinitely. Telomeres at the end of each chromosome are shortened at cell division and when they reach a critical length, the cell will enter permanent cell cycle arrest—a state known as senescence. This mechanism is thought to be tumor suppressing, as it helps prevent precancerous cells from dividing uncontrollably. Stem cells express the enzyme telomerase, which elongates the telomeres, thereby postponing senescence. However, unlike germ cells and most types of cancer cells, stem cells only express telomerase at levels insufficient to fully maintain the length of their telomeres, leading to a slow decline in proliferation potential. It is not yet fully understood how this decline influences the risk of cancer and the longevity of the organism. We here develop a stochastic model to explore the role of telomere dynamics in relation to both senescence and cancer. The model describes the accumulation of cancerous mutations in a multicellular organism and creates a coherent theoretical framework for interpreting the results of several recent experiments on telomerase regulation. We demonstrate that the longest average cancer-free lifespan before cancer onset is obtained when stem cells start with relatively long telomeres that are shortened at a steady rate at cell division. Furthermore, the risk of cancer early in life can be reduced by having a short initial telomere length. Finally, our model suggests that evolution will favor a shorter than optimal average cancer-free lifespan in order to postpone cancer onset until late in life.

  10. Quantitative proteomic analysis of human breast epithelial cells with differential telomere length

    SciTech Connect

    Yu, Li-Rong . E-mail: lyu@ncifcrf.gov; Chan, King C.; Tahara, Hidetoshi; Lucas, David A.; Chatterjee, Koushik; Issaq, Haleem J.; Veenstra, Timothy D. . E-mail: veenstra@ncifcrf.gov

    2007-05-18

    Telomeres play important functional roles in cell proliferation, cell cycle regulation, and genetic stability, in which telomere length is critical. In this study, quantitative proteome comparisons for the human breast epithelial cells with short and long telomeres (184-hTERT{sub L} vs. 184-hTERT{sub S} and 90P-hTERT{sub L} vs. 90P-hTERT{sub S}), resulting from transfection of the human telomerase reverse transcriptase (hTERT) gene, were performed using cleavable isotope-coded affinity tags. More than 2000 proteins were quantified in each comparative experiment, with approximately 77% of the proteins identified in both analyses. In the cells with long telomeres, significant and consistent alterations were observed in metabolism (amino acid, nucleotide, and lipid metabolism), genetic information transmission (transcription and translation regulation, spliceosome and ribosome complexes), and cell signaling. Interestingly, the DNA excision repair pathway is enhanced, while integrin and its ligands are downregulated in the cells with long telomeres. These results may provide valuable information related to telomere functions.

  11. Sod2 haploinsufficiency does not accelerate aging of telomere dysfunctional mice.

    PubMed

    Guachalla, Luis Miguel; Ju, Zhenyu; Koziel, Rafal; von Figura, Guido; Song, Zhangfa; Fusser, Markus; Epe, Bernd; Jansen-Durr, Pidder; Rudolph, K Lenhard

    2009-03-05

    Telomere shortening represents a causal factor of cellular senescence. At the same time, several lines of evidence indicate a pivotal role of oxidative DNA damage for the aging process in vivo. A causal connection between the two observations was suggested by experiments showing accelerated telomere shorting under conditions of oxidative stress in cultured cells, but has never been studied in vivo. We therefore have analysed whether an increase in mitochondrial derived oxidative stress in response to heterozygous deletion of superoxide dismutase (Sod2(+/-)) would exacerbate aging phenotypes in telomere dysfunctional (mTerc(-/-)) mice. Heterozygous deletion of Sod2 resulted in reduced SOD2 protein levels and increased oxidative stress in aging telomere dysfunctional mice, but this did not lead to an increase in basal levels of oxidative nuclear DNA damage, an accumulation of nuclear DNA breaks, or an increased rate of telomere shortening in the mice. Moreover, heterozygous deletion of Sod2 did not accelerate the depletion of stem cells and the impairment in organ maintenance in aging mTerc(-/-) mice. In agreement with these observations, Sod2 haploinsufficiency did not lead to a further reduction in lifespan of mTerc(-/-) mice. Together, these results indicate that a decrease in SOD2-dependent antioxidant defence does not exacerbate aging in the context of telomere dysfunction.

  12. Telomere diminution as a cause of immune failure in old age: an unfashionable demurral.

    PubMed

    Miller, R A

    2000-02-01

    The hypothesis that cellular proliferation leads to telomere shortening, which in turn leads to replicative failure, which in turn leads to a failure of immune function in aged individuals, is here evaluated against the published evidence about the nature and pace of immune decline in animals and humans. Although the evidence is strong that telomere shortening in late-passage human lymphocyte and non-lymphocytic cell lines induces a state in which the cells can no longer divide, there is no compelling evidence to suggest that replicative senescence of this kind is an important contributor to immune deficiency in old age. On the contrary, the accelerated pace of immune decline in mice and rats, whose telomeres are much longer than those of humans, argues strongly that the factors that pace age-dependent immune decline do not include telomere shortening. In addition, three subsidiary arguments - (a) the decline with age in naive T cell proliferation despite their relatively long telomeres; (b) the preservation of T cell proliferation in Werner's syndrome patients despite their cell lines' proclivity to replicative senescence in vitro; and (c) the ability of PMA and ionomycin to stimulate proliferation in T cells from old donors, but not in late-passage T celt lines - all support the conclusion that aging of the immune system in living animals is not a consequence of the kind of replicative senescence typically caused by short telomeres in vitro.

  13. Transient anomalous diffusion of telomeres in the nucleus of mammalian cells.

    PubMed

    Bronstein, I; Israel, Y; Kepten, E; Mai, S; Shav-Tal, Y; Barkai, E; Garini, Y

    2009-07-01

    We measured individual trajectories of fluorescently labeled telomeres in the nucleus of eukaryotic cells in the time range of 10(-2)-10(4)sec by combining a few acquisition methods. At short times the motion is subdiffusive with r2 approximately talpha and it changes to normal diffusion at longer times. The short times diffusion may be explained by the reptation model and the transient diffusion is consistent with a model of telomeres that are subject to a local binding mechanism with a wide but finite distribution of waiting times. These findings have important biological implications with respect to the genome organization in the nucleus.

  14. How homologous recombination maintains telomere integrity.

    PubMed

    Tacconi, Eliana M C; Tarsounas, Madalena

    2015-06-01

    Telomeres protect the ends of linear chromosomes against loss of genetic information and inappropriate processing as damaged DNA and are therefore crucial to the maintenance of chromosome integrity. In addition to providing a pathway for genome-wide DNA repair, homologous recombination (HR) plays a key role in telomere replication and capping. Consistent with this, the genomic instability characteristic of HR-deficient cells and tumours is driven in part by telomere dysfunction. Here, we discuss the mechanisms by which HR modulates the response to intrinsic cellular challenges that arise during telomere replication, as well as its impact on the assembly of telomere protective structures. How normal and tumour cells differ in their ability to maintain telomeres is deeply relevant to the search for treatments that would selectively eliminate cells whose capacity for HR-mediated repair has been compromised.

  15. The association of telomere length and genetic variation in telomere biology genes.

    PubMed

    Mirabello, Lisa; Yu, Kai; Kraft, Peter; De Vivo, Immaculata; Hunter, David J; Prescott, Jennifer; Wong, Jason Y Y; Chatterjee, Nilanjan; Hayes, Richard B; Savage, Sharon A

    2010-09-01

    Telomeres cap chromosome ends and are critical for genomic stability. Many telomere-associated proteins are important for telomere length maintenance. Recent genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) in genes encoding telomere-associated proteins (RTEL1 and TERT-CLPTM1) as markers of cancer risk. We conducted an association study of telomere length and 743 SNPs in 43 telomere biology genes. Telomere length in peripheral blood DNA was determined by Q-PCR in 3,646 participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and Nurses' Health Study. We investigated associations by SNP, gene, and pathway (functional group). We found no associations between telomere length and SNPs in TERT-CLPTM1L or RTEL1. Telomere length was not significantly associated with specific functional groups. Thirteen SNPs from four genes (MEN1, MRE11A, RECQL5, and TNKS) were significantly associated with telomere length. The strongest findings were in MEN1 (gene-based P=0.006), menin, which associates with the telomerase promoter and may negatively regulate telomerase. This large association study did not find strong associations with telomere length. The combination of limited diversity and evolutionary conservation suggest that these genes may be under selective pressure. More work is needed to explore the role of genetic variants in telomere length regulation.

  16. An H2A Histone Isotype, H2ac, Associates with Telomere and Maintains Telomere Integrity

    PubMed Central

    Tzeng, Tsai-Yu; Lin, I-Hsuan; Hsu, Ming-Ta

    2016-01-01

    Telomeres are capped at the ends of eukaryotic chromosomes and are composed of TTAGGG repeats bound to the shelterin complex. Here we report that a replication-dependent histone H2A isotype, H2ac, was associated with telomeres in human cells and co-immunoprecipitates with telomere repeat factor 2 (TRF2) and protection of telomeres protein 1 (POT1), whereas other histone H2A isotypes and mutations of H2ac did not bind to telomeres or these two proteins. The amino terminal basic domain of TRF2 was necessary for the association with H2ac and for the recruitment of H2ac to telomeres. Depletion of H2ac led to loss of telomeric repeat sequences, the appearance of dysfunctional telomeres, and chromosomal instability, including chromosomal breaks and anaphase bridges, as well as accumulation of telomere-associated DNA damage factors in H2ac depleted cells. Additionally, knockdown of H2ac elicits an ATM-dependent DNA damage response at telomeres and depletion of XPF protects telomeres against H2ac-deficiency-induced G-strand overhangs loss and DNA damage response, and prevents chromosomal instability. These findings suggest that the H2A isotype, H2ac, plays an essential role in maintaining telomere functional integrity. PMID:27228173

  17. Telomeric repeat-containing RNA TERRA: a noncoding RNA connecting telomere biology to genome integrity.

    PubMed

    Cusanelli, Emilio; Chartrand, Pascal

    2015-01-01

    Telomeres are dynamic nucleoprotein structures that protect the ends of chromosomes from degradation and activation of DNA damage response. For this reason, telomeres are essential to genome integrity. Chromosome ends are enriched in heterochromatic marks and proper organization of telomeric chromatin is important to telomere stability. Despite their heterochromatic state, telomeres are transcribed giving rise to long noncoding RNAs (lncRNA) called TERRA (telomeric repeat-containing RNA). TERRA molecules play critical roles in telomere biology, including regulation of telomerase activity and heterochromatin formation at chromosome ends. Emerging evidence indicate that TERRA transcripts form DNA-RNA hybrids at chromosome ends which can promote homologous recombination among telomeres, delaying cellular senescence and sustaining genome instability. Intriguingly, TERRA RNA-telomeric DNA hybrids are involved in telomere length homeostasis of telomerase-negative cancer cells. Furthermore, TERRA transcripts play a role in the DNA damage response (DDR) triggered by dysfunctional telomeres. We discuss here recent developments on TERRA's role in telomere biology and genome integrity, and its implication in cancer.

  18. TERRA and the state of the telomere.

    PubMed

    Rippe, Karsten; Luke, Brian

    2015-11-01

    Long noncoding telomeric repeat-containing RNA (TERRA) has been implicated in telomere maintenance in a telomerase-dependent and a telomerase-independent manner during replicative senescence and cancer. TERRA's proposed activities are diverse, thus making it difficult to pinpoint the critical roles that TERRA may have. We propose that TERRA orchestrates different activities at chromosome ends in a manner that depends on the state of the telomere.

  19. SORBS2 transcription is activated by telomere position effect-over long distance upon telomere shortening in muscle cells from patients with facioscapulohumeral dystrophy.

    PubMed

    Robin, Jérôme D; Ludlow, Andrew T; Batten, Kimberly; Gaillard, Marie-Cécile; Stadler, Guido; Magdinier, Frédérique; Wright, Woodring E; Shay, Jerry W

    2015-12-01

    DNA is organized into complex three-dimensional chromatin structures, but how this spatial organization regulates gene expression remains a central question. These DNA/chromatin looping structures can range in size from 10-20 kb (enhancers/repressors) to many megabases during intra- and inter-chromosomal interactions. Recently, the influence of telomere length on chromatin organization prior to senescence has revealed the existence of long-distance chromatin loops that dictate the expression of genes located up to 10 Mb from the telomeres (Telomere Position Effect-Over Long Distances [TPE-OLD]). Here, we demonstrate the existence of a telomere loop at the 4q35 locus involving the sorbin and SH3 domain-containing protein 2 gene, SORBS2, a skeletal muscle protein using a modification of the chromosome conformation capture method. The loop reveals a cis-acting mechanism modifying SORBS2 transcription. The expression of this gene is altered by TPE-OLD in myoblasts from patients affected with the age-associated genetic disease, facioscapulohumeral muscular dystrophy (FSHD1A, MIM 158900). SORBS2 is expressed in FSHD myoblasts with short telomeres, while not detectable in FSHD myoblasts with long telomeres or in healthy myoblasts regardless of telomere length. This indicates that TPE-OLD may modify the regulation of the 4q35 locus in a pathogenic context. Upon differentiation, both FSHD and healthy myotubes express SORBS2, suggesting that SORBS2 is normally up-regulated by maturation/differentiation of skeletal muscle and is misregulated by TPE-OLD-dependent variegation in FSHD myoblasts. These findings provide additional insights for the complexity and age-related symptoms of FSHD.

  20. SORBS2 transcription is activated by telomere position effect–over long distance upon telomere shortening in muscle cells from patients with facioscapulohumeral dystrophy

    PubMed Central

    Robin, Jérôme D.; Ludlow, Andrew T.; Batten, Kimberly; Gaillard, Marie-Cécile; Stadler, Guido; Magdinier, Frédérique; Wright, Woodring E.; Shay, Jerry W.

    2015-01-01

    DNA is organized into complex three-dimensional chromatin structures, but how this spatial organization regulates gene expression remains a central question. These DNA/chromatin looping structures can range in size from 10–20 kb (enhancers/repressors) to many megabases during intra- and inter-chromosomal interactions. Recently, the influence of telomere length on chromatin organization prior to senescence has revealed the existence of long-distance chromatin loops that dictate the expression of genes located up to 10 Mb from the telomeres (Telomere Position Effect–Over Long Distances [TPE-OLD]). Here, we demonstrate the existence of a telomere loop at the 4q35 locus involving the sorbin and SH3 domain-containing protein 2 gene, SORBS2, a skeletal muscle protein using a modification of the chromosome conformation capture method. The loop reveals a cis-acting mechanism modifying SORBS2 transcription. The expression of this gene is altered by TPE-OLD in myoblasts from patients affected with the age-associated genetic disease, facioscapulohumeral muscular dystrophy (FSHD1A, MIM 158900). SORBS2 is expressed in FSHD myoblasts with short telomeres, while not detectable in FSHD myoblasts with long telomeres or in healthy myoblasts regardless of telomere length. This indicates that TPE-OLD may modify the regulation of the 4q35 locus in a pathogenic context. Upon differentiation, both FSHD and healthy myotubes express SORBS2, suggesting that SORBS2 is normally up-regulated by maturation/differentiation of skeletal muscle and is misregulated by TPE-OLD-dependent variegation in FSHD myoblasts. These findings provide additional insights for the complexity and age-related symptoms of FSHD. PMID:26359233

  1. SORBS2 transcription is activated by telomere position effect-over long distance upon telomere shortening in muscle cells from patients with facioscapulohumeral dystrophy.

    PubMed

    Robin, Jérôme D; Ludlow, Andrew T; Batten, Kimberly; Gaillard, Marie-Cécile; Stadler, Guido; Magdinier, Frédérique; Wright, Woodring E; Shay, Jerry W

    2015-12-01

    DNA is organized into complex three-dimensional chromatin structures, but how this spatial organization regulates gene expression remains a central question. These DNA/chromatin looping structures can range in size from 10-20 kb (enhancers/repressors) to many megabases during intra- and inter-chromosomal interactions. Recently, the influence of telomere length on chromatin organization prior to senescence has revealed the existence of long-distance chromatin loops that dictate the expression of genes located up to 10 Mb from the telomeres (Telomere Position Effect-Over Long Distances [TPE-OLD]). Here, we demonstrate the existence of a telomere loop at the 4q35 locus involving the sorbin and SH3 domain-containing protein 2 gene, SORBS2, a skeletal muscle protein using a modification of the chromosome conformation capture method. The loop reveals a cis-acting mechanism modifying SORBS2 transcription. The expression of this gene is altered by TPE-OLD in myoblasts from patients affected with the age-associated genetic disease, facioscapulohumeral muscular dystrophy (FSHD1A, MIM 158900). SORBS2 is expressed in FSHD myoblasts with short telomeres, while not detectable in FSHD myoblasts with long telomeres or in healthy myoblasts regardless of telomere length. This indicates that TPE-OLD may modify the regulation of the 4q35 locus in a pathogenic context. Upon differentiation, both FSHD and healthy myotubes express SORBS2, suggesting that SORBS2 is normally up-regulated by maturation/differentiation of skeletal muscle and is misregulated by TPE-OLD-dependent variegation in FSHD myoblasts. These findings provide additional insights for the complexity and age-related symptoms of FSHD. PMID:26359233

  2. Complex telomere-associated repeat units in members of the genus Chironomus evolve from sequences similar to simple telomeric repeats.

    PubMed Central

    Nielsen, L; Edström, J E

    1993-01-01

    The dipteran Chironomus tentans has complex tandemly repeated 350-bp DNA sequences at or near the chromosome ends. As in Drosophila melanogaster, short simple repeats with cytosines and guanines in different strands have never been observed. We were therefore interested in learning whether the Chironomus repeats could have evolved from simple sequence telomeric DNA, which might suggest that they constitute a functional equivalent. We screened for repeat units with evolutionarily ancient features within the tandem arrays and recovered two clones with a less-evolved structure. Sequence analysis reveals that the present-day 350-bp unit probably evolved from a simpler 165-bp unit through the acquisition of transposed sequences. The 165-bp unit contains DNA with a highly biased distribution of cytosine and guanine between the two strands, although with the ratios inverted in two minor parts of the repeat. It is largely built up of short degenerate subrepeats for which most of the sequence can be reconstructed. The consensus for the subrepeat sequence is similar to the simple telomeric repeat sequences of several kinds of eukaryotes. We propose that the present-day unit has evolved from telomeric, simple sequence, asymmetric DNA from which it has retained some original sequence features and possibly functions. Images PMID:8441399

  3. Complex telomere-associated repeat units in members of the genus Chironomus evolve from sequences similar to simple telomeric repeats.

    PubMed

    Nielsen, L; Edström, J E

    1993-03-01

    The dipteran Chironomus tentans has complex tandemly repeated 350-bp DNA sequences at or near the chromosome ends. As in Drosophila melanogaster, short simple repeats with cytosines and guanines in different strands have never been observed. We were therefore interested in learning whether the Chironomus repeats could have evolved from simple sequence telomeric DNA, which might suggest that they constitute a functional equivalent. We screened for repeat units with evolutionarily ancient features within the tandem arrays and recovered two clones with a less-evolved structure. Sequence analysis reveals that the present-day 350-bp unit probably evolved from a simpler 165-bp unit through the acquisition of transposed sequences. The 165-bp unit contains DNA with a highly biased distribution of cytosine and guanine between the two strands, although with the ratios inverted in two minor parts of the repeat. It is largely built up of short degenerate subrepeats for which most of the sequence can be reconstructed. The consensus for the subrepeat sequence is similar to the simple telomeric repeat sequences of several kinds of eukaryotes. We propose that the present-day unit has evolved from telomeric, simple sequence, asymmetric DNA from which it has retained some original sequence features and possibly functions.

  4. Widespread telomere instability in prostatic lesions.

    PubMed

    Tu, LiRen; Huda, Nazmul; Grimes, Brenda R; Slee, Roger B; Bates, Alison M; Cheng, Liang; Gilley, David

    2016-05-01

    A critical function of the telomere is to disguise chromosome ends from cellular recognition as double strand breaks, thereby preventing aberrant chromosome fusion events. Such chromosome end-to-end fusions are known to initiate genomic instability via breakage-fusion-bridge cycles. Telomere dysfunction and other forms of genomic assault likely result in misregulation of genes involved in growth control, cell death, and senescence pathways, lowering the threshold to malignancy and likely drive disease progression. Shortened telomeres and anaphase bridges have been reported in a wide variety of early precursor and malignant cancer lesions including those of the prostate. These findings are being extended using methods for the analysis of telomere fusions (decisive genetic markers for telomere dysfunction) specifically within human tissue DNA. Here we report that benign prostatic hyperplasia (BPH), high-grade prostatic intraepithelial neoplasia (PIN), and prostate cancer (PCa) prostate lesions all contain similarly high frequencies of telomere fusions and anaphase bridges. Tumor-adjacent, histologically normal prostate tissue generally did not contain telomere fusions or anaphase bridges as compared to matched PCa tissues. However, we found relatively high levels of telomerase activity in this histologically normal tumor-adjacent tissue that was reduced but closely correlated with telomerase levels in corresponding PCa samples. Thus, we present evidence of high levels of telomere dysfunction in BPH, an established early precursor (PIN) and prostate cancer lesions but not generally in tumor adjacent normal tissue. Our results suggest that telomere dysfunction may be a common gateway event leading to genomic instability in prostate tumorigenesis. .

  5. A role for Separase in telomere protection

    PubMed Central

    Cipressa, Francesca; Morciano, Patrizia; Bosso, Giuseppe; Mannini, Linda; Galati, Alessandra; Daniela Raffa, Grazia; Cacchione, Stefano; Musio, Antonio; Cenci, Giovanni

    2016-01-01

    Drosophila telomeres are elongated by transposition of specialized retroelements rather than telomerase activity and are assembled independently of the sequence. Fly telomeres are protected by the terminin complex that localizes and functions exclusively at telomeres and by non-terminin proteins that do not serve telomere-specific functions. We show that mutations in the Drosophila Separase encoding gene Sse lead not only to endoreduplication but also telomeric fusions (TFs), suggesting a role for Sse in telomere capping. We demonstrate that Separase binds terminin proteins and HP1, and that it is enriched at telomeres. Furthermore, we show that loss of Sse strongly reduces HP1 levels, and that HP1 overexpression in Sse mutants suppresses TFs, suggesting that TFs are caused by a HP1 diminution. Finally, we find that siRNA-induced depletion of ESPL1, the Sse human orthologue, causes telomere dysfunction and HP1 level reduction in primary fibroblasts, highlighting a conserved role of Separase in telomere protection. PMID:26778495

  6. Therapeutic inhibition of TRF1 impairs the growth of p53-deficient K-RasG12V-induced lung cancer by induction of telomeric DNA damage

    PubMed Central

    García-Beccaria, María; Martínez, Paula; Méndez-Pertuz, Marinela; Martínez, Sonia; Blanco-Aparicio, Carmen; Cañamero, Marta; Mulero, Francisca; Ambrogio, Chiara; Flores, Juana M; Megias, Diego; Barbacid, Mariano; Pastor, Joaquín; Blasco, Maria A

    2015-01-01

    Telomeres are considered anti-cancer targets, as telomere maintenance above a minimum length is necessary for cancer growth. Telomerase abrogation in cancer-prone mouse models, however, only decreased tumor growth after several mouse generations when telomeres reach a critically short length, and this effect was lost upon p53 mutation. Here, we address whether induction of telomere uncapping by inhibition of the TRF1 shelterin protein can effectively block cancer growth independently of telomere length. We show that genetic Trf1 ablation impairs the growth of p53-null K-RasG12V-induced lung carcinomas and increases mouse survival independently of telomere length. This is accompanied by induction of telomeric DNA damage, apoptosis, decreased proliferation, and G2 arrest. Long-term whole-body Trf1 deletion in adult mice did not impact on mouse survival and viability, although some mice showed a moderately decreased cellularity in bone marrow and blood. Importantly, inhibition of TRF1 binding to telomeres by small molecules blocks the growth of already established lung carcinomas without affecting mouse survival or tissue function. Thus, induction of acute telomere uncapping emerges as a potential new therapeutic target for lung cancer. PMID:25971796

  7. Therapeutic inhibition of TRF1 impairs the growth of p53-deficient K-RasG12V-induced lung cancer by induction of telomeric DNA damage.

    PubMed

    García-Beccaria, María; Martínez, Paula; Méndez-Pertuz, Marinela; Martínez, Sonia; Blanco-Aparicio, Carmen; Cañamero, Marta; Mulero, Francisca; Ambrogio, Chiara; Flores, Juana M; Megias, Diego; Barbacid, Mariano; Pastor, Joaquín; Blasco, Maria A

    2015-05-13

    Telomeres are considered anti-cancer targets, as telomere maintenance above a minimum length is necessary for cancer growth. Telomerase abrogation in cancer-prone mouse models, however, only decreased tumor growth after several mouse generations when telomeres reach a critically short length, and this effect was lost upon p53 mutation. Here, we address whether induction of telomere uncapping by inhibition of the TRF1 shelterin protein can effectively block cancer growth independently of telomere length. We show that genetic Trf1 ablation impairs the growth of p53-null K-Ras(G12V)-induced lung carcinomas and increases mouse survival independently of telomere length. This is accompanied by induction of telomeric DNA damage, apoptosis, decreased proliferation, and G2 arrest. Long-term whole-body Trf1 deletion in adult mice did not impact on mouse survival and viability, although some mice showed a moderately decreased cellularity in bone marrow and blood. Importantly, inhibition of TRF1 binding to telomeres by small molecules blocks the growth of already established lung carcinomas without affecting mouse survival or tissue function. Thus, induction of acute telomere uncapping emerges as a potential new therapeutic target for lung cancer.

  8. HIV Infection Is Associated with Shortened Telomere Length in Ugandans with Suspected Tuberculosis

    PubMed Central

    Auld, Elizabeth; Lin, Jue; Chang, Emily; Byanyima, Patrick; Ayakaka, Irene; Musisi, Emmanuel; Worodria, William; Davis, J. Lucian; Segal, Mark; Blackburn, Elizabeth; Huang, Laurence

    2016-01-01

    Introduction HIV infection is a risk factor for opportunistic pneumonias such as tuberculosis (TB) and for age-associated health complications. Short telomeres, markers of biological aging, are also associated with an increased risk of age-associated diseases and mortality. Our goals were to use a single cohort of HIV-infected and HIV-uninfected individuals hospitalized with pneumonia to assess whether shortened telomere length was associated with HIV infection, TB diagnosis, and 2-month mortality. Methods This was a sub-study of the IHOP Study, a prospective observational study. Participants consisted of 184 adults admitted to Mulago Hospital in Kampala, Uganda who underwent evaluation for suspected TB and were followed for 2 months. Standardized questionnaires were administered to collect demographic and clinical data. PBMCs were isolated and analyzed using quantitative PCR to determine telomere length. The association between HIV infection, demographic and clinical characteristics, and telomere length was assessed, as were the associations between telomere length, TB diagnosis and 2-month mortality. Variables with a P≤0.2 in bivariate analysis were included in multivariate models. Results No significant demographic or clinical differences were observed between the HIV-infected and HIV-uninfected subjects. Older age (P<0.0001), male gender (P = 0.04), total pack-years smoked (P<0.001), alcohol consumption in the past year (P = 0.12), and asthma (P = 0.08) were all associated (P≤0.2) with shorter telomere length in bivariate analysis. In multivariate analysis adjusting for these five variables, HIV-positive participants had significantly shorter telomeres than HIV-negative participants (β = -0.0621, 95% CI -0.113 to -0.011, P = 0.02). Shortened telomeres were not associated with TB or short-term mortality. Conclusions The association between HIV infection and shorter telomeres suggests that HIV may play a role in cellular senescence and biological aging and

  9. Paroxysmal nocturnal hemoglobinuria and telomere length predicts response to immunosuppressive therapy in pediatric aplastic anemia.

    PubMed

    Narita, Atsushi; Muramatsu, Hideki; Sekiya, Yuko; Okuno, Yusuke; Sakaguchi, Hirotoshi; Nishio, Nobuhiro; Yoshida, Nao; Wang, Xinan; Xu, Yinyan; Kawashima, Nozomu; Doisaki, Sayoko; Hama, Asahito; Takahashi, Yoshiyuki; Kudo, Kazuko; Moritake, Hiroshi; Kobayashi, Masao; Kobayashi, Ryoji; Ito, Etsuro; Yabe, Hiromasa; Ohga, Shouichi; Ohara, Akira; Kojima, Seiji

    2015-12-01

    Acquired aplastic anemia is an immune-mediated disease characterized by severe defects in stem cell number resulting in hypocellular marrow and peripheral blood cytopenias. Minor paroxysmal nocturnal hemoglobinuria populations and a short telomere length were identified as predictive biomarkers of immunosuppressive therapy responsiveness in aplastic anemia. We enrolled 113 aplastic anemia patients (63 boys and 50 girls) in this study to evaluate their response to immunosuppressive therapy. The paroxysmal nocturnal hemoglobinuria populations and telomere length were detected by flow cytometry. Forty-seven patients (42%) carried a minor paroxysmal nocturnal hemoglobinuria population. The median telomere length of aplastic anemia patients was -0.99 standard deviation (SD) (range -4.01-+3.01 SD). Overall, 60 patients (53%) responded to immunosuppressive therapy after six months. Multivariate logistic regression analysis identified the absence of a paroxysmal nocturnal hemoglobinuria population and a shorter telomere length as independent unfavorable predictors of immunosuppressive therapy response at six months. The cohort was stratified into a group of poor prognosis (paroxysmal nocturnal hemoglobinuria negative and shorter telomere length; 37 patients) and good prognosis (paroxysmal nocturnal hemoglobinuria positive and/or longer telomere length; 76 patients), respectively. The response rates of the poor prognosis and good prognosis groups at six months were 19% and 70%, respectively (P<0.001). The combined absence of a minor paroxysmal nocturnal hemoglobinuria population and a short telomere length is an efficient predictor of poor immunosuppressive therapy response, which should be considered while deciding treatment options: immunosuppressive therapy or first-line hematopoietic stem cell transplantation. The trial was registered in www.umin.ac.jp with number UMIN000017972.

  10. Telomere hypervariability in Magnaporthe oryzae.

    PubMed

    Farman, Mark L; Kim, Yun-Sik

    2005-05-01

    SUMMARY The gray leaf spot disease of perennial ryegrass and tall fescue is caused by the fungus Magnaporthe oryzae (anamorph = Pyricularia oryzae). A collection of single-copy and repetitive DNA markers was used to investigate genetic diversity among 22 isolates of the gray leaf spot pathogen. The single-copy DNA markers revealed only three polymorphisms among 95 restriction fragments spanning approximately 0.6% of the genome. In addition, Southern hybridization analysis and mating tests revealed that all isolates possessed the MAT1-2 mating-type allele. Fingerprinting of repetitive DNA loci using the Pot2 and MGR583 probes also revealed a high degree of genetic similarity (> 85%) among isolates. These data are consistent with the gray leaf spot pathogens having a recent evolutionary origin. In contrast to the results obtained with probes for internal chromosome loci, a telomere probe revealed that the chromosome ends of the very same isolates are highly divergent, with most isolates sharing less than 20% fingerprint similarity with any other isolate. Telomere mutations arise extremely frequently and changes in telomere fingerprint profiles were readily observed during vegetative growth and among cultures derived from single spores isolated from agar medium and from lesions on perennial ryegrass leaves. PMID:20565657

  11. Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility.

    PubMed

    Hosgood, H Dean; Cawthon, Richard; He, Xingzhou; Chanock, Stephen; Lan, Qing

    2009-11-01

    Telomeres are responsible for the protection of the chromosome ends and shortened telomere length has been associated with risk of multiple cancers. Genetic variation in telomere-related genes may alter cancer risk associated with telomere length. Using lung cancer cases (n=120) and population-based controls (n=110) from Xuanwei, China, we analyzed telomere length separately and in conjunction with single nucleotide polymorphisms in the telomere maintenance genes POT1, TERT, and TERF2, which we have previously reported were associated with risk of lung cancer in this study. POT1 rs10244817, TERT rs2075786, and TERF2 rs251796 were significantly associated with lung cancer (p(trend)< or =0.05). The shortest tertile of telomere length was not significantly associated with risk of lung cancer (OR=1.58; 95% CI=0.79-3.18) when compared to the longest tertile of telomere length. When stratified by genotype, there was a suggestion of a dose-response relationship between tertiles of telomere length and risk of lung cancer among the POT1 rs10244817 common variant carriers (OR (95% CI)=1.33 (0.47-3.75), 3.30 (1.14-9.56), respectively) but not among variant genotype carriers (p(interaction)=0.05). Our findings provide evidence that telomere length and genetic variation in telomere maintenance genes may be associated with risk of lung cancer susceptibility and warrant replication in larger studies.

  12. Mitochondrial Localization of Telomeric Protein TIN2 Links Telomere Regulation to Metabolic Control

    PubMed Central

    Chen, Liuh-Yow; Zhang, Yi; Zhang, Qinfen; Li, Hongzhi; Luo, Zhenhua; Fang, Hezhi; Kim, Sok Ho; Qin, Li; Yotnda, Patricia; Xu, Jianmin; Tu, Benjamin P.; Bai, Yidong; Songyang, Zhou

    2012-01-01

    Summary Both mitochondria, which are metabolic powerhouses, and telomeres, which help maintain genomic stability, have been implicated in cancer and aging. However, the signaling events that connect these two cellular structures remain poorly understood. Here we report that the canonical telomeric protein TIN2 is also a regulator of metabolism. TIN2 is recruited to telomeres and associates with multiple telomere regulators including TPP1. TPP1 interacts with TIN2 N-terminus, which contains overlapping mitochondrial and telomeric targeting sequences, and controls TIN2 localization. We have found that TIN2 is post-translationally processed in mitochondria, and regulates mitochondria oxidative phosphorylation. Reducing TIN2 expression by RNAi knockdown inhibited glycolysis and reactive oxygen species (ROS) and production, and enhanced ATP levels and oxygen consumption in cancer cells. These results suggest a link between telomeric proteins and metabolic control, providing an additional mechanism by which telomeric proteins regulate cancer and aging. PMID:22885005

  13. Meiotic abnormalities

    SciTech Connect

    1993-12-31

    Chapter 19, describes meiotic abnormalities. These include nondisjunction of autosomes and sex chromosomes, genetic and environmental causes of nondisjunction, misdivision of the centromere, chromosomally abnormal human sperm, male infertility, parental age, and origin of diploid gametes. 57 refs., 2 figs., 1 tab.

  14. Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

    PubMed

    González-García, Mary-Paz; Pavelescu, Irina; Canela, Andrés; Sevillano, Xavier; Leehy, Katherine A; Nelson, Andrew D L; Ibañes, Marta; Shippen, Dorothy E; Blasco, Maria A; Caño-Delgado, Ana I

    2015-05-12

    Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants.

  15. Lymphocyte telomere length is long in BRCA1 and BRCA2 mutation carriers regardless of cancer-affected status

    PubMed Central

    McGuffog, Lesley; Barrowdale, Daniel; Frost, Debra; Ellis, Steve D.; Platte, Radka; Fineberg, Elena; Izatt, Louise; Adlard, Julian; Bardwell, Julian; Brewer, Carole; Cole, Trevor; Cook, Jackie; Davidson, Rosemary; Donaldson, Alan; Dorkins, Huw; Douglas, Fiona; Eason, Jacqueline; Houghton, Catherine; Kennedy, M. John; McCann, Emma; Miedzybrobzka, Zosia; Murray, Alex; Porteous, Mary E.; Rogers, Mark T.; Side, Lucy E.; Tischkowitz, Marc; Walker, Lisa; Hodgson, Shirley; Eccles, Diana M.; Morrison, Patrick J.; Evans, D. Gareth; Eeles, Rosalind A.; Antoniou, Antonis C.; Easton, Douglas F.

    2014-01-01

    Background Telomere length has been linked to risk of common diseases, including cancer, and has previously been proposed as a biomarker for cancer risk. Germline BRCA1 and BRCA2 mutations predispose to breast, ovarian and other cancer types. Methods We investigated telomere length in BRCA mutation carriers and their non-carrier relatives and further examined whether telomere length is a modifier of cancer risk in mutation carriers. We measured mean telomere length in DNA extracted from whole blood using high-throughput Q-PCR. Participants were from the EMBRACE study in the UK and Eire (n=4,822) and comprised BRCA1 (n=1,628) and BRCA2 (n=1,506) mutation carriers and their non-carrier relatives (n=1,688). Results We find no significant evidence that mean telomere length is associated with breast or ovarian cancer risk in BRCA mutation carriers. However, we find mutation carriers to have longer mean telomere length than their non-carrier relatives (all carriers vs. non-carriers, P-trend=0.0018), particularly in families with BRCA2 mutations (BRCA2 mutation carriers vs. all non-carriers, P-trend=0.0016). Our findings lend little support to the hypothesis that short mean telomere length predisposes to cancer. Conversely, our main and unexpected finding is that BRCA mutation carriers (regardless of cancer status) have longer telomeres than their non-mutation carrier, non-cancer-affected relatives. The longer telomere length in BRCA2 mutation carriers is consistent with its role in DNA damage response. Conclusions Overall, it appears that increased telomere length may be a consequence of these mutations, but is not itself directly related to the increased cancer risk in carriers. Impact The finding that mutation carriers to have longer mean telomere lengths than their non-carrier relatives is unexpected but biologically plausible and could open up new lines of research into the functions of the BRCA proteins. To our knowledge, this is the largest study of telomere length

  16. Problem-Solving Test: Telomere Replication

    ERIC Educational Resources Information Center

    Szeberenyi, Jozsef

    2010-01-01

    The Nobel Prize in Physiology or Medicine in 2009 was awarded to Elizabeth H. Blackburn, Carol W. Greider, and Jack W. Szostak for the discovery of "how chromosomes are protected by telomeres and the enzyme telomerase." The discovery has important implications in the processes of cellular aging and carcinogenesis. Telomeres are satellite DNA…

  17. One Identity or More for Telomeres?

    PubMed Central

    Giraud-Panis, Marie-Josèphe; Pisano, Sabrina; Benarroch-Popivker, Delphine; Pei, Bei; Le Du, Marie-Hélène; Gilson, Eric

    2013-01-01

    A major issue in telomere research is to understand how the integrity of chromosome ends is controlled. The fact that different types of nucleoprotein complexes have been described at the telomeres of different organisms raises the question of whether they have in common a structural identity that explains their role in chromosome protection. We will review here how telomeric nucleoprotein complexes are structured, comparing different organisms and trying to link these structures to telomere biology. It emerges that telomeres are formed by a complex and specific network of interactions between DNA, RNA, and proteins. The fact that these interactions and associated activities are reinforcing each other might help to guarantee the robustness of telomeric functions across the cell cycle and in the event of cellular perturbations. We will also discuss the recent notion that telomeres have evolved specific systems to overcome the DNA topological stress generated during their replication and transcription. This will lead to revisit the way we envisage the functioning of telomeric complexes since the regulation of topology is central to DNA stability, replication, recombination, and transcription as well as to chromosome higher-order organization. PMID:23509004

  18. A single internal telomere tract ensures meiotic spindle formation

    PubMed Central

    Tomita, Kazunori; Bez, Cécile; Fennell, Alex; Cooper, Julia Promisel

    2013-01-01

    Contact between telomeres and the fission yeast spindle pole body during meiotic prophase is crucial for subsequent spindle assembly, but the feature of telomeres that confers their ability to promote spindle formation remains mysterious. Here we show that while strains harbouring circular chromosomes devoid of telomere repeat tracts undergo aberrant meiosis with defective spindles, the insertion of a single internal telomere repeat stretch rescues the spindle defects. Moreover, the telomeric overhang-binding protein Pot1 is dispensable for rescue of spindle formation. Hence, an inherent feature of the double-strand telomeric region endows telomeres with the capacity to promote spindle formation. PMID:23295325

  19. Telomere Chromatin Condensation Assay (TCCA): a novel approach to study structural telomere integrity.

    PubMed

    Gonzalez-Vasconcellos, Iria; Alonso-Rodríguez, Silvia; López-Baltar, Isidoro; Fernández, José Luis

    2015-01-01

    Telomeres, the DNA-protein complexes located at the end of linear eukaryotic chromosomes are essential for genome stability. Improper higher-order chromatin organization at the chromosome ends can give rise to telomeric recombination and genomic instability. We report the development of an assay to quantify differences in the condensation of telomeric chromatin, thereby offering new opportunities to study telomere biology and stability. We have combined a DNA nuclease digestion with a quantitative PCR (qPCR) assay of telomeric DNA, which we term the Telomere Chromatin Condensation Assay (TCCA). By quantifying the relative quantities of telomeric DNA that are progressively digested with the exonuclease Bal 31 the method can discriminate between different levels of telomeric chromatin condensation. The structural chromatin packaging at telomeres shielded against exonuclease digestion delivered an estimate, which we term Chromatin Protection Factor (CPF) that ranged from 1.7 to 2.3 fold greater than that present in unpacked DNA. The CPF was significantly decreased when cell cultures were incubated with the DNA hypomethylating agent 5-azacytidine, demonstrating the ability of the TCCA assay to discriminate between packaging levels of telomeric DNA.

  20. Novel features of telomere biology revealed by the absence of telomeric DNA methylation.

    PubMed

    Vega-Vaquero, Alejandro; Bonora, Giancarlo; Morselli, Marco; Vaquero-Sedas, María I; Rubbi, Liudmilla; Pellegrini, Matteo; Vega-Palas, Miguel A

    2016-08-01

    Cytosine methylation regulates the length and stability of telomeres, which can affect a wide variety of biological features, including cell differentiation, development, or illness. Although it is well established that subtelomeric regions are methylated, the presence of methylated cytosines at telomeres has remained controversial. Here, we have analyzed multiple bisulfite sequencing studies to address the methylation status of Arabidopsis thaliana telomeres. We found that the levels of estimated telomeric DNA methylation varied among studies. Interestingly, we estimated higher levels of telomeric DNA methylation in studies that produced C-rich telomeric strands with lower efficiency. However, these high methylation estimates arose due to experimental limitations of the bisulfite technique. We found a similar phenomenon for mitochondrial DNA: The levels of mitochondrial DNA methylation detected were higher in experiments with lower mitochondrial read production efficiencies. Based on experiments with high telomeric C-rich strand production efficiencies, we concluded that Arabidopsis telomeres are not methylated, which was confirmed by methylation-dependent restriction enzyme analyses. Thus, our studies indicate that telomeres are refractory to de novo DNA methylation by the RNA-directed DNA methylation machinery. This result, together with previously reported data, reveals that subtelomeric DNA methylation controls the homeostasis of telomere length. PMID:27405804

  1. Break-induced replication and recombinational telomere elongation in yeast.

    PubMed

    McEachern, Michael J; Haber, James E

    2006-01-01

    When a telomere becomes unprotected or if only one end of a chromosomal double-strand break succeeds in recombining with a template sequence, DNA can be repaired by a recombination-dependent DNA replication process termed break-induced replication (BIR). In budding yeasts, there are two BIR pathways, one dependent on the Rad51 recombinase protein and one Rad51 independent; these two repair processes lead to different types of survivors in cells lacking the telomerase enzyme that is required for normal telomere maintenance. Recombination at telomeres is triggered by either excessive telomere shortening or disruptions in the function of telomere-binding proteins. Telomere elongation by BIR appears to often occur through a "roll and spread" mechanism. In this process, a telomeric circle produced by recombination at a dysfunctional telomere acts as a template for a rolling circle BIR event to form an elongated telomere. Additional BIR events can then copy the elongated sequence to all other telomeres.

  2. Craniofacial Abnormalities

    MedlinePlus

    ... of the skull and face. Craniofacial abnormalities are birth defects of the face or head. Some, like cleft ... palate, are among the most common of all birth defects. Others are very rare. Most of them affect ...

  3. Chromosome Abnormalities

    MedlinePlus

    ... decade, newer techniques have been developed that allow scientists and doctors to screen for chromosomal abnormalities without using a microscope. These newer methods compare the patient's DNA to a normal DNA ...

  4. Walking abnormalities

    MedlinePlus

    ... include: Arthritis of the leg or foot joints Conversion disorder (a psychological disorder) Foot problems (such as a ... injuries. For an abnormal gait that occurs with conversion disorder, counseling and support from family members are strongly ...

  5. Nail abnormalities

    MedlinePlus

    Beau's lines; Fingernail abnormalities; Spoon nails; Onycholysis; Leukonychia; Koilonychia; Brittle nails ... Just like the skin, the fingernails tell a lot about your health: ... the fingernail. These lines can occur after illness, injury to ...

  6. Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells

    PubMed Central

    Ci, Xinyu; Li, Bingnan; Ma, Xueping; Kong, Feng; Zheng, Chengyun; Björkholm, Magnus; Jia, Jihui; Xu, Dawei

    2015-01-01

    Bortezomib inhibits the ubiquitin/proteasome pathway to achieve its anti-cancer effect and its well characterized activity is the NF-κB inhibition through which the anti-apoptotic bcl-2 expression is down-regulated and apoptosis is subsequently induced. However, the downstream molecular targets of bortezomib are still incompletely defined. Because telomere stabilization via activation of telomerase, induction of telomerase reverse transcriptase (hTERT) and appropriate expression of shelterin proteins is essential to cancer development and progression, we investigated the effect of bortezomib on telomere homeostasis/function in malignant cells. The bortezomib treatment of leukemic (HEL) and gastric cancer cells (BGC-823) led to significant inhibition of hTERT and telomerase expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggering telomere dysfunction and DNA damage. hTERT over-expression attenuated bortezomib-induced telomere shortening, abnormal shelterin expression and telomere dysfunction. Importantly, bortezomib-mediated apoptosis of malignant cells was partially prevented by hTERT over-expression. Mechanistically, hTERT first robustly enhances bcl2 expression and maintains significantly high residual levels of bcl2 even in bortezomib-treated HEL cells. Second, hTERT protects against bortezomib-induced DNA damage. Our findings collectively reveal a profound impact of bortezomib on telomere homeostasis/function. Down-regulation of hTERT expression and telomere dysfunction induced by bortezomib both contribute to its cancer cell killing actions. It is evident from the present study that hTERT can confer resistance of malignant cells to bortezomib-based target cancer therapy, which may have important clinical implications. PMID:26472030

  7. Bortezomib-mediated down-regulation of telomerase and disruption of telomere homeostasis contributes to apoptosis of malignant cells.

    PubMed

    Ci, Xinyu; Li, Bingnan; Ma, Xueping; Kong, Feng; Zheng, Chengyun; Björkholm, Magnus; Jia, Jihui; Xu, Dawei

    2015-11-10

    Bortezomib inhibits the ubiquitin/proteasome pathway to achieve its anti-cancer effect and its well characterized activity is the NF-κB inhibition through which the anti-apoptotic bcl-2 expression is down-regulated and apoptosis is subsequently induced. However, the downstream molecular targets of bortezomib are still incompletely defined. Because telomere stabilization via activation of telomerase, induction of telomerase reverse transcriptase (hTERT) and appropriate expression of shelterin proteins is essential to cancer development and progression, we investigated the effect of bortezomib on telomere homeostasis/function in malignant cells. The bortezomib treatment of leukemic (HEL) and gastric cancer cells (BGC-823) led to significant inhibition of hTERT and telomerase expression, widespread dysregulation of shelterin protein expression, and telomere shortening, thereby triggering telomere dysfunction and DNA damage. hTERT over-expression attenuated bortezomib-induced telomere shortening, abnormal shelterin expression and telomere dysfunction. Importantly, bortezomib-mediated apoptosis of malignant cells was partially prevented by hTERT over-expression. Mechanistically, hTERT first robustly enhances bcl2 expression and maintains significantly high residual levels of bcl2 even in bortezomib-treated HEL cells. Second, hTERT protects against bortezomib-induced DNA damage. Our findings collectively reveal a profound impact of bortezomib on telomere homeostasis/function. Down-regulation of hTERT expression and telomere dysfunction induced by bortezomib both contribute to its cancer cell killing actions. It is evident from the present study that hTERT can confer resistance of malignant cells to bortezomib-based target cancer therapy, which may have important clinical implications.

  8. The Huntington disease locus is most likely within 325 kilobases of the chromosome 4p telomere

    SciTech Connect

    Doggett, N.A.; Cheng, J.F.; Smith, C.L.; Cantor, C.R. )

    1989-12-01

    The genetic defect responsible for Huntington disease was originally localized near the tip of the short arm of chromosome 4 by genetic linkage to the locus D4S10. Several markers closer to Huntington disease have since been isolated, but these all appear to be proximal to the defect. A physical map that extends from the most distal of these loci, D4S90, to the telomere of chromosome 4 was constructed. This map identifies at least two CpG islands as markers for Huntington disease candidate genes and places the most likely location of the Huntington disease defect remarkably close (within 325 kilobases) to the telomere.

  9. An interstitial deletion of 7.1Mb in chromosome band 6p22.3 associated with developmental delay and dysmorphic features including heart defects, short neck, and eye abnormalities.

    PubMed

    Bremer, Anna; Schoumans, Jacqueline; Nordenskjöld, Magnus; Anderlid, Britt-Marie; Giacobini, Maibritt

    2009-01-01

    Seven cases with an interstitial deletion of the short arm of chromosome 6 involving the 6p22 region have previously been reported. The clinical phenotype of these cases includes developmental delay, brain-, heart-, and kidney defects, eye abnormalities, short neck, craniofacial malformations, hypotonia, as well as clinodactyly or syndactyly. Here, we report a patient with a 7.1Mb interstitial deletion of chromosome band 6p22.3, detected by genome-wide screening array CGH. The patient is a 4-year-old girl with developmental delay and dysmorphic features including eye abnormalities, short neck, and a ventricular septum defect. The deleted region at 6p22.3 in our patient overlaps with six out of the seven previously reported cases with a 6p22-24 interstitial deletion. This enabled us to further narrow down the critical region for the 6p22 deletion phenotype to 2.2Mb. Twelve genes are mapped to the overlapping deleted region, among them the gene encoding the ataxin-1 protein, the ATXN1 gene. Mice with homozygous deletions in ATXN1 are phenotypically normal but show cognitive delay. Haploinsufficiency of ATXN1 may therefore contribute to the learning difficulties observed in the patients harboring a 6p22 deletion.

  10. Acquisition of telomere repeat sequences by transfected DNA integrated at the site of a chromosome break

    SciTech Connect

    Murnane, J.P.; Lohchung Yu )

    1993-02-01

    Rearrangement of the human genome is an important element in both cancer biology and genetic disease. Rearrangements that have been observed include deletions, translocations, chromosome breakage or loss, and gene amplification. Transfection of the DNA into mammalian cells can created instability in the genome. The characterization of DNA rearrangement associated with transfected DNA may provide information about the general mechanisms involved in genomic instability. This genomic instability is an important aspect of tumor cell progression. This research examines chromosome breakage and rearrangement that results in interstitial telomere repeat sequences within the human genome. These sequences could promote genomic instability because short repeat sequences can be recombination hotspots. Also, DNA rearrangements involving telomere repeat sequences can be associated with chromosome breaks. The introduction of telomere repeat sequences at spontaneous or ionizing radiation-induced DNA strand breaks may therefore also be a mechanism of chromosome fragmentation. 52 refs., 7 figs.

  11. rasiRNA pathway controls antisense expression of Drosophila telomeric retrotransposons in the nucleus

    PubMed Central

    Shpiz, Sergey; Kwon, Dmitry; Rozovsky, Yakov; Kalmykova, Alla

    2009-01-01

    Telomeres in Drosophila are maintained by the specialized telomeric retrotransposons HeT-A, TART and TAHRE. Sense transcripts of telomeric retroelements were shown to be the targets of a specialized RNA-interference mechanism, a repeat-associated short interfering (rasi)RNA-mediated system. Antisense rasiRNAs play a key role in this mechanism, highlighting the importance of antisense expression in retrotransposon silencing. Previously, bidirectional transcription was reported for the telomeric element TART. Here, we show that HeT-A is also bidirectionally transcribed, and HeT-A antisense transcription in ovaries is regulated by a promoter localized within its 3′ untranslated region. A remarkable feature of noncoding HeT-A antisense transcripts is the presence of multiple introns. We demonstrate that sense and antisense HeT-A-specific rasiRNAs are present in the same tissue, indicating that transcripts of both directions may be considered as natural targets of the rasiRNA pathway. We found that the expression of antisense transcripts of telomeric elements is regulated by the RNA silencing machinery, suggesting rasiRNA-mediated interplay between sense and antisense transcripts in the cell. Finally, this regulation occurs in the nucleus since disruption of the rasiRNA pathway leads to an accumulation of TART and HeT-A transcripts in germ cell nuclei. PMID:19036789

  12. Alterations of telomere length and DNA methylation in hairdressers: A cross-sectional study.

    PubMed

    Li, Huiqi; Åkerman, Gabriella; Lidén, Carola; Alhamdow, Ayman; Wojdacz, Tomasz K; Broberg, Karin; Albin, Maria

    2016-03-01

    Working as hairdressers has been associated with increased risk for cancer, particularly bladder cancer. To evaluate if current hairdressers have elevated risks of adverse health effects, we measured several biomarkers related to cancer-related DNA alterations. We enrolled 295 hairdressers and 92 non-hairdressers (all female non-smokers) from Stockholm and southern Sweden. Questionnaire data were collected for each participant, including work tasks for the hairdressers. We measured telomere length in peripheral blood leucocytes using quantitative PCR and DNA methylation status of genes relevant for bladder cancer using methylation sensitive high resolution melting analysis. The hairdressers had shorter telomeres (β = -0.069, P = 0.019) compared with non-hairdressers. Shorter telomeres were found in hairdressers up to 32 years old performing hair waving more than once per week as compared with hairdressers in the same age group performing hair waving less often (β = -0.12, P = 0.037). Hair waving was associated with less frequent CDKN2A methylation (odds ratio, OR = 0.19, P = 0.033). Shorter telomeres in hairdressers may indicate a genotoxic effect. Performing hair waving was associated with short telomere length, although the effect was only observed in young hairdressers. No clear patterns were discerned with regard to DNA methylation of bladder cancer-related genes. The observed changes of methylation were not all in the expected direction and warrant further investigation. PMID:26637967

  13. Loving-Kindness Meditation practice associated with longer telomeres in women.

    PubMed

    Hoge, Elizabeth A; Chen, Maxine M; Orr, Esther; Metcalf, Christina A; Fischer, Laura E; Pollack, Mark H; De Vivo, Immaculata; Simon, Naomi M

    2013-08-01

    Relatively short telomere length may serve as a marker of accelerated aging, and shorter telomeres have been linked to chronic stress. Specific lifestyle behaviors that can mitigate the effects of stress might be associated with longer telomere lengths. Previous research suggests a link between behaviors that focus on the well-being of others, such as volunteering and caregiving, and overall health and longevity. We examined relative telomere length in a group of individuals experienced in Loving-Kindness Meditation (LKM), a practice derived from the Buddhist tradition which utilizes a focus on unselfish kindness and warmth towards all people, and control participants who had done no meditation. Blood was collected by venipuncture, and Genomic DNA was extracted from peripheral blood leukocytes. Quantitative real time PCR was used to measure relative telomere length (RTL) (Cawthon, 2002) in fifteen LKM practitioners and 22 control participants. There were no significant differences in age, gender, race, education, or exposure to trauma, but the control group had a higher mean body mass index (BMI) and lower rates of past depression. The LKM practitioners had longer RTL than controls at the trend level (p=.083); among women, the LKM practitioners had significantly longer RTL than controls, (p=.007), which remained significant even after controlling for BMI and past depression. Although limited by small sample size, these results offer the intriguing possibility that LKM practice, especially in women, might alter RTL, a biomarker associated with longevity. PMID:23602876

  14. Environmental and occupational exposure to chemicals and telomere length in human studies.

    PubMed

    Zhang, Xiao; Lin, Shao; Funk, William E; Hou, Lifang

    2013-12-01

    Telomeres are complexes of tandem repeats of DNA (5'-TTAGGG-3') and protein that cap eukaryotic chromosomes and play a critical role in chromosome stability. Telomeres shorten with aging and this process can be accelerated by increased oxidative stress and episodes of inflammation. Evidence is rapidly growing that telomere length (TL) may be affected by environmental chemicals that have frequently been associated with chronic diseases. In this article, we review the published data on TL in relation to environmental and occupational exposure to several chemicals based on our own and others' studies. The environmental and occupational exposures associated with shorter TL include traffic-related air pollution (ie, particulate matter (PM), black carbon (BC), and benzene and toluene), polycyclic aromatic hydrocarbons (PAHs), N-nitrosamines, pesticides, lead, exposure in car mechanical workshops, and hazardous waste exposure. Arsenic, persistent organic pollutants (POPs) and short-term exposure to PM are associated with longer TL. We discuss the possible reasons for the differences in results, including time- and dose-related issues, study design, and possible mechanisms involved in telomere regulation. We also discuss the future directions and challenges for TL-related environmental and occupational health research, such as investigation of TL in subpopulations of blood leukocytes, and the study of genetic and epigenetic factors that may regulate telomere integrity using longitudinal designs.

  15. Environmental and occupational exposure to chemicals and telomere length in human studies.

    PubMed

    Zhang, Xiao; Lin, Shao; Funk, William E; Hou, Lifang

    2013-10-01

    Telomeres are complexes of tandem repeats of DNA (5'-TTAGGG-3') and protein that cap eukaryotic chromosomes and play a critical role in chromosome stability. Telomeres shorten with aging and this process can be accelerated by increased oxidative stress and episodes of inflammation. Evidence is rapidly growing that telomere length (TL) may be affected by environmental chemicals that have frequently been associated with chronic diseases. In this article, we review the published data on TL in relation to environmental and occupational exposure to several chemicals based on our own and others' studies. The environmental and occupational exposures associated with shorter TL include traffic-related air pollution (ie, particulate matter (PM), black carbon (BC), and benzene and toluene), polycyclic aromatic hydrocarbons (PAHs), N-nitrosamines, pesticides, lead, exposure in car mechanical workshops, and hazardous waste exposure. Arsenic, persistent organic pollutants (POPs) and short-term exposure to PM are associated with longer TL. We discuss the possible reasons for the differences in results, including time- and dose-related issues, study design, and possible mechanisms involved in telomere regulation. We also discuss the future directions and challenges for TL-related environmental and occupational health research, such as investigation of TL in subpopulations of blood leukocytes, and the study of genetic and epigenetic factors that may regulate telomere integrity using longitudinal designs.

  16. Two retrotransposons maintain telomeres in Drosophila

    PubMed Central

    Pardue, M.-L.; Rashkova, S.; Casacuberta, E.; DeBaryshe, P.G.; George, J. A.; Traverse, K.L.

    2005-01-01

    Telomeres across the genus Drosophila are maintained, not by telomerase, but by two non-LTR retrotransposons, HeT-A and TART, that transpose specifically to chromosome ends. Successive transpositions result in long head-to-tail arrays of these elements. Thus Drosophila telomeres, like those produced by telomerase, consist of repeated sequences reverse transcribed from RNA templates. The Drosophila repeats, complete and 5′-truncated copies of HeT-A and TART, are more complex than telomerase repeats; nevertheless these evolutionary variants have functional similarities to the more common telomeres. Like other telomeres, the Drosophila arrays are dynamic, fluctuating around an average length that can be changed by changes in the genetic background. Several proteins that interact with telomeres in other species have been found to have homologues that interact with Drosophila telomeres. Although they have hallmarks of non-LTR retrotransposons, HeT-A and TART appear to have a special relationship to Drosophila. Their Gag proteins are efficiently transported into diploid nuclei where HeT-A Gag recruits TART Gag to chromosome ends. Gags of other non-LTR elements remain predominantly in the cytoplasm. These studies provide intriguing evolutionary links between telomeres and retrotransposable elements. PMID:16132810

  17. [Hair shaft abnormalities].

    PubMed

    Itin, P H; Düggelin, M

    2002-05-01

    Hair shaft disorders may lead to brittleness and uncombable hair. In general the hair feels dry and lusterless. Hair shaft abnormalities may occur as localized or generalized disorders. Genetic predisposition or exogenous factors are able to produce and maintain hair shaft abnormalities. In addition to an extensive history and physical examination the most important diagnostic examination to analyze a hair shaft problem is light microscopy. Therapy of hair shaft disorders should focus to the cause. In addition, minimizing traumatic influences to hair shafts, such as dry hair with an electric dryer, permanent waves and dyes is important. A short hair style is more suitable for such patients with hair shaft disorders.

  18. Increased expression of telomere-regulating genes in endurance athletes with long leukocyte telomeres.

    PubMed

    Denham, Joshua; O'Brien, Brendan J; Prestes, Priscilla R; Brown, Nicholas J; Charchar, Fadi J

    2016-01-15

    Leukocyte telomeres shorten with age, and excessive shortening is associated with age-related cardiometabolic diseases. Exercise training may prevent disease through telomere length maintenance although the optimal amount of exercise that attenuates telomere attrition is unknown. Furthermore, the underlying molecular mechanisms responsible for the enhanced telomere maintenance observed in endurance athletes is poorly understood. We quantified the leukocyte telomere length and analyzed the expression of telomere-regulating genes in endurance athletes and healthy controls (both n = 61), using quantitative PCR. We found endurance athletes have significantly longer (7.1%, 208-416 nt) leukocyte telomeres and upregulated TERT (2.0-fold) and TPP1 (1.3-fold) mRNA expression compared with controls in age-adjusted analysis. The telomere length and telomere-regulating gene expression differences were no longer statistically significant after adjustment for resting heart rate and relative V̇O(2 max) (all P > 0.05). Resting heart rate emerged as an independent predictor of leukocyte telomere length and TERT and TPP1 mRNA expression in stepwise regression models. To gauge whether volume of exercise was associated with leukocyte telomere length, we divided subjects into running and cycling tertiles (distance covered per week) and found individuals in the middle and highest tertiles had longer telomeres than individuals in the lowest tertile. These data emphasize the importance of cardiorespiratory fitness and exercise training in the prevention of biological aging. They also support the concept that moderate amounts of exercise training protects against biological aging, while higher amounts may not elicit additional benefits.

  19. Molecular Cytogenetic Analysis of Telomere Rearrangements

    PubMed Central

    Martin, Christa Lese; Ledbetter, David H.

    2015-01-01

    Genomic imbalances involving the telomeric regions of human chromosomes, which contain the highest gene concentration in the genome, are proposed to have severe phenotypic consequences. For this reason, it is important to identify telomere rearrangements and assess their contribution to human pathology. This unit describes the structure and function of human telomeres and outlines several FISH-based methodologies that can be employed to study these unique regions of human chromosomes. It is a revision of the original version of the unit published in 2000, now including an introductory section describing advances in the discipline that have taken place since the original publication. PMID:25599669

  20. Allium telomeres unmasked: the unusual telomeric sequence (CTCGGTTATGGG)n is synthesized by telomerase.

    PubMed

    Fajkus, Petr; Peška, Vratislav; Sitová, Zdeňka; Fulnečková, Jana; Dvořáčková, Martina; Gogela, Roman; Sýkorová, Eva; Hapala, Jan; Fajkus, Jiří

    2016-02-01

    Phylogenetic divergence in Asparagales plants is associated with switches in telomere sequences. The last switch occurred with divergence of the genus Allium (Amaryllidaceae) from the other Allioideae (formerly Alliaceae) genera, resulting in uncharacterized telomeres maintained by an unknown mechanism. To characterize the unknown Allium telomeres, we applied a combination of bioinformatic processing of transcriptomic and genomic data with standard approaches in telomere biology such as BAL31 sensitivity tests, terminal restriction fragment analysis, the telomere repeat amplification protocol (TRAP), and fluorescence in situ hybridization (FISH). Using these methods, we characterize the unusual telomeric sequence (CTCGGTTATGGG)n present in Allium species, demonstrate its synthesis by telomerase, and characterize the telomerase reverse transcriptase (TERT) subunit of Allium cepa. Our findings open up the possibility of studying the molecular details of the evolutionary genetic change in Allium telomeres and its possible role in speciation. Experimental studies addressing the implications of this change in terms of the interplay of telomere components may now be designed to shed more light on telomere functions and evolution in general. PMID:26716914

  1. MAJIN Links Telomeric DNA to the Nuclear Membrane by Exchanging Telomere Cap.

    PubMed

    Shibuya, Hiroki; Hernández-Hernández, Abrahan; Morimoto, Akihiro; Negishi, Lumi; Höög, Christer; Watanabe, Yoshinori

    2015-11-19

    In meiosis, telomeres attach to the inner nuclear membrane (INM) and drive the chromosome movement required for homolog pairing and recombination. Here, we address the question of how telomeres are structurally adapted for the meiotic task. We identify a multi-subunit meiotic telomere-complex, TERB1/2-MAJIN, which takes over telomeric DNA from the shelterin complex in mouse germ cells. TERB1/2-MAJIN initially assembles on the INM sequestered by its putative transmembrane subunit MAJIN. In early meiosis, telomere attachment is achieved by the formation of a chimeric complex of TERB1/2-MAJIN and shelterin. The chimeric complex matures during prophase into DNA-bound TERB1/2-MAJIN by releasing shelterin, forming a direct link between telomeric DNA and the INM. These hierarchical processes, termed "telomere cap exchange," are regulated by CDK-dependent phosphorylation and the DNA-binding activity of MAJIN. Further, we uncover a positive feedback between telomere attachment and chromosome movement, revealing a comprehensive regulatory network underlying meiosis-specific telomere function in mammals.

  2. Extreme variability in the Xp:Yp pseudoautosomal telomere revealed by telomere variant repeat mapping

    SciTech Connect

    Baird, D.M.; Jeffreys A.J.; Royle, N.J.

    1994-09-01

    The presence of telomere variant repeat units in the proximal regions of human telomeres has been demonstrated but the distribution of these repeats and the extent of allelic variation has not been examined. We have developed a PCR based system to assay the distribution of standard (TTAGGG) and variant (TGAGGG, TCAGGG) repeats at the proximal end of the Xp:Yp telomere repeat array. The 1 kb of DNA immediately adjacent to this telomere exhibits a high level of base substitutional polymorphism. In individuals heterozygous for a flanking polymorphism, allele specific primers have been designed to discriminate between the alleles and, in conjunction with a primer complementary to either TTAGGG, TGAGGG or TCAGGG repeats, to determine the distribution of telomere and variant repeat units at the proximal end of an individual telomere. Among the 41 Xp:Yp telomeres mapped to date only 5 are identical and composed solely of (TTAGGG) repeats at the proximal end. The remaining 36 mapped telomeres are all different, although a subset show similarities and are found in association with the same flanking DNA haplotype, suggesting a common ancestry. The telomere variant repeat mapping technique can be used to examine the turnover of these sequences in human populations and in somatic tissues and tumors.

  3. Telomeric DNA in ALT Cells Is Characterized by Free Telomeric Circles and Heterogeneous t-Loops

    PubMed Central

    Cesare, Anthony J.; Griffith, Jack D.

    2004-01-01

    A prerequisite for cellular immortalization in human cells is the elongation of telomeres through the upregulation of telomerase or by the alternative lengthening of telomeres (ALT) pathway. In this study, telomere structure in multiple ALT cell lines was examined by electron microscopy. Nuclei were isolated from GM847, GM847-Tert, and WI-38 VA13 ALT cells, psoralen photo-cross-linked in situ, and the telomere restriction fragments were purified by gel filtration chromatography. Examination of telomere-enriched fractions revealed frequent extrachromosomal circles, ranging from 0.7 to 56.8 kb. t-loops were also observed, with the loop portion ranging from 0.5 to 70.2 kb. The total length of the loop plus tail of the t-loops corresponded to the telomere restriction fragment length from the ALT cell lines as determined by pulsed-field gel electrophoresis. The presence of extrachromosomal circles containing telomeric DNA was confirmed by two-dimensional pulsed-field gel electrophoresis. These results show that extrachromosomal telomeric DNA circles are present in ALT nuclei and suggest a roll-and-spread mechanism of telomere elongation similar to that seen in previous observations of multiple yeast species. Results presented here also indicate that expression of telomerase in GM847 cells does not affect t-loop or extrachromosomal circle formation. PMID:15509797

  4. Telomere repeat binding proteins are functional components of Arabidopsis telomeres and interact with telomerase

    PubMed Central

    Procházková Schrumpfová, Petra; Vychodilová, Ivona; Dvořáčková, Martina; Majerská, Jana; Dokládal, Ladislav; Schořová, Šárka; Fajkus, Jiří

    2014-01-01

    Although telomere-binding proteins constitute an essential part of telomeres, in vivo data indicating the existence of a structure similar to mammalian shelterin complex in plants are limited. Partial characterization of a number of candidate proteins has not identified true components of plant shelterin or elucidated their functional mechanisms. Telomere repeat binding (TRB) proteins from Arabidopsis thaliana bind plant telomeric repeats through a Myb domain of the telobox type in vitro, and have been shown to interact with POT1b (Protection of telomeres 1). Here we demonstrate co-localization of TRB1 protein with telomeres in situ using fluorescence microscopy, as well as in vivo interaction using chromatin immunoprecipitation. Classification of the TRB1 protein as a component of plant telomeres is further confirmed by the observation of shortening of telomeres in knockout mutants of the trb1 gene. Moreover, TRB proteins physically interact with plant telomerase catalytic subunits. These findings integrate TRB proteins into the telomeric interactome of A. thaliana. PMID:24397874

  5. HSV-1 Remodels Host Telomeres To Facilitate Viral Replication

    PubMed Central

    Deng, Zhong; Kim, Eui Tae; Vladimirova, Olga; Dheekollu, Jayaraju; Wang, Zhuo; Newhart, Alyshia; Liu, Dongmei; Myers, Jaclyn L.; Hensley, Scott E.; Moffat, Jennifer; Janicki, Susan M.; Fraser, Nigel W.; Knipe, David M.; Weitzman, Matthew D.; Lieberman, Paul M.

    2015-01-01

    Summary Telomeres protect the ends of cellular chromosomes. We show here that infection with herpes simplex virus 1 (HSV-1) results in chromosomal structural aberrations at telomeres and the accumulation of telomere dysfunction-induced DNA damage foci (TIFs). At the molecular level, HSV-1 induces transcription of telomere repeat-containing RNA (TERRA), followed by the proteolytic degradation of the telomere protein TPP1, and loss of the telomere repeat DNA signal. The HSV-1 encoded E3 ubiquitin ligase ICP0 is required for TERRA transcription and facilitates TPP1 degradation. shRNA depletion of TPP1 increases viral replication, arguing that TPP1inhibits viral replication. Viral replication protein ICP8 forms foci that coincide with telomeric proteins and ICP8 null virus failed to degrade telomere DNA signal. These findings suggest that HSV-1 reorganizes telomeres to form ICP8-associated pre-replication foci and promotes viral genomic replication. PMID:25497088

  6. Maternal telomere length inheritance in the king penguin

    PubMed Central

    Reichert, S; Rojas, E R; Zahn, S; Robin, J-P; Criscuolo, F; Massemin, S

    2015-01-01

    Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age. PMID:25052413

  7. Maternal telomere length inheritance in the king penguin.

    PubMed

    Reichert, S; Rojas, E R; Zahn, S; Robin, J-P; Criscuolo, F; Massemin, S

    2015-01-01

    Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age. PMID:25052413

  8. Maternal telomere length inheritance in the king penguin.

    PubMed

    Reichert, S; Rojas, E R; Zahn, S; Robin, J-P; Criscuolo, F; Massemin, S

    2015-01-01

    Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age.

  9. Association between telomere length and chromosome 21 nondisjunction in the oocyte.

    PubMed

    Albizua, I; Rambo-Martin, B L; Allen, E G; He, W; Amin, A S; Sherman, S L

    2015-11-01

    Chromosome 21 nondisjunction in oocytes is the most common cause of trisomy 21, the primary chromosomal abnormality responsible for Down syndrome (DS). This specific type of error is estimated to account for over 90 % of live births with DS, with maternal age being the best known risk factor for chromosome 21 nondisjunction. The loss of telomere length and the concomitant shortening of chromosomes are considered a biological marker for aging. Thus, we tested the hypothesis that mothers who had a maternal nondisjunction error leading to a live birth with DS (n = 404) have shorter telomeres than mothers with live births without DS (n = 42). In effect, our hypothesis suggests that mothers of children with DS will appear "biologically older" as compared to the mothers of euploid children. We applied a quantitative PCR assay to measure the genome-wide relative telomere length to test this hypothesis. The results of our study support the hypothesis that young mothers of DS babies are "biologically older" than mothers of euploid babies in the same age group and supports telomere length as a biomarker of age and hence risk for chromosome nondisjunction. PMID:26407969

  10. [Enhanced control of proliferation in telomerized cells].

    PubMed

    Egorov, E E; Moldaver, M V; Vishniakova, Kh S; Terekhov, S M; Dashinimaev, E B; Cheglakov, I B; Toropygin, I Iu; Iarygin, K N; Chumakov, P M; Korochkin, L I; Antonova, G A; Rybalkina, E Iu; Saburina, I N; Burnaevskiĭ, N S; Zelenin, A V

    2007-01-01

    Clones of telomerized fibroblasts of adult human skin have earlier been obtained. It was shown that despite their fast growth in mass cultures, these cells poorly form colonies. Conditioned medium, antioxidants, and reduced partial oxygen pressure enhanced their colony formation, but not to the level characteristic of the initial cells. The conditioned medium of telomerized cells enhanced colony formation to a much greater extent than that of the initial cells. A study of proteome of the telomerized fibroblasts has revealed changes in the activities of tens of genes. A general trend consists in weakening and increased lability of the cytoskeleton and in activation of the mechanisms controlling protein degradation. However, these changes are not very pronounced. During the formation of immortal telomerized cells, selection takes place, which appears to determine changes in the expression of some genes. It was proposed that a decrease in the capacity of telomerized cells for colony formation is due to increased requirements of these cells to cell-cell contacts. The rate of cell growth reached that characteristic of mass cultures only in the largest colonies. In this respect, the telomerized fibroblasts resembled stem cells: they are capable of self-maintenance, but "escape" to differentiation in the absence of the corresponding microenvironment (niche), which is represented by other fibroblasts. Non-dividing cells in the test of colony formation should be regarded as differentiated cells, since they have no features of degradation, preserve their viability, actively move, grow, phagocytized debris, etc. It was also shown that telomerization did not prevent differentiation of myoblasts and human neural stem cells. Thus, the results obtained suggest the existence of normal mechanisms underlying the regulation of proliferation in the telomerized cells, which opens possibilities of their use in cell therapy, especially in the case of autotransplantation to senior people

  11. Telomeres and the ethics of human cloning.

    PubMed

    Allhoff, Fritz

    2004-01-01

    In search of a potential problem with cloning, I investigate the phenomenon of telomere shortening which is caused by cell replication; clones created from somatic cells will have shortened telomeres and therefore reach a state of senescence more rapidly. While genetic intervention might fix this problem at some point in the future, I ask whether, absent technological advances, this biological phenomenon undermines the moral permissibility of cloning.

  12. Regulation of Telomere Length Requires a Conserved N-Terminal Domain of Rif2 in Saccharomyces cerevisiae.

    PubMed

    Kaizer, Hannah; Connelly, Carla J; Bettridge, Kelsey; Viggiani, Christopher; Greider, Carol W

    2015-10-01

    The regulation of telomere length equilibrium is essential for cell growth and survival since critically short telomeres signal DNA damage and cell cycle arrest. While the broad principles of length regulation are well established, the molecular mechanism of how these steps occur is not fully understood. We mutagenized the RIF2 gene in Saccharomyces cerevisiae to understand how this protein blocks excess telomere elongation. We identified an N-terminal domain in Rif2 that is essential for length regulation, which we have termed BAT domain for Blocks Addition of Telomeres. Tethering this BAT domain to Rap1 blocked telomere elongation not only in rif2Δ mutants but also in rif1Δ and rap1C-terminal deletion mutants. Mutation of a single amino acid in the BAT domain, phenylalanine at position 8 to alanine, recapitulated the rif2Δ mutant phenotype. Substitution of F8 with tryptophan mimicked the wild-type phenylalanine, suggesting the aromatic amino acid represents a protein interaction site that is essential for telomere length regulation.

  13. Isolation of chromatin from dysfunctional telomeres reveals an important role for Ring1b in NHEJ-mediated chromosome fusions.

    PubMed

    Bartocci, Cristina; Diedrich, Jolene K; Ouzounov, Iliana; Li, Julia; Piunti, Andrea; Pasini, Diego; Yates, John R; Lazzerini Denchi, Eros

    2014-05-22

    When telomeres become critically short, DNA damage response factors are recruited at chromosome ends, initiating a cellular response to DNA damage. We performed proteomic isolation of chromatin fragments (PICh) in order to define changes in chromatin composition that occur upon onset of acute telomere dysfunction triggered by depletion of the telomere-associated factor TRF2. This unbiased purification of telomere-associated proteins in functional or dysfunctional conditions revealed the dynamic changes in chromatin composition that take place at telomeres upon DNA damage induction. On the basis of our results, we describe a critical role for the polycomb group protein Ring1b in nonhomologous end-joining (NHEJ)-mediated end-to-end chromosome fusions. We show that cells with reduced levels of Ring1b have a reduced ability to repair uncapped telomeric chromatin. Our data represent an unbiased isolation of chromatin undergoing DNA damage and are a valuable resource to map the changes in chromatin composition in response to DNA damage activation. PMID:24813883

  14. Bottom of the Heap: Having Heavier Competitors Accelerates Early-Life Telomere Loss in the European Starling, Sturnus vulgaris

    PubMed Central

    Nettle, Daniel; Monaghan, Pat; Boner, Winnie; Gillespie, Robert; Bateson, Melissa

    2013-01-01

    Early-life adversity is associated with poorer health and survival in adulthood in humans and other animals. One pathway by which early-life environmental stressors could affect the adult phenotype is via effects on telomere dynamics. Several studies have shown that early-life adversity is associated with relatively short telomeres, but these are often cross-sectional and usually correlational in design. Here, we present a novel experimental system for studying the relationship between early-life adversity and telomere dynamics using a wild bird, the European starling (Sturnus vulgaris). We used cross-fostering to experimentally assign sibling chicks to either small or large broods for twelve days of the growth period. We measured telomere length in red blood cells using quantitative PCR near the beginning of the experimental manipulation (4 days old), at the end of the experimental manipulation (15 days old), and once the birds were independent (55 days old). Being in a larger brood slowed growth and retarded wing development and the timing of fledging. We found no evidence that overall brood size affected telomere dynamics. However, the greater the number of competitors above the focal bird in the within-brood size hierarchy, the greater was the telomere loss during the period of the experimental manipulation. The number of competitors below the focal in the hierarchy had no effect. The effect of heavier competitors was still evident when we controlled for the weight of the focal bird at the end of the manipulation, suggesting it was not due to retarded growth per se. Moreover, the impact of early competition on telomeres was still evident at independence, suggesting persistence beyond early life. Our study provides experimental support for the hypothesis that social stress, in this case induced by the presence of a greater number of dominant competitors, accelerates the rate of telomere loss. PMID:24386235

  15. Bottom of the heap: having heavier competitors accelerates early-life telomere loss in the European starling, Sturnus vulgaris.

    PubMed

    Nettle, Daniel; Monaghan, Pat; Boner, Winnie; Gillespie, Robert; Bateson, Melissa

    2013-01-01

    Early-life adversity is associated with poorer health and survival in adulthood in humans and other animals. One pathway by which early-life environmental stressors could affect the adult phenotype is via effects on telomere dynamics. Several studies have shown that early-life adversity is associated with relatively short telomeres, but these are often cross-sectional and usually correlational in design. Here, we present a novel experimental system for studying the relationship between early-life adversity and telomere dynamics using a wild bird, the European starling (Sturnus vulgaris). We used cross-fostering to experimentally assign sibling chicks to either small or large broods for twelve days of the growth period. We measured telomere length in red blood cells using quantitative PCR near the beginning of the experimental manipulation (4 days old), at the end of the experimental manipulation (15 days old), and once the birds were independent (55 days old). Being in a larger brood slowed growth and retarded wing development and the timing of fledging. We found no evidence that overall brood size affected telomere dynamics. However, the greater the number of competitors above the focal bird in the within-brood size hierarchy, the greater was the telomere loss during the period of the experimental manipulation. The number of competitors below the focal in the hierarchy had no effect. The effect of heavier competitors was still evident when we controlled for the weight of the focal bird at the end of the manipulation, suggesting it was not due to retarded growth per se. Moreover, the impact of early competition on telomeres was still evident at independence, suggesting persistence beyond early life. Our study provides experimental support for the hypothesis that social stress, in this case induced by the presence of a greater number of dominant competitors, accelerates the rate of telomere loss.

  16. Bottom of the heap: having heavier competitors accelerates early-life telomere loss in the European starling, Sturnus vulgaris.

    PubMed

    Nettle, Daniel; Monaghan, Pat; Boner, Winnie; Gillespie, Robert; Bateson, Melissa

    2013-01-01

    Early-life adversity is associated with poorer health and survival in adulthood in humans and other animals. One pathway by which early-life environmental stressors could affect the adult phenotype is via effects on telomere dynamics. Several studies have shown that early-life adversity is associated with relatively short telomeres, but these are often cross-sectional and usually correlational in design. Here, we present a novel experimental system for studying the relationship between early-life adversity and telomere dynamics using a wild bird, the European starling (Sturnus vulgaris). We used cross-fostering to experimentally assign sibling chicks to either small or large broods for twelve days of the growth period. We measured telomere length in red blood cells using quantitative PCR near the beginning of the experimental manipulation (4 days old), at the end of the experimental manipulation (15 days old), and once the birds were independent (55 days old). Being in a larger brood slowed growth and retarded wing development and the timing of fledging. We found no evidence that overall brood size affected telomere dynamics. However, the greater the number of competitors above the focal bird in the within-brood size hierarchy, the greater was the telomere loss during the period of the experimental manipulation. The number of competitors below the focal in the hierarchy had no effect. The effect of heavier competitors was still evident when we controlled for the weight of the focal bird at the end of the manipulation, suggesting it was not due to retarded growth per se. Moreover, the impact of early competition on telomeres was still evident at independence, suggesting persistence beyond early life. Our study provides experimental support for the hypothesis that social stress, in this case induced by the presence of a greater number of dominant competitors, accelerates the rate of telomere loss. PMID:24386235

  17. [Telomere Recombination in Normal Mammalian Cells].

    PubMed

    Zhdanova, N S; Rubtsov, N B

    2016-01-01

    Two mechanisms of telomere length maintenance are known to date. The first includes the use of a special enzymatic telomerase complex to solve the problems that arise during the replication of linear DNA in a normal diploid and part of tumor cells. Alternative lengthening of telomeres (ALT), which is based on the homologous recombination of telomere DNA, represents the second mechanism. Until recently, ALT was assumed to be expressed only in 15-20% of tumors lacking active telomerase and, together with telomerase reactivation represented one of two possibilities to overcome the replicative senescence observed in somatic mammalian cells due to aging or during cell culturing in vitro. Previously described sporadic cases of combinations of the two mechanisms of telomere length maintenance in several cell lines in vitro were attributed to the experimental design rather than to a real biological phenomenon, since active cellular division without active telomerase was considered to be the "gold standard" of ALT. The present review describes the morphological and functional reorganizations of mammalian telomeres observed with ALT activation, as well as recently observed,and well-documented cases of combinations between ALT-like and telomerase-dependent mechanisms in mammalian cells. The possible role of telomere recombination in telomerase-dependent cells is discussed.

  18. Telomeres, NAFLD and Chronic Liver Disease.

    PubMed

    Donati, Benedetta; Valenti, Luca

    2016-01-01

    Telomeres consist of repeat DNA sequences located at the terminal portion of chromosomes that shorten during mitosis, protecting the tips of chromosomes. During chronic degenerative conditions associated with high cell replication rate, progressive telomere attrition is accentuated, favoring senescence and genomic instability. Several lines of evidence suggest that this process is involved in liver disease progression: (a) telomere shortening and alterations in the expression of proteins protecting the telomere are associated with cirrhosis and hepatocellular carcinoma; (b) advanced liver damage is a feature of a spectrum of genetic diseases impairing telomere function, and inactivating germline mutations in the telomerase complex (including human Telomerase Reverse Transcriptase (hTERT) and human Telomerase RNA Component (hTERC)) are enriched in cirrhotic patients independently of the etiology; and (c) experimental models suggest that telomerase protects from liver fibrosis progression. Conversely, reactivation of telomerase occurs during hepatocarcinogenesis, allowing the immortalization of the neoplastic clone. The role of telomere attrition may be particularly relevant in the progression of nonalcoholic fatty liver, an emerging cause of advanced liver disease. Modulation of telomerase or shelterins may be exploited to prevent liver disease progression, and to define specific treatments for different stages of liver disease. PMID:26999107

  19. Protection of Telomeres 1 Is Required for Telomere Integrity in the Moss Physcomitrella patens[W

    PubMed Central

    Shakirov, Eugene V.; Perroud, Pierre-François; Nelson, Andrew D.; Cannell, Maren E.; Quatrano, Ralph S.; Shippen, Dorothy E.

    2010-01-01

    In vertebrates, the single-stranded telomeric DNA binding protein Protection of Telomeres 1 (POT1) shields chromosome ends and prevents them from eliciting a DNA damage response. By contrast, Arabidopsis thaliana encodes two divergent full-length POT1 paralogs that do not exhibit telomeric DNA binding in vitro and have evolved to mediate telomerase regulation instead of chromosome end protection. To further investigate the role of POT1 in plants, we established the moss Physcomitrella patens as a new model for telomere biology and a counterpoint to Arabidopsis. The sequence and architecture of the telomere tract is similar in P. patens and Arabidopsis, but P. patens harbors only a single-copy POT1 gene. Unlike At POT1 proteins, Pp POT1 efficiently bound single-stranded telomeric DNA in vitro. Deletion of the P. patens POT1 gene resulted in the rapid onset of severe developmental defects and sterility. Although telomerase activity levels were unperturbed, telomeres were substantially shortened, harbored extended G-overhangs, and engaged in end-to-end fusions. We conclude that the telomere capping function of POT1 is conserved in early diverging land plants but is subsequently lost in Arabidopsis. PMID:20515974

  20. [Association study of telomere length with idiopathic male infertility].

    PubMed

    Shuyuan, Liu; Changjun, Zhang; Haiying, Peng; Xiaoqin, Huang; Hao, Sun; Keqin, Lin; Kai, Huang; Jiayou, Chu; Zhaoqing, Yang

    2015-11-01

    Telomeres are evolutionary conserved, multifunctional DNA-protein complexes located at the ends of eukaryotic chromosomes. Telomeres maintain chromosome stability and genome integrity and also play an important role in meiosis which aid in synapsis, homologous recombination, and segregation. Sperm telomere has been reported to play an important role in fertilization and embryo development. Nowadays, the association between telomere and reproduction is one of the major areas of interest, however whether sperm telomere associated with male infertility is not clear. In this study, in order to find out the association between Chinese idiopathic infertility and sperm telomere length, we analyzed the difference of sperm telomere length between idiopathic infertile men and normal fertile men, as well as the correlations between sperm telomere length and human semen characteristics. We analyzed 126 Chinese idiopathic infertile men and 138 normal fertile men for sperm telomere length by using quantitative PCR. We found that the relative sperm mean telomere length of infertile men was significantly shorter than that of fertile men (2.894 ± 0.115 vs. 4.016 ± 0.603, P=5.097 x 10⁻⁵). Both sperm count and semen progressive motility are related with telomere length. Our results suggest that sperm telomere length is associated with idiopathic male infertility of China and we proposed the possibility that shorter telomeres in sperm chromosome will reduce spermatogenesis and sperm functions, which finally affected the fertility of male.

  1. Paternal imprint essential for the inheritance of telomere identity in Drosophila.

    PubMed

    Gao, Guanjun; Cheng, Yan; Wesolowska, Natalia; Rong, Yikang S

    2011-03-22

    Chromatin remodeling during sperm maturation could erase epigenetic landmarks on the paternal genome, creating a challenge for its reestablishment on fertilization. Here, we show that selective retention of a chromosomal protein in mature sperm protects the identity of paternal telomeres in Drosophila. The ms(3)k81 (k81) gene is a duplication of hiphop that encodes a telomeric protein. Although HipHop protects telomeres in somatic cells, K81 is produced exclusively in males and localizes to telomeres in postmitotic cells, including mature sperm. In embryos fathered by k81 mutants, the maternal supplies fail to reestablish a protective cap on paternal telomeres, leading to their fusions. These fusions hinder the segregation of the paternal genome and result in haploid embryos with maternal chromosomes. The functional divergence between hiphop and k81 manifests not only in their expression patterns but also in the protein functions that they encode. By swapping the two coding regions, we show that K81 can replace HipHop for somatic protection; however, HipHop cannot replace K81 in the germ line to specify telomere identity, because HipHop ectopically expressed in the testis is removed from chromatin during sperm maturation. HipHop lacks a short motif in K81 that is essential for K81 to survive the remodeling process. We show that the combined functions of HipHop and K81 are likely fulfilled by the single ancestral hiphop locus in other Drosophila species, supporting the hypothesis that the evolutionary process of subfunctionalization was responsible for the preservation of the hiphop-k81 duplicate. PMID:21383184

  2. Paternal imprint essential for the inheritance of telomere identity in Drosophila.

    PubMed

    Gao, Guanjun; Cheng, Yan; Wesolowska, Natalia; Rong, Yikang S

    2011-03-22

    Chromatin remodeling during sperm maturation could erase epigenetic landmarks on the paternal genome, creating a challenge for its reestablishment on fertilization. Here, we show that selective retention of a chromosomal protein in mature sperm protects the identity of paternal telomeres in Drosophila. The ms(3)k81 (k81) gene is a duplication of hiphop that encodes a telomeric protein. Although HipHop protects telomeres in somatic cells, K81 is produced exclusively in males and localizes to telomeres in postmitotic cells, including mature sperm. In embryos fathered by k81 mutants, the maternal supplies fail to reestablish a protective cap on paternal telomeres, leading to their fusions. These fusions hinder the segregation of the paternal genome and result in haploid embryos with maternal chromosomes. The functional divergence between hiphop and k81 manifests not only in their expression patterns but also in the protein functions that they encode. By swapping the two coding regions, we show that K81 can replace HipHop for somatic protection; however, HipHop cannot replace K81 in the germ line to specify telomere identity, because HipHop ectopically expressed in the testis is removed from chromatin during sperm maturation. HipHop lacks a short motif in K81 that is essential for K81 to survive the remodeling process. We show that the combined functions of HipHop and K81 are likely fulfilled by the single ancestral hiphop locus in other Drosophila species, supporting the hypothesis that the evolutionary process of subfunctionalization was responsible for the preservation of the hiphop-k81 duplicate.

  3. Paternal imprint essential for the inheritance of telomere identity in Drosophila

    PubMed Central

    Gao, Guanjun; Cheng, Yan; Wesolowska, Natalia; Rong, Yikang S.

    2011-01-01

    Chromatin remodeling during sperm maturation could erase epigenetic landmarks on the paternal genome, creating a challenge for its reestablishment on fertilization. Here, we show that selective retention of a chromosomal protein in mature sperm protects the identity of paternal telomeres in Drosophila. The ms(3)k81 (k81) gene is a duplication of hiphop that encodes a telomeric protein. Although HipHop protects telomeres in somatic cells, K81 is produced exclusively in males and localizes to telomeres in postmitotic cells, including mature sperm. In embryos fathered by k81 mutants, the maternal supplies fail to reestablish a protective cap on paternal telomeres, leading to their fusions. These fusions hinder the segregation of the paternal genome and result in haploid embryos with maternal chromosomes. The functional divergence between hiphop and k81 manifests not only in their expression patterns but also in the protein functions that they encode. By swapping the two coding regions, we show that K81 can replace HipHop for somatic protection; however, HipHop cannot replace K81 in the germ line to specify telomere identity, because HipHop ectopically expressed in the testis is removed from chromatin during sperm maturation. HipHop lacks a short motif in K81 that is essential for K81 to survive the remodeling process. We show that the combined functions of HipHop and K81 are likely fulfilled by the single ancestral hiphop locus in other Drosophila species, supporting the hypothesis that the evolutionary process of subfunctionalization was responsible for the preservation of the hiphop-k81 duplicate. PMID:21383184

  4. Spatially confined polymer chains: implications of chromatin fibre flexibility and peripheral anchoring on telomere telomere interaction

    NASA Astrophysics Data System (ADS)

    Gehlen, L. R.; Rosa, A.; Klenin, K.; Langowski, J.; Gasser, S. M.; Bystricky, K.

    2006-04-01

    We simulate the extension of spatially confined chromatin fibres modelled as polymer chains and examine the effect of the flexibility of the fibre and its degree of freedom. The developed formalism was used to analyse experimental data of telomere-telomere distances in living yeast cells in the absence of confining factors as identified by the proteins Sir4 and yKu70. Our analysis indicates that intrinsic properties of the chromatin fibre, in particular its elastic properties and flexibility, can influence the juxtaposition of the telomeric ends of chromosomes. However, measurements in intact yeast cells showed that the telomeres of chromosomes 3 and 6 come even closer together than the parameters of constraint imposed on the simulations would predict. This juxtaposition was specific to telomeres on one contiguous chromosome and overrode a tendency for separation that is imposed by anchoring.

  5. Origin of human chromosome 2: An ancestral telomere-telomere fusion

    SciTech Connect

    Ijdo, J.W.; Baldini, A.; Ward, D.C.; Reeders, S.T.; Wells, R.A. )

    1991-10-15

    The authors identified two allelic genomic cosmids from human chromosome 2, c8.1 and c29B, each containing two inverted arrays of the vertebrate telomeric repeat in a head-to-head arrangement, 5{prime}(TTAGGG){sub n}-(CCCTAA){sub m}3{prime}. Sequences flanking this telomeric repeat are characteristic of present-day human pretelomeres. BAL-31 nuclease experiments with yeast artificial chromosome clones of human telomeres and fluorescence in situ hybridization reveal that sequences flanking these inverted repeats hybridize both to band 2q13 and to different, but overlapping, subsets of human chromosome ends. They conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2.

  6. Telomere Capping Proteins are Structurally Related to RPA with an additional Telomere-Specific Domain

    SciTech Connect

    Gelinas, A.; Paschini, M; Reyes, F; Heroux, A; Batey, R; Lundblad, V; Wuttke, D

    2009-01-01

    Telomeres must be capped to preserve chromosomal stability. The conserved Stn1 and Ten1 proteins are required for proper capping of the telomere, although the mechanistic details of how they contribute to telomere maintenance are unclear. Here, we report the crystal structures of the C-terminal domain of the Saccharomyces cerevisiae Stn1 and the Schizosaccharomyces pombe Ten1 proteins. These structures reveal striking similarities to corresponding subunits in the replication protein A complex, further supporting an evolutionary link between telomere maintenance proteins and DNA repair complexes. Our structural and in vivo data of Stn1 identify a new domain that has evolved to support a telomere-specific role in chromosome maintenance. These findings endorse a model of an evolutionarily conserved mechanism of DNA maintenance that has developed as a result of increased chromosomal structural complexity.

  7. Are the leukocyte telomere length attrition and telomerase activity alteration potential predictor biomarkers for sporadic TAA in aged individuals?

    PubMed

    Balistreri, Carmela R; Pisano, Calogera; Martorana, Adriana; Triolo, Oreste F; Lio, Domenico; Candore, Giuseppina; Ruvolo, Giovanni

    2014-01-01

    A large variability in occurrence, complications, and age/gender manifestations characterizes individual susceptibility of sporadic thoracic aortic aneurysms (TAA), even in subjects with the same risk factor profiles. The reasons are poorly understood. On the other hand, TAA pathophysiology mechanisms remain unclear than those involved in abdominal aorta aneurysms. However, recent evidence is suggesting a crucial role of biological ageing in inter-individual risk variation of cardiovascular diseases, including sporadic TAA. Biological age rather than chronological age is a better predictor of vascular risk. Relevant assumptions support this concept. In confirming this evidence and our preliminary data, the mean of blood leukocyte telomere length, through use of terminal restriction fragment assay and in blood samples from sporadic TAA patients and controls, was examined. Telomerase activity was also analyzed in two groups. In addition, we verified the weight of genetic inflammatory variants and the major TAA risk factors in telomere/telomerase impairment. Aorta histopathological abnormalities and systemic inflammatory mediators were ultimately correlated with telomere/telomerase impairment. Data obtained demonstrated shorter telomeres and a reduced telomerase activity in TAA patients significantly associated with a genetic inflammatory risk profile, age, gender, smoking, hypertension, a histopathological phenotype, and higher levels of systemic inflammatory mediators than controls. In conclusion, telomere and telomerase activity's detection might be used as predictor biomarkers of sporadic TAA. Their impairment also suggests a strong role of vascular ageing in sporadic TAA, evocated by both environmental and genetic inflammatory factors.

  8. X-linked congenital ptosis and associated intellectual disability, short stature, microcephaly, cleft palate, digital and genital abnormalities define novel Xq25q26 duplication syndrome.

    PubMed

    Møller, R S; Jensen, L R; Maas, S M; Filmus, J; Capurro, M; Hansen, C; Marcelis, C L M; Ravn, K; Andrieux, J; Mathieu, M; Kirchhoff, M; Rødningen, O K; de Leeuw, N; Yntema, H G; Froyen, G; Vandewalle, J; Ballon, K; Klopocki, E; Joss, S; Tolmie, J; Knegt, A C; Lund, A M; Hjalgrim, H; Kuss, A W; Tommerup, N; Ullmann, R; de Brouwer, A P M; Strømme, P; Kjaergaard, S; Tümer, Z; Kleefstra, T

    2014-05-01

    Submicroscopic duplications along the long arm of the X-chromosome with known phenotypic consequences are relatively rare events. The clinical features resulting from such duplications are various, though they often include intellectual disability, microcephaly, short stature, hypotonia, hypogonadism and feeding difficulties. Female carriers are often phenotypically normal or show a similar but milder phenotype, as in most cases the X-chromosome harbouring the duplication is subject to inactivation. Xq28, which includes MECP2 is the major locus for submicroscopic X-chromosome duplications, whereas duplications in Xq25 and Xq26 have been reported in only a few cases. Using genome-wide array platforms we identified overlapping interstitial Xq25q26 duplications ranging from 0.2 to 4.76 Mb in eight unrelated families with in total five affected males and seven affected females. All affected males shared a common phenotype with intrauterine- and postnatal growth retardation and feeding difficulties in childhood. Three had microcephaly and two out of five suffered from epilepsy. In addition, three males had a distinct facial appearance with congenital bilateral ptosis and large protruding ears and two of them showed a cleft palate. The affected females had various clinical symptoms similar to that of the males with congenital bilateral ptosis in three families as most remarkable feature. Comparison of the gene content of the individual duplications with the respective phenotypes suggested three critical regions with candidate genes (AIFM1, RAB33A, GPC3 and IGSF1) for the common phenotypes, including candidate loci for congenital bilateral ptosis, small head circumference, short stature, genital and digital defects.

  9. Insomnia and Telomere Length in Older Adults

    PubMed Central

    Carroll, Judith E.; Esquivel, Stephanie; Goldberg, Alyssa; Seeman, Teresa E.; Effros, Rita B.; Dock, Jeffrey; Olmstead, Richard; Breen, Elizabeth C.; Irwin, Michael R.

    2016-01-01

    Study Objectives: Insomnia, particularly in later life, may raise the risk for chronic diseases of aging and mortality through its effect on cellular aging. The current study examines the effects of insomnia on telomere length, a measure of cellular aging, and tests whether insomnia interacts with chronological age to increase cellular aging. Methods: A total of 126 males and females (60–88 y) were assessed for insomnia using the Diagnostic and Statistical Manual IV criterion for primary insomnia and the International Classification of Sleep Disorders, Second Edition for general insomnia (45 insomnia cases; 81 controls). Telomere length in peripheral blood mononuclear cells (PBMC) was determined using real-time quantitative polymerase chain reaction (qPCR) methodology. Results: In the analysis of covariance model adjusting for body mass index and sex, age (60–69 y versus 70–88 y) and insomnia diagnosis interacted to predict shorter PBMC telomere length (P = 0.04). In the oldest age group (70–88 y), PBMC telomere length was significantly shorter in those with insomnia, mean (standard deviation) M(SD) = 0.59(0.2) compared to controls with no insomnia M(SD) = 0.78(0.4), P = 0.04. In the adults aged 60–69 y, PBMC telomere length was not different between insomnia cases and controls, P = 0.44. Conclusions: Insomnia is associated with shorter PBMC telomere length in adults aged 70–88 y, but not in those younger than 70 y, suggesting that clinically severe sleep disturbances may increase cellular aging, especially in the later years of life. These findings highlight insomnia as a vulnerability factor in later life, with implications for risk for diseases of aging. Citation: Carroll JE, Esquivel S, Goldberg A, Seeman TE, Effros RB, Dock J, Olmstead R, Breen EC, Irwin MR. Insomnia and telomere length in older adults. SLEEP 2016;39(3):559–564. PMID:26715231

  10. Swi1Timeless Prevents Repeat Instability at Fission Yeast Telomeres

    PubMed Central

    Gadaleta, Mariana C.; Das, Mukund M.; Tanizawa, Hideki; Chang, Ya-Ting; Noma, Ken-ichi; Nakamura, Toru M.; Noguchi, Eishi

    2016-01-01

    Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC) is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus. However, little is known about the role of the FPC at other natural impediments including telomeres. Telomeres are considered to be difficult to replicate due to the presence of repetitive GT-rich sequences and telomere-binding proteins. However, the regulatory mechanism that ensures telomere replication is not fully understood. Here, we report the role of the fission yeast Swi1Timeless, a subunit of the FPC, in telomere replication. Loss of Swi1 causes telomere shortening in a telomerase-independent manner. Our epistasis analyses suggest that heterochromatin and telomere-binding proteins are not major impediments for telomere replication in the absence of Swi1. Instead, repetitive DNA sequences impair telomere integrity in swi1Δ mutant cells, leading to the loss of repeat DNA. In the absence of Swi1, telomere shortening is accompanied with an increased recruitment of Rad52 recombinase and more frequent amplification of telomere/subtelomeres, reminiscent of tumor cells that utilize the alternative lengthening of telomeres pathway (ALT) to maintain telomeres. These results suggest that Swi1 ensures telomere replication by suppressing recombination and repeat instability at telomeres. Our studies may also be relevant in understanding the potential role of Swi1Timeless in regulation of telomere stability in cancer cells. PMID:26990647

  11. Recombination-Mediated Telomere Maintenance in Saccharomyces cerevisiae Is Not Dependent on the Shu Complex.

    PubMed

    van Mourik, Paula M; de Jong, Jannie; Agpalo, Danielle; Claussin, Clémence; Rothstein, Rodney; Chang, Michael

    2016-01-01

    In cells lacking telomerase, telomeres shorten progressively during each cell division due to incomplete end-replication. When the telomeres become very short, cells enter a state that blocks cell division, termed senescence. A subset of these cells can overcome senescence and maintain their telomeres using telomerase-independent mechanisms. In Saccharomyces cerevisiae, these cells are called 'survivors' and are dependent on Rad52-dependent homologous recombination and Pol32-dependent break-induced replication. There are two main types of survivors: type I and type II. The type I survivors require Rad51 and maintain telomeres by amplification of subtelomeric elements, while the type II survivors are Rad51-independent, but require the MRX complex and Sgs1 to amplify the C1-3A/TG1-3 telomeric sequences. Rad52, Pol32, Rad51, and Sgs1 are also important to prevent accelerated senescence, indicating that recombination processes are important at telomeres even before the formation of survivors. The Shu complex, which consists of Shu1, Shu2, Psy3, and Csm2, promotes Rad51-dependent homologous recombination and has been suggested to be important for break-induced replication. It also promotes the formation of recombination intermediates that are processed by the Sgs1-Top3-Rmi1 complex, as mutations in the SHU genes can suppress various sgs1, top3, and rmi1 mutant phenotypes. Given the importance of recombination processes during senescence and survivor formation, and the involvement of the Shu complex in many of the same processes during DNA repair, we hypothesized that the Shu complex may also have functions at telomeres. Surprisingly, we find that this is not the case: the Shu complex does not affect the rate of senescence, does not influence survivor formation, and deletion of SHU1 does not suppress the rapid senescence and type II survivor formation defect of a telomerase-negative sgs1 mutant. Altogether, our data suggest that the Shu complex is not important for

  12. Chromothripsis and Kataegis Induced by Telomere Crisis.

    PubMed

    Maciejowski, John; Li, Yilong; Bosco, Nazario; Campbell, Peter J; de Lange, Titia

    2015-12-17

    Telomere crisis occurs during tumorigenesis when depletion of the telomere reserve leads to frequent telomere fusions. The resulting dicentric chromosomes have been proposed to drive genome instability. Here, we examine the fate of dicentric human chromosomes in telomere crisis. We observed that dicentric chromosomes invariably persisted through mitosis and developed into 50-200 μm chromatin bridges connecting the daughter cells. Before their resolution at 3-20 hr after anaphase, the chromatin bridges induced nuclear envelope rupture in interphase, accumulated the cytoplasmic 3' nuclease TREX1, and developed RPA-coated single stranded (ss) DNA. CRISPR knockouts showed that TREX1 contributed to the generation of the ssDNA and the resolution of the chromatin bridges. Post-crisis clones showed chromothripsis and kataegis, presumably resulting from DNA repair and APOBEC editing of the fragmented chromatin bridge DNA. We propose that chromothripsis in human cancer may arise through TREX1-mediated fragmentation of dicentric chromosomes formed in telomere crisis.

  13. The yeast telomere length regulator TEL2 encodes a protein that binds to telomeric DNA.

    PubMed Central

    Kota, R S; Runge, K W

    1998-01-01

    TEL2 is required for telomere length regulation and viability in Saccharomyces cerevisiae. To investigate the mechanism by which Tel2p regulates telomere length, the majority (65%) of the TEL2 ORF was fused to the 3'-end of the gene for maltose binding protein, expressed in bacteria and the purified protein used in DNA binding studies. Rap1p, the major yeast telomere binding protein, recognizes a 13 bp duplex site 5'-GGTGTGTGGGTGT-3' in yeast telomeric DNA with high affinity. Gel shift experiments revealed that the MBP-Tel2p fusion binds the double-stranded yeast telomeric Rap1p site in a sequence-specific manner. Analysis of mutated sites showed that MBP-Tel2p could bind 5'-GTGTGTGG-3' within this 13 bp site. Methylation interference analysis revealed that Tel2p contacts the 5'-terminal guanine in the major groove. MBP-Tel2p did not bind duplex telomeric DNA repeats from vertebrates, Tetrahymena or Oxytricha. These results suggest that Tel2p is a DNA binding protein that recognizes yeast telomeric DNA. PMID:9490802

  14. Telomere-bound TRF1 and TRF2 stall the replication fork at telomeric repeats

    PubMed Central

    Ohki, Rieko; Ishikawa, Fuyuki

    2004-01-01

    Vertebrate telomeres consist of tandem repeats of T2AG3 and associated proteins including the telomeric DNA-binding proteins, TRF1 and TRF2. It has been proposed that telomeres assume two interswitchable states, the open state that is accessible to various trans-acting factors and the closed state that excludes those factors. TRF1 and TRF2 are believed to promote the formation of the closed state. However, little is known about how those two states influence DNA replication. We analyzed the effects of TRF1 and TRF2 on telomeric replication both in vitro and in vivo. By exploiting the in vitro replication system of linear SV40 DNA, we found that telomeric repeats are a poor replication template. Moreover, the addition of recombinant TRF1 and TRF2 significantly stalled the replication fork progression at telomeric repeats. When TRF1 was overexpressed in HeLa cells, cells with 4N DNA content were accumulated. Furthermore, cytological analyses revealed that the replication focus overlapped with telomere signals at a significantly higher frequency in TRF1-overexpressing cells than in control cells. The results suggest that TRF1 and TRF2 exert inhibitory effects on replication fork progression. PMID:15007108

  15. Molecular architecture of classical cytological landmarks: Centromeres and telomeres

    SciTech Connect

    Meyne, J.

    1994-11-01

    Both the human telomere repeat and the pericentromeric repeat sequence (GGAAT)n were isolated based on evolutionary conservation. Their isolation was based on the premise that chromosomal features as structurally and functionally important as telomeres and centromeres should be highly conserved. Both sequences were isolated by high stringency screening of a human repetitive DNA library with rodent repetitive DNA. The pHuR library (plasmid Human Repeat) used for this project was enriched for repetitive DNA by using a modification of the standard DNA library preparation method. Usually DNA for a library is cut with restriction enzymes, packaged, infected, and the library is screened. A problem with this approach is that many tandem repeats don`t have any (or many) common restriction sites. Therefore, many of the repeat sequences will not be represented in the library because they are not restricted to a viable length for the vector used. To prepare the pHuR library, human DNA was mechanically sheared to a small size. These relatively short DNA fragments were denatured and then renatured to C{sub o}t 50. Theoretically only repetitive DNA sequences should renature under C{sub o}t 50 conditions. The single-stranded regions were digested using S1 nuclease, leaving the double-stranded, renatured repeat sequences.

  16. Association between Maternal Symptoms of Sleep Disordered Breathing and Fetal Telomere Length

    PubMed Central

    Salihu, Hamisu M.; King, Lindsey; Patel, Priyanshi; Paothong, Arnut; Pradhan, Anupam; Louis, Judette; Naik, Eknath; Marty, Phillip J.; Whiteman, Valerie

    2015-01-01

    Study Objectives: Our investigation aims to assess the impact of symptoms of maternal sleep-disordered breathing, specifically sleep apnea risk and daytime sleepiness, on fetal leukocyte telomere length. Participants and Setting: Pregnant women were recruited upon hospital delivery admission. Interventions: Sleep exposure outcomes were measured using the Berlin Questionnaire to quantify sleep apnea and the Epworth Sleepiness Scale to measure daytime sleepiness. Participants were classified as “High Risk” or “Low Risk” for sleep apnea based on responses to the Berlin, while “Normal” or “Abnormal” daytime sleepiness was determined based on responses to the Epworth. Design: Neonatal umbilical cord blood samples (N = 67) were collected and genomic DNA was isolated from cord blood leukocytes using Quantitative PCR. A ratio of relative telomere length was derived by telomere repeat copy number and single copy gene copy number (T/S ratio) and used to compare telomere lengths. Bootstrap and ANOVA statistical procedures were employed. Measurements and Results: On the Berlin, 68.7% of participants were classified as Low Risk while 31.3% were classified as High Risk for sleep apnea. According to the Epworth scale, 80.6% were determined to have Normal daytime sleepiness, and 19.4% were found to have Abnormal daytime sleepiness. The T/S ratio among pregnant women at High Risk for sleep apnea was significantly shorter than for those at Low Risk (P value < 0.05), and the T/S ratio among habitual snorers was significantly shorter than among non-habitual snorers (P value < 0.05). Although those with Normal Sleepiness had a longer T/S ratio than those with Abnormal Sleepiness, the difference was not statistically significant. Conclusion: Our results provide the first evidence demonstrating shortened telomere length among fetuses exposed to maternal symptoms of sleep disordered breathing during pregnancy, and suggest sleep disordered breathing as a possible mechanism

  17. Urinary antimony and leukocyte telomere length: An analysis of NHANES 1999-2002.

    PubMed

    Scinicariello, Franco; Buser, Melanie C

    2016-10-01

    Telomeres are repetitive DNA sequences (TTAGGG) at the end of chromosomes. Cells with critically short telomeres enter replicative senescence and apoptosis. Several in vitro studies report that antimony causes cell apoptosis in human leukocyte cell lines. The goal of this analysis was to investigate whether there is an association between antimony exposure and leukocyte telomere length (LTL) among US adults aged 20 and older based on the National Health and Nutrition Examination Survey (NHANES) 1999-2002. We used multivariate linear regression to analyze the association of urinary antimony with LTL. LTL was log-natural transformed and the results were re-transformed and presented as percent differences. After adjustment for potential confounders, individuals in the 3rd and 4th quartiles of urinary antimony had statistically significantly shorter LTL (-4.78%, 95% CI: -8.42,-0.90; and -6.11%, 95% CI: -11.04,-1.00, respectively) compared to the lowest referent quartile, with evidence of a dose-response relationship (p-value for trend =0.03). Shorter LTL with antimony was driven by middle aged (40-59 years) and older (60-85 years) adult groups. The association may be biologically plausible because of reported oxidative stress and apoptosis effects of antimony on blood cells, effects known to shorten telomere length. PMID:27423705

  18. Urinary antimony and leukocyte telomere length: An analysis of NHANES 1999-2002.

    PubMed

    Scinicariello, Franco; Buser, Melanie C

    2016-10-01

    Telomeres are repetitive DNA sequences (TTAGGG) at the end of chromosomes. Cells with critically short telomeres enter replicative senescence and apoptosis. Several in vitro studies report that antimony causes cell apoptosis in human leukocyte cell lines. The goal of this analysis was to investigate whether there is an association between antimony exposure and leukocyte telomere length (LTL) among US adults aged 20 and older based on the National Health and Nutrition Examination Survey (NHANES) 1999-2002. We used multivariate linear regression to analyze the association of urinary antimony with LTL. LTL was log-natural transformed and the results were re-transformed and presented as percent differences. After adjustment for potential confounders, individuals in the 3rd and 4th quartiles of urinary antimony had statistically significantly shorter LTL (-4.78%, 95% CI: -8.42,-0.90; and -6.11%, 95% CI: -11.04,-1.00, respectively) compared to the lowest referent quartile, with evidence of a dose-response relationship (p-value for trend =0.03). Shorter LTL with antimony was driven by middle aged (40-59 years) and older (60-85 years) adult groups. The association may be biologically plausible because of reported oxidative stress and apoptosis effects of antimony on blood cells, effects known to shorten telomere length.

  19. Rif1: A Conserved Regulator of DNA Replication and Repair Hijacked by Telomeres in Yeasts

    PubMed Central

    Mattarocci, Stefano; Hafner, Lukas; Lezaja, Aleksandra; Shyian, Maksym; Shore, David

    2016-01-01

    Rap1-interacting factor 1 (Rif1) was originally identified in the budding yeast Saccharomyces cerevisiae as a telomere-binding protein that negatively regulates telomerase-mediated telomere elongation. Although this function is conserved in the distantly related fission yeast Schizosaccharomyces pombe, recent studies, both in yeasts and in metazoans, reveal that Rif1 also functions more globally, both in the temporal control of DNA replication and in DNA repair. Rif1 proteins are large and characterized by N-terminal HEAT repeats, predicted to form an elongated alpha-helical structure. In addition, all Rif1 homologs contain two short motifs, abbreviated RVxF/SILK, that are implicated in recruitment of the PP1 (yeast Glc7) phosphatase. In yeasts the RVxF/SILK domains have been shown to play a role in control of DNA replication initiation, at least in part through targeted de-phosphorylation of proteins in the pre-Replication Complex. In human cells Rif1 is recruited to DNA double-strand breaks through an interaction with 53BP1 where it counteracts DNA resection, thus promoting repair by non-homologous end-joining. This function requires the N-terminal HEAT repeat-containing domain. Interestingly, this domain is also implicated in DNA end protection at un-capped telomeres in yeast. We conclude by discussing the deployment of Rif1 at telomeres in yeasts from both an evolutionary perspective and in light of its recently discovered global functions. PMID:27066066

  20. Telomere length is a prognostic biomarker in elderly advanced ovarian cancer patients: a multicenter GINECO study

    PubMed Central

    Falandry, Claire; Horard, Béatrice; Bruyas, Amandine; Legouffe, Eric; Cretin, Jacques; Meunier, Jérôme; Alexandre, Jérôme; Delecroix, Valérie; Fabbro, Michel; Certain, Marie-Noëlle; Maraval-Gaget, Raymonde; Pujade-Lauraine, Eric; Gilson, Eric; Freyer, Gilles

    2015-01-01

    Purpose Age induces a progressive decline in functional reserve and impacts cancer treatments. Telomere attrition leads to tissue senescence. We tested the hypothesis that telomere length (TL) could predict patient vulnerability and outcome with cancer treatment. Patients and methods An ancillary study in the Elderly Women GINECO Trial 3 was performed to evaluate the impact of geriatric covariates on survival in elderly advanced ovarian cancer patients receiving six cycles of carboplatin. TL was estimated from peripheral blood at inclusion using standard procedures. Results TL (in base pairs) was estimated for 109/111 patients (median 6.1 kb; range [4.5-8.3 kb]). With a cut-off of 5.77 kb, TL discriminated two patient groups, long telomere (LT) and short telomeres (ST), with significantly different treatment completion rates of 0.80 (95%CI [0.71-0.89]) and 0.59 (95%CI [0.41-0.76]), respectively (odds ratio [OR]=2.8, p=0.02). ST patients were at higher risk of serious adverse events (SAE, OR=2.7; p=0.02) and had more unplanned hospital admissions (OR=2.1; p=0.08). After adjustment on FIGO stage, TL shorter than 6 kb was a risk factor of premature death (HR=1.57; p=0.06). Conclusion This exploratory study identifies TL as predictive factor of decreased treatment completion, SAE risk, unplanned hospital admissions and OS after adjustment on FIGO stage. PMID:26638179

  1. Telomere and Telomerase Therapeutics in Cancer.

    PubMed

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

    Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics.

  2. c-Myc quadruplex-forming sequence Pu-27 induces extensive damage in both telomeric and nontelomeric regions of DNA.

    PubMed

    Islam, Md Ashraful; Thomas, Shelia D; Murty, Vundavalli V; Sedoris, Kara J; Miller, Donald M

    2014-03-21

    Quadruplex-forming DNA sequences are present throughout the eukaryotic genome, including in telomeric DNA. We have shown that the c-Myc promoter quadruplex-forming sequence Pu-27 selectively kills transformed cells (Sedoris, K. C., Thomas, S. D., Clarkson, C. R., Muench, D., Islam, A., Singh, R., and Miller, D. M. (2012) Genomic c-Myc quadruplex DNA selectively kills leukemia. Mol. Cancer Ther. 11, 66-76). In this study, we show that Pu-27 induces profound DNA damage, resulting in striking chromosomal abnormalities in the form of chromatid or chromosomal breaks, radial formation, and telomeric DNA loss, which induces γ-H2AX in U937 cells. Pu-27 down-regulates telomeric shelterin proteins, DNA damage response mediators (RAD17 and RAD50), double-stranded break repair molecule 53BP1, G2 checkpoint regulators (CHK1 and CHK2), and anti-apoptosis gene survivin. Interestingly, there are no changes of DNA repair molecules H2AX, BRCA1, and the telomere maintenance gene, hTERT. ΔB-U937, where U937 cells stably transfected with deleted basic domain of TRF2 is partially sensitive to Pu-27 but exhibits no changes in expression of shelterin proteins. However, there is an up-regulation of CHK1, CHK2, H2AX, BRCA1, and survivin. Telomere dysfunction-induced foci assay revealed co-association of TRF1with γ-H2AX in ATM deficient cells, which are differentially sensitive to Pu-27 than ATM proficient cells. Alt (alternating lengthening of telomere) cells are relatively resistant to Pu-27, but there are no significant changes of telomerase activity in both Alt and non-Alt cells. Lastly, we show that this Pu-27-mediated sensitivity is p53-independent. The data therefore support two conclusions. First, Pu-27 induces DNA damage within both telomeric and nontelomeric regions of the genome. Second, Pu-27-mediated telomeric damage is due, at least in part, to compromise of the telomeric shelterin protein complex.

  3. Telomerase and telomere length in pulmonary fibrosis.

    PubMed

    Liu, Tianju; Ullenbruch, Matthew; Young Choi, Yoon; Yu, Hongfeng; Ding, Lin; Xaubet, Antoni; Pereda, Javier; Feghali-Bostwick, Carol A; Bitterman, Peter B; Henke, Craig A; Pardo, Annie; Selman, Moises; Phan, Sem H

    2013-08-01

    In addition to its expression in stem cells and many cancers, telomerase activity is transiently induced in murine bleomycin (BLM)-induced pulmonary fibrosis with increased levels of telomerase transcriptase (TERT) expression, which is essential for fibrosis. To extend these observations to human chronic fibrotic lung disease, we investigated the expression of telomerase activity in lung fibroblasts from patients with interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF). The results showed that telomerase activity was induced in more than 66% of IPF lung fibroblast samples, in comparison with less than 29% from control samples, some of which were obtained from lung cancer resections. Less than 4% of the human IPF lung fibroblast samples exhibited shortened telomeres, whereas less than 6% of peripheral blood leukocyte samples from patients with IPF or hypersensitivity pneumonitis demonstrated shortened telomeres. Moreover, shortened telomeres in late-generation telomerase RNA component knockout mice did not exert a significant effect on BLM-induced pulmonary fibrosis. In contrast, TERT knockout mice exhibited deficient fibrosis that was independent of telomere length. Finally, TERT expression was up-regulated by a histone deacetylase inhibitor, while the induction of TERT in lung fibroblasts was associated with the binding of acetylated histone H3K9 to the TERT promoter region. These findings indicate that significant telomerase induction was evident in fibroblasts from fibrotic murine lungs and a majority of IPF lung samples, whereas telomere shortening was not a common finding in the human blood and lung fibroblast samples. Notably, the animal studies indicated that the pathogenesis of pulmonary fibrosis was independent of telomere length.

  4. Determination of Arabidopsis thaliana telomere length by PCR

    PubMed Central

    Vaquero-Sedas, María I.; Vega-Palas, Miguel A.

    2014-01-01

    In humans, telomere length studies have acquired great relevance because the length of telomeres has been related to natural processes like disease, aging and cancer. However, very little is known about the influence of telomere length on the biology of wild type plants. The length of plant telomeres has been usually studied by Terminal Restriction Fragment (TRF) analyses. This technique requires high amounts of tissue, including multiple cell types, which might be the reason why very little is known about the influence of telomere length on plant natural processes. In contrast, many of the human telomere length studies have focused on homogenous cell populations. Most of these studies have been performed by PCR, using telomeric degenerated primers, which allow the determination of telomere length from small amounts of human cells. Here, we have adapted the human PCR procedure to analyze the length of Arabidopsis thaliana telomeres. This PCR approach will facilitate the analysis of telomere length from low amounts of tissue. We have used it to determine that CG and non CG DNA methylation positively regulates Arabidopsis telomere length. PMID:24986269

  5. Assessing Telomere Length Using Surface Enhanced Raman Scattering

    NASA Astrophysics Data System (ADS)

    Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Cui, Yiping

    2014-11-01

    Telomere length can provide valuable insight into telomeres and telomerase related diseases, including cancer. Here, we present a brand-new optical telomere length measurement protocol using surface enhanced Raman scattering (SERS). In this protocol, two single strand DNA are used as SERS probes. They are labeled with two different Raman molecules and can specifically hybridize with telomeres and centromere, respectively. First, genome DNA is extracted from cells. Then the telomere and centromere SERS probes are added into the genome DNA. After hybridization with genome DNA, excess SERS probes are removed by magnetic capturing nanoparticles. Finally, the genome DNA with SERS probes attached is dropped onto a SERS substrate and subjected to SERS measurement. Longer telomeres result in more attached telomere probes, thus a stronger SERS signal. Consequently, SERS signal can be used as an indicator of telomere length. Centromere is used as the inner control. By calibrating the SERS intensity of telomere probe with that of the centromere probe, SERS based telomere measurement is realized. This protocol does not require polymerase chain reaction (PCR) or electrophoresis procedures, which greatly simplifies the detection process. We anticipate that this easy-operation and cost-effective protocol is a fine alternative for the assessment of telomere length.

  6. The role of telomere dynamics in aging and cancer

    NASA Astrophysics Data System (ADS)

    Blagoev, Krastan; Goodwin, Edwin

    2006-03-01

    Telomere length changes are far more dynamic than previously thought. In addition to a gradual loss of ˜100 base pairs per telomere in each cell division, losses as well as gains may occur within a single cell cycle. We are investigating how telomere exchange, extension, and deletion affect the proliferative potential of telomerase-negative somatic cells. Experimental techniques are being devised to detect dynamic telomere processes and quantify both the frequency and length changes of each. In parallel, a ``dynamic telomere model'' is being used that incorporates telomere dynamics to study how the telomere size distribution evolves with time. This is an essential step towards understanding the role that telomere dynamics play in the normal aging of tissues and organisms. The model casts light on relationships not otherwise easily explained by a deterministic ``mitotic clock,'' or to what extent the shortest initial telomere determines the onset of senescence. We also expect to identify biomarkers that will correlate with aging better than average telomere length and to shed light on the transition to unlimited growth found in telomerase-negative tumor cells having the ALT (alternative lengthening of telomeres) phenotype, and to evaluate strategies to suppress the growth of these tumors.

  7. Determination of Arabidopsis thaliana telomere length by PCR.

    PubMed

    Vaquero-Sedas, María I; Vega-Palas, Miguel A

    2014-07-02

    In humans, telomere length studies have acquired great relevance because the length of telomeres has been related to natural processes like disease, aging and cancer. However, very little is known about the influence of telomere length on the biology of wild type plants. The length of plant telomeres has been usually studied by Terminal Restriction Fragment (TRF) analyses. This technique requires high amounts of tissue, including multiple cell types, which might be the reason why very little is known about the influence of telomere length on plant natural processes. In contrast, many of the human telomere length studies have focused on homogenous cell populations. Most of these studies have been performed by PCR, using telomeric degenerated primers, which allow the determination of telomere length from small amounts of human cells. Here, we have adapted the human PCR procedure to analyze the length of Arabidopsis thaliana telomeres. This PCR approach will facilitate the analysis of telomere length from low amounts of tissue. We have used it to determine that CG and non CG DNA methylation positively regulates Arabidopsis telomere length.

  8. Determination of Arabidopsis thaliana telomere length by PCR.

    PubMed

    Vaquero-Sedas, María I; Vega-Palas, Miguel A

    2014-01-01

    In humans, telomere length studies have acquired great relevance because the length of telomeres has been related to natural processes like disease, aging and cancer. However, very little is known about the influence of telomere length on the biology of wild type plants. The length of plant telomeres has been usually studied by Terminal Restriction Fragment (TRF) analyses. This technique requires high amounts of tissue, including multiple cell types, which might be the reason why very little is known about the influence of telomere length on plant natural processes. In contrast, many of the human telomere length studies have focused on homogenous cell populations. Most of these studies have been performed by PCR, using telomeric degenerated primers, which allow the determination of telomere length from small amounts of human cells. Here, we have adapted the human PCR procedure to analyze the length of Arabidopsis thaliana telomeres. This PCR approach will facilitate the analysis of telomere length from low amounts of tissue. We have used it to determine that CG and non CG DNA methylation positively regulates Arabidopsis telomere length. PMID:24986269

  9. Does Reproductive Investment Decrease Telomere Length in Menidia menidia?

    PubMed Central

    Gao, Jin; Munch, Stephan B.

    2015-01-01

    Given finite resources, intense investment in one life history trait is expected to reduce investment in others. Although telomere length appears to be strongly tied to age in many taxa, telomere maintenance requires energy. We therefore hypothesize that telomere maintenance may trade off against other life history characters. We used natural variation in laboratory populations of Atlantic silversides (Menidia menidia) to study the relationship between growth, fecundity, life expectancy, and relative telomere length. In keeping with several other studies on fishes, we found no clear dependence of telomere length on age. However, we did find that more fecund fish tended to have both reduced life expectancy and shorter telomeres. This result is consistent with the hypothesis that there is a trade-off between telomere maintenance and reproductive output. PMID:25938489

  10. TERRA promotes telomerase-mediated telomere elongation in Schizosaccharomyces pombe.

    PubMed

    Moravec, Martin; Wischnewski, Harry; Bah, Amadou; Hu, Yan; Liu, Na; Lafranchi, Lorenzo; King, Megan C; Azzalin, Claus M

    2016-07-01

    Telomerase-mediated telomere elongation provides cell populations with the ability to proliferate indefinitely. Telomerase is capable of recognizing and extending the shortest telomeres in cells; nevertheless, how this mechanism is executed remains unclear. Here, we show that, in the fission yeast Schizosaccharomyces pombe, shortened telomeres are highly transcribed into the evolutionarily conserved long noncoding RNA TERRA A fraction of TERRA produced upon telomere shortening is polyadenylated and largely devoid of telomeric repeats, and furthermore, telomerase physically interacts with this polyadenylated TERRA in vivo We also show that experimentally enhanced transcription of a manipulated telomere promotes its association with telomerase and concomitant elongation. Our data represent the first direct evidence that TERRA stimulates telomerase recruitment and activity at chromosome ends in an organism with human-like telomeres.

  11. Telomere Length: A Review of Methods for Measurement

    PubMed Central

    Montpetit, Alison J.; Alhareeri, Areej A.; Montpetit, Marty; Starkweather, Angela R.; Elmore, Lynne W.; Filler, Kristin; Mohanraj, Lathika; Burton, Candace W.; Menzies, Victoria S.; Lyon, Debra E.; Collins, Judith B.; Teefey, Joseph M.; Jackson-Cook, Colleen K.

    2014-01-01

    Background The exciting discovery that telomere shortening is associated with many health conditions, and that telomere lengths can be altered in response to social and environmental exposures, has underscored the need for methods to accurately and consistently quantify telomere length. Objectives The purpose of this paper is to provide a comprehensive summary that compares and contrasts the current technologies used to assess telomere length. Discussion Multiple methods have been developed for the study of telomeres. These techniques include quantification of telomere length by terminal restriction fragmentation—which was one of the earliest tools used for length assessment—making it the gold standard in telomere biology. Quantitative-PCR provides the advantage of being able to use smaller amounts of DNA, thereby making it amenable to epidemiology studies involving large numbers of people. An alternative method uses fluorescent probes to quantify not only mean telomere lengths, but also chromosome-specific telomere lengths; however, the downside of this approach is that it can only be used on mitotically active cells. Additional methods that permit assessment of the length of a subset of chromosome-specific telomeres, or the subset of telomeres that demonstrate shortening, are also reviewed. Conclusion Given the increased utility for telomere assessments as a biomarker in physiological, psychological and biobehavioral research, it is important that investigators become familiar with the methodological nuances of the various procedures used for measuring telomere length. This will ensure that they are empowered to select an optimal assessment approach to meet the needs of their study designs. Gaining a better understanding of the benefits and drawbacks of various measurement techniques is important not only in individual studies, but also to further establish the science of telomere associations with biobehavioral phenomena. PMID:24977726

  12. Multifunctional role of ATM/Tel1 kinase in genome stability: from the DNA damage response to telomere maintenance.

    PubMed

    Di Domenico, Enea Gino; Romano, Elena; Del Porto, Paola; Ascenzioni, Fiorentina

    2014-01-01

    The mammalian protein kinase ataxia telangiectasia mutated (ATM) is a key regulator of the DNA double-strand-break response and belongs to the evolutionary conserved phosphatidylinositol-3-kinase-related protein kinases. ATM deficiency causes ataxia telangiectasia (AT), a genetic disorder that is characterized by premature aging, cerebellar neuropathy, immunodeficiency, and predisposition to cancer. AT cells show defects in the DNA damage-response pathway, cell-cycle control, and telomere maintenance and length regulation. Likewise, in Saccharomyces cerevisiae, haploid strains defective in the TEL1 gene, the ATM ortholog, show chromosomal aberrations and short telomeres. In this review, we outline the complex role of ATM/Tel1 in maintaining genomic stability through its control of numerous aspects of cellular survival. In particular, we describe how ATM/Tel1 participates in the signal transduction pathways elicited by DNA damage and in telomere homeostasis and its importance as a barrier to cancer development.

  13. Chromosomal localization of 18S rDNA and telomere sequence in the aye-aye, Daubentonia madagascariensis.

    PubMed

    Rakotoarisoa, G; Hirai, Y; Go, Y; Kawamoto, Y; Shima, T; Koyama, N; Randrianjafy, A; Mora, R; Hirai, H

    2000-10-01

    Chromosomal localization of 18S rDNA and telomere sequence was attempted on the chromosomes of the aye-aye (2n = 30) using fluorescence in situ hybridization (FISH) and primed in situ labeling (PRINS), respectively. The rDNA was localized at the tip or whole of the short arm of acrocentric chromosomes 13 and 14 in all spreads observed. However, post-FISH silver-nitrate (Ag) staining showed that transcriptional activity of the rRNA genes was variable, particularly in chromosome 14, which was most frequently negative in one homologue carrying the smaller copy number of rDNA. This observation supports, at the molecular cytogenetic level, previous data concerning the relationship between the copy number of rDNA and its trancriptional activity. On the other hand, telomere sequence was localized only at the telomeric region of all chromosomes, the so-called telomere-only pattern, a characteristic similar to that of the greater bushbaby. These data may provide information on the chromosomal evolution of the lemur, because locations of rDNA and telomere sequences frequently offer important clues in reconstruction of karyotype differentiation. PMID:11245223

  14. Elevated levels of TRF2 induce telomeric ultrafine anaphase bridges and rapid telomere deletions

    PubMed Central

    Nera, Bernadette; Huang, Hui-Shun; Lai, Thao; Xu, Lifeng

    2015-01-01

    The shelterin protein TRF2 is essential for chromosome-end protection. Depletion of TRF2 causes chromosome end-to-end fusions, initiating genomic instability that can be cancer promoting. Paradoxically, significant increased levels of TRF2 are observed in a subset of human cancers. Experimental overexpression of TRF2 has also been shown to induce telomere shortening, through an unknown mechanism. Here we report that TRF2 overexpression results in replication stalling in duplex telomeric repeat tracts and the subsequent formation of telomeric ultrafine anaphase bridges (UFBs), ultimately leading to stochastic loss of telomeric sequences. These TRF2 overexpression-induced telomere deletions generate chromosome fusions resembling those detected in human cancers and in mammalian cells containing critically shortened telomeres. Therefore, our findings have uncovered a second pathway by which altered TRF2 protein levels can induce end-to-end fusions. The observations also provide mechanistic insight into the molecular basis of genomic instability in tumour cells containing significantly increased TRF2 levels. PMID:26640040

  15. The relationship between DNA methylation and telomere length in dyskeratosis congenita.

    PubMed

    Gadalla, Shahinaz M; Katki, Hormuzd A; Shebl, Fatma M; Giri, Neelam; Alter, Blanche P; Savage, Sharon A

    2012-02-01

    The regulation of telomere length (TL) is a complex process, requiring the telomerase enzyme complex and numerous regulatory proteins. Epigenetic regulation may also be important in telomere maintenance. Specifically, methylation at subtelomeres is associated with changes in TL in vitro and in mouse models. Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome characterized by exceedingly short telomeres and mutations in telomere biology genes. To understand the interaction between methylation and TL in humans, we measured LINE-1, pericentromeric (NBL2), and subtelomeric (D4Z4) methylation in peripheral blood DNA derived from 40 patients with DC and 51 mutation-negative relatives. Pearson's correlation coefficient and linear regression models were used to evaluate the relationship between age-standardized lymphocyte TL measured by flow FISH and % DNA methylation. No differences in % subtelomeric, LINE-1, or pericentromeric methylation between patients with DC and relatives were noted except for an increase in % subtelomeric methylation in DC patients with a telomerase-complex mutation (TERC, TERT, DKC1, or TCAB1) (63.0% in DC vs. 61.8% in relatives, P = 0.03). Positive correlations between TL and DNA methylation at LINE-1 (r = 0.39, P = 0.01) and subtelomeric (r = 0.32, P = 0.05) sites were present in patients with DC. The positive correlation between TL and % LINE-1 methylation was restricted to TINF2 mutations. In contrast, statistically nonsignificant inverse correlations between TL and % LINE-1 (r = -0.17), subtelomeric (r = -0.20) were present in unaffected relatives. This study suggests an interaction between TL and both subtelomeric and LINE-1 methylation, which may be altered based on mutation status of telomere biology genes. PMID:21981348

  16. Telomere Length, Proviral Load and Neurologic Impairment in HTLV-1 and HTLV-2-Infected Subjects.

    PubMed

    Usadi, Benjamin; Bruhn, Roberta; Lin, Jue; Lee, Tzong-Hae; Blackburn, Elizabeth; Murphy, Edward L

    2016-01-01

    Short or damaged telomeres have been implicated in degenerative conditions. We hypothesized that analysis of telomere length (TL) in human T-cell lymphotropic virus (HTLV) infection and HTLV-associated neuropathy might provide clues to the etiology of HTLV-associated disease and viral dynamics. A subset of 45 human T-cell lymphotropic virus type 1 (HTLV-1), 45 human T-cell lymphotropic virus type 2 (HTLV-2), and 45 seronegative subjects was selected from the larger HTLV Outcomes Study (HOST) cohort, matched on age, sex and race/ethnicity. Telomere-to-single-copy gene (T/S) ratio (a measure of TL) and HTLV-1 and HTLV-2 proviral loads were measured in peripheral blood mononuclear cells (PBMCs) using quantitative PCR (qPCR). Vibration sensation measured by tuning fork during neurologic examinations performed as part of the HOST study allowed for an assessment of peripheral neuropathy. TL was compared between groups using t-tests, linear and logistic regression. Mean T/S ratio was 1.02 ± 0.16 in HTLV-1, 1.03 ± 0.17 in HTLV-2 and 0.99 ± 0.18 in HTLV seronegative subjects (p = 0.322). TL was not associated with HTLV-1 or -2 proviral load. Shorter TL was significantly associated with impaired vibration sense in the HTLV-2 positive group only. Overall, we found no evidence that telomere length was affected by chronic HTLV-1 and HTLV-2 infection. That TL was only associated with peripheral neuropathy in the HTLV-2-positive group is intriguing, but should be interpreted cautiously. Studies with larger sample size and telomere length measurement in lymphocyte subsets may clarify the relationship between TL and HTLV-infection. PMID:27529270

  17. Telomere Length, Proviral Load and Neurologic Impairment in HTLV-1 and HTLV-2-Infected Subjects

    PubMed Central

    Usadi, Benjamin; Bruhn, Roberta; Lin, Jue; Lee, Tzong-Hae; Blackburn, Elizabeth; Murphy, Edward L.

    2016-01-01

    Short or damaged telomeres have been implicated in degenerative conditions. We hypothesized that analysis of telomere length (TL) in human T-cell lymphotropic virus (HTLV) infection and HTLV-associated neuropathy might provide clues to the etiology of HTLV-associated disease and viral dynamics. A subset of 45 human T-cell lymphotropic virus type 1 (HTLV-1), 45 human T-cell lymphotropic virus type 2 (HTLV-2), and 45 seronegative subjects was selected from the larger HTLV Outcomes Study (HOST) cohort, matched on age, sex and race/ethnicity. Telomere-to-single-copy gene (T/S) ratio (a measure of TL) and HTLV-1 and HTLV-2 proviral loads were measured in peripheral blood mononuclear cells (PBMCs) using quantitative PCR (qPCR). Vibration sensation measured by tuning fork during neurologic examinations performed as part of the HOST study allowed for an assessment of peripheral neuropathy. TL was compared between groups using t-tests, linear and logistic regression. Mean T/S ratio was 1.02 ± 0.16 in HTLV-1, 1.03 ± 0.17 in HTLV-2 and 0.99 ± 0.18 in HTLV seronegative subjects (p = 0.322). TL was not associated with HTLV-1 or -2 proviral load. Shorter TL was significantly associated with impaired vibration sense in the HTLV-2 positive group only. Overall, we found no evidence that telomere length was affected by chronic HTLV-1 and HTLV-2 infection. That TL was only associated with peripheral neuropathy in the HTLV-2-positive group is intriguing, but should be interpreted cautiously. Studies with larger sample size and telomere length measurement in lymphocyte subsets may clarify the relationship between TL and HTLV-infection. PMID:27529270

  18. Age-related telomere uncapping is associated with cellular senescence and inflammation independent of telomere shortening in human arteries.

    PubMed

    Morgan, Richard G; Ives, Stephen J; Lesniewski, Lisa A; Cawthon, Richard M; Andtbacka, Robert H I; Noyes, R Dirk; Richardson, Russell S; Donato, Anthony J

    2013-07-15

    Arterial telomere dysfunction may contribute to chronic arterial inflammation by inducing cellular senescence and subsequent senescence-associated inflammation. Although telomere shortening has been associated with arterial aging in humans, age-related telomere uncapping has not been described in non-cultured human tissues and may have substantial prognostic value. In skeletal muscle feed arteries from 104 younger, middle-aged, and older adults, we assessed the potential role of age-related telomere uncapping in arterial inflammation. Telomere uncapping, measured by p-histone γ-H2A.X (ser139) localized to telomeres (chromatin immunoprecipitation; ChIP), and telomeric repeat binding factor 2 bound to telomeres (ChIP) was greater in arteries from older adults compared with those from younger adults. There was greater tumor suppressor protein p53 (P53)/cyclin-dependent kinase inhibitor 1A (P21)-induced senescence, measured by P53 bound to P21 gene promoter (ChIP), and greater expression of P21, interleukin 8, and monocyte chemotactic protein 1 mRNA (RT-PCR) in arteries from older adults compared with younger adults. Telomere uncapping was a highly influential covariate for the age-group difference in P53/P21-induced senescence. Despite progressive age-related telomere shortening in human arteries, mean telomere length was not associated with telomere uncapping or P53/P21-induced senescence. Collectively, these findings demonstrate that advancing age is associated with greater telomere uncapping in arteries, which is linked to P53/P21-induced senescence independent of telomere shortening.

  19. Detection of cryptic chromosomal abnormalities in unexplained mental retardation: a general strategy using hypervariable subtelomeric DNA polymorphisms.

    PubMed Central

    Wilkie, A O

    1993-01-01

    Given the availability of DNA from both parents, unusual segregation of hypervariable DNA polymorphisms (HVPs) in the offspring may be attributable to deletion, unbalanced chromosomal translocation, or uniparental disomy. The telomeric regions of chromosomes are rich in both genes and hypervariable minisatellite sequences and may also be particularly prone to cryptic breakage events. Here I describe and analyze a general approach to the detection of subtelomeric abnormalities and uniparental disomy in patients with unexplained mental retardation. With 29 available polymorphic systems, approximately 50%-70% of these abnormalities could currently be detected. Development of subtelomeric HVPs physically localized with respect to their telomeres should provide a valuable resource in routine diagnostics. PMID:8352277

  20. ARSENIC EFFECTS ON TELOMERE AND TELOMERASE ACTIVITY

    EPA Science Inventory

    Arsenic effects on telomere and telomerase activity. T-C. Zhang, M. T. Schmitt, J. Mo, J. L. Mumford, National Research Council and U.S Environmental Protection Agency, NHEERL, Research Triangle Park, NC 27711
    Arsenic is a known carcinogen and also an anticancer agent for acut...

  1. Responses to telomere erosion in plants.

    PubMed

    Amiard, Simon; Da Ines, Olivier; Gallego, Maria Eugenia; White, Charles I

    2014-01-01

    In striking contrast to animals, plants are able to develop and reproduce in the presence of significant levels of genome damage. This is seen clearly in both the viability of plants carrying knockouts for key recombination and DNA repair genes, which are lethal in vertebrates, and in the impact of telomere dysfunction. Telomerase knockout mice show accelerated ageing and severe developmental phenotypes, with effects on both highly proliferative and on more quiescent tissues, while cell death in Arabidopsis tert mutants is mostly restricted to actively dividing meristematic cells. Through phenotypic and whole-transcriptome RNAseq studies, we present here an analysis of the response of Arabidopsis plants to the continued presence of telomere damage. Comparison of second-generation and seventh-generation tert mutant plants has permitted separation of the effects of the absence of the telomerase enzyme and the ensuing chromosome damage. In addition to identifying a large number of genes affected by telomere damage, many of which are of unknown function, the striking conclusion of this study is the clear difference observed at both cellular and transcriptome levels between the ways in which mammals and plants respond to chronic telomeric damage.

  2. Chromosome abnormalities in glioma

    SciTech Connect

    Li, Y.S.; Ramsay, D.A.; Fan, Y.S.

    1994-09-01

    Cytogenetic studies were performed in 25 patients with gliomas. An interesting finding was a seemingly identical abnormality, an extra band on the tip of the short arm of chromosome 1, add(1)(p36), in two cases. The abnormality was present in all cells from a patient with a glioblastoma and in 27% of the tumor cells from a patient with a recurrent irradiated anaplastic astrocytoma; in the latter case, 7 unrelated abnormal clones were identified except 4 of those clones shared a common change, -Y. Three similar cases have been described previously. In a patient with pleomorphic astrocytoma, the band 1q42 in both homologues of chromosome 1 was involved in two different rearrangements. A review of the literature revealed that deletion of the long arm of chromosome 1 including 1q42 often occurs in glioma. This may indicate a possible tumor suppressor gene in this region. Cytogenetic follow-up studies were carried out in two patients and emergence of unrelated clones were noted in both. A total of 124 clonal breakpoints were identified in the 25 patients. The breakpoints which occurred three times or more were: 1p36, 1p22, 1q21, 1q25, 3q21, 7q32, 8q22, 9q22, 16q22, and 22q13.

  3. Telomere maintenance and the etiology of adult glioma.

    PubMed

    Walsh, Kyle M; Wiencke, John K; Lachance, Daniel H; Wiemels, Joseph L; Molinaro, Annette M; Eckel-Passow, Jeanette E; Jenkins, Robert B; Wrensch, Margaret R

    2015-11-01

    A growing body of epidemiologic and tumor genomic research has identified an important role for telomere maintenance in glioma susceptibility, initiation, and prognosis. Telomere length has long been investigated in relation to cancer, but whether longer or shorter telomere length might be associated with glioma risk has remained elusive. Recent data address this question and are reviewed here. Common inherited variants near the telomerase-component genes TERC and TERT are associated both with longer telomere length and increased risk of glioma. Exome sequencing of glioma patients from families with multiple affected members has identified rare inherited mutations in POT1 (protection of telomeres protein 1) as high-penetrance glioma risk factors. These heritable POT1 mutations are also associated with increased telomere length in leukocytes. Tumor sequencing studies further indicate that acquired somatic mutations of TERT and ATRX are among the most frequent alterations found in adult gliomas. These mutations facilitate telomere lengthening, thus bypassing a critical mechanism of apoptosis. Although future research is needed, mounting evidence suggests that glioma is, at least in part, a disease of telomere dysregulation. Specifically, several inherited and acquired variants underlying gliomagenesis affect telomere pathways and are also associated with increased telomere length.

  4. Functional characterization of the TERRA transcriptome at damaged telomeres.

    PubMed

    Porro, Antonio; Feuerhahn, Sascha; Delafontaine, Julien; Riethman, Harold; Rougemont, Jacques; Lingner, Joachim

    2014-10-31

    Telomere deprotection occurs during tumorigenesis and aging upon telomere shortening or loss of the telomeric shelterin component TRF2. Deprotected telomeres undergo changes in chromatin structure and elicit a DNA damage response (DDR) that leads to cellular senescence. The telomeric long noncoding RNA TERRA has been implicated in modulating the structure and processing of deprotected telomeres. Here, we characterize the human TERRA transcriptome at normal and TRF2-depleted telomeres and demonstrate that TERRA upregulation is occurring upon depletion of TRF2 at all transcribed telomeres. TRF2 represses TERRA transcription through its homodimerization domain, which was previously shown to induce chromatin compaction and to prevent the early steps of DDR activation. We show that TERRA associates with SUV39H1 H3K9 histone methyltransferase, which promotes accumulation of H3K9me3 at damaged telomeres and end-to-end fusions. Altogether our data elucidate the TERRA landscape and defines critical roles for this RNA in the telomeric DNA damage response.

  5. Telomeres, Age and Reproduction in a Long-Lived Reptile

    PubMed Central

    Plot, Virginie; Criscuolo, François; Zahn, Sandrine; Georges, Jean-Yves

    2012-01-01

    A major interest has recently emerged in understanding how telomere shortening, mechanism triggering cell senescence, is linked to organism ageing and life history traits in wild species. However, the links between telomere length and key history traits such as reproductive performances have received little attention and remain unclear to date. The leatherback turtle Dermochelys coriacea is a long-lived species showing rapid growth at early stages of life, one of the highest reproductive outputs observed in vertebrates and a dichotomised reproductive pattern related to migrations lasting 2 or 3 years, supposedly associated with different environmental conditions. Here we tested the prediction of blood telomere shortening with age in this species and investigated the relationship between blood telomere length and reproductive performances in leatherback turtles nesting in French Guiana. We found that blood telomere length did not differ between hatchlings and adults. The absence of blood telomere shortening with age may be related to an early high telomerase activity. This telomere-restoring enzyme was formerly suggested to be involved in preventing early telomere attrition in early fast-growing and long-lived species, including squamate reptiles. We found that within one nesting cycle, adult females having performed shorter migrations prior to the considered nesting season had shorter blood telomeres and lower reproductive output. We propose that shorter blood telomeres may result from higher oxidative stress in individuals breeding more frequently (i.e., higher costs of reproduction) and/or restoring more quickly their body reserves in cooler feeding areas during preceding migration (i.e., higher foraging costs). This first study on telomeres in the giant leatherback turtle suggests that blood telomere length predicts not only survival chances, but also reproductive performances. Telomeres may therefore be a promising new tool to evaluate individual reproductive

  6. Telomeres, age and reproduction in a long-lived reptile.

    PubMed

    Plot, Virginie; Criscuolo, François; Zahn, Sandrine; Georges, Jean-Yves

    2012-01-01

    A major interest has recently emerged in understanding how telomere shortening, mechanism triggering cell senescence, is linked to organism ageing and life history traits in wild species. However, the links between telomere length and key history traits such as reproductive performances have received little attention and remain unclear to date. The leatherback turtle Dermochelys coriacea is a long-lived species showing rapid growth at early stages of life, one of the highest reproductive outputs observed in vertebrates and a dichotomised reproductive pattern related to migrations lasting 2 or 3 years, supposedly associated with different environmental conditions. Here we tested the prediction of blood telomere shortening with age in this species and investigated the relationship between blood telomere length and reproductive performances in leatherback turtles nesting in French Guiana. We found that blood telomere length did not differ between hatchlings and adults. The absence of blood telomere shortening with age may be related to an early high telomerase activity. This telomere-restoring enzyme was formerly suggested to be involved in preventing early telomere attrition in early fast-growing and long-lived species, including squamate reptiles. We found that within one nesting cycle, adult females having performed shorter migrations prior to the considered nesting season had shorter blood telomeres and lower reproductive output. We propose that shorter blood telomeres may result from higher oxidative stress in individuals breeding more frequently (i.e., higher costs of reproduction) and/or restoring more quickly their body reserves in cooler feeding areas during preceding migration (i.e., higher foraging costs). This first study on telomeres in the giant leatherback turtle suggests that blood telomere length predicts not only survival chances, but also reproductive performances. Telomeres may therefore be a promising new tool to evaluate individual reproductive

  7. ATM is required for telomere maintenance and chromosome stability during Drosophila development.

    PubMed

    Silva, Elizabeth; Tiong, Stanley; Pedersen, Michael; Homola, Ellen; Royou, Anne; Fasulo, Barbara; Siriaco, Giorgia; Campbell, Shelagh D

    2004-08-10

    ATM is a large, multifunctional protein kinase that regulates responses required for surviving DNA damage: including DNA repair, apoptosis, and cell cycle checkpoints. Here, we show that Drosophila ATM function is essential for normal adult development. Extensive, inappropriate apoptosis occurs in proliferating atm mutant tissues, and in clonally derived atm mutant embryos, frequent mitotic defects were seen. At a cellular level, spontaneous telomere fusions and other chromosomal abnormalities are common in atm larval neuroblasts, suggesting a conserved and essential role for dATM in the maintenance of normal telomeres and chromosome stability. Evidence from other systems supports the idea that DNA double-strand break (DSB) repair functions of ATM kinases promote telomere maintenance by inhibition of illegitimate recombination or fusion events between the legitimate ends of chromosomes and spontaneous DSBs. Drosophila will be an excellent model system for investigating how these ATM-dependent chromosome structural maintenance functions are deployed during development. Because neurons appear to be particularly sensitive to loss of ATM in both flies and humans, this system should be particularly useful for identifying cell-specific factors that influence sensitivity to loss of dATM and are relevant for understanding the human disease, ataxia-telangiectasia.

  8. ERCC1 and telomere status in breast tumours treated with neoadjuvant chemotherapy and their association with patient prognosis

    PubMed Central

    Gay‐Bellile, Mathilde; Romero, Pierre; Cayre, Anne; Véronèse, Lauren; Privat, Maud; Singh, Shalini; Combes, Patricia; Kwiatkowski, Fabrice; Abrial, Catherine; Bignon, Yves‐Jean; Vago, Philippe; Penault‐Llorca, Frédérique

    2016-01-01

    Abstract Dysfunctional telomeres and DNA damage repair (DDR) play important roles in cancer progression. Studies have reported correlations between these factors and tumour aggressiveness and clinical outcome in breast cancer. We studied the characteristics of telomeres and expression of ERCC1, a protein involved in a number of DNA repair pathways and in telomere homeostasis, to assess their prognostic value, alone or in combination, in 90 residual breast tumours after treatment with neoadjuvant chemotherapy (NCT). ERCC1 status was investigated at different molecular levels (protein and gene expression and gene copy‐number variations) by immunohistochemistry, qRT‐PCR and quantitative multiplex fluorescent‐PCR (QMF‐PCR). A comprehensive analysis of telomere characteristics was performed using qPCR for telomere length and qRT‐PCR for telomerase (hTERT), tankyrase 1 (TNKS) and shelterin complex (TRF1, TRF2, POT1, TPP1, RAP1 and TIN2) gene expression. Short telomeres, high hTERT and TNKS expression and low ERCC1 protein expression were independently associated with worse survival outcome. Interestingly, ERCC1 gains and losses correlated with worse disease‐free (p = 0.026) and overall (p = 0.043) survival as compared to survival of patients with normal gene copy‐numbers. Unsupervised hierarchical clustering of all ERCC1 and telomere parameters identified four subgroups with distinct prognosis. In particular, a cluster combining low ERCC1, ERCC1 gene alterations, dysfunctional telomeres and high hTERT and a cluster with high TNKS and shelterin expression correlated with poor disease‐free (HR= 5.41, p= 0.0044) and overall survival (HR= 6.01, p= 0.0023) irrespective of tumour stage and grade. This comprehensive study demonstrates that telomere dysfunction and DDR can contribute synergistically to tumour progression and chemoresistance. These parameters are predictors of clinical outcome in breast cancer patients treated with NCT and could be useful

  9. Accelerated Telomere Shortening in Acromegaly; IGF-I Induces Telomere Shortening and Cellular Senescence

    PubMed Central

    Matsumoto, Ryusaku; Fukuoka, Hidenori; Iguchi, Genzo; Odake, Yukiko; Yoshida, Kenichi; Bando, Hironori; Suda, Kentaro; Nishizawa, Hitoshi; Takahashi, Michiko; Yamada, Shozo; Ogawa, Wataru; Takahashi, Yutaka

    2015-01-01

    Objective Patients with acromegaly exhibit reduced life expectancy and increased prevalence of age-related diseases, such as diabetes, hypertension, and cardiovascular disease. However, the underlying mechanism has not been fully elucidated. Telomere shortening is reportedly associated with reduced life expectancy and increased prevalence of these age-related diseases. Methods We measured telomere length in patients with acromegaly using quantitative PCR method. The effect of GH and IGF-I on telomere length and cellular senescence was examined in human skin fibroblasts. Results Patients with acromegaly exhibited shorter telomere length than age-, sex-, smoking-, and diabetes-matched control patients with non-functioning pituitary adenoma (0.62 ± 0.23 vs. 0.75 ± 0.35, respectively, P = 0.047). In addition, telomere length in acromegaly was negatively correlated with the disease duration (R2 = 0.210, P = 0.003). In vitro analysis revealed that not GH but IGF-I induced telomere shortening in human skin fibroblasts. Furthermore, IGF-I-treated cells showed increased senescence-associated β-galactosidase activity and expression of p53 and p21 protein. IGF-I-treated cells reached the Hayflick limit earlier than GH- or vehicle-treated cells, indicating that IGF-I induces cellular senescence. Conclusion Shortened telomeres in acromegaly and cellular senescence induced by IGF-I can explain, in part, the underlying mechanisms by which acromegaly exhibits an increased morbidity and mortality in association with the excess secretion of IGF-I. PMID:26448623

  10. A POT1 mutation implicates defective telomere end fill-in and telomere truncations in Coats plus.

    PubMed

    Takai, Hiroyuki; Jenkinson, Emma; Kabir, Shaheen; Babul-Hirji, Riyana; Najm-Tehrani, Nasrin; Chitayat, David A; Crow, Yanick J; de Lange, Titia

    2016-04-01

    Coats plus (CP) can be caused by mutations in the CTC1 component of CST, which promotes polymerase α (polα)/primase-dependent fill-in throughout the genome and at telomeres. The cellular pathology relating to CP has not been established. We identified a homozygous POT1 S322L substitution (POT1(CP)) in two siblings with CP. POT1(CP)induced a proliferative arrest that could be bypassed by telomerase. POT1(CP)was expressed at normal levels, bound TPP1 and telomeres, and blocked ATR signaling. POT1(CP)was defective in regulating telomerase, leading to telomere elongation rather than the telomere shortening observed in other telomeropathies. POT1(CP)was also defective in the maintenance of the telomeric C strand, causing extended 3' overhangs and stochastic telomere truncations that could be healed by telomerase. Consistent with shortening of the telomeric C strand, metaphase chromosomes showed loss of telomeres synthesized by leading strand DNA synthesis. We propose that CP is caused by a defect in POT1/CST-dependent telomere fill-in. We further propose that deficiency in the fill-in step generates truncated telomeres that halt proliferation in cells lacking telomerase, whereas, in tissues expressing telomerase (e.g., bone marrow), the truncations are healed. The proposed etiology can explain why CP presents with features distinct from those associated with telomerase defects (e.g., dyskeratosis congenita).

  11. CTC1 deletion results in defective telomere replication, leading to catastrophic telomere loss and stem cell exhaustion

    PubMed Central

    Gu, Peili; Min, Jin-Na; Wang, Yang; Huang, Chenhui; Peng, Tao; Chai, Weihang; Chang, Sandy

    2012-01-01

    The proper maintenance of telomeres is essential for genome stability. Mammalian telomere maintenance is governed by a number of telomere binding proteins, including the newly identified CTC1–STN1–TEN1 (CST) complex. However, the in vivo functions of mammalian CST remain unclear. To address this question, we conditionally deleted CTC1 from mice. We report here that CTC1 null mice experience rapid onset of global cellular proliferative defects and die prematurely from complete bone marrow failure due to the activation of an ATR-dependent G2/M checkpoint. Acute deletion of CTC1 does not result in telomere deprotection, suggesting that mammalian CST is not involved in capping telomeres. Rather, CTC1 facilitates telomere replication by promoting efficient restart of stalled replication forks. CTC1 deletion results in increased loss of leading C-strand telomeres, catastrophic telomere loss and accumulation of excessive ss telomere DNA. Our data demonstrate an essential role for CTC1 in promoting efficient replication and length maintenance of telomeres. PMID:22531781

  12. A POT1 mutation implicates defective telomere end fill-in and telomere truncations in Coats plus

    PubMed Central

    Takai, Hiroyuki; Jenkinson, Emma; Kabir, Shaheen; Babul-Hirji, Riyana; Najm-Tehrani, Nasrin; Chitayat, David A.; Crow, Yanick J.; de Lange, Titia

    2016-01-01

    Coats plus (CP) can be caused by mutations in the CTC1 component of CST, which promotes polymerase α (polα)/primase-dependent fill-in throughout the genome and at telomeres. The cellular pathology relating to CP has not been established. We identified a homozygous POT1 S322L substitution (POT1CP) in two siblings with CP. POT1CP induced a proliferative arrest that could be bypassed by telomerase. POT1CP was expressed at normal levels, bound TPP1 and telomeres, and blocked ATR signaling. POT1CP was defective in regulating telomerase, leading to telomere elongation rather than the telomere shortening observed in other telomeropathies. POT1CP was also defective in the maintenance of the telomeric C strand, causing extended 3′ overhangs and stochastic telomere truncations that could be healed by telomerase. Consistent with shortening of the telomeric C strand, metaphase chromosomes showed loss of telomeres synthesized by leading strand DNA synthesis. We propose that CP is caused by a defect in POT1/CST-dependent telomere fill-in. We further propose that deficiency in the fill-in step generates truncated telomeres that halt proliferation in cells lacking telomerase, whereas, in tissues expressing telomerase (e.g., bone marrow), the truncations are healed. The proposed etiology can explain why CP presents with features distinct from those associated with telomerase defects (e.g., dyskeratosis congenita). PMID:27013236

  13. The principal role of Ku in telomere length maintenance is promotion of Est1 association with telomeres.

    PubMed

    Williams, Jaime M; Ouenzar, Faissal; Lemon, Laramie D; Chartrand, Pascal; Bertuch, Alison A

    2014-08-01

    Telomere length is tightly regulated in cells that express telomerase. The Saccharomyces cerevisiae Ku heterodimer, a DNA end-binding complex, positively regulates telomere length in a telomerase-dependent manner. Ku associates with the telomerase RNA subunit TLC1, and this association is required for TLC1 nuclear retention. Ku-TLC1 interaction also impacts the cell-cycle-regulated association of the telomerase catalytic subunit Est2 to telomeres. The promotion of TLC1 nuclear localization and Est2 recruitment have been proposed to be the principal role of Ku in telomere length maintenance, but neither model has been directly tested. Here we study the impact of forced recruitment of Est2 to telomeres on telomere length in the absence of Ku's ability to bind TLC1 or DNA ends. We show that tethering Est2 to telomeres does not promote efficient telomere elongation in the absence of Ku-TLC1 interaction or DNA end binding. Moreover, restoration of TLC1 nuclear localization, even when combined with Est2 recruitment, does not bypass the role of Ku. In contrast, forced recruitment of Est1, which has roles in telomerase recruitment and activation, to telomeres promotes efficient and progressive telomere elongation in the absence of Ku-TLC1 interaction, Ku DNA end binding, or Ku altogether. Ku associates with Est1 and Est2 in a TLC1-dependent manner and enhances Est1 recruitment to telomeres independently of Est2. Together, our results unexpectedly demonstrate that the principal role of Ku in telomere length maintenance is to promote the association of Est1 with telomeres, which may in turn allow for efficient recruitment and activation of the telomerase holoenzyme.

  14. Puma and p21 represent cooperating checkpoints limiting self-renewal and chromosomal instability of somatic stem cells in response to telomere dysfunction.

    PubMed

    Sperka, Tobias; Song, Zhangfa; Morita, Yohei; Nalapareddy, Kodandaramireddy; Guachalla, Luis Miguel; Lechel, André; Begus-Nahrmann, Yvonne; Burkhalter, Martin D; Mach, Monika; Schlaudraff, Falk; Liss, Birgit; Ju, Zhenyu; Speicher, Michael R; Rudolph, K Lenhard

    2011-12-04

    The tumour suppressor p53 activates Puma-dependent apoptosis and p21-dependent cell-cycle arrest in response to DNA damage. Deletion of p21 improved stem-cell function and organ maintenance in progeroid mice with dysfunctional telomeres, but the function of Puma has not been investigated in this context. Here we show that deletion of Puma improves stem- and progenitor-cell function, organ maintenance and lifespan of telomere-dysfunctional mice. Puma deletion impairs the clearance of stem and progenitor cells that have accumulated DNA damage as a consequence of critically short telomeres. However, further accumulation of DNA damage in these rescued progenitor cells leads to increasing activation of p21. RNA interference experiments show that upregulation of p21 limits proliferation and evolution of chromosomal imbalances of Puma-deficient stem and progenitor cells with dysfunctional telomeres. These results provide experimental evidence that p53-dependent apoptosis and cell-cycle arrest act in cooperating checkpoints limiting tissue maintenance and evolution of chromosomal instability at stem- and progenitor-cell levels in response to telomere dysfunction. Selective inhibition of Puma-dependent apoptosis can result in temporary improvements in maintenance of telomere-dysfunctional organs.

  15. Telomere maintenance through recruitment of internal genomic regions

    PubMed Central

    Seo, Beomseok; Kim, Chuna; Hills, Mark; Sung, Sanghyun; Kim, Hyesook; Kim, Eunkyeong; Lim, Daisy S.; Oh, Hyun-Seok; Choi, Rachael Mi Jung; Chun, Jongsik; Shim, Jaegal; Lee, Junho

    2015-01-01

    Cells surviving crisis are often tumorigenic and their telomeres are commonly maintained through the reactivation of telomerase. However, surviving cells occasionally activate a recombination-based mechanism called alternative lengthening of telomeres (ALT). Here we establish stably maintained survivors in telomerase-deleted Caenorhabditis elegans that escape from sterility by activating ALT. ALT survivors trans-duplicate an internal genomic region, which is already cis-duplicated to chromosome ends, across the telomeres of all chromosomes. These ‘Template for ALT' (TALT) regions consist of a block of genomic DNA flanked by telomere-like sequences, and are different between two genetic background. We establish a model that an ancestral duplication of a donor TALT region to a proximal telomere region forms a genomic reservoir ready to be incorporated into telomeres on ALT activation. PMID:26382656

  16. Insights into Cdc13 Dependent Telomere Length Regulation

    SciTech Connect

    M Mason; E Skordalakes

    2011-12-31

    Cdc13 is a single stranded telomere binding protein that specifically localizes to the telomere ends of budding yeasts and is essential for cell viability. It caps the ends of chromosomes thus preventing chromosome end-to-end fusions and exonucleolytic degradation, events that could lead to genomic instability and senescence, the hallmark of aging. Cdc13 is also involved in telomere length regulation by recruiting or preventing access of telomerase to the telomeric overhang. Recruitment of telomerase to the telomeres for G-strand extension is required for continuous cell division, while preventing its access to the telomeres through capping the chromosome ends prevents mitotic events that could lead to cell immortality, the hall mark of carcinogenesis. Cdc13 and its putative homologues human CTC1 and POT1 are therefore key to many biological processes directly associated with life extension and cancer prevention and can be viewed as an ideal target for cancer and age related therapies.

  17. Telomere shortening in neurological disorders: an abundance of unanswered questions.

    PubMed

    Eitan, Erez; Hutchison, Emmette R; Mattson, Mark P

    2014-05-01

    Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer's and Parkinson's patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders. PMID:24698125

  18. Telomere Shortening in Neurological Disorders: An Abundance of Unanswered Questions

    PubMed Central

    Eitan, Erez; Hutchison, Emmette R.; Mattson, Mark P.

    2014-01-01

    Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer’s and Parkinson’s patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders. PMID:24698125

  19. DNA Repair at Telomeres: Keeping the Ends Intact

    PubMed Central

    Webb, Christopher J.; Wu, Yun; Zakian, Virginia A.

    2013-01-01

    The molecular era of telomere biology began with the discovery that telomeres usually consist of G-rich simple repeats and end with 3′ single-stranded tails. Enormous progress has been made in identifying the mechanisms that maintain and replenish telomeric DNA and the proteins that protect them from degradation, fusions, and checkpoint activation. Although telomeres in different organisms (or even in the same organism under different conditions) are maintained by different mechanisms, the disparate processes have the common goals of repairing defects caused by semiconservative replication through G-rich DNA, countering the shortening caused by incomplete replication, and postreplication regeneration of G tails. In addition, standard DNA repair mechanisms must be suppressed or modified at telomeres to prevent their being recognized and processed as DNA double-strand breaks. Here, we discuss the players and processes that maintain and regenerate telomere structure. PMID:23732473

  20. Clinical and cytogenetic findings in seven cases of inverted duplication of 8p with evidence of a telomeric deletion using fluorescence in situ hybridization

    SciTech Connect

    Guo, Wen-Jun; Callif-Daley, F.; Zapata, M.C.; Miller, M.E.

    1995-09-11

    We report on the clinical and cytogenetic findings in 7 cases of inverted duplication of region 8p11.2-p23. The phenotype of inv dup (8p) compiled from this series and the literature (N = 29) consists of severe mental retardation (100%), minor facial alterations (97%), agenesis of the corpus callosum (80%), hypotonia (66%), orthopedic abnormalities (58%), scoliosis/kyphosis (40%), and congenital heart defect (26%). A telomeric deletion of region 8p23.3-pter was confirmed in 3 of our cases studied using fluorescent in situ hybridization with a telomeric probe for 8p. Thus, these karyotypes are inv dup del(8) (qter{r_arrow} p23.1::p23.1{r_arrow}p11.2:). Our findings suggest that most cases of inv dup(8p) probably have a telomeric deletion. 20 refs., 4 figs., 2 tabs.

  1. Association of leukocyte telomere length in peripheral blood leukocytes with endometrial cancer risk in Caucasian Americans.

    PubMed

    Sun, Yuhui; Zhang, Liren; Zhao, Lina; Wu, Xifeng; Gu, Jian

    2015-11-01

    Telomeres are the protective structure at the ends of each chromosome and play an important role in maintaining genomic integrity. Interindividual variation of telomere length in peripheral blood leukocytes has been associated with the risks of developing many human diseases including several cancers. The association between leukocyte telomere length (LTL) and endometrial cancer risk is still inconsistent. Using a case-control study of endometrial cancer patients (n = 139) and control subjects (n = 139) in a Caucasian population, we assessed the association of relative LTL with the risk of endometrial cancer. We calculated odds ratios and 95% confidence intervals using multivariate logistic regression. We also determined the joint effects of LTL with established risk factors of endometrial cancer. The normalized LTL was significantly longer in endometrial cancer cases (median, 0.93; range, 0.19-1.62) than in controls (median, 0.70; range, 0.03-2.14) (P < 0.001). When individuals were dichotomized into long and short groups based on the median LTL value in the controls, individuals with long LTL had a significantly increased risk of endometrial cancer (adjusted OR, 3.84; 95%CI, 2.16-6.85; P < 0.001) compared to those with short LTL. When individuals were categorized into three groups or four groups according to tertile or quartile LTL value in the controls, there was a significant dose-response association between LTL and the risk of endometrial cancer (P < 0.001). Joint effects between LTL and smoking status, body mass index and a history of hypertension or diabetes in elevating endometrial cancer risk were observed. Long telomere length in peripheral blood leukocytes is associated with a significantly increased risk of endometrial cancer.

  2. Maternal and genetic factors determine early life telomere length

    PubMed Central

    Asghar, Muhammad; Bensch, Staffan; Tarka, Maja; Hansson, Bengt; Hasselquist, Dennis

    2015-01-01

    In a broad range of species—including humans—it has been demonstrated that telomere length declines throughout life and that it may be involved in cell and organismal senescence. This potential link to ageing and thus to fitness has triggered recent interest in understanding how variation in telomere length is inherited and maintained. However, previous studies suffer from two main drawbacks that limit the possibility of understanding the relative importance of genetic, parental and environmental influences on telomere length variation. These studies have been based on (i) telomere lengths measured at different time points in different individuals, despite the fact that telomere length changes over life, and (ii) parent–offspring regression techniques, which do not enable differentiation between genetic and parental components of inheritance. To overcome these drawbacks, in our study of a songbird, the great reed warbler, we have analysed telomere length measured early in life in both parents and offspring and applied statistical models (so-called ‘animal models') that are based on long-term pedigree data. Our results showed a significant heritability of telomere length on the maternal but not on the paternal side, and that the mother's age was positively correlated with their offspring's telomere length. Furthermore, the pedigree-based analyses revealed a significant heritability and an equally large maternal effect. Our study demonstrates strong maternal influence on telomere length and future studies now need to elucidate possible underlying factors, including which types of maternal effects are involved. PMID:25621325

  3. SMARCAL1 maintains telomere integrity during DNA replication.

    PubMed

    Poole, Lisa A; Zhao, Runxiang; Glick, Gloria G; Lovejoy, Courtney A; Eischen, Christine M; Cortez, David

    2015-12-01

    The SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) DNA translocase is one of several related enzymes, including ZRANB3 (zinc finger, RAN-binding domain containing 3) and HLTF (helicase-like transcription factor), that are recruited to stalled replication forks to promote repair and restart replication. These enzymes can perform similar biochemical reactions such as fork reversal; however, genetic studies indicate they must have unique cellular activities. Here, we present data showing that SMARCAL1 has an important function at telomeres, which present an endogenous source of replication stress. SMARCAL1-deficient cells accumulate telomere-associated DNA damage and have greatly elevated levels of extrachromosomal telomere DNA (C-circles). Although these telomere phenotypes are often found in tumor cells using the alternative lengthening of telomeres (ALT) pathway for telomere elongation, SMARCAL1 deficiency does not yield other ALT phenotypes such as elevated telomere recombination. The activity of SMARCAL1 at telomeres can be separated from its genome-maintenance activity in bulk chromosomal replication because it does not require interaction with replication protein A. Finally, this telomere-maintenance function is not shared by ZRANB3 or HLTF. Our results provide the first identification, to our knowledge, of an endogenous source of replication stress that requires SMARCAL1 for resolution and define differences between members of this class of replication fork-repair enzymes.

  4. Molecular Dynamics Simulation of Telomere and TRF1

    NASA Astrophysics Data System (ADS)

    Kaburagi, Masaaki; Fukuda, Masaki; Yamada, Hironao; Miyakawa, Takeshi; Morikawa, Ryota; Takasu, Masako; Kato, Takamitsu A.; Uesaka, Mitsuru

    Telomeres play a central role in determining longevity of a cell. Our study focuses on the interaction between telomeric guanines and TRF1 as a means to observe the telomeric based mechanism of the genome protection. In this research, we performed molecular dynamics simulations of a telomeric DNA and TRF1. Our results show a stable structure with a high affinity for the specific protein. Additionally, we calculated the distance between guanines and the protein in their complex state. From this comparison, we found the calculated values of distance to be very similar, and the angle of guanines in their complex states was larger than that in their single state.

  5. SMARCAL1 maintains telomere integrity during DNA replication

    PubMed Central

    Poole, Lisa A.; Zhao, Runxiang; Glick, Gloria G.; Lovejoy, Courtney A.; Eischen, Christine M.; Cortez, David

    2015-01-01

    The SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) DNA translocase is one of several related enzymes, including ZRANB3 (zinc finger, RAN-binding domain containing 3) and HLTF (helicase-like transcription factor), that are recruited to stalled replication forks to promote repair and restart replication. These enzymes can perform similar biochemical reactions such as fork reversal; however, genetic studies indicate they must have unique cellular activities. Here, we present data showing that SMARCAL1 has an important function at telomeres, which present an endogenous source of replication stress. SMARCAL1-deficient cells accumulate telomere-associated DNA damage and have greatly elevated levels of extrachromosomal telomere DNA (C-circles). Although these telomere phenotypes are often found in tumor cells using the alternative lengthening of telomeres (ALT) pathway for telomere elongation, SMARCAL1 deficiency does not yield other ALT phenotypes such as elevated telomere recombination. The activity of SMARCAL1 at telomeres can be separated from its genome-maintenance activity in bulk chromosomal replication because it does not require interaction with replication protein A. Finally, this telomere-maintenance function is not shared by ZRANB3 or HLTF. Our results provide the first identification, to our knowledge, of an endogenous source of replication stress that requires SMARCAL1 for resolution and define differences between members of this class of replication fork-repair enzymes. PMID:26578802

  6. Air Pollution Stress and the Aging Phenotype: The Telomere Connection.

    PubMed

    Martens, Dries S; Nawrot, Tim S

    2016-09-01

    Aging is a complex physiological phenomenon. The question why some subjects grow old while remaining free from disease whereas others prematurely die remains largely unanswered. We focus here on the role of air pollution in biological aging. Hallmarks of aging can be grouped into three main categories: genomic instability, telomere attrition, and epigenetic alterations leading to altered mitochondrial function and cellular senescence. At birth, the initial telomere length of a person is largely determined by environmental factors. Telomere length shortens with each cell division and exposure to air pollution as well as low residential greens space exposure is associated with shorter telomere length. Recent studies show that the estimated effects of particulate air pollution exposure on the telomere mitochondrial axis of aging may play an important role in chronic health effects of air pollution. The exposome encompasses all exposures over an entire life. As telomeres can be considered as the cellular memories of exposure to oxidative stress and inflammation, telomere maintenance may be a proxy for assessing the "exposome". If telomeres are causally related to the aging phenotype and environmental air pollution is an important determinant of telomere length, this might provide new avenues for future preventive strategies. PMID:27357566

  7. Air Pollution Stress and the Aging Phenotype: The Telomere Connection.

    PubMed

    Martens, Dries S; Nawrot, Tim S

    2016-09-01

    Aging is a complex physiological phenomenon. The question why some subjects grow old while remaining free from disease whereas others prematurely die remains largely unanswered. We focus here on the role of air pollution in biological aging. Hallmarks of aging can be grouped into three main categories: genomic instability, telomere attrition, and epigenetic alterations leading to altered mitochondrial function and cellular senescence. At birth, the initial telomere length of a person is largely determined by environmental factors. Telomere length shortens with each cell division and exposure to air pollution as well as low residential greens space exposure is associated with shorter telomere length. Recent studies show that the estimated effects of particulate air pollution exposure on the telomere mitochondrial axis of aging may play an important role in chronic health effects of air pollution. The exposome encompasses all exposures over an entire life. As telomeres can be considered as the cellular memories of exposure to oxidative stress and inflammation, telomere maintenance may be a proxy for assessing the "exposome". If telomeres are causally related to the aging phenotype and environmental air pollution is an important determinant of telomere length, this might provide new avenues for future preventive strategies.

  8. Cancer and aging: The importance of telomeres in genome maintenance

    SciTech Connect

    Rodier, Francis; Kim, Sahn-ho; Nijjar, Tarlochan; Yaswen, Paul; Campisi, Judith

    2004-10-01

    Telomeres are the specialized DNA-protein structures that cap the ends of linear chromosomes, thereby protecting them from degradation and fusion by cellular DNA repair processes. In vertebrate cells, telomeres consist of several kilobase pairs of DNA having the sequence TTAGGG, a few hundred base pairs of single-stranded DNA at the 3' end of the telomeric DNA tract, and a host of proteins that organize the telomeric double and single stranded DNA into a protective structure. Functional telomeres are essential for maintaining the integrity and stability of genomes. When combined with loss of cell cycle checkpoint controls, telomere dysfunction can lead to genomic instability, a common cause and hallmark of cancer. Consequently, normal mammalian cells respond to dysfunctional telomeres by undergoing apoptosis (programmed cell death) or cellular senescence (permanent cell cycle arrest), two cellular tumor suppressor mechanisms. These tumor suppressor mechanisms are potent suppressors of cancer, but recent evidence suggests that they can antagonistically also contribute to aging phenotypes. Here, we review what is known about the structure and function of telomeres in mammalian cells, particularly human cells, and how telomere dysfunction may arise and contribute to cancer and aging phenotypes.

  9. DNA sequence analysis of newly formed telomeres in yeast.

    PubMed

    Wang, S S; Pluta, A F; Zakian, V A

    1989-01-01

    A plasmid can be maintained in linear form in baker's yeast if it bears telomeric sequences at each end. Linear plasmids bearing cloned telomeric C4A4 repeats at one end (test end) and a natural DNA terminus with approximately 300 bps of C4A2 repeats at the other or control end were introduced by transformation into yeast. Test-end termini of 28 to 112 bps supported telomere formation. During telomere formation, C4A2 repeats were often transferred to test-end termini. To determine in greater detail the fate of test-end sequences on these plasmids after propagation in yeast, test-end telomeres were subcloned into E. coli and sequenced. DNA sequencing established a number of points about the molecular events involved in telomere formation in yeast. The results suggest that there are at least two mechanisms for telomere formation in yeast. One is mediated by a recombination event that requires neither a long stretch of homology nor the RAD52 gene product. The other mechanism is by addition of C1-3A repeats to the termini of linear DNA molecules. The telomeric sequence required to support C1-3A addition need not be at the very end of a molecule for telomere formation.

  10. Variation in early-life telomere dynamics in a long-lived bird: links to environmental conditions and survival

    PubMed Central

    Watson, Hannah; Bolton, Mark; Monaghan, Pat

    2015-01-01

    ABSTRACT Conditions experienced during early life can have profound consequences for both short- and long-term fitness. Variation in the natal environment has been shown to influence survival and reproductive performance of entire cohorts in wild vertebrate populations. Telomere dynamics potentially provide a link between the early environment and long-term fitness outcomes, yet we know little about how the environment can influence telomere dynamics in early life. We found that environmental conditions during growth have an important influence on early-life telomere length (TL) and attrition in nestlings of a long-lived bird, the European storm petrel Hydrobates pelagicus. Nestlings reared under unfavourable environmental conditions experienced significantly greater telomere loss during postnatal development compared with nestlings reared under more favourable natal conditions, which displayed a negligible change in TL. There was, however, no significant difference in pre-fledging TL between cohorts. The results suggest that early-life telomere dynamics could contribute to the marked differences in life-history traits that can arise among cohorts reared under different environmental conditions. Early-life TL was also found to be a significant predictor of survival during the nestling phase, providing further evidence for a link between variation in TL and individual fitness. To what extent the relationship between early-life TL and mortality during the nestling phase is a consequence of genetic, parental and environmental factors is currently unknown, but it is an interesting area for future research. Accelerated telomere attrition under unfavourable conditions, as observed in this study, might play a role in mediating the effects of the early-life environment on later-life performance. PMID:25617465

  11. Variation in early-life telomere dynamics in a long-lived bird: links to environmental conditions and survival.

    PubMed

    Watson, Hannah; Bolton, Mark; Monaghan, Pat

    2015-03-01

    Conditions experienced during early life can have profound consequences for both short- and long-term fitness. Variation in the natal environment has been shown to influence survival and reproductive performance of entire cohorts in wild vertebrate populations. Telomere dynamics potentially provide a link between the early environment and long-term fitness outcomes, yet we know little about how the environment can influence telomere dynamics in early life. We found that environmental conditions during growth have an important influence on early-life telomere length (TL) and attrition in nestlings of a long-lived bird, the European storm petrel Hydrobates pelagicus. Nestlings reared under unfavourable environmental conditions experienced significantly greater telomere loss during postnatal development compared with nestlings reared under more favourable natal conditions, which displayed a negligible change in TL. There was, however, no significant difference in pre-fledging TL between cohorts. The results suggest that early-life telomere dynamics could contribute to the marked differences in life-history traits that can arise among cohorts reared under different environmental conditions. Early-life TL was also found to be a significant predictor of survival during the nestling phase, providing further evidence for a link between variation in TL and individual fitness. To what extent the relationship between early-life TL and mortality during the nestling phase is a consequence of genetic, parental and environmental factors is currently unknown, but it is an interesting area for future research. Accelerated telomere attrition under unfavourable conditions, as observed in this study, might play a role in mediating the effects of the early-life environment on later-life performance.

  12. Variation in early-life telomere dynamics in a long-lived bird: links to environmental conditions and survival.

    PubMed

    Watson, Hannah; Bolton, Mark; Monaghan, Pat

    2015-03-01

    Conditions experienced during early life can have profound consequences for both short- and long-term fitness. Variation in the natal environment has been shown to influence survival and reproductive performance of entire cohorts in wild vertebrate populations. Telomere dynamics potentially provide a link between the early environment and long-term fitness outcomes, yet we know little about how the environment can influence telomere dynamics in early life. We found that environmental conditions during growth have an important influence on early-life telomere length (TL) and attrition in nestlings of a long-lived bird, the European storm petrel Hydrobates pelagicus. Nestlings reared under unfavourable environmental conditions experienced significantly greater telomere loss during postnatal development compared with nestlings reared under more favourable natal conditions, which displayed a negligible change in TL. There was, however, no significant difference in pre-fledging TL between cohorts. The results suggest that early-life telomere dynamics could contribute to the marked differences in life-history traits that can arise among cohorts reared under different environmental conditions. Early-life TL was also found to be a significant predictor of survival during the nestling phase, providing further evidence for a link between variation in TL and individual fitness. To what extent the relationship between early-life TL and mortality during the nestling phase is a consequence of genetic, parental and environmental factors is currently unknown, but it is an interesting area for future research. Accelerated telomere attrition under unfavourable conditions, as observed in this study, might play a role in mediating the effects of the early-life environment on later-life performance. PMID:25617465

  13. Telomeres, stem cells, senescence, and cancer

    PubMed Central

    Sharpless, Norman E.; DePinho, Ronald A.

    2004-01-01

    Mammalian aging occurs in part because of a decline in the restorative capacity of tissue stem cells. These self-renewing cells are rendered malignant by a small number of oncogenic mutations, and overlapping tumor suppressor mechanisms (e.g., p16INK4a-Rb, ARF-p53, and the telomere) have evolved to ward against this possibility. These beneficial antitumor pathways, however, appear also to limit the stem cell life span, thereby contributing to aging. PMID:14722605

  14. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length.

    PubMed

    Cook, Daniel E; Zdraljevic, Stefan; Tanny, Robyn E; Seo, Beomseok; Riccardi, David D; Noble, Luke M; Rockman, Matthew V; Alkema, Mark J; Braendle, Christian; Kammenga, Jan E; Wang, John; Kruglyak, Leonid; Félix, Marie-Anne; Lee, Junho; Andersen, Erik C

    2016-09-01

    Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans.

  15. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length.

    PubMed

    Cook, Daniel E; Zdraljevic, Stefan; Tanny, Robyn E; Seo, Beomseok; Riccardi, David D; Noble, Luke M; Rockman, Matthew V; Alkema, Mark J; Braendle, Christian; Kammenga, Jan E; Wang, John; Kruglyak, Leonid; Félix, Marie-Anne; Lee, Junho; Andersen, Erik C

    2016-09-01

    Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans. PMID:27449056

  16. The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length

    PubMed Central

    Cook, Daniel E.; Zdraljevic, Stefan; Tanny, Robyn E.; Seo, Beomseok; Riccardi, David D.; Noble, Luke M.; Rockman, Matthew V.; Alkema, Mark J.; Braendle, Christian; Kammenga, Jan E.; Wang, John; Kruglyak, Leonid; Félix, Marie-Anne; Lee, Junho; Andersen, Erik C.

    2016-01-01

    Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans. PMID:27449056

  17. Telomere length homeostasis and telomere position effect on a linear human artificial chromosome are dictated by the genetic background

    PubMed Central

    Weuts, An; Voet, Thierry; Verbeeck, Jelle; Lambrechts, Nathalie; Wirix, Evelyne; Schoonjans, Luc; Danloy, Sophie; Marynen, Peter; Froyen, Guy

    2012-01-01

    Telomere position effect (TPE) is the influence of telomeres on subtelomeric epigenetic marks and gene expression. Previous studies suggested that TPE depends on genetic background. As these analyses were performed on different chromosomes, cell types and species, it remains unclear whether TPE represents a chromosome—rather than genetic background-specific regulation. We describe the development of a Linear Human Artificial Chromosome (L-HAC) as a new tool for telomere studies. The L-HAC was generated through the Cre-loxP-mediated addition of telomere ends to an existing circular HAC (C-HAC). As it can be transferred to genetically distinct cell lines and animal models the L-HAC enables the study of TPE in an unprecedented manner. The HAC was relocated to four telomerase-positive cell lines via microcell-mediated chromosome transfer and subsequently to mice via blastocyst injection of L-HAC+-ES-cells. We could show consistent genetic background-dependent adaptation of telomere length and telomere-associated de novo subtelomeric DNA methylation in mouse ES-R1 cells as well as in mice. Expression of the subtelomeric neomycin gene was inversely correlated with telomere length and subtelomeric methylation. We thus provide a new tool for functional telomere studies and provide strong evidence that telomere length, subtelomeric chromatin marks and expression of subtelomeric genes are genetic background dependent. PMID:23066103

  18. Telomere length homeostasis and telomere position effect on a linear human artificial chromosome are dictated by the genetic background.

    PubMed

    Weuts, An; Voet, Thierry; Verbeeck, Jelle; Lambrechts, Nathalie; Wirix, Evelyne; Schoonjans, Luc; Danloy, Sophie; Marynen, Peter; Froyen, Guy

    2012-12-01

    Telomere position effect (TPE) is the influence of telomeres on subtelomeric epigenetic marks and gene expression. Previous studies suggested that TPE depends on genetic background. As these analyses were performed on different chromosomes, cell types and species, it remains unclear whether TPE represents a chromosome-rather than genetic background-specific regulation. We describe the development of a Linear Human Artificial Chromosome (L-HAC) as a new tool for telomere studies. The L-HAC was generated through the Cre-loxP-mediated addition of telomere ends to an existing circular HAC (C-HAC). As it can be transferred to genetically distinct cell lines and animal models the L-HAC enables the study of TPE in an unprecedented manner. The HAC was relocated to four telomerase-positive cell lines via microcell-mediated chromosome transfer and subsequently to mice via blastocyst injection of L-HAC(+)-ES-cells. We could show consistent genetic background-dependent adaptation of telomere length and telomere-associated de novo subtelomeric DNA methylation in mouse ES-R1 cells as well as in mice. Expression of the subtelomeric neomycin gene was inversely correlated with telomere length and subtelomeric methylation. We thus provide a new tool for functional telomere studies and provide strong evidence that telomere length, subtelomeric chromatin marks and expression of subtelomeric genes are genetic background dependent.

  19. Telomere and Telomerase Therapeutics in Cancer

    PubMed Central

    Xu, Yucheng; Goldkorn, Amir

    2016-01-01

    Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics. PMID:27240403

  20. ATRX represses alternative lengthening of telomeres.

    PubMed

    Napier, Christine E; Huschtscha, Lily I; Harvey, Adam; Bower, Kylie; Noble, Jane R; Hendrickson, Eric A; Reddel, Roger R

    2015-06-30

    The unlimited proliferation of cancer cells requires a mechanism to prevent telomere shortening. Alternative Lengthening of Telomeres (ALT) is an homologous recombination-mediated mechanism of telomere elongation used in tumors, including osteosarcomas, soft tissue sarcoma subtypes, and glial brain tumors. Mutations in the ATRX/DAXX chromatin remodeling complex have been reported in tumors and cell lines that use the ALT mechanism, suggesting that ATRX may be an ALT repressor. We show here that knockout or knockdown of ATRX in mortal cells or immortal telomerase-positive cells is insufficient to activate ALT. Notably, however, in SV40-transformed mortal fibroblasts ATRX loss results in either a significant increase in the proportion of cell lines activating ALT (instead of telomerase) or in a significant decrease in the time prior to ALT activation. These data indicate that loss of ATRX function cooperates with one or more as-yet unidentified genetic or epigenetic alterations to activate ALT. Moreover, transient ATRX expression in ALT-positive/ATRX-negative cells represses ALT activity. These data provide the first direct, functional evidence that ATRX represses ALT.

  1. Offspring's leukocyte telomere length, paternal age, and telomere elongation in sperm.

    PubMed

    Kimura, Masayuki; Cherkas, Lynn F; Kato, Bernet S; Demissie, Serkalem; Hjelmborg, Jacob B; Brimacombe, Michael; Cupples, Adrienne; Hunkin, Janice L; Gardner, Jefferey P; Lu, Xiaobin; Cao, Xiaojian; Sastrasinh, Malinee; Province, Michael A; Hunt, Steven C; Christensen, Kaare; Levy, Daniel; Spector, Tim D; Aviv, Abraham

    2008-02-01

    Leukocyte telomere length (LTL) is a complex genetic trait. It shortens with age and is associated with a host of aging-related disorders. Recent studies have observed that offspring of older fathers have longer LTLs. We explored the relation between paternal age and offspring's LTLs in 4 different cohorts. Moreover, we examined the potential cause of the paternal age on offspring's LTL by delineating telomere parameters in sperm donors. We measured LTL by Southern blots in Caucasian men and women (n=3365), aged 18-94 years, from the Offspring of the Framingham Heart Study (Framingham Offspring), the NHLBI Family Heart Study (NHLBI-Heart), the Longitudinal Study of Aging Danish Twins (Danish Twins), and the UK Adult Twin Registry (UK Twins). Using Southern blots, Q-FISH, and flow-FISH, we also measured telomere parameters in sperm from 46 young (<30 years) and older (>50 years) donors. Paternal age had an independent effect, expressed by a longer LTL in males of the Framingham Offspring and Danish Twins, males and females of the NHLBI-Heart, and females of UK Twins. For every additional year of paternal age, LTL in offspring increased at a magnitude ranging from half to more than twice of the annual attrition in LTL with age. Moreover, sperm telomere length analyses were compatible with the emergence in older men of a subset of sperm with elongated telomeres. Paternal age exerts a considerable effect on the offspring's LTL, a phenomenon which might relate to telomere elongation in sperm from older men. The implications of this effect deserve detailed study. PMID:18282113

  2. Targeted DNA damage at individual telomeres disrupts their integrity and triggers cell death.

    PubMed

    Sun, Luxi; Tan, Rong; Xu, Jianquan; LaFace, Justin; Gao, Ying; Xiao, Yanchun; Attar, Myriam; Neumann, Carola; Li, Guo-Min; Su, Bing; Liu, Yang; Nakajima, Satoshi; Levine, Arthur S; Lan, Li

    2015-07-27

    Cellular DNA is organized into chromosomes and capped by a unique nucleoprotein structure, the telomere. Both oxidative stress and telomere shortening/dysfunction cause aging-related degenerative pathologies and increase cancer risk. However, a direct connection between oxidative damage to telomeric DNA, comprising <1% of the genome, and telomere dysfunction has not been established. By fusing the KillerRed chromophore with the telomere repeat binding factor 1, TRF1, we developed a novel approach to generate localized damage to telomere DNA and to monitor the real time damage response at the single telomere level. We found that DNA damage at long telomeres in U2OS cells is not repaired efficiently compared to DNA damage in non-telomeric regions of the same length in heterochromatin. Telomeric DNA damage shortens the average length of telomeres and leads to cell senescence in HeLa cells and cell death in HeLa, U2OS and IMR90 cells, when DNA damage at non-telomeric regions is undetectable. Telomere-specific damage induces chromosomal aberrations, including chromatid telomere loss and telomere associations, distinct from the damage induced by ionizing irradiation. Taken together, our results demonstrate that oxidative damage induces telomere dysfunction and underline the importance of maintaining telomere integrity upon oxidative damage.

  3. Human telomeric G-quadruplex: thermodynamic and kinetic studies of telomeric quadruplex stability

    PubMed Central

    Chaires, Jonathan B.

    2010-01-01

    Summary Thermodynamic and kinetic studies complement high-resolution structures of G-quadruplexes. Such studies are essential for a thorough understanding of the mechanisms that govern quadruplex folding and conformational changes in quadruplexes. This perspective article reviews representative thermodynamic and kinetic studies of the folding of human telomeric quadruplex structures. Published thermodynamic data vary widely and are inconsistent. Possible reasons for these inconsistencies are discussed. The key issue of whether or not such folding reactions are a simple two-state process is examined. A tentative energy balance for the folding of telomeric quadruplexes in Na+ and K+ solution, and for conformational transition between these forms will be presented. PMID:19951355

  4. Heregulin, a new regulator of telomere length in human cells.

    PubMed

    Menendez, Javier A; Rubio, Miguel A; Campisi, Judith; Lupu, Ruth

    2015-11-24

    The growth factor heregulin (HRG) promotes breast cancer (BC) tumorigenesis and metastasis and differentially modulates BC cell responses to DNA-damaging agents via its dual extracellular and nuclear localization. Given the central role of telomere dysfunction to drive carcinogenesis and to alter the chemotherapeutic profile of transformed cells, we hypothesized that an unanticipated nuclear function of HRG might be to regulate telomere length. Engineered overexpression of the HRGβ2 isoform in non-aggressive, HRG-negative MCF-7 BC cells resulted in a significant shortening of telomeres (up to 1.3 kb) as measured by Southern blotting of telomere terminal restriction fragments. Conversely, antisense-mediated suppression of HRGβ2 in highly aggressive, HRG-overexpressing MDA-MB-231 and Hs578T cells increased telomere length up to 3.0 kb. HRGβ2 overexpression promoted a marked upregulation of telomere-binding protein 2 (TRF2) protein expression, whereas its knockdown profoundly decreased TRF2 expression. Double staining of endogenous HRGβ2 with telomere-specific peptide nucleic acid probe/fluorescence in situ hybridization (PNA/FISH) revealed the partial localization of HRG at the chromosome ends. Moreover, a predominantly nucleoplasmic staining pattern of endogenous HRGβ2 appeared to co-localize with TRF2 and, concomitantly with RAP1, a telomere regulator that specifically interacts with TRF2. Small interfering RNA-mediated knockdown of HRG decreased the expression of TRF2 and RAP1, decreased their presence at chromosome ends, and coincidentally resulted in the formation of longer telomeres. This study uncovers a new function for HRGβ2 in controlling telomere length, in part due to its ability to regulate and interact with the telomere-associated proteins TRF2 and RAP1.

  5. Accelerated Telomere Shortening and Replicative Senescence in Human Fibroblasts Overexpressing Mutant and Wild Type Lamin A

    PubMed Central

    Huang, Shurong; Risques, Rosa Ana; Martin, George M.; Rabinovitch, Peter S.; Oshima, Junko

    2008-01-01

    LMNA mutations are responsible for a variety of genetic disorders, including muscular dystrophy, lipodystrophy, and certain progeroid syndromes, notably Hutchinson-Gilford Progeria. Although a number of clinical features of these disorders are suggestive of accelerated aging, it is not known whether cells derived from these patients exhibit cellular phenotypes associated with accelerated aging. We examined a series of isogenic skin fibroblast lines transfected with LMNA constructs bearing known pathogenic point mutations or deletion mutations found in progeroid syndromes. Fibroblasts overexpressing mutant lamin A exhibited accelerated rates of loss of telomeres and shortened replicative lifespans, in addition to abnormal nuclear morphology. To our surprise, these abnormalities were also observed in lines overexpressing wild-type lamin A. Copy number variants are common in human populations; those involving LMNA, whether arising meiotically or mitotically, might lead to progeroid phenotypes. In an initial pilot study of 23 progeroid cases without detectible WRN or LMNA mutations, however, no cases of altered LMNA copy number were detected. Nevertheless, our findings raise a hypothesis that changes in lamina organization may cause accelerated telomere attrition, with different kinetics for overexpession of wild-type and mutant lamin A, which leads to rapid replicative senescence and progroid phenotypes. PMID:17870066

  6. PSYCHIATRIC DISORDERS AND LEUKOCYTE TELOMERE LENGTH: UNDERLYING MECHANISMS LINKING MENTAL ILLNESS WITH CELLULAR AGING

    PubMed Central

    Lindqvist, Daniel; Epel, Elissa S.; Mellon, Synthia H.; Penninx, Brenda W.; Révész, Dóra; Verhoeven, Josine E.; Reus, Victor I.; Lin, Jue; Mahan, Laura; Hough, Christina M.; Rosser, Rebecca; Bersani, F. Saverio; Blackburn, Elizabeth H.; Wolkowitz, Owen M.

    2015-01-01

    Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell’s mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets. PMID:25999120

  7. Conserved DNA sequences adjacent to chromosome fragmentation and telomere addition sites in Euplotes crassus.

    PubMed

    Klobutcher, L A; Gygax, S E; Podoloff, J D; Vermeesch, J R; Price, C M; Tebeau, C M; Jahn, C L

    1998-09-15

    During the formation of a new macronucleus in the ciliate Euplotes crassus, micronuclear chromosomes are reproducibly broken at approximately 10 000 sites. This chromosome fragmentation process is tightly coupled with de novo telomere synthesis by the telomerase ribonucleoprotein complex, generating short linear macronuclear DNA molecules. In this study, the sequences of 58 macronuclear DNA termini and eight regions of the micronuclear genome containing chromosome fragmentation/telomere addition sites were determined. Through a statistically based analysis of these data, along with previously published sequences, we have defined a 10 bp conserved sequence element (E-Cbs, 5'-HATTGAAaHH-3', H = A, C or T) near chromosome fragmentation sites. The E-Cbs typically resides within the DNA destined to form a macronuclear DNA molecule, but can also reside within flanking micronuclear DNA that is eliminated during macronuclear development. The location of the E-Cbs in macronuclear-destined versus flanking micronuclear DNA leads us to propose a model of chromosome fragmentation that involves a 6 bp staggered cut in the chromosome. The identification of adjacent macronuclear-destined sequences that overlap by 6 bp provides support for the model. Finally, our data provide evidence that telomerase is able to differentiate between newly generated ends that contain partial telomeric repeats and those that do not in vivo.

  8. A distinct type of heterochromatin at the telomeric region of the Drosophila melanogaster Y chromosome.

    PubMed

    Wang, Sidney H; Nan, Ruth; Accardo, Maria C; Sentmanat, Monica; Dimitri, Patrizio; Elgin, Sarah C R

    2014-01-01

    Heterochromatin assembly and its associated phenotype, position effect variegation (PEV), provide an informative system to study chromatin structure and genome packaging. In the fruit fly Drosophila melanogaster, the Y chromosome is entirely heterochromatic in all cell types except the male germline; as such, Y chromosome dosage is a potent modifier of PEV. However, neither Y heterochromatin composition, nor its assembly, has been carefully studied. Here, we report the mapping and characterization of eight reporter lines that show male-specific PEV. In all eight cases, the reporter insertion sites lie in the telomeric transposon array (HeT-A and TART-B2 homologous repeats) of the Y chromosome short arm (Ys). Investigations of the impact on the PEV phenotype of mutations in known heterochromatin proteins (i.e., modifiers of PEV) show that this Ys telomeric region is a unique heterochromatin domain: it displays sensitivity to mutations in HP1a, EGG and SU(VAR)3-9, but no sensitivity to Su(z)2 mutations. It appears that the endo-siRNA pathway plays a major targeting role for this domain. Interestingly, an ectopic copy of 1360 is sufficient to induce a piRNA targeting mechanism to further enhance silencing of a reporter cytologically localized to the Ys telomere. These results demonstrate the diversity of heterochromatin domains, and the corresponding variation in potential targeting mechanisms.

  9. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins.

    PubMed

    Sepsiova, Regina; Necasova, Ivona; Willcox, Smaranda; Prochazkova, Katarina; Gorilak, Peter; Nosek, Jozef; Hofr, Ctirad; Griffith, Jack D; Tomaska, Lubomir

    2016-01-01

    Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast. PMID:27101289

  10. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins.

    PubMed

    Sepsiova, Regina; Necasova, Ivona; Willcox, Smaranda; Prochazkova, Katarina; Gorilak, Peter; Nosek, Jozef; Hofr, Ctirad; Griffith, Jack D; Tomaska, Lubomir

    2016-01-01

    Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast.

  11. Evolution of Telomeres in Schizosaccharomyces pombe and Its Possible Relationship to the Diversification of Telomere Binding Proteins

    PubMed Central

    Sepsiova, Regina; Necasova, Ivona; Willcox, Smaranda; Prochazkova, Katarina; Gorilak, Peter; Nosek, Jozef; Hofr, Ctirad; Griffith, Jack D.

    2016-01-01

    Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast. PMID:27101289

  12. Differential Expression of Non-Shelterin Genes Associated with High Telomerase Levels and Telomere Shortening in Plasma Cell Disorders

    PubMed Central

    Panero, Julieta; Stella, Flavia; Schutz, Natalia; Fantl, Dorotea Beatriz; Slavutsky, Irma

    2015-01-01

    Telomerase, shelterin proteins and various interacting factors, named non-shelterin proteins, are involved in the regulation of telomere length (TL). Altered expression of any of these telomere-associated genes can lead to telomere dysfunction, causing genomic instability and disease development. In this study, we investigated the expression profile of a set of non-shelterin genes involved in essential processes such as replication (RPA1), DNA damage repair pathways (MRE11-RAD50-NBS1) and stabilization of telomerase complex (DKC1), in 35 patients with monoclonal gammopathy of undetermined significance (MGUS) and 40 cases with multiple myeloma (MM). Results were correlated with hTERT expression, TL and clinical parameters. Overall, a significant increase in DKC1, RAD50, MRE11, NBS1 and RPA1 expression along with an upregulation of hTERT in MM compared with MGUS was observed (p≤0.032). Interestingly, in both entities high mRNA levels of non-shelterin genes were associated with short TLs and increased hTERT expression. Significant differences were observed for DKC1 in MM (p ≤0.026), suggesting an important role for this gene in the maintenance of short telomeres by telomerase in myeloma plasma cells. With regard to clinical associations, we observed a significant increase in DKC1, RAD50, MRE11 and RPA1 expression in MM cases with high bone marrow infiltration (p≤0.03) and a tendency towards cases with advanced ISS stage, providing the first evidence of non-shelterin genes associated to risk factors in MM. Taken together, our findings bring new insights into the intricate mechanisms by which telomere-associated proteins collaborate in the maintenance of plasma cells immortalization and suggest a role for the upregulation of these genes in the progression of the disease. PMID:26366868

  13. Obesity and weight gain in adulthood and telomere length.

    PubMed

    Kim, Sangmi; Parks, Christine G; DeRoo, Lisa A; Chen, Honglei; Taylor, Jack A; Cawthon, Richard M; Sandler, Dale P

    2009-03-01

    Obesity and weight gain in adulthood are associated with an increased risk of several cancers. Telomeres play a critical role in maintaining genomic integrity and may be involved in carcinogenesis. Using data from 647 women ages 35 to 74 years in the United States and Puerto Rico (2003-2004), we examined the association between current and past anthropometric characteristics and telomere length in blood. In a multivariate linear regression model, higher current body mass index (BMI) and hip circumference were inversely associated with telomere length. Higher BMI in the 30s was associated with shorter telomere length among women ages>or=40 years (Ptrend<0.01). Weight gain since the age 30s (Ptrend=0.07) and weight cycling (Ptrend=0.04) were also inversely associated with telomere length. When current BMI and BMI at ages 30 to 39 years were considered together, the most marked decrease in telomere length was found for women who had overweight or obese BMI at both time points (mean telomere repeat copy number to single-copy gene copy number ratio=1.26; 95% confidence interval, 1.21-1.30) compared with women who had normal BMI at both times (mean telomere repeat copy number to single-copy gene copy number ratio=1.33; 95% confidence interval, 1.30-1.36). These findings support the hypothesis that obesity may accelerate aging, and highlight the importance of maintaining a desirable weight in adulthood.

  14. Assessment of Telomere Length, Phenotype, and DNA Content

    PubMed Central

    Kelesidis, Theodoros; Schmid, Ingrid

    2016-01-01

    Telomere sequences at the end of chromosomes control somatic cell division; therefore, telomere length in a given cell population provides information about its replication potential. This unit describes a method for flow cytometric measurement of telomere length in subpopulations using fluorescence in situ hybridization of fluorescently-labeled probes (Flow-FISH) without prior cell separation. After cells are stained for surface immunofluorescence, antigen-antibody complexes are covalently cross-linked onto cell membranes before FISH with a telomere-specific probe. Cells with long telomeres are included as internal standards. Addition of a DNA dye permits exclusion of proliferating cells during data analysis. DNA ploidy measurements of cells of interest and internal standard are performed on separate aliquots in parallel to Flow-FISH. Telomere fluorescence of G0/1 cells of subpopulations and internal standards obtained from Flow-FISH are normalized for DNA ploidy and telomere length in subsets of interest is expressed as a fraction of the internal standard telomere length. PMID:18770803

  15. Socioecological variables predict telomere length in wild spotted hyenas.

    PubMed

    Lewin, Nora; Treidel, Lisa A; Holekamp, Kay E; Place, Ned J; Haussmann, Mark F

    2015-02-01

    Telomeres are regarded as important biomarkers of ageing and serve as useful tools in revealing how stress acts at the cellular level. However, the effects of social and ecological factors on telomere length remain poorly understood, particularly in free-ranging mammals. Here, we investigated the influences of within-group dominance rank and group membership on telomere length in wild adult spotted hyenas (Crocuta crocuta). We found large effects of both factors; high-ranking hyenas exhibited significantly greater mean telomere length than did subordinate animals, and group membership significantly predicted mean telomere length within high-ranking females. We further inquired whether prey availability mediates the observed effect of group membership on telomere length, but this hypothesis was not supported. Interestingly, adult telomere length was not predicted by age. Our work shows for the first time, to the best of our knowledge, the effects of social rank on telomere length in a wild mammal and enhances our understanding of how social and ecological variables may contribute to organismal senescence. PMID:25716089

  16. Function, replication and structure of the mammalian telomere.

    PubMed

    Broccoli, Dominique

    2004-06-01

    Telomeres are specialized structures at the ends of linear chromosomes that were originally defined functionally based on observations first by Muller (1938) and subsequently by McClintock (1941) that naturally occurring chromosome ends do not behave as double-stranded DNA breaks, in spite of the fact that they are the physical end of a linear, duplex DNA molecule. Double-stranded DNA breaks are highly unstable entities, being susceptible to nucleolytic attack and giving rise to chromosome rearrangements through end-to-end fusions and recombination events. In contrast, telomeres confer stability upon chromosome termini, as evidenced by the fact that chromosomes are extraordinarily stable through multiple cell divisions and even across evolutionary time. This protective function of telomeres is due to the formation of a nucleoprotein complex that sequesters the end of the DNA molecule, rendering it inaccessible to nucleases and recombinases as well as preventing the telomere from activating the DNA damage checkpoint pathways. The capacity of a functional end-protective complex to form is dependent upon maintenance of sufficient telomeric DNA. We have learned a great deal about telomere structure and how this specialized nucleoprotein complex confers stability on chromosome ends since the original observations that defined telomeres were made. This review summarizes our current understanding of mammalian telomere replication, structure and function.

  17. Telomere length in Hutchinson-Gilford progeria syndrome.

    PubMed

    Decker, Michelle L; Chavez, Elizabeth; Vulto, Irma; Lansdorp, Peter M

    2009-06-01

    Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare premature aging disorder caused by mutations in the gene LMNA, which encodes the nuclear matrix protein lamin A. Previous research has shown that the average telomere length in fibroblasts from HGPS patients is shorter than in age-matched controls. How mutations in lamin A lead to shortened telomere lengths is not known nor is the contribution of individual chromosome ends to the low average length understood. To measure the telomere length of individual chromosomes, we used quantitative fluorescence in situ hybridization (Q-FISH). In agreement with previous studies, we found that the average telomere length in HPGS fibroblasts is greatly reduced; however, the telomere length at chromosome ends was variable. In contrast, the telomere length in hematopoietic cells which typically do not express lamin A, was within the normal range for three out of four HGPS patient samples. Our results suggest that mutant lamin A decreases telomere length via a direct effect and that expression of mutant LMNA is necessary for telomere loss in HGPS.

  18. Telomeres, early-life stress and mental illness.

    PubMed

    Ridout, Samuel J; Ridout, Kathryn K; Kao, Hung-Teh; Carpenter, Linda L; Philip, Noah S; Tyrka, Audrey R; Price, Lawrence H

    2015-01-01

    Telomeres are structures of tandem TTAGGG repeats that are found at the ends of chromosomes and preserve genomic DNA by serving as a disposable buffer to protect DNA termini during chromosome replication. In this process, the telomere itself shortens with each cell division and can consequently be thought of as a cellular 'clock', reflecting the age of a cell and the time until senescence. Telomere shortening and changes in the levels of telomerase, the enzyme that maintains telomeres, occur in the context of certain somatic diseases and in response to selected physical stressors. Emerging evidence indicates that telomeres shorten with exposure to psychosocial stress (including early-life stress) and perhaps in association with some psychiatric disorders. These discoveries suggest that telomere shortening might be a useful biomarker for the overall stress response of an organism to various pathogenic conditions. In this regard, telomeres and their response to both somatic and psychiatric illness could serve as a unifying stress-response biomarker that crosses the brain/body distinction that is often made in medicine. Prospective studies will help to clarify whether this biomarker has broad utility in psychiatry and medicine for the evaluation of responses to psychosocial stressors. The possibility that telomere shortening can be slowed or reversed by psychiatric and psychosocial interventions could represent an opportunity for developing novel preventative and therapeutic approaches.

  19. Telomeres, Early-Life Stress and Mental Illness

    PubMed Central

    Ridout, Samuel J.; Ridout, Kathryn K.; Kao, Hung-Teh; Carpenter, Linda L.; Philip, Noah S.; Tyrka, Audrey R.; Price, Lawrence H.

    2015-01-01

    Telomeres are structures of tandem TTAGGG repeats at the ends of chromosomes which preserve the encoding DNA by serving as a disposable brake to terminate DNA duplication during chromosome replication. In this process, the telomere itself shortens with each cell division, and can consequently be thought of as a cellular “clock” reflecting the age of a cell and the time until senescence. Telomere shortening, and changes in levels of telomerase, the enzyme that maintains telomeres, occur in the context of certain somatic diseases and in response to selected physical stressors. Emerging evidence indicates that telomeres shorten with exposure to psychosocial stress (including early-life stress [ELS]), and perhaps in association with some psychiatric disorders. These discoveries suggest that telomere shortening might be a useful biomarker for the overall stress response of an organism to various pathogenic conditions. In this regard, telomeres and their response to both somatic and psychiatric illness could serve as a unifying biomarker of stress response that crosses the brain/body distinction often made in medicine. Prospective studies will help to clarify whether this biomarker has broad utility in psychiatry and medicine in the evaluation of responses to psychosocial stressors. The possibility that telomere shortening can be slowed or reversed by psychiatric and psychosocial interventions could represent an opportunity for developing novel preventative and therapeutic approaches. PMID:25832516

  20. DNA-PKcs is critical for telomere capping

    SciTech Connect

    Gilley, David; Tanaka, Hiromi; Hande, M. Prakash; Kurimasa,Akihiro; Li, Gloria C.; Chen, David J.

    2001-04-10

    The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is critical for DNA repair via the non-homologous end joining (NHEJ) pathway. Previously, it was reported that bone marrow cells and spontaneously transformed fibroblasts from SCID (severe combined immunodeficiency) mice have defects in telomere maintenance. The genetically defective SCID mouse arose spontaneously from its parental strain CB17. One known genomic alteration in SCID mice is a truncation of the extreme carboxyl-terminus of DNA-PKcs, but other as yet unidentified alterations may also exist. We have used a defined system, the DNA-PKcs knockout mouse, to investigate specifically the role DNA-PKcs specifically plays in telomere maintenance. We report that primary mouse embryonic fibroblasts (MEFs) and primary cultured kidney cells from 6-8 month old DNA-PKcs deficient mice accumulate a large number of telomere fusions, yet still retain wildtype telomere length. Thus, the phenotype of this defect separates the two-telomere related phenotypes, capping and length maintenance. DNA-PKcs deficient MEFs also exhibit elevated levels of chromosome fragments and breaks, which correlate with increased telomere fusions. Based on the high levels of telomere fusions observed in DNA-PKcs deficient cells, we conclude that DNA-PKcs plays an important capping role at the mammalian telomere.

  1. Socioecological variables predict telomere length in wild spotted hyenas.

    PubMed

    Lewin, Nora; Treidel, Lisa A; Holekamp, Kay E; Place, Ned J; Haussmann, Mark F

    2015-02-01

    Telomeres are regarded as important biomarkers of ageing and serve as useful tools in revealing how stress acts at the cellular level. However, the effects of social and ecological factors on telomere length remain poorly understood, particularly in free-ranging mammals. Here, we investigated the influences of within-group dominance rank and group membership on telomere length in wild adult spotted hyenas (Crocuta crocuta). We found large effects of both factors; high-ranking hyenas exhibited significantly greater mean telomere length than did subordinate animals, and group membership significantly predicted mean telomere length within high-ranking females. We further inquired whether prey availability mediates the observed effect of group membership on telomere length, but this hypothesis was not supported. Interestingly, adult telomere length was not predicted by age. Our work shows for the first time, to the best of our knowledge, the effects of social rank on telomere length in a wild mammal and enhances our understanding of how social and ecological variables may contribute to organismal senescence.

  2. Polymerase η suppresses telomere defects induced by DNA damaging agents

    PubMed Central

    Pope-Varsalona, Hannah; Liu, Fu-Jun; Guzik, Lynda; Opresko, Patricia L.

    2014-01-01

    Telomeres at chromosome ends are normally masked from proteins that signal and repair DNA double strand breaks (DSBs). Bulky DNA lesions can cause DSBs if they block DNA replication, unless they are bypassed by translesion (TLS) DNA polymerases. Here, we investigated roles for TLS polymerase η, (polη) in preserving telomeres following acute physical UVC exposure and chronic chemical Cr(VI) exposure, which both induce blocking lesions. We report that polη protects against cytotoxicity and replication stress caused by Cr(VI), similar to results with ultraviolet C light (UVC). Both exposures induce ataxia telangiectasia and Rad3-related (ATR) kinase and polη accumulation into nuclear foci and localization to individual telomeres, consistent with replication fork stalling at DNA lesions. Polη-deficient cells exhibited greater numbers of telomeres that co-localized with DSB response proteins after exposures. Furthermore, the genotoxic exposures induced telomere aberrations associated with failures in telomere replication that were suppressed by polη. We propose that polη's ability to bypass bulky DNA lesions at telomeres is critical for proper telomere replication following genotoxic exposures. PMID:25355508

  3. Telomere variability in the monocotyledonous plant order Asparagales.

    PubMed Central

    Sýkorová, E; Lim, K Y; Kunická, Z; Chase, M W; Bennett, M D; Fajkus, J; Leitch, A R

    2003-01-01

    A group of monocotyledonous plants within the order Asparagales, forming a distinct clade in phylogenetic analyses, was reported previously to lack the 'typical' Arabidopsis-type telomere (TTTAGGG)(n). This stimulated us to determine what has replaced these sequences. Using slot-blot and fluorescent in situ hybridization (FISH) to species within this clade, our results indicate the following. 1. The typical Arabidopsis-type telomeric sequence has been partly or fully replaced by the human-type telomeric sequence (TTAGGG)(n). Species in Allium lack the human-type variant. 2. In most cases the human variant occurs along with a lower abundance of two or more variants of the minisatellite sequences (of seven types evaluated), usually these being the consensus telomeric sequence of Arabidopsis, Bombyx (TTAGG)(n) and Tetrahymena (TTGGGG)(n). FISH shows that the variants can occur mixed together at the telomere. 3. Telomerases generate products with a 6 base pair periodicity and when sequenced they reveal predominantly a reiterated human-type motif. These motifs probably form the 'true telomere' but the error rate of motif synthesis is higher compared with 'typical' plant telomerases. The data indicate that the Asparagales clade is unified by a mutation resulting in a switch from synthesis of Arabidopsis-like telomeres to a low-fidelity synthesis of human-like telomeres. PMID:14561302

  4. Leukocyte telomere length in relation to the risk of Barrett's esophagus and esophageal adenocarcinoma.

    PubMed

    Wennerström, E Christina M; Risques, Rosa A; Prunkard, Donna; Giffen, Carol; Corley, Douglas A; Murray, Liam J; Whiteman, David C; Wu, Anna H; Bernstein, Leslie; Ye, Weimin; Chow, Wong-Ho; Vaughan, Thomas L; Liao, Linda M

    2016-09-01

    Chronic inflammation and oxidative damage caused by obesity, cigarette smoking, and chronic gastroesophageal reflux disease (GERD) are major risk factors associated with Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). EAC has been increasing the past few decades, and early discovery and treatment are crucial for survival. Telomere shortening due to cell division and oxidative damage may reflect the impact of chronic inflammation and could possibly be used as predictor for disease development. We examined the prevalence of shorter leukocyte telomere length (LTL) among individuals with GERD, BE, or EAC using a pooled analysis of studies from the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON). Telomere length was measured in leukocyte DNA samples by Q-PCR. Participants included 1173 patients (386 with GERD, 384 with EAC, 403 with BE) and 736 population-based controls. The association of LTL (in tertiles) along the continuum of disease progression from GERD to BE to EAC was calculated using study-specific odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression models adjusted for potential confounders. Shorter LTL were less prevalent among GERD patients (OR 0.57; 95% CI: 0.35-0.93), compared to population-based controls. No statistically significant increased prevalence of short/long LTL among individuals with BE or EAC was observed. In contrast to some earlier reports, our findings add to the evidence that leukocyte telomere length is not a biomarker of risk related to the etiology of EAC. The findings do not suggest a relationship between LTL and BE or EAC. PMID:27384379

  5. Leukocyte telomere length in relation to the risk of Barrett's esophagus and esophageal adenocarcinoma.

    PubMed

    Wennerström, E Christina M; Risques, Rosa A; Prunkard, Donna; Giffen, Carol; Corley, Douglas A; Murray, Liam J; Whiteman, David C; Wu, Anna H; Bernstein, Leslie; Ye, Weimin; Chow, Wong-Ho; Vaughan, Thomas L; Liao, Linda M

    2016-09-01

    Chronic inflammation and oxidative damage caused by obesity, cigarette smoking, and chronic gastroesophageal reflux disease (GERD) are major risk factors associated with Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). EAC has been increasing the past few decades, and early discovery and treatment are crucial for survival. Telomere shortening due to cell division and oxidative damage may reflect the impact of chronic inflammation and could possibly be used as predictor for disease development. We examined the prevalence of shorter leukocyte telomere length (LTL) among individuals with GERD, BE, or EAC using a pooled analysis of studies from the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON). Telomere length was measured in leukocyte DNA samples by Q-PCR. Participants included 1173 patients (386 with GERD, 384 with EAC, 403 with BE) and 736 population-based controls. The association of LTL (in tertiles) along the continuum of disease progression from GERD to BE to EAC was calculated using study-specific odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression models adjusted for potential confounders. Shorter LTL were less prevalent among GERD patients (OR 0.57; 95% CI: 0.35-0.93), compared to population-based controls. No statistically significant increased prevalence of short/long LTL among individuals with BE or EAC was observed. In contrast to some earlier reports, our findings add to the evidence that leukocyte telomere length is not a biomarker of risk related to the etiology of EAC. The findings do not suggest a relationship between LTL and BE or EAC.

  6. QTL mapping and candidate gene analysis of telomere length control factors in maize (Zea mays L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Telomere length is under genetic control and important for essential telomere functions. Failure to regulate telomere length homeostasis contributes to cancers and aging-related diseases in animals, but the effects of telomere length defects in plants remains poorly understood. To learn more about t...

  7. Telomere Replication Stress Induced by POT1 Inactivation Accelerates Tumorigenesis.

    PubMed

    Pinzaru, Alexandra M; Hom, Robert A; Beal, Angela; Phillips, Aaron F; Ni, Eric; Cardozo, Timothy; Nair, Nidhi; Choi, Jaehyuk; Wuttke, Deborah S; Sfeir, Agnel; Denchi, Eros Lazzerini

    2016-06-01

    Genome sequencing studies have revealed a number of cancer-associated mutations in the telomere-binding factor POT1. Here, we show that when combined with p53 deficiency, depletion of murine POT1a in common lymphoid progenitor cells fosters genetic instability, accelerates the onset, and increases the severity of T cell lymphomas. In parallel, we examined human and mouse cells carrying POT1 mutations found in cutaneous T cell lymphoma (CTCL) patients. Inhibition of POT1 activates ATR-dependent DNA damage signaling and induces telomere fragility, replication fork stalling, and telomere elongation. Our data suggest that these phenotypes are linked to impaired CST (CTC1-STN1-TEN1) function at telomeres. Lastly, we show that proliferation of cancer cells lacking POT1 is enabled by the attenuation of the ATR kinase pathway. These results uncover a role for defective telomere replication during tumorigenesis.

  8. Computing the Length of the Shortest Telomere in the Nucleus

    NASA Astrophysics Data System (ADS)

    Dao Duc, K.; Holcman, D.

    2013-11-01

    The telomere length can either be shortened or elongated by an enzyme called telomerase after each cell division. Interestingly, the shortest telomere is involved in controlling the ability of a cell to divide. Yet, its dynamics remains elusive. We present here a stochastic approach where we model this dynamics using a Markov jump process. We solve the forward Fokker-Planck equation to obtain the steady state distribution and the statistical moments of telomere lengths. We focus specifically on the shortest one and we estimate its length difference with the second shortest telomere. After extracting key parameters such as elongation and shortening dynamics from experimental data, we compute the length of telomeres in yeast and obtain as a possible prediction the minimum concentration of telomerase required to ensure a proper cell division.

  9. Herpesvirus Genome Integration into Telomeric Repeats of Host Cell Chromosomes.

    PubMed

    Osterrieder, Nikolaus; Wallaschek, Nina; Kaufer, Benedikt B

    2014-11-01

    It is well known that numerous viruses integrate their genetic material into host cell chromosomes. Human herpesvirus 6 (HHV-6) and oncogenic Marek's disease virus (MDV) have been shown to integrate their genomes into host telomeres of latently infected cells. This is unusual for herpesviruses as most maintain their genomes as circular episomes during the quiescent stage of infection. The genomic DNA of HHV-6, MDV, and several other herpesviruses harbors telomeric repeats (TMRs) that are identical to host telomere sequences (TTAGGG). At least in the case of MDV, viral TMRs facilitate integration into host telomeres. Integration of HHV-6 occurs not only in lymphocytes but also in the germline of some individuals, allowing vertical virus transmission. Although the molecular mechanism of telomere integration is poorly understood, the presence of TMRs in a number of herpesviruses suggests it is their default program for genome maintenance during latency and also allows efficient reactivation.

  10. An antiapoptotic role for telomerase RNA in human immune cells independent of telomere integrity or telomerase enzymatic activity

    PubMed Central

    Gazzaniga, Francesca S.

    2014-01-01

    Telomerase is a ribonucleoprotein complex that adds telomeric DNA to the ends of linear chromosomes. It contains two core canonical components: the essential RNA component, hTR, which provides the template for DNA synthesis, and the reverse transcriptase protein component, hTERT. Low telomerase activity in circulating peripheral blood mononuclear cells has been associated with a variety of diseases. It is unknown, however, whether telomerase, in addition to its long-term requirement for telomere maintenance, is also necessary for short-term immune cell proliferation and survival. We report that overexpression of enzymatically inactive hTR mutants protected against dexamethasone-induced apoptosis in stimulated CD4 T cells. Furthermore, hTR knockdown reproducibly induced apoptosis in the absence of any detectable telomere shortening or DNA damage response. In contrast, hTERT knockdown did not induce apoptosis. Strikingly, overexpression of hTERT protein caused apoptosis that was rescued by overexpression of enzymatically inactive hTR mutants. Hence, we propose that hTR can function as a noncoding RNA that protects from apoptosis independent of its function in telomerase enzymatic activity and long-term telomere maintenance in normal human immune cells. These results imply that genetic or environmental factors that alter hTR levels can directly affect immune cell function to influence health and disease. PMID:25320237

  11. [Telomere lengthening by trichostatin A treatment in cloned pigs].

    PubMed

    Xie, Bing-Teng; Ji, Guang-Zhen; Kong, Qing-Ran; Mao, Jian; Shi, Yong-Qian; Liu, Shi-Chao; Wu, Mei-Ling; Wang, Juan; Liu, Lin; Liu, Zhong-Hua

    2012-12-01

    Telomeres are repeated GC rich sequences at the end of chromosomes, and shorten with each cell division due to DNA end replication problem. Previously, reprogrammed somatic cells of cloned animals display variable telomere elongation. However, it was reported that the cloned animals including Dolly do not reset telomeres and show premature aging. In this study, we investigated telomere function in cloned or transgenic cloned pigs, including the cloned Northeast Min pigs, eGFP, Mx, and PGC1α transgenic cloned pigs, and found that the telomere lengths of cloned pigs were significantly shorter than the nuclear donor adult fibroblasts and age-matched noncloned pigs (P<0.05), indicating that nuclear reprogramming did not restore cellular age of donor cells after somatic cell nuclear transfer (SCNT). Trichostatin A (TSA), an inhibitor of histone deacetylase, has proven to enhance the efficiency of nuclear reprogramming in several species. In order to test whether TSA also can effectively enhance reprogramming of telomeres, TSA (40 nmol/L) was used to treat porcine cloned embryos at 1-cell stage for 24 h. Consistent with previous reports, the developmental rate of SCNT embryos to the blastocyst stage was significantly increased compared with those of the control group (16.35% vs. 27.09%, 21.60% vs. 34.90%, P<0.05). Notably, the telomere length of cloned porcine blastocysts was also significantly elongated (P<0.05). Although TSA did not improve the cloning efficiency (1.3% vs. 1.7%, TSA vs. control), the telomere lengths of cloned pig-lets were significantly longer compared with those of the control group and the donor fibroblasts (P<0.05). In conclusion, telomeres have not been effectively restored by SCNT in pigs but TSA can effectively lengthen the telomere lengths of cloned pigs.

  12. [Telomere lengthening by trichostatin A treatment in cloned pigs].

    PubMed

    Xie, Bing-Teng; Ji, Guang-Zhen; Kong, Qing-Ran; Mao, Jian; Shi, Yong-Qian; Liu, Shi-Chao; Wu, Mei-Ling; Wang, Juan; Liu, Lin; Liu, Zhong-Hua

    2012-12-01

    Telomeres are repeated GC rich sequences at the end of chromosomes, and shorten with each cell division due to DNA end replication problem. Previously, reprogrammed somatic cells of cloned animals display variable telomere elongation. However, it was reported that the cloned animals including Dolly do not reset telomeres and show premature aging. In this study, we investigated telomere function in cloned or transgenic cloned pigs, including the cloned Northeast Min pigs, eGFP, Mx, and PGC1α transgenic cloned pigs, and found that the telomere lengths of cloned pigs were significantly shorter than the nuclear donor adult fibroblasts and age-matched noncloned pigs (P<0.05), indicating that nuclear reprogramming did not restore cellular age of donor cells after somatic cell nuclear transfer (SCNT). Trichostatin A (TSA), an inhibitor of histone deacetylase, has proven to enhance the efficiency of nuclear reprogramming in several species. In order to test whether TSA also can effectively enhance reprogramming of telomeres, TSA (40 nmol/L) was used to treat porcine cloned embryos at 1-cell stage for 24 h. Consistent with previous reports, the developmental rate of SCNT embryos to the blastocyst stage was significantly increased compared with those of the control group (16.35% vs. 27.09%, 21.60% vs. 34.90%, P<0.05). Notably, the telomere length of cloned porcine blastocysts was also significantly elongated (P<0.05). Although TSA did not improve the cloning efficiency (1.3% vs. 1.7%, TSA vs. control), the telomere lengths of cloned pig-lets were significantly longer compared with those of the control group and the donor fibroblasts (P<0.05). In conclusion, telomeres have not been effectively restored by SCNT in pigs but TSA can effectively lengthen the telomere lengths of cloned pigs. PMID:23262106

  13. Integration of Telomere Length Dynamics into Systems Biology Framework: A Review

    PubMed Central

    Nersisyan, Lilit

    2016-01-01

    Telomere length dynamics plays a crucial role in regulation of cellular processes and cell fate. In contrast to epidemiological studies revealing the association of telomere length with age, age-related diseases, and cancers, the role of telomeres in regulation of transcriptome and epigenome and the role of genomic variations in telomere lengthening are not extensively analyzed. This is explained by the fact that experimental assays for telomere length measurement are resource consuming, and there are very few studies where high-throughput genomics, transcriptomics, and/or epigenomics experiments have been coupled with telomere length measurements. Recent development of computational approaches for assessment of telomere length from whole genome sequencing data pave a new perspective on integration of telomeres into high-throughput systems biology analysis framework. Herein, we review existing methodologies for telomere length measurement and compare them to computational approaches, as well as discuss their applications in large-scale studies on telomere length dynamics. PMID:27346946

  14. P66SHC deletion improves fertility and progeric phenotype of late-generation TERC-deficient mice but not their short lifespan.

    PubMed

    Giorgio, Marco; Stendardo, Massimo; Migliaccio, Enrica; Pelicci, Pier Giuseppe

    2016-06-01

    Oxidative stress and telomere attrition are considered the driving factors of aging. As oxidative damage to telomeric DNA favors the erosion of chromosome ends and, in turn, telomere shortening increases the sensitivity to pro-oxidants, these two factors may trigger a detrimental vicious cycle. To check whether limiting oxidative stress slows down telomere shortening and related progeria, we have investigated the effect of p66SHC deletion, which has been shown to reduce oxidative stress and mitochondrial apoptosis, on late-generation TERC (telomerase RNA component)-deficient mice having short telomeres and reduced lifespan. Double mutant (TERC(-/-) p66SHC(-/-) ) mice were generated, and their telomere length, fertility, and lifespan investigated in different generations. Results revealed that p66SHC deletion partially rescues sterility and weight loss, as well as organ atrophy, of TERC-deficient mice, but not their short lifespan and telomere erosion. Therefore, our data suggest that p66SHC-mediated oxidative stress and telomere shortening synergize in some tissues (including testes) to accelerate aging; however, early mortality of late-generation mice seems to be independent of any link between p66SHC-mediated oxidative stress and telomere attrition.

  15. MicroRNA396-Targeted SHORT VEGETATIVE PHASE Is Required to Repress Flowering and Is Related to the Development of Abnormal Flower Symptoms by the Phyllody Symptoms1 Effector.

    PubMed

    Yang, Chiao-Yin; Huang, Yu-Hsin; Lin, Chan-Pin; Lin, Yen-Yu; Hsu, Hao-Chun; Wang, Chun-Neng; Liu, Li-Yu Daisy; Shen, Bing-Nan; Lin, Shih-Shun

    2015-08-01

    Leafy flowers are the major symptoms of peanut witches' broom (PnWB) phytoplasma infection in Catharanthus roseus. The orthologs of the phyllody symptoms1 (PHYL1) effector of PnWB from other species of phytoplasma can trigger the proteasomal degradation of several MADS box transcription factors, resulting in leafy flower formation. In contrast, the flowering negative regulator gene SHORT VEGETATIVE PHASE (SVP) was up-regulated in PnWB-infected C. roseus plants, but most microRNA (miRNA) genes had repressed expression. Coincidentally, transgenic Arabidopsis (Arabidopsis thaliana) plants expressing the PHYL1 gene of PnWB (PHYL1 plants), which show leafy flower phenotypes, up-regulate SVP of Arabidopsis (AtSVP) but repress a putative regulatory miRNA of AtSVP, miR396. However, the mechanism by which PHYL1 regulates AtSVP and miR396 is unknown, and the evidence of miR396-mediated AtSVP degradation is lacking. Here, we show that miR396 triggers AtSVP messenger RNA (mRNA) decay using genetic approaches, a reporter assay, and high-throughput degradome profiles. Genetic evidence indicates that PHYL1 plants and atmir396a-1 mutants have higher AtSVP accumulation, whereas the transgenic plants overexpressing MIR396 display lower AtSVP expression. The reporter assay indicated that target-site mutation results in decreasing the miR396-mediated repression efficiency. Moreover, degradome profiles revealed that miR396 triggers AtSVP mRNA decay rather than miRNA-mediated cleavage, implying that AtSVP caused miR396-mediated translation inhibition. We hypothesize that PHYL1 directly or indirectly interferes with miR396-mediated AtSVP mRNA decay and synergizes with other effects (e.g. MADS box transcription factor degradation), resulting in abnormal flower formation. We anticipate our findings to be a starting point for studying the posttranscriptional regulation of PHYL1 effectors in symptom development.

  16. MicroRNA396-Targeted SHORT VEGETATIVE PHASE Is Required to Repress Flowering and Is Related to the Development of Abnormal Flower Symptoms by the Phyllody Symptoms1 Effector1

    PubMed Central

    Yang, Chiao-Yin; Huang, Yu-Hsin; Lin, Chan-Pin; Lin, Yen-Yu; Hsu, Hao-Chun; Wang, Chun-Neng; Liu, Li-Yu Daisy; Shen, Bing-Nan; Lin, Shih-Shun

    2015-01-01

    Leafy flowers are the major symptoms of peanut witches’ broom (PnWB) phytoplasma infection in Catharanthus roseus. The orthologs of the phyllody symptoms1 (PHYL1) effector of PnWB from other species of phytoplasma can trigger the proteasomal degradation of several MADS box transcription factors, resulting in leafy flower formation. In contrast, the flowering negative regulator gene SHORT VEGETATIVE PHASE (SVP) was up-regulated in PnWB-infected C. roseus plants, but most microRNA (miRNA) genes had repressed expression. Coincidentally, transgenic Arabidopsis (Arabidopsis thaliana) plants expressing the PHYL1 gene of PnWB (PHYL1 plants), which show leafy flower phenotypes, up-regulate SVP of Arabidopsis (AtSVP) but repress a putative regulatory miRNA of AtSVP, miR396. However, the mechanism by which PHYL1 regulates AtSVP and miR396 is unknown, and the evidence of miR396-mediated AtSVP degradation is lacking. Here, we show that miR396 triggers AtSVP messenger RNA (mRNA) decay using genetic approaches, a reporter assay, and high-throughput degradome profiles. Genetic evidence indicates that PHYL1 plants and atmir396a-1 mutants have higher AtSVP accumulation, whereas the transgenic plants overexpressing MIR396 display lower AtSVP expression. The reporter assay indicated that target-site mutation results in decreasing the miR396-mediated repression efficiency. Moreover, degradome profiles revealed that miR396 triggers AtSVP mRNA decay rather than miRNA-mediated cleavage, implying that AtSVP caused miR396-mediated translation inhibition. We hypothesize that PHYL1 directly or indirectly interferes with miR396-mediated AtSVP mRNA decay and synergizes with other effects (e.g. MADS box transcription factor degradation), resulting in abnormal flower formation. We anticipate our findings to be a starting point for studying the posttranscriptional regulation of PHYL1 effectors in symptom development. PMID:26103992

  17. U-shaped association between telomere length and esophageal squamous cell carcinoma risk: a case-control study in Chinese population.

    PubMed

    Du, Jiangbo; Xue, Wenjie; Ji, Yong; Zhu, Xun; Gu, Yayun; Zhu, Meng; Wang, Cheng; Gao, Yong; Dai, Juncheng; Ma, Hongxia; Jiang, Yue; Chen, Jiaping; Hu, Zhibin; Jin, Guangfu; Shen, Hongbing

    2015-12-01

    Telomeres play a critical role in biological ageing by maintaining chromosomal integrity and preventing chromosome ends fusion. Epidemiological studies have suggested that inter-individual differences of telomere length could affect predisposition to multiple cancers, but evidence regarding esophageal squamous cell carcinoma (ESCC) was still uncertain. Several telomere length-related single nucleotide polymorphisms (TLSNPs) in Caucasians have been reported in genome-wide association studies. However, the effects of telomere length and TL-SNPs on ESCC development are unclear. Therefore, we conducted a case-control study (1045 ESCC cases and 1433 controls) to evaluate the associations between telomere length, TL-SNPs, and ESCC risk in Chinese population. As a result, ESCC cases showed overall shorter relative telomere length (RTL) (median: 1.34) than controls (median: 1.50, P < 0.001). More interestingly, an evident nonlinear U-shaped association was observed between RTL and ESCC risk (P < 0.001), with odds ratios (95% confidence interval) equal to 2.40 (1.84-3.14), 1.36 (1.03-1.79), 1.01 (0.76-1.35), and 1.37 (1.03-1.82) for individuals in the 1st (the shortest), 2nd, 3rd, and 5th (the longest) quintile, respectively, compared with those in the 4th quintile as reference group. No significant associations were observed between the eight reported TL-SNPs and ESCC susceptibility. These findings suggest that either short or extremely long telomeres may be risk factors for ESCC in the Chinese population.

  18. Telomere binding of checkpoint sensor and DNA repair proteins contributes to maintenance of functional fission yeast telomeres.

    PubMed Central

    Nakamura, Toru M; Moser, Bettina A; Russell, Paul

    2002-01-01

    Telomeres, the ends of linear chromosomes, are DNA double-strand ends that do not trigger a cell cycle arrest and yet require checkpoint and DNA repair proteins for maintenance. Genetic and biochemical studies in the fission yeast Schizosaccharomyces pombe were undertaken to understand how checkpoint and DNA repair proteins contribute to telomere maintenance. On the basis of telomere lengths of mutant combinations of various checkpoint-related proteins (Rad1, Rad3, Rad9, Rad17, Rad26, Hus1, Crb2, Chk1, Cds1), Tel1, a telomere-binding protein (Taz1), and DNA repair proteins (Ku70, Rad32), we conclude that Rad3/Rad26 and Tel1/Rad32 represent two pathways required to maintain telomeres and prevent chromosome circularization. Rad1/Rad9/Hus1/Rad17 and Ku70 are two additional epistasis groups, which act in the Rad3/Rad26 pathway. However, Rad3/Rad26 must have additional target(s), as cells lacking Tel1/Rad32, Rad1/Rad9/Hus1/Rad17, and Ku70 groups did not circularize chromosomes. Cells lacking Rad3/Rad26 and Tel1/Rad32 senesced faster than a telomerase trt1Delta mutant, suggesting that these pathways may contribute to telomere protection. Deletion of taz1 did not suppress chromosome circularization in cells lacking Rad3/Rad26 and Tel1/Rad32, also suggesting that two pathways protect telomeres. Chromatin immunoprecipitation analyses found that Rad3, Rad1, Rad9, Hus1, Rad17, Rad32, and Ku70 associate with telomeres. Thus, checkpoint sensor and DNA repair proteins contribute to telomere maintenance and protection through their association with telomeres. PMID:12196391

  19. Multiple Pathways Suppress Telomere Addition to DNA Breaks in the Drosophila Germline

    PubMed Central

    Beaucher, Michelle; Zheng, Xiao-Feng; Amariei, Flavia; Rong, Yikang S.

    2012-01-01

    Telomeres protect chromosome ends from being repaired as double-strand breaks (DSBs). Just as DSB repair is suppressed at telomeres, de novo telomere addition is suppressed at the site of DSBs. To identify factors responsible for this suppression, we developed an assay to monitor de novo telomere formation in Drosophila, an organism in which telomeres can be established on chromosome ends with essentially any sequence. Germline expression of the I-SceI endonuclease resulted in precise telomere formation at its cut site with high efficiency. Using this assay, we quantified the frequency of telomere formation in different genetic backgrounds with known or possible defects in DNA damage repair. We showed that disruption of DSB repair factors (Rad51 or DNA ligase IV) or DSB sensing factors (ATRIP or MDC1) resulted in more efficient telomere formation. Interestingly, partial disruption of factors that normally regulate telomere protection (ATM or NBS) also led to higher frequencies of telomere formation, suggesting that these proteins have opposing roles in telomere maintenance vs. establishment. In the ku70 mutant background, telomere establishment was preceded by excessive degradation of DSB ends, which were stabilized upon telomere formation. Most strikingly, the removal of ATRIP caused a dramatic increase in telomeric retrotransposon attachment to broken ends. Our study identifies several pathways thatsuppress telomere addition at DSBs, paving the way for future mechanistic studies. PMID:22446318

  20. FEN1 ensures telomere stability by facilitating replication fork re-initiation.

    PubMed

    Saharia, Abhishek; Teasley, Daniel C; Duxin, Julien P; Dao, Benjamin; Chiappinelli, Katherine B; Stewart, Sheila A

    2010-08-27

    Telomeres are terminal repetitive DNA sequences whose stability requires the coordinated actions of telomere-binding proteins and the DNA replication and repair machinery. Recently, we demonstrated that the DNA replication and repair protein Flap endonuclease 1 (FEN1) is required for replication of lagging strand telomeres. Here, we demonstrate for the first time that FEN1 is required for efficient re-initiation of stalled replication forks. At the telomere, we find that FEN1 depletion results in replicative stress as evidenced by fragile telomere expression and sister telomere loss. We show that FEN1 participation in Okazaki fragment processing is not required for efficient telomere replication. Instead we find that FEN1 gap endonuclease activity, which processes DNA structures resembling stalled replication forks, and the FEN1 interaction with the RecQ helicases are vital for telomere stability. Finally, we find that FEN1 depletion neither impacts cell cycle progression nor in vitro DNA replication through non-telomeric sequences. Our finding that FEN1 is required for efficient replication fork re-initiation strongly suggests that the fragile telomere expression and sister telomere losses observed upon FEN1 depletion are the direct result of replication fork collapse. Together, these findings suggest that other nucleases compensate for FEN1 loss throughout the genome during DNA replication but fail to do so at the telomere. We propose that FEN1 maintains stable telomeres by facilitating replication through the G-rich lagging strand telomere, thereby ensuring high fidelity telomere replication.

  1. The relationship between telomere length and beekeeping among Malaysians.

    PubMed

    Nasir, Nurul Fatihah Mohamad; Kannan, Thirumulu Ponnuraj; Sulaiman, Siti Amrah; Shamsuddin, Shaharum; Azlina, Ahmad; Stangaciu, Stefan

    2015-06-01

    The belief that beekeepers live longer than anyone else is present since ages. However, no research has been done to explore the longevity of life in beekeepers. Here, we investigated the telomere length in 30 male beekeepers and 30 male non-beekeepers and associated them with the longevity of life using Southern analysis of terminal restriction fragments (TRFs) generated by Hinf I/Rsa I digestion of human genomic DNA using TeloTAGGG Telomere Length Assay. Interestingly, we found that the telomere length of male beekeepers was significantly longer than those of male non-beekeepers with a p value of less than 0.05, suggesting that beekeepers may have longer life compared to non-beekeepers. We further found that the consumption of bee products for a long period and frequent consumption of bee products per day are associated with telomere length. An increase of year in consuming bee products is associated with a mean increase in telomere length of 0.258 kbp. In addition, an increase in frequency of eating bee products per day was also associated with a mean increase of 2.66 kbp in telomere length. These results suggested that bee products might play some roles in telomere length maintenance.

  2. DNA damage and repair in telomeres: relation to aging.

    PubMed Central

    Kruk, P A; Rampino, N J; Bohr, V A

    1995-01-01

    We have established a method for the detection of DNA damage and its repair in human telomeres, the natural ends of chromosomes which are necessary for replication and critical for chromosomal stability. We find that ultraviolet light-induced pyrimidine dimers in telomeric DNA are repaired less efficiently than endogenous genes but more efficiently than inactive, noncoding regions. We have also measured telomeric length, telomeric DNA damage, and its repair in relation to the progression of aging. Telomeres are shorter in fibroblasts from an old donor compared to fibroblasts from a young donor, shortest in cells from a patient with the progeroid disorder Werner syndrome, and relatively long in fibroblasts from a patient with Alzheimer disease. Telomeric DNA repair efficiency is lower in cells from an old donor than in cells from a young donor, normal in Alzheimer cells, and slightly lower in Werner cells. It is possible that this decline in telomeric repair with aging is of functional significance to an age-related decline in genomic stability. Images Fig. 1 Fig. 2 PMID:7816828

  3. Translin and Trax differentially regulate telomere-associated transcript homeostasis

    PubMed Central

    Alshehri, Zafer; Thallinger, Gerhard G.; Wakeman, Jane A.; McFarlane, Ramsay J.

    2016-01-01

    Translin and Trax proteins are highly conserved nucleic acid binding proteins that have been implicated in RNA regulation in a range of biological processes including tRNA processing, RNA interference, microRNA degradation during oncogenesis, spermatogenesis and neuronal regulation. Here, we explore the function of this paralogue pair of proteins in the fission yeast. Using transcript analysis we demonstrate a reciprocal mechanism for control of telomere-associated transcripts. Mutation of tfx1+ (Trax) elevates transcript levels from silenced sub-telomeric regions of the genome, but not other silenced regions, such as the peri-centromeric heterochromatin. In the case of some sub-telomeric transcripts, but not all, this elevation is dependent on the Trax paralogue, Tsn1 (Translin). In a reciprocal fashion, Tsn1 (Translin) serves to repress levels of transcripts (TERRAs) from the telomeric repeats, whereas Tfx1 serves to maintain these elevated levels. This reveals a novel mechanism for the regulation of telomeric transcripts. We extend this to demonstrate that human Translin and Trax also control telomere-associated transcript levels in human cells in a telomere-specific fashion. PMID:27183912

  4. Mathematical model of alternative mechanism of telomere length maintenance

    NASA Astrophysics Data System (ADS)

    Kollár, Richard; Bod'ová, Katarína; Nosek, Jozef; Tomáška, L'ubomír

    2014-03-01

    Biopolymer length regulation is a complex process that involves a large number of biological, chemical, and physical subprocesses acting simultaneously across multiple spatial and temporal scales. An illustrative example important for genomic stability is the length regulation of telomeres—nucleoprotein structures at the ends of linear chromosomes consisting of tandemly repeated DNA sequences and a specialized set of proteins. Maintenance of telomeres is often facilitated by the enzyme telomerase but, particularly in telomerase-free systems, the maintenance of chromosomal termini depends on alternative lengthening of telomeres (ALT) mechanisms mediated by recombination. Various linear and circular DNA structures were identified to participate in ALT, however, dynamics of the whole process is still poorly understood. We propose a chemical kinetics model of ALT with kinetic rates systematically derived from the biophysics of DNA diffusion and looping. The reaction system is reduced to a coagulation-fragmentation system by quasi-steady-state approximation. The detailed treatment of kinetic rates yields explicit formulas for expected size distributions of telomeres that demonstrate the key role played by the J factor, a quantitative measure of bending of polymers. The results are in agreement with experimental data and point out interesting phenomena: an appearance of very long telomeric circles if the total telomere density exceeds a critical value (excess mass) and a nonlinear response of the telomere size distributions to the amount of telomeric DNA in the system. The results can be of general importance for understanding dynamics of telomeres in telomerase-independent systems as this mode of telomere maintenance is similar to the situation in tumor cells lacking telomerase activity. Furthermore, due to its universality, the model may also serve as a prototype of an interaction between linear and circular DNA structures in various settings.

  5. Telomere length and cortisol reactivity in children of depressed mothers.

    PubMed

    Gotlib, I H; LeMoult, J; Colich, N L; Foland-Ross, L C; Hallmayer, J; Joormann, J; Lin, J; Wolkowitz, O M

    2015-05-01

    A growing body of research demonstrates that individuals diagnosed with major depressive disorder (MDD) are characterized by shortened telomere length, which has been posited to underlie the association between depression and increased instances of medical illness. The temporal nature of the relation between MDD and shortened telomere length, however, is not clear. Importantly, both MDD and telomere length have been associated independently with high levels of stress, implicating dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and anomalous levels of cortisol secretion in this relation. Despite these associations, no study has assessed telomere length or its relation with HPA-axis activity in individuals at risk for depression, before the onset of disorder. In the present study, we assessed cortisol levels in response to a laboratory stressor and telomere length in 97 healthy young daughters of mothers either with recurrent episodes of depression (i.e., daughters at familial risk for depression) or with no history of psychopathology. We found that daughters of depressed mothers had shorter telomeres than did daughters of never-depressed mothers and, further, that shorter telomeres were associated with greater cortisol reactivity to stress. This study is the first to demonstrate that children at familial risk of developing MDD are characterized by accelerated biological aging, operationalized as shortened telomere length, before they had experienced an onset of depression; this may predispose them to develop not only MDD but also other age-related medical illnesses. It is critical, therefore, that we attempt to identify and distinguish genetic and environmental mechanisms that contribute to telomere shortening.

  6. ORNL FISH Telomere Segmentation GUI and Instruction Manual

    2002-12-01

    The ORNL FISH Telomere Segmentation GUI takes images of cellular chromosomes and telomeres obtained through Fluorescent in-situ Hybridization and automatically labels the pixels that belong to the chromosomes and telomeres, which are cellular structures of interest to cancer researchers. The process of labeling the pixels is called segmentation. The resulting segmentation can be edited through the use of an extensive graphical user-interface or GUI, saved, and exported to a data file suitable for use withmore » data analysis programs such as Microsoft Excel.« less

  7. ORNL FISH Telomere Segmentation GUI and Instruction Manual

    SciTech Connect

    2002-12-01

    The ORNL FISH Telomere Segmentation GUI takes images of cellular chromosomes and telomeres obtained through Fluorescent in-situ Hybridization and automatically labels the pixels that belong to the chromosomes and telomeres, which are cellular structures of interest to cancer researchers. The process of labeling the pixels is called segmentation. The resulting segmentation can be edited through the use of an extensive graphical user-interface or GUI, saved, and exported to a data file suitable for use with data analysis programs such as Microsoft Excel.

  8. Time of replication of yeast centromeres and telomeres.

    PubMed

    McCarroll, R M; Fangman, W L

    1988-08-12

    The time of replication of centromeres and telomeres of the yeast S. cerevisiae was determined by performing Meselson-Stahl experiments with synchronized cells. The nine centromeres examined become hybrid in density early in S phase, eliminating the possibility that a delay in the replication of centromeres until mitosis is responsible for sister chromatid adherence and proper chromosome segregation at anaphase. The conserved sequence element Y', present at most telomeres, replicates late in S phase, as do the unique sequences adjacent to five specific telomeres. The early and late replication times of these structural elements may be either essential for their proper function or a consequence of some architectural feature of the chromosome.

  9. Telomere Lengths and Telomerase Activity in Dog Tissues: A Potential Model System to Study Human Telomere and Telomerase Biology

    PubMed Central

    Nasir, Lubna; Devlin, Pauline; Mckevitt, Tom; Rutteman, Gerard; Argyle, David J

    2001-01-01

    Abstract Studies on telomere and telomerase biology are fundamental to the understanding of aging and age-related diseases such as cancer. However, human studies have been hindered by differences in telomere biology between humans and the classical murine animal model system. In this paper, we describe basic studies of telomere length and telomerase activity in canine normal and neoplastic tissues and propose the dog as an alternative model system. Briefly, telomere lengths were measured in normal canine peripheral blood mononuclear cells (PBMCs), a range of normal canine tissues, and in a panel of naturally occurring soft tissue tumours by terminal restriction fragment (TRF) analysis. Further, telomerase activity was measured in canine cell lines and multiple canine tissues using a combined polymerase chain reaction/enzyme-linked immunosorbent assay method. TRF analysis in canine PBMCs and tissues demonstrated mean TRF lengths to range between 12 and 23 kbp with heterogeneity in telomere lengths being observed in a range of normal somatic tissues. In soft tissue sarcomas, two subgroups were identified with mean TRFs of 22.2 and 18.2 kbp. Telomerase activity in canine tissue was present in tumour tissue and testis with little or no activity in normal somatic tissues. These results suggest that the dog telomere biology is similar to that in humans and may represent an alternative model system for studying telomere biology and telomerase-targeted anticancer therapies. PMID:11571635

  10. Single-strand DNA binding protein SSB1 facilitates TERT recruitment to telomeres and maintains telomere G-overhangs

    PubMed Central

    Pandita, Raj K.; Chow, Tracy T.; Udayakumar, Durga; Bain, Amanda L.; Cubeddu, Liza; Hunt, Clayton R.; Shi, Wei; Horikoshi, Nobuo; Zhao, Yong; Wright, Woodring E.; Khanna, Kum Kum; Shay, Jerry W.; Pandita, Tej K.

    2015-01-01

    Proliferating mammalian stem and cancer cells express telomerase (TERT) in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA binding protein SSB1, which has a critical role in DNA double-strand break repair. Here we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacted with the TERT catalytic subunit and regulates its interaction with telomeres. Deletion of SSB1 reduced TERT interaction with telomeres and lead to G-overhang loss. While SSB1 was recruited to DSB sites, we found no corresponding change in TERT levels at these sites, implying that SSB1-TERT interaction relied upon a specific chromatin structure or context. Our findings offer an explanation for how telomerase is recruited to telomeres to facilitate G-strand DNA extension, a critical step in maintaining telomere ends and cell viability in all cancer cells. PMID:25589350

  11. Telomere- and Telomerase-Associated Proteins and Their Functions in the Plant Cell

    PubMed Central

    Procházková Schrumpfová, Petra; Schořová, Šárka; Fajkus, Jiří

    2016-01-01

    Telomeres, as physical ends of linear chromosomes, are targets of a number of specific proteins, including primarily telomerase reverse transcriptase. Access of proteins to the telomere may be affected by a number of diverse factors, e.g., protein interaction partners, local DNA or chromatin structures, subcellular localization/trafficking, or simply protein modification. Knowledge of composition of the functional nucleoprotein complex of plant telomeres is only fragmentary. Moreover, the plant telomeric repeat binding proteins that were characterized recently appear to also be involved in non-telomeric processes, e.g., ribosome biogenesis. This interesting finding was not totally unexpected since non-telomeric functions of yeast or animal telomeric proteins, as well as of telomerase subunits, have been reported for almost a decade. Here we summarize known facts about the architecture of plant telomeres and compare them with the well-described composition of telomeres in other organisms. PMID:27446102

  12. Schizosaccharomyces pombe protection of telomeres 1 utilizes alternate binding modes to accommodate different telomeric sequences.

    PubMed

    Altschuler, Sarah E; Dickey, Thayne H; Wuttke, Deborah S

    2011-09-01

    The ends of eukaryotic chromosomes consist of long tracts of repetitive GT-rich DNA with variable sequence homogeneity between and within organisms. Telomeres terminate in a conserved 3'-ssDNA overhang that, regardless of sequence variability, is specifically and tightly bound by proteins of the telomere-end protection family. The high affinity ssDNA-binding activity of S. pombe Pot1 protein (SpPot1) is conferred by a DNA-binding domain consisting of two subdomains, Pot1pN and Pot1pC. Previous work has shown that Pot1pN binds a single repeat of the core telomere sequence (GGTTAC) with exquisite specificity, while Pot1pC binds an extended sequence of nine nucleotides (GGTTACGGT) with modest specificity requirements. We find that full-length SpPot1 binds the composite 15mer, (GGTTAC)(2)GGT, and a shorter two-repeat 12mer, (GGTTAC)(2), with equally high affinity (<3 pM), but with substantially different kinetic and thermodynamic properties. The binding mode of the SpPot1/15mer complex is more stable than that of the 12mer complex, with a 2-fold longer half-life and increased tolerance to nucleotide and amino acid substitutions. Our data suggest that SpPot1 protection of heterogeneous telomeres is mediated through 5'-sequence recognition and the use of alternate binding modes to maintain high affinity interaction with the G-strand, while simultaneously discriminating against the complementary strand.

  13. Finding a human telomere DNA-RNA hybrid G-quadruplex formed by human telomeric 6-mer RNA and 16-mer DNA using click chemistry: a protective structure for telomere end.

    PubMed

    Xu, Yan; Suzuki, Yuta; Ishizuka, Takumi; Xiao, Chao-Da; Liu, Xiao; Hayashi, Tetsuya; Komiyama, Makoto

    2014-08-15

    Telomeric repeat-containing RNA is a non-coding RNA molecule newly found in mammalian cells. The telomere RNA has been found to localize to the telomere DNA, but how the newly discovered RNA molecule interacts with telomere DNA is less known. In this study, using the click chemistry we successfully found that a 6-mer human telomere RNA and 16-mer human telomere DNA sequence can form a DNA-RNA hybrid type G-quadruplex structure. Detection of the click-reaction products directly probes DNA-RNA G-quadruplex structures in a complicated solution, whereas traditional methods such as NMR and crystallography may not be suitable. Importantly, we found that formation of DNA-RNA G-quadruplex induced an exonuclease resistance for telomere DNA, indicating that such structures might be important for protecting telomeric DNA from enzyme digestion to avoid telomere DNA shortening. These results provide the direct evidence for formation of DNA-RNA hybrid G-quadruplex structure by human telomere DNA and RNA sequence, suggesting DNA-RNA hybrid G-quadruplex structure associated between telomere DNA and RNA may respond to chromosome end protection and/or present a valuable target for drug design.

  14. CpG-island promoters drive transcription of human telomeres

    PubMed Central

    Nergadze, Solomon G.; Farnung, Benjamin O.; Wischnewski, Harry; Khoriauli, Lela; Vitelli, Valerio; Chawla, Raghav; Giulotto, Elena; Azzalin, Claus M.

    2009-01-01

    The longstanding dogma that telomeres, the heterochromatic extremities of linear eukaryotic chromosomes, are transcriptionally silent was overturned by the discovery that DNA-dependent RNA polymerase II (RNAPII) transcribes telomeric DNA into telomeric repeat-containing RNA (TERRA). Here, we show that CpG dinucleotide-rich DNA islands, shared among multiple human chromosome ends, promote transcription of TERRA molecules. TERRA promoters sustain cellular expression of reporter genes, are located immediately upstream of TERRA transcription start sites, and are bound by active RNAPII in vivo. Finally, the identified promoter CpG dinucleotides are methylated in vivo, and cytosine methylation negatively regulates TERRA abundance. The existence of subtelomeric promoters, driving TERRA transcription from independent chromosome ends, supports the idea that TERRA exerts fundamental functions in the context of telomere biology. PMID:19850908

  15. Mutations in Ran system affected telomere silencing in Saccharomyces cerevisiae

    SciTech Connect

    Hayashi, Naoyuki Kobayashi, Masahiko; Shimizu, Hiroko; Yamamoto, Ken-ichi; Murakami, Seishi; Nishimoto, Takeharu

    2007-11-23

    The Ran GTPase system regulates the direction and timing of several cellular events, such as nuclear-cytosolic transport, centrosome formation, and nuclear envelope assembly in telophase. To gain insight into the Ran system's involvement in chromatin formation, we investigated gene silencing at the telomere in several mutants of the budding yeast Saccharomyces cerevisiae, which had defects in genes involved in the Ran system. A mutation of the RanGAP gene, rna1-1, caused reduced silencing at the telomere, and partial disruption of the nuclear Ran binding factor, yrb2-{delta}2, increased this silencing. The reduced telomere silencing in rna1-1 cells was suppressed by a high dosage of the SIR3 gene or the SIT4 gene. Furthermore, hyperphosphorylated Sir3 protein accumulated in the rna1-1 mutant. These results suggest that RanGAP is required for the heterochromatin structure at the telomere in budding yeast.

  16. Mild oxidative stress is beneficial for sperm telomere length maintenance

    PubMed Central

    Mishra, Swetasmita; Kumar, Rajeev; Malhotra, Neena; Singh, Neeta; Dada, Rima

    2016-01-01

    AIM: To evaluate telomere length in sperm DNA and its correlation with oxidative stress (normal, mild, severe). METHODS: The study included infertile men (n = 112) and age matched fertile controls (n = 102). The average telomere length from the sperm DNA was measured using a quantitative real time PCR based assay. Seminal reactive oxygen species (ROS) and 8-Isoprostane (8-IP) levels were measured by chemiluminescence assay and ELISA respectively. RESULTS: Average sperm telomere length in infertile men and controls was 0.609 ± 0.15 and 0.789 ± 0.060, respectively (P < 0.0001). Seminal ROS levels in infertile was higher [66.61 ± 28.32 relative light units (RLU)/s/million sperm] than in controls (14.04 ± 10.67 RLU/s/million sperm) (P < 0.0001). The 8-IP level in infertile men was significantly higher (421.55 ± 131.29 pg/mL) than in controls (275.94 ± 48.13 pg/mL) (P < 0.001). When correlated to oxidative stress, in normal range of oxidative stress (ROS, 0-21.3 RLU/s/million sperm) the average telomere length in cases was 0.663 ± 0.14, in mild oxidative stress (ROS, 21.3-35 RLU/s/million sperm) it was elevated (0.684 ± 0.12) and in severe oxidative stress (ROS > 35 RLU/s/million sperm) average telomere length was decreased to 0.595 ± 0.15. CONCLUSION: Mild oxidative stress results in lengthening of telomere length, but severe oxidative stress results in shorter telomeres. Although telomere maintenance is a complex trait, the study shows that mild oxidative stress is beneficial in telomere length maintenance and thus a delicate balance needs to be established to maximize the beneficial effects of free radicals and prevent harmful effects of supra physiological levels. Detailed molecular evaluation of telomere structure, its correlation with oxidative stress would aid in elucidating the cause of accelerated telomere length attrition. PMID:27376021

  17. Interstitial telomeric sequences in human chromosomes cluster with common fragile sites, mutagen sensitive sites, viral integration sites, cancer breakpoints, proto-oncogenes and breakpoints involved in primate evolution

    SciTech Connect

    Adekunle, S.S.A.; Wyandt, H.; Mark, H.F.L.

    1994-09-01

    Recently we mapped the telomeric repeat sequences to 111 interstitial sites in the human genome and to sites of gaps and breaks induced by aphidicolin and sister chromatid exchange sites detected by BrdU. Many of these sites correspond to conserved fragile sites in man, gorilla and chimpazee, to sites of conserved sister chromatid exchange in the mammalian X chromosome, to mutagenic sensitive sites, mapped locations of proto-oncogenes, breakpoints implicated in primate evolution and to breakpoints indicated as the sole anomaly in neoplasia. This observation prompted us to investigate if the interstitial telomeric sites cluster with these sites. An extensive literature search was carried out to find all the available published sites mentioned above. For comparison, we also carried out a statistical analysis of the clustering of the sites of the telomeric repeats with the gene locations where only nucleotide mutations have been observed as the only chromosomal abnormality. Our results indicate that the telomeric repeats cluster most with fragile sites, mutagenic sensitive sites and breakpoints implicated in primate evolution and least with cancer breakpoints, mapped locations of proto-oncogenes and other genes with nucleotide mutations.

  18. Telomere Fragment Induced Amnion Cell Senescence: A Contributor to Parturition?

    PubMed

    Polettini, Jossimara; Behnia, Faranak; Taylor, Brandie D; Saade, George R; Taylor, Robert N; Menon, Ramkumar

    2015-01-01

    Oxidative stress (OS)-induced senescence of the amniochorion has been associated with parturition at term. We investigated whether telomere fragments shed into the amniotic fluid (AF) correlated with labor status and tested if exogenous telomere fragments (T-oligos) could induce human and murine amnion cell senescence. In a cross-sectional clinical study, AF telomere fragment concentrations quantitated by a validated real-time PCR assay were higher in women in labor at term compared to those not in labor. In vitro treatment of primary human amnion epithelial cells with 40 μM T-oligos ([TTAGGG]2) that mimic telomere fragments, activated p38MAPK, produced senescence-associated (SA) β-gal staining and increased interleukin (IL)-6 and IL-8 production compared to cells treated with complementary DNA sequences (Cont-oligos, [AATCCC]2). T-oligos injected into the uteri of pregnant CD1 mice on day 14 of gestation, led to increased p38MAPK, SA-β-gal (SA β-gal) staining in murine amniotic sacs and higher AF IL-8 levels on day 18, compared to saline treated controls. In summary, term labor AF samples had higher telomere fragments than term not in labor AF. In vitro and in situ telomere fragments increased human and murine amnion p38MAPK, senescence and inflammatory cytokines. We propose that telomere fragments released from senescent fetal cells are indicative of fetal cell aging. Based on our data, these telomere fragments cause oxidative stress associated damages to the term amniotic sac and force them to release other DAMPS, which, in turn, provide a sterile immune response that may be one of the many inflammatory signals required to initiate parturition at term.

  19. Telomere Fragment Induced Amnion Cell Senescence: A Contributor to Parturition?

    PubMed Central

    Polettini, Jossimara; Behnia, Faranak; Taylor, Brandie D.; Saade, George R.; Taylor, Robert N.; Menon, Ramkumar

    2015-01-01

    Oxidative stress (OS)-induced senescence of the amniochorion has been associated with parturition at term. We investigated whether telomere fragments shed into the amniotic fluid (AF) correlated with labor status and tested if exogenous telomere fragments (T-oligos) could induce human and murine amnion cell senescence. In a cross-sectional clinical study, AF telomere fragment concentrations quantitated by a validated real-time PCR assay were higher in women in labor at term compared to those not in labor. In vitro treatment of primary human amnion epithelial cells with 40 μM T-oligos ([TTAGGG]2) that mimic telomere fragments, activated p38MAPK, produced senescence-associated (SA) β-gal staining and increased interleukin (IL)-6 and IL-8 production compared to cells treated with complementary DNA sequences (Cont-oligos, [AATCCC]2). T-oligos injected into the uteri of pregnant CD1 mice on day 14 of gestation, led to increased p38MAPK, SA-β-gal (SA β-gal) staining in murine amniotic sacs and higher AF IL-8 levels on day 18, compared to saline treated controls. In summary, term labor AF samples had higher telomere fragments than term not in labor AF. In vitro and in situ telomere fragments increased human and murine amnion p38MAPK, senescence and inflammatory cytokines. We propose that telomere fragments released from senescent fetal cells are indicative of fetal cell aging. Based on our data, these telomere fragments cause oxidative stress associated damages to the term amniotic sac and force them to release other DAMPS, which, in turn, provide a sterile immune response that may be one of the many inflammatory signals required to initiate parturition at term. PMID:26397719

  20. Telomeres and their possible role in chromosome stabilization

    SciTech Connect

    Day, J.P.; Marder, B.A.; Morgan, W.F. )

    1993-01-01

    The evidence to date generally supports the hypothesis that telomere capping makes chromosome fragments refractory to subsequent rejoining events, but this control may be somewhat relaxed after chromosome breakage. Cell survival requires that the fragments rejoin before metaphase. Unprotected ends such as those produced by DNA damage are subject to degradation, presumably by endogenous cellular exo- and endonucleases. Telomere repeat sequences may be added to broken chromosome ends to protect the ends from further degradation. That telomeric DNA does not always prevent rejoining raises interesting questions as to what constitutes capping, and how rapidly it occurs after DNA damage in relation to chromosome break rejoining. The prevention of degradation and control of rejoining may be mediated by telomere-specific binding proteins, especially the telomere terminal binding protein. Some of these proteins may be involved in scavenging telomeric DNA when the cell senses that chromosomal breaks have occurred. Although chromosome break rejoining is an efficient process in eukaryotic cells, some breaks are never rejoined and can result in terminal delections and chromatid and isochromatid deletions at metaphase. It is unclear why these breaks are not rejoined, but it may be due to one or more of the following: (1) chance: broken chromosomes are separated, do not approach sufficiently close to one another, and are consequently physically unable to rejoin; (2) a large number of added telomere repeat sequences indicating to the cell that the chromosome has an authentic telomere; (3) some other DNA modification event that protects DNA ends from degradation, e.g., folding back of DNA ends to form a hairpin, as has been implicated in VDJ recombination.

  1. Molecular adaptation of telomere associated genes in mammals

    PubMed Central

    2013-01-01

    Background Placental mammals display a huge range of life history traits, including size, longevity, metabolic rate and germ line generation time. Although a number of general trends have been proposed between these traits, there are exceptions that warrant further investigation. Species such as naked mole rat, human and certain bat species all exhibit extreme longevity with respect to body size. It has long been established that telomeres and telomere maintenance have a clear role in ageing but it has not yet been established whether there is evidence for adaptation in telomere maintenance proteins that could account for increased longevity in these species. Results Here we carry out a molecular investigation of selective pressure variation, specifically focusing on telomere associated genes across placental mammals. In general we observe a large number of instances of positive selection acting on telomere genes. Although these signatures of selection overall are not significantly correlated with either longevity or body size we do identify positive selection in the microbat species Myotis lucifugus in functionally important regions of the telomere maintenance genes DKC1 and TERT, and in naked mole rat in the DNA repair gene BRCA1. Conclusion These results demonstrate the multifarious selective pressures acting across the mammal phylogeny driving lineage-specific adaptations of telomere associated genes. Our results show that regardless of the longevity of a species, these proteins have evolved under positive selection thereby removing increased longevity as the single selective force driving this rapid rate of evolution. However, evidence of molecular adaptations specific to naked mole rat and Myotis lucifugus highlight functionally significant regions in genes that may alter the way in which telomeres are regulated and maintained in these longer-lived species. PMID:24237966

  2. Impaired Telomere Maintenance and Decreased Canonical WNT Signaling but Normal Ribosome Biogenesis in Induced Pluripotent Stem Cells from X-Linked Dyskeratosis Congenita Patients

    PubMed Central

    Gu, Bai-Wei; Apicella, Marisa; Mills, Jason; Fan, Jian-Meng; Reeves, Dara A.; French, Deborah; Podsakoff, Gregory M.; Bessler, Monica; Mason, Philip J.

    2015-01-01

    Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome characterized by the presence of short telomeres at presentation. Mutations in ten different genes, whose products are involved in the telomere maintenance pathway, have been shown to cause DC. The X-linked form is the most common form of the disease and is caused by mutations in the gene DKC1, encoding the protein dyskerin. Dyskerin is required for the assembly and stability of telomerase and is also involved in ribosomal RNA (rRNA) processing where it converts specific uridines to pseudouridine. DC is thought to result from failure to maintain tissues, like blood, that are renewed by stem cell activity, but research into pathogenic mechanisms has been hampered by the difficulty of obtaining stem cells from patients. We reasoned that induced pluripotent stem (iPS) cells from X-linked DC patients may provide information about the mechanisms involved. Here we describe the production of iPS cells from DC patients with DKC1 mutations Q31E, A353V and ΔL37. In addition we constructed “corrected” lines with a copy of the wild type dyskerin cDNA expressed from the AAVS1 safe harbor locus. We show that in iPS cells with DKC1 mutations telomere maintenance is compromised with short telomere lengths and decreased telomerase activity. The degree to which telomere lengths are affected by expression of telomerase during reprograming, or with ectopic expression of wild type dyskerin, is variable. The recurrent mutation A353V shows the most severe effect on telomere maintenance. A353V cells but not Q31E or ΔL37 cells, are refractory to correction by expression of wild type DKC1 cDNA. Because dyskerin is involved in both telomere maintenance and ribosome biogenesis it has been postulated that defective ribosome biogenesis and translation may contribute to the disease phenotype. Evidence from mouse and zebra fish models has supported the involvement of ribosome biogenesis but primary cells from human

  3. Human Rap1 modulates TRF2 attraction to telomeric DNA

    PubMed Central

    Janoušková, Eliška; Nečasová, Ivona; Pavloušková, Jana; Zimmermann, Michal; Hluchý, Milan; Marini, Victoria; Nováková, Monika; Hofr, Ctirad

    2015-01-01

    More than two decades of genetic research have identified and assigned main biological functions of shelterin proteins that safeguard telomeres. However, a molecular mechanism of how each protein subunit contributes to the protecting function of the whole shelterin complex remains elusive. Human Repressor activator protein 1 (Rap1) forms a multifunctional complex with Telomeric Repeat binding Factor 2 (TRF2). Rap1–TRF2 complex is a critical part of shelterin as it suppresses homology-directed repair in Ku 70/80 heterodimer absence. To understand how Rap1 affects key functions of TRF2, we investigated full-length Rap1 binding to TRF2 and Rap1–TRF2 complex interactions with double-stranded DNA by quantitative biochemical approaches. We observed that Rap1 reduces the overall DNA duplex binding affinity of TRF2 but increases the selectivity of TRF2 to telomeric DNA. Additionally, we observed that Rap1 induces a partial release of TRF2 from DNA duplex. The improved TRF2 selectivity to telomeric DNA is caused by less pronounced electrostatic attractions between TRF2 and DNA in Rap1 presence. Thus, Rap1 prompts more accurate and selective TRF2 recognition of telomeric DNA and TRF2 localization on single/double-strand DNA junctions. These quantitative functional studies contribute to the understanding of the selective recognition of telomeric DNA by the whole shelterin complex. PMID:25675958

  4. Telomere attrition and Chk2 activation in human heart failure

    PubMed Central

    Oh, Hidemasa; Wang, Sam C.; Prahash, Arun; Sano, Motoaki; Moravec, Christine S.; Taffet, George E.; Michael, Lloyd H.; Youker, Keith A.; Entman, Mark L.; Schneider, Michael D.

    2003-01-01

    The “postmitotic” phenotype in adult cardiac muscle exhibits similarities to replicative senescence more generally and constitutes a barrier to effective restorative growth in heart disease. Telomere dysfunction is implicated in senescence and apoptotic signaling but its potential role in heart disorders is unknown. Here, we report that cardiac apoptosis in human heart failure is associated specifically with defective expression of the telomere repeat- binding factor TRF2, telomere shortening, and activation of the DNA damage checkpoint kinase, Chk2. In cultured cardiomyocytes, interference with either TRF2 function or expression triggered telomere erosion and apoptosis, indicating that cell death can occur via this pathway even in postmitotic, noncycling cells; conversely, exogenous TRF2 conferred protection from oxidative stress. In vivo, mechanical stress was sufficient to down-regulate TRF2, shorten telomeres, and activate Chk2 in mouse myocardium, and transgenic expression of telomerase reverse transcriptase conferred protection from all three responses. Together, these data suggest that apoptosis in chronic heart failure is mediated in part by telomere dysfunction and suggest an essential role for TRF2 even in postmitotic cells. PMID:12702777

  5. Telomere dynamics in the lower plant Physcomitrella patens.

    PubMed

    Fojtová, Miloslava; Sýkorová, Eva; Najdekrová, Lucie; Polanská, Pavla; Zachová, Dagmar; Vagnerová, Radka; Angelis, Karel J; Fajkus, Jiří

    2015-04-01

    A comparative approach in biology is needed to assess the universality of rules governing this discipline. In plant telomere research, most of the key principles were established based on studies in only single model plant, Arabidopsis thaliana. These principles include the absence of telomere shortening during plant development and the corresponding activity of telomerase in dividing (meristem) plant cells. Here we examine these principles in Physcomitrella patens as a representative of lower plants. To follow telomerase expression, we first characterize the gene coding for the telomerase reverse transcriptase subunit PpTERT in P. patens, for which only incomplete prediction has been available so far. In protonema cultures of P. patens, growing by filament apical cell division, the proportion of apical (dividing) cells was quantified and telomere length, telomerase expression and activity were determined. Our results show telomere stability and demonstrate proportionality of telomerase activity and expression with the number of apical cells. In addition, we analyze telomere maintenance in mre11, rad50, nbs1, ku70 and lig4 mutants of P. patens and compare the impact of these mutations in double-strand-break (DSB) repair pathways with earlier observations in corresponding A. thaliana mutants. Telomere phenotypes are absent and DSB repair kinetics is not affected in P. patens mutants for DSB factors involved in non-homologous end joining (NHEJ). This is compliant with the overall dominance of homologous recombination over NHEJ pathways in the moss, contrary to the inverse situation in flowering plants.

  6. Telomere Transcripts Target Telomerase in Human Cancer Cells.

    PubMed

    Kreilmeier, Theresa; Mejri, Doris; Hauck, Marlene; Kleiter, Miriam; Holzmann, Klaus

    2016-01-01

    Long non-coding transcripts from telomeres, called telomeric repeat-containing RNA (TERRA), were identified as blocking telomerase activity (TA), a telomere maintenance mechanism (TMM), in tumors. We expressed recombinant TERRA transcripts in tumor cell lines with TA and with alternative lengthening of telomeres (ALT) to study effects on TMM and cell growth. Adeno- and lentivirus constructs (AV and LV) were established for transient and stable expression of approximately 130 units of telomere hexanucleotide repeats under control of cytomegalovirus (CMV) and human RNase P RNA H1 (hH1) promoters with and without polyadenylation, respectively. Six human tumor cell lines either using telomerase or ALT were infected and analyzed for TA levels. Pre-infection cells using telomerase had 1%-3% of the TERRA expression levels of ALT cells. AV and LV expression of recombinant TERRA in telomerase positive cells showed a 1.3-2.6 fold increase in TERRA levels, and a decrease in TA of 25%-58%. Dominant-negative or small hairpin RNA (shRNA) viral expression against human telomerase reverse transcriptase (hTERT) results in senescence, not induced by TERRA expression. Population doubling time, cell viability and TL (telomere length) were not impacted by ectopic TERRA expression. Clonal growth was reduced by TERRA expression in TA but not ALT cell lines. ALT cells were not affected by treatments applied. Established cell models and tools may be used to better understand the role of TERRA in the cell, especially for targeting telomerase. PMID:27537914

  7. Telomeric Trans-Silencing in Drosophila melanogaster: Tissue Specificity, Development and Functional Interactions between Non-Homologous Telomeres

    PubMed Central

    Josse, Thibaut; Maurel-Zaffran, Corinne; de Vanssay, Augustin; Teysset, Laure; Todeschini, Anne-Laure; Delmarre, Valerie; Chaminade, Nicole; Anxolabéhère, Dominique; Ronsseray, Stéphane

    2008-01-01

    Background The study of P element repression in Drosophila melanogaster led to the discovery of the telomeric Trans-Silencing Effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin (Telomeric Associated Sequences, “TAS”) has the capacity to repress in trans, in the female germline, a homologous P-lacZ transgene located in euchromatin. TSE can show variegation in ovaries, displays a maternal effect as well as an epigenetic transmission through meiosis and involves heterochromatin and RNA silencing pathways. Principal Findings Here, we analyze phenotypic and genetic properties of TSE. We report that TSE does not occur in the soma at the adult stage, but appears restricted to the female germline. It is detectable during development at the third instar larvae where it presents the same tissue specificity and maternal effect as in adults. Transgenes located in TAS at the telomeres of the main chromosomes can be silencers which in each case show the maternal effect. Silencers located at non-homologous telomeres functionally interact since they stimulate each other via the maternally-transmitted component. All germinally-expressed euchromatic transgenes tested, located on all major chromosomes, were found to be repressed by a telomeric silencer: thus we detected no TSE escaper. The presence of the euchromatic target transgene is not necessary to establish the maternal inheritance of TSE, responsible for its epigenetic behavior. A single telomeric silencer locus can simultaneously repress two P-lacZ targets located on different chromosomal arms. Conclusions and Significance Therefore TSE appears to be a widespread phenomenon which can involve different telomeres and work across the genome. It can explain the P cytotype establishment by telomeric P elements in natural Drosophila populations. PMID:18813361

  8. Factors that influence telomeric oxidative base damage and repair by DNA glycosylase OGG1

    PubMed Central

    Rhee, David B.; Ghosh, Avik; Lu, Jian; Bohr, Vilhelm A.; Liu, Yie

    2010-01-01

    Telomeres are nucleoprotein complexes at the ends of linear chromosomes in eukaryotes, and are essential in preventing chromosome termini from being recognized as broken DNA ends. Telomere shortening has been linked to cellular senescence and human aging, with oxidative stress as a major contributing factor. 7, 8-dihydro-8-oxogaunine (8-oxodG) is one of the most abundant oxidative guanine lesions, and 8-oxoguanine DNA Glycosylase (OGG1) is involved in its removal. In this study, we examined if telomeric DNA is particularly susceptible to oxidative base damage and if telomere-specific factors affect the incision of oxidized guanines by OGG1. We demonstrated that telomeric TTAGGG repeats were more prone to oxidative base damage and repaired less efficiently than non-telomeric TG repeats in vivo. We also showed that the 8-oxodG-incision activity of OGG1 is similar in telomeric and non-telomeric double-stranded substrates. In addition, telomere repeat binding factors TRF1 and TRF2 do not impair OGG1 incision activity. Yet, 8-oxodG in some telomere structures (e.g., fork-opening, 3’-overhang, and D-loop) were less effectively excised by OGG1, depending upon its position in these substrates. Collectively, our data indicate that the sequence context of telomere repeats and certain telomere configurations may contribute to telomere vulnerability to oxidative DNA damage processing. PMID:20951653

  9. Tooth - abnormal shape

    MedlinePlus

    Hutchinson incisors; Abnormal tooth shape; Peg teeth; Mulberry teeth; Conical teeth ... The appearance of normal teeth varies, especially the molars. ... conditions. Specific diseases can affect tooth shape, tooth ...

  10. Automated Assay of Telomere Length Measurement and Informatics for 100,000 Subjects in the Genetic Epidemiology Research on Adult Health and Aging (GERA) Cohort

    PubMed Central

    Lapham, Kyle; Kvale, Mark N.; Lin, Jue; Connell, Sheryl; Croen, Lisa A.; Dispensa, Brad P.; Fang, Lynn; Hesselson, Stephanie; Hoffmann, Thomas J.; Iribarren, Carlos; Jorgenson, Eric; Kushi, Lawrence H.; Ludwig, Dana; Matsuguchi, Tetsuya; McGuire, William B.; Miles, Sunita; Quesenberry, Charles P.; Rowell, Sarah; Sadler, Marianne; Sakoda, Lori C.; Smethurst, David; Somkin, Carol P.; Van Den Eeden, Stephen K.; Walter, Lawrence; Whitmer, Rachel A.; Kwok, Pui-Yan; Risch, Neil; Schaefer, Catherine; Blackburn, Elizabeth H.

    2015-01-01

    The Kaiser Permanente Research Program on Genes, Environment, and Health (RPGEH) Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort includes DNA specimens extracted from saliva samples of 110,266 individuals. Because of its relationship to aging, telomere length measurement was considered an important biomarker to develop on these subjects. To assay relative telomere length (TL) on this large cohort over a short time period, we created a novel high throughput robotic system for TL analysis and informatics. Samples were run in triplicate, along with control samples, in a randomized design. As part of quality control, we determined the within-sample variability and employed thresholds for the elimination of outlying measurements. Of 106,902 samples assayed, 105,539 (98.7%) passed all quality control (QC) measures. As expected, TL in general showed a decline with age and a sex difference. While telomeres showed a negative correlation with age up to 75 years, in those older than 75 years, age positively correlated with longer telomeres, indicative of an association of longer telomeres with more years of survival in those older than 75. Furthermore, while females in general had longer telomeres than males, this difference was significant only for those older than age 50. An additional novel finding was that the variance of TL between individuals increased with age. This study establishes reliable assay and analysis methodologies for measurement of TL in large, population-based human studies. The GERA cohort represents the largest currently available such resource, linked to comprehensive electronic health and genotype data for analysis. PMID:26092717

  11. Interaction of Telomeric Retroelement HeT-A Transcripts and Their Protein Product Gag in Early Embryogenesis of Drosophila.

    PubMed

    Olovnikov, I A; Morgunova, V V; Mironova, A A; Kordyukova, M Y; Radion, E I; Olenkina, O M; Akulenko, N V; Kalmykova, A I

    2016-09-01

    The telomere is a nucleoprotein complex at the ends of linear chromosomes that protects them from fusion and degradation. The telomere consists of telomeric DNA, a protective protein complex and telomeric RNA. Biogenesis of telomeric transcripts in development is still far from being understood. Drosophila telomeres are elongated by a transposition of specialized telomeric retrotransposons that encode proteins. Using transgenic constructs encoding tagged telomeric protein, we found that transcripts of Drosophila telomeric element HeT-A bind Gag-HeT-A protein encoded by these transcripts. Maternal HeT-A transcripts and Gag-HeT-A form ribonucleoprotein granules around centrosomes, centers of microtubule organization, during blastoderm formation, upon disruption of telomere silencing during oogenesis. The specific localization of HeT-A RNA is dependent on microtubules since disruption of microtubules caused delocalization of HeT-A transcripts. This transgenic system is a valuable model for the study of telomeric RNA biogenesis. PMID:27682174

  12. DNA profiling, telomere analysis and antioxidant properties as tools for monitoring ex situ seed longevity

    PubMed Central

    Donà, M.; Balestrazzi, A.; Mondoni, A.; Rossi, G.; Ventura, L.; Buttafava, A.; Macovei, A.; Sabatini, M. E.; Valassi, A.; Carbonera, D.

    2013-01-01

    deeper insights to study seed viability during storage. Telomere lengthening is a promising tool to discriminate between short- and long-lived species. PMID:23532044

  13. Social isolation shortens telomeres in African Grey parrots (Psittacus erithacus erithacus).

    PubMed

    Aydinonat, Denise; Penn, Dustin J; Smith, Steve; Moodley, Yoshan; Hoelzl, Franz; Knauer, Felix; Schwarzenberger, Franz

    2014-01-01

    Telomeres, the caps of eukaryotic chromosomes, control chromosome stability and cellular senescence, but aging and exposure to chronic stress are suspected to cause attrition of telomere length. We investigated the effect of social isolation on telomere length in the highly social and intelligent African Grey parrot (Psittacus erithacus erithacus). Our study population consisted of single-housed (n = 26) and pair-housed (n = 19) captive individuals between 0.75 to 45 years of age. Relative telomere length of erythrocyte DNA was measured by quantitative real-time PCR. We found that telomere length declined with age (p<0.001), and socially isolated parrots had significantly shorter telomeres compared to pair-housed birds (p<0.001) - even among birds of similar ages. Our findings provide the first evidence that social isolation affects telomere length, which supports the hypothesis that telomeres provide a biomarker indicating exposure to chronic stress.

  14. Human telomere biology: A contributory and interactive factor in aging, disease risks, and protection.

    PubMed

    Blackburn, Elizabeth H; Epel, Elissa S; Lin, Jue

    2015-12-01

    Telomeres are the protective end-complexes at the termini of eukaryotic chromosomes. Telomere attrition can lead to potentially maladaptive cellular changes, block cell division, and interfere with tissue replenishment. Recent advances in the understanding of human disease processes have clarified the roles of telomere biology, especially in diseases of human aging and in some aging-related processes. Greater overall telomere attrition predicts mortality and aging-related diseases in inherited telomere syndrome patients, and also in general human cohorts. However, genetically caused variations in telomere maintenance either raise or lower risks and progression of cancers, in a highly cancer type-specific fashion. Telomere maintenance is determined by genetic factors and is also cumulatively shaped by nongenetic influences throughout human life; both can interact. These and other recent findings highlight both causal and potentiating roles for telomere attrition in human diseases.

  15. Tiptoeing to chromosome tips: facts, promises and perils of today's human telomere biology.

    PubMed Central

    Fajkus, J; Simícková, M; Maláska, J

    2002-01-01

    The past decade has witnessed an explosion of knowledge concerning the structure and function of chromosome terminal structures-telomeres. Today's telomere research has advanced from a pure descriptive approach of DNA and protein components to an elementary understanding of telomere metabolism, and now to promising applications in medicine. These applications include 'passive' ones, among which the use of analysis of telomeres and telomerase (a cellular reverse transcriptase that synthesizes telomeres) for cancer diagnostics is the best known. The 'active' applications involve targeted downregulation or upregulation of telomere synthesis, either to mortalize immortal cancer cells, or to rejuvenate mortal somatic cells and tissues for cellular transplantations, respectively. This article reviews the basic data on structure and function of human telomeres and telomerase, as well as both passive and active applications of human telomere biology. PMID:12028791

  16. Variations in telomere maintenance and the role of telomerase inhibition in gastrointestinal cancer

    PubMed Central

    Heeg, Steffen

    2015-01-01

    Immortalization is an important step toward the malignant transformation of human cells and is critically dependent upon telomere maintenance. There are two known mechanisms to maintain human telomeres. The process of telomere maintenance is either mediated through activation of the enzyme telomerase or through an alternative mechanism of telomere lengthening called ALT. While 85% of all human tumors show reactivation of telomerase, the remaining 15% are able to maintain telomeres via ALT. The therapeutic potential of telomerase inhibitors is currently investigated in a variety of human cancers. Gastrointestinal tumors are highly dependent on telomerase as a mechanism of telomere maintenance, rendering telomeres as well as telomerase potential targets for cancer therapy. This article focuses on the molecular mechanisms of telomere biology and telomerase activation in gastrointestinal cancers and reviews strategies of telomerase inhibition and their potential therapeutic use in these tumor entities. PMID:26675332

  17. Structurally abnormal human autosomes

    SciTech Connect

    1993-12-31

    Chapter 25, discusses structurally abnormal human autosomes. This discussion includes: structurally abnormal chromosomes, chromosomal polymorphisms, pericentric inversions, paracentric inversions, deletions or partial monosomies, cri du chat (cat cry) syndrome, ring chromosomes, insertions, duplication or pure partial trisomy and mosaicism. 71 refs., 8 figs.

  18. Stress and telomere shortening among central Indian conservation refugees.

    PubMed

    Zahran, Sammy; Snodgrass, Jeffrey G; Maranon, David G; Upadhyay, Chakrapani; Granger, Douglas A; Bailey, Susan M

    2015-03-01

    Research links psychosocial stress to premature telomere shortening and accelerated human aging; however, this association has only been demonstrated in so-called "WEIRD" societies (Western, educated, industrialized, rich, and democratic), where stress is typically lower and life expectancies longer. By contrast, we examine stress and telomere shortening in a non-Western setting among a highly stressed population with overall lower life expectancies: poor indigenous people--the Sahariya--who were displaced (between 1998 and 2002) from their ancestral homes in a central Indian wildlife sanctuary. In this setting, we examined adult populations in two representative villages, one relocated to accommodate the introduction of Asiatic lions into the sanctuary (n = 24 individuals), and the other newly isolated in the sanctuary buffer zone after their previous neighbors were moved (n = 22). Our research strategy combined physical stress measures via the salivary analytes cortisol and α-amylase with self-assessments of psychosomatic stress, ethnographic observations, and telomere length assessment [telomere-fluorescence in situ hybridization (TEL-FISH) coupled with 3D imaging of buccal cell nuclei], providing high-resolution data amenable to multilevel statistical analysis. Consistent with expectations, we found significant associations between each of our stress measures--the two salivary analytes and the psychosomatic symptom survey--and telomere length, after adjusting for relevant behavioral, health, and demographic traits. As the first study (to our knowledge) to link stress to telomere length in a non-WEIRD population, our research strengthens the case for stress-induced telomere shortening as a pancultural biomarker of compromised health and aging. PMID:25730846

  19. Genome-wide association study of relative telomere length.

    PubMed

    Prescott, Jennifer; Kraft, Peter; Chasman, Daniel I; Savage, Sharon A; Mirabello, Lisa; Berndt, Sonja I; Weissfeld, Joel L; Han, Jiali; Hayes, Richard B; Chanock, Stephen J; Hunter, David J; De Vivo, Immaculata

    2011-05-10

    Telomere function is essential to maintaining the physical integrity of linear chromosomes and healthy human aging. The probability of forming proper telomere structures depends on the length of the telomeric DNA tract. We attempted to identify common genetic variants associated with log relative telomere length using genome-wide genotyping data on 3,554 individuals from the Nurses' Health Study and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial that took part in the National Cancer Institute Cancer Genetic Markers of Susceptibility initiative for breast and prostate cancer. After genotyping 64 independent SNPs selected for replication in additional Nurses' Health Study and Women's Genome Health Study participants, we did not identify genome-wide significant loci; however, we replicated the inverse association of log relative telomere length with the minor allele variant [C] of rs16847897 at the TERC locus (per allele β = -0.03, P = 0.003) identified by a previous genome-wide association study. We did not find evidence for an association with variants at the OBFC1 locus or other loci reported to be associated with telomere length. With this sample size we had >80% power to detect β estimates as small as ±0.10 for SNPs with minor allele frequencies of ≥0.15 at genome-wide significance. However, power is greatly reduced for β estimates smaller than ±0.10, such as those for variants at the TERC locus. In general, common genetic variants associated with telomere length homeostasis have been difficult to detect. Potential biological and technical issues are discussed.

  20. Telomeres and telomerase: Pharmacological targets for new anticancer strategies?

    PubMed

    Pendino, F; Tarkanyi, I; Dudognon, C; Hillion, J; Lanotte, M; Aradi, J; Ségal-Bendirdjian, E

    2006-03-01

    Telomeres are located at the ends of eukaryotic chromosomes. Human telomerase, a cellular reverse transcriptase, is a ribonucleoprotein enzyme that catalyzes the synthesis and extension of telomeric DNA. It is composed of at least, a template RNA component (hTR; human Telomerase RNA) and a catalytic subunit, the telomerase reverse transcriptase (hTERT). The absence of telomerase is associated with telomere shortening and aging of somatic cells, while high telomerase activity is observed in over 85% of human cancer cells, strongly indicating its key role during tumorigenesis. Several details regarding telomere structure and telomerase regulation have already been elucidated, providing new targets for therapeutic exploitation. Further support for anti-telomerase approaches comes from recent studies indicating that telomerase is endowed of additional functions in the control of growth and survival of tumor cells that do not depend only on the ability of this enzyme to maintain telomere length. This observation suggests that inhibiting telomerase or its synthesis may have additional anti-proliferative and apoptosis inducing effect, independently of the reduction of telomere length during cell divisions. This article reviews the basic information about the biology of telomeres and telomerase and attempts to present various approaches that are currently under investigation to inhibit its expression and its activity. We summarize herein distinct anti-telomerase approaches like antisense strategies, reverse transcriptase inhibitors, and G-quadruplex interacting agents, and also review molecules targeting hTERT expression, such as retinoids and evaluate them for their therapeutic potential. "They conceive a certain theory, and everything has to fit into that theory. If one little fact will not fit it, they throw it aside. But it is always the facts that will not fit in that are significant". "Death on the Nile". Agatha Christie.

  1. Morphological abnormalities among lampreys

    USGS Publications Warehouse

    Manion, Patrick J.

    1967-01-01

    The experimental control of the sea lamprey (Petromyzon marinus) in the Great Lakes has required the collection of thousands of lampreys. Representatives of each life stage of the four species of the Lake Superior basin were examined for structural abnormalities. The most common aberration was the presence of additional tails. The accessory tails were always postanal and smaller than the normal tail. The point of origin varied; the extra tails occurred on dorsal, ventral, or lateral surfaces. Some of the extra tails were misshaped and curled, but others were normal in shape and pigment pattern. Other abnormalities in larval sea lampreys were malformed or twisted tails and bodies. The cause of the structural abnormalities is unknown. The presence of extra caudal fins could be genetically controlled, or be due to partial amputation or injury followed by abnormal regeneration. Few if any lampreys with structural abnormalities live to sexual maturity.

  2. Direct Comparison of Flow-FISH and qPCR as Diagnostic Tests for Telomere Length Measurement in Humans

    PubMed Central

    Gutierrez-Rodrigues, Fernanda; Santana-Lemos, Bárbara A.; Scheucher, Priscila S.; Alves-Paiva, Raquel M.; Calado, Rodrigo T.

    2014-01-01

    Telomere length measurement is an essential test for the diagnosis of telomeropathies, which are caused by excessive telomere erosion. Commonly used methods are terminal restriction fragment (TRF) analysis by Southern blot, fluorescence in situ hybridization coupled with flow cytometry (flow-FISH), and quantitative PCR (qPCR). Although these methods have been used in the clinic, they have not been comprehensively compared. Here, we directly compared the performance of flow-FISH and qPCR to measure leukocytes' telomere length of healthy individuals and patients evaluated for telomeropathies, using TRF as standard. TRF and flow-FISH showed good agreement and correlation in the analysis of healthy subjects (R2 = 0.60; p<0.0001) and patients (R2 = 0.51; p<0.0001). In contrast, the comparison between TRF and qPCR yielded modest correlation for the analysis of samples of healthy individuals (R2 = 0.35; p<0.0001) and low correlation for patients (R2 = 0.20; p = 0.001); Bland-Altman analysis showed poor agreement between the two methods for both patients and controls. Quantitative PCR and flow-FISH modestly correlated in the analysis of healthy individuals (R2 = 0.33; p<0.0001) and did not correlate in the comparison of patients' samples (R2 = 0.1, p = 0.08). Intra-assay coefficient of variation (CV) was similar for flow-FISH (10.8±7.1%) and qPCR (9.5±7.4%; p = 0.35), but the inter-assay CV was lower for flow-FISH (9.6±7.6% vs. 16±19.5%; p = 0.02). Bland-Altman analysis indicated that flow-FISH was more precise and reproducible than qPCR. Flow-FISH and qPCR were sensitive (both 100%) and specific (93% and 89%, respectively) to distinguish very short telomeres. However, qPCR sensitivity (40%) and specificity (63%) to detect telomeres below the tenth percentile were lower compared to flow-FISH (80% sensitivity and 85% specificity). In the clinical setting, flow-FISH was more accurate, reproducible, sensitive, and specific in the

  3. Genetic and epigenetic trends in telomere research: a novel way in immunoepigenetics.

    PubMed

    Melicher, Dora; Buzas, Edit I; Falus, Andras

    2015-11-01

    Telomeres are protective heterochromatic structures that cap the end of linear chromosomes and play a key role in preserving genomic stability. Telomere length represents a balance between processes that shorten telomeres during cell divisions with incomplete DNA replication and the ones that lengthen telomeres by the action of telomerase, an RNA-protein complex with reverse transcriptase activity which adds telomeric repeats to DNA molecule ends. Telomerase activity and telomere length have a crucial role in cellular ageing and in the pathobiology of several human diseases attracting intense research. The last few decades have witnessed remarkable advances in our understanding about telomeres, telomere-associated proteins, and the biogenesis and regulation of the telomerase holoenzyme complex, as well as about telomerase activation and the telomere-independent functions of telomerase. Emerging data have revealed that telomere length can be modified by genetic and epigenetic factors, sex hormones, reactive oxygen species and inflammatory reactions. It has become clear that, in order to find out more about the factors influencing the rate of telomere attrition in vivo, it is crucial to explore both genetic and epigenetic mechanisms. Since the telomere/telomerase assembly is under the control of multiple epigenetic influences, the unique design of twin studies could help disentangle genetic and environmental factors in the functioning of the telomere/telomerase system. It is surprising that the literature on twin studies investigating this topic is rather scarce. This review aims to provide an overview of some important immune response- and epigenetics-related aspects of the telomere/telomerase system demanding more research, while presenting the available twin data published in connection with telomere research so far. By emphasising what we know and what we still do not know in these areas, another purpose of this review is to urge more twin studies in telomere

  4. Genetic and epigenetic trends in telomere research: a novel way in immunoepigenetics.

    PubMed

    Melicher, Dora; Buzas, Edit I; Falus, Andras

    2015-11-01

    Telomeres are protective heterochromatic structures that cap the end of linear chromosomes and play a key role in preserving genomic stability. Telomere length represents a balance between processes that shorten telomeres during cell divisions with incomplete DNA replication and the ones that lengthen telomeres by the action of telomerase, an RNA-protein complex with reverse transcriptase activity which adds telomeric repeats to DNA molecule ends. Telomerase activity and telomere length have a crucial role in cellular ageing and in the pathobiology of several human diseases attracting intense research. The last few decades have witnessed remarkable advances in our understanding about telomeres, telomere-associated proteins, and the biogenesis and regulation of the telomerase holoenzyme complex, as well as about telomerase activation and the telomere-independent functions of telomerase. Emerging data have revealed that telomere length can be modified by genetic and epigenetic factors, sex hormones, reactive oxygen species and inflammatory reactions. It has become clear that, in order to find out more about the factors influencing the rate of telomere attrition in vivo, it is crucial to explore both genetic and epigenetic mechanisms. Since the telomere/telomerase assembly is under the control of multiple epigenetic influences, the unique design of twin studies could help disentangle genetic and environmental factors in the functioning of the telomere/telomerase system. It is surprising that the literature on twin studies investigating this topic is rather scarce. This review aims to provide an overview of some important immune response- and epigenetics-related aspects of the telomere/telomerase system demanding more research, while presenting the available twin data published in connection with telomere research so far. By emphasising what we know and what we still do not know in these areas, another purpose of this review is to urge more twin studies in telomere

  5. A retrospective examination of mean relative telomere length in the Tasmanian Familial Hematological Malignancies Study

    PubMed Central

    BLACKBURN, NICHOLAS B.; CHARLESWORTH, JAC C.; MARTHICK, JAMES R.; TEGG, ELIZABETH M.; MARSDEN, KATHERINE A.; SRIKANTH, VELANDAI; BLANGERO, JOHN; LOWENTHAL, RAY M.; FOOTE, SIMON J.; DICKINSON, JOANNE L.

    2015-01-01

    Telomere length has a biological link to cancer, with excessive telomere shortening leading to genetic instability and resultant malignant transformation. Telomere length is heritable and genetic variants determining telomere length have been identified. Telomere biology has been implicated in the development of hematological malignancies (HMs), therefore, closer examination of telomere length in HMs may provide further insight into genetic etiology of disease development and support for telomere length as a prognostic factor in HMs. We retrospectively examined mean relative telomere length in the Tasmanian Familial Hematological Malignancies Study using a quantitative PCR method on genomic DNA from peripheral blood samples. Fifty-five familial HM cases, 191 unaffected relatives of familial HM cases and 75 non-familial HM cases were compared with 758 population controls. Variance components modeling was employed to identify factors influencing variation in telomere length. Overall, HM cases had shorter mean relative telomere length (P=2.9×10−6) and this was observed across both familial and non-familial HM cases (P=2.2×10−4 and 2.2×10−5, respectively) as well as additional subgroupings of HM cases according to broad subtypes. Mean relative telomere length was also significantly heritable (62.6%; P=4.7×10−5) in the HM families in the present study. We present new evidence of significantly shorter mean relative telomere length in both familial and non-familial HM cases from the same population adding further support to the potential use of telomere length as a prognostic factor in HMs. Whether telomere shortening is the cause of or the result of HMs is yet to be determined, but as telomere length was found to be highly heritable in our HM families this suggests that genetics driving the variation in telomere length is related to HM disease risk. PMID:25351806

  6. Telomeric G-Tail Length and Hospitalization for Cardiovascular Events in Hemodialysis Patients

    PubMed Central

    Hirashio, Shuma; Nakashima, Ayumu; Doi, Shigehiro; Anno, Kumiko; Aoki, Eriko; Shimamoto, Akira; Yorioka, Noriaki; Kohno, Nobuoki; Masaki, Takao

    2014-01-01

    Background and objectives Telomeric G-tails play a pivotal role in maintaining the intramolecular loop structure of telomeres. Previous in vitro studies have suggested that the erosion of telomeric G-tails triggers cellular senescence, leading to organ dysfunction and atherosclerosis. The authors recently established a method to measure telomeric G-tail length using a hybridization protection assay. Using this method, this study investigated whether telomeric G-tail length could be used as a novel predictor for future cardiovascular events in hemodialysis patients. Design, setting, participants, & measurements A prospective observational study was performed involving a cohort of 203 Japanese hemodialysis patients to examine the lengths of telomeric G-tails and total telomeres and subsequent cardiovascular events during a median follow-up period of 48 months. The lengths of telomeric G-tails and total telomeres were also measured in 203 participants who did not have CKD and who were age- and sex-matched to hemodialysis patients. Results The lengths of telomeric G-tails and total telomeres were significantly shorter in hemodialysis patients than in control subjects. Telomeric G-tails, but not total telomeres, were independently and negatively associated with clinical history of cardiovascular disease. During follow-up, 80 cardiovascular events occurred. Total telomere length did not predict cardiovascular events. However, the length of telomeric G-tails was associated with new-onset cardiovascular events (hazard ratio per log luminescence signals, 0.12; 95% confidence interval, 0.12 to 0.50) that persisted after adjustment for age, sex, diabetes mellitus, clinical history of cardiovascular disease, inflammation, use of vitamin D, and serum levels of phosphate and intact parathyroid hormone. Conclusions Longer telomeric G-tail length is associated with a lower risk of future cardiovascular events in hemodialysis patients. PMID:25237070

  7. Accelerated telomere shortening and replicative senescence in human fibroblasts overexpressing mutant and wild-type lamin A

    SciTech Connect

    Huang Shurong; Risques, Rosa Ana; Martin, George M.; Rabinovitch, Peter S.; Oshima, Junko

    2008-01-01

    LMNA mutations are responsible for a variety of genetic disorders, including muscular dystrophy, lipodystrophy, and certain progeroid syndromes, notably Hutchinson-Gilford Progeria. Although a number of clinical features of these disorders are suggestive of accelerated aging, it is not known whether cells derived from these patients exhibit cellular phenotypes associated with accelerated aging. We examined a series of isogenic skin fibroblast lines transfected with LMNA constructs bearing known pathogenic point mutations or deletion mutations found in progeroid syndromes. Fibroblasts overexpressing mutant lamin A exhibited accelerated rates of loss of telomeres and shortened replicative lifespans, in addition to abnormal nuclear morphology. To our surprise, these abnormalities were also observed in lines overexpressing wild-type lamin A. Copy number variants are common in human populations; those involving LMNA, whether arising meiotically or mitotically, might lead to progeroid phenotypes. In an initial pilot study of 23 progeroid cases without detectable WRN or LMNA mutations, however, no cases of altered LMNA copy number were detected. Nevertheless, our findings raise a hypothesis that changes in lamina organization may cause accelerated telomere attrition, with different kinetics for overexpession of wild-type and mutant lamin A, which leads to rapid replicative senescence and progroid phenotypes.

  8. The Association between Telomere Length and Cancer Prognosis: Evidence from a Meta-Analysis

    PubMed Central

    Li, Lu; Zhou, Ying; Wang, Chao; Hou, Shuxun

    2015-01-01

    Background Telomeres are essential for chromosomal integrity and stability. Shortened telomere length (TL) has been associated with risk of cancers and aging-related diseases. Several studies have explored associations between TL and cancer prognosis, but the results are conflicting. Methods Prospective studies on the relationship between TL and cancer survival were identified by a search of PubMed up to May 25, 2015. There were no restrictions on the cancer type or DNA source. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Meta-analysis approaches were conducted to determine pooled relative risks and 95% confidence intervals. Results Thirty-three articles containing forty-five independent studies were ultimately involved in our meta-analysis, of which twenty-seven were about overall cancer survival and eighteen were about cancer progression. Short TL was associated with increased cancer mortality risk (RR = 1.30, 95%CI: 1.06–1.59) and poor cancer progression (RR = 1.44, 95%CI: 1.10–1.88), both with high levels of heterogeneity (I2 = 83.5%, P = 0.012for overall survival and I2 = 75.4%, P = 0.008 for progression). TL was an independent predictor of overall cancer survival and progression in chronic lymphocytic leukemia. Besides, short telomeres were also associated with increased colorectal cancer mortality and decreased overall survival of esophageal cancer, but not in other cancers. Cancer progression was associated with TL in Asian and America populations and short TL predicted poor cancer survival in older populations. Compared with tumor tissue cells, TL in blood lymphocyte cells was better for prediction. In addition, the associations remained significant when restricted to studies with adjustments for age, with larger sample sizes, measuring TL using southern blotting or estimating risk effects by hazard ratios. Conclusion Short TL demonstrated a significant association with poor cancer survival, suggesting the

  9. Insertion of a Telomere Repeat Sequence into a Mammalian Gene Causes Chromosome Instability

    PubMed Central

    Kilburn, April E.; Shea, Martin J.; Sargent, R. Geoffrey; Wilson, John H.

    2001-01-01

    Telomere repeat sequences cap the ends of eucaryotic chromosomes and help stabilize them. At interstitial sites, however, they may destabilize chromosomes, as suggested by cytogenetic studies in mammalian cells that correlate interstitial telomere sequence with sites of spontaneous and radiation-induced chromosome rearrangements. In no instance is the length, purity, or orientation of the telomere repeats at these potentially destabilizing interstitial sites known. To determine the effects of a defined interstitial telomere sequence on chromosome instability, as well as other aspects of DNA metabolism, we deposited 800 bp of the functional vertebrate telomere repeat, TTAGGG, in two orientations in the second intron of the adenosine phosphoribosyltransferase (APRT) gene in Chinese hamster ovary cells. In one orientation, the deposited telomere sequence did not interfere with expression of the APRT gene, whereas in the other it reduced mRNA levels slightly. The telomere sequence did not induce chromosome truncation and the seeding of a new telomere at a frequency above the limits of detection. Similarly, the telomere sequence did not alter the rate or distribution of homologous recombination events. The interstitial telomere repeat sequence in both orientations, however, dramatically increased gene rearrangements some 30-fold. Analysis of individual rearrangements confirmed the involvement of the telomere sequence. These studies define the telomere repeat sequence as a destabilizing element in the interior of chromosomes in mammalian cells. PMID:11113187

  10. Human UPF1 interacts with TPP1 and telomerase and sustains telomere leading-strand replication

    PubMed Central

    Chawla, Raghav; Redon, Sophie; Raftopoulou, Christina; Wischnewski, Harry; Gagos, Sarantis; Azzalin, Claus M

    2011-01-01

    Eukaryotic up-frameshift 1 (UPF1) is a nucleic acid-dependent ATPase and 5′-to-3′ helicase, best characterized for its roles in cytoplasmic RNA quality control. We previously demonstrated that human UPF1 binds to telomeres in vivo and its depletion leads to telomere instability. Here, we show that UPF1 is present at telomeres at least during S and G2/M phases and that UPF1 association with telomeres is stimulated by the phosphoinositide 3-kinase (PI3K)-related protein kinase ataxia telangiectasia mutated and Rad3-related (ATR) and by telomere elongation. UPF1 physically interacts with the telomeric factor TPP1 and with telomerase. Akin to UPF1 binding to telomeres, this latter interaction is mediated by ATR. Moreover, the ATPase activity of UPF1 is required to prevent the telomeric defects observed upon UPF1 depletion, and these defects stem predominantly from inefficient telomere leading-strand replication. Our results portray a scenario where UPF1 orchestrates crucial aspects of telomere biology, including telomere replication and telomere length homeostasis. PMID:21829167

  11. NAP-1, Nucleosome assembly protein 1, a histone chaperone involved in Drosophila telomeres.

    PubMed

    López-Panadès, Elisenda; Casacuberta, Elena

    2016-03-01

    Telomere elongation is a function that all eukaryote cells must accomplish in order to guarantee, first, the stability of the end of the chromosomes and second, to protect the genetic information from the inevitable terminal erosion. The targeted transposition of the telomere transposons HeT-A, TART and TAHRE perform this function in Drosophila, while the telomerase mechanism elongates the telomeres in most eukaryotes. In order to integrate telomere maintenance together with cell cycle and metabolism, different components of the cell interact, regulate, and control the proteins involved in telomere elongation. Different partners of the telomerase mechanism have already been described, but in contrast, very few proteins have been related with assisting the telomere transposons of Drosophila. Here, we describe for the first time, the implication of NAP-1 (Nucleosome assembly protein 1), a histone chaperone that has been involved in nuclear transport, transcription regulation, and chromatin remodeling, in telomere biology. We find that Nap-1 and HeT-A Gag, one of the major components of the Drosophila telomeres, are part of the same protein complex. We also demonstrate that their close interaction is necessary to guarantee telomere stability in dividing cells. We further show that NAP-1 regulates the transcription of the HeT-A retrotransposon, pointing to a positive regulatory role of NAP-1 in telomere expression. All these results facilitate the understanding of the transposon telomere maintenance mechanism, as well as the integration of telomere biology with the rest of the cell metabolism.

  12. Homologous recombination-dependent repair of telomeric DSBs in proliferating human cells

    PubMed Central

    Mao, Pingsu; Liu, Jingfan; Zhang, Zepeng; Zhang, Hong; Liu, Haiying; Gao, Song; Rong, Yikang S.; Zhao, Yong

    2016-01-01

    Telomeres prevent chromosome ends from being recognized as double-stranded breaks (DSBs). Meanwhile, G/C-rich repetitive telomeric DNA is susceptible to attack by DNA-damaging agents. How cells balance the need to protect DNA ends and the need to repair DNA lesions in telomeres is unknown. Here we show that telomeric DSBs are efficiently repaired in proliferating cells, but are irreparable in stress-induced and replicatively senescent cells. Using the CRISPR-Cas9 technique, we specifically induce DSBs at telomeric or subtelomeric regions. We find that DSB repair (DSBR) at subtelomeres occurs in an error-prone manner resulting in small deletions, suggestive of NHEJ. However, DSBR in telomeres involves ‘telomere-clustering', 3′-protruding C-rich telomeric ssDNA, and HR between sister-chromatid or interchromosomal telomeres. DSBR in telomeres is suppressed by deletion or inhibition of Rad51. These findings reveal proliferation-dependent DSBR in telomeres and suggest that telomeric HR, which is normally constitutively suppressed, is activated in the context of DSBR. PMID:27396625

  13. Alternative end joining, clonal evolution, and escape from a telomere-driven crisis.

    PubMed

    Hendrickson, Eric A; Baird, Duncan M

    2015-01-01

    Telomere dysfunction and fusion play key roles in driving genomic instability and clonal evolution in many tumor types. We have recently described a role for DNA ligase III (LIG3) in facilitating the escape of cells from crisis induced by telomere dysfunction. Our data indicate that LIG3-mediated telomere fusion is important in facilitating clonal evolution.

  14. Age intrinsic loss of telomere protection via TRF1 reduction in endothelial cells.

    PubMed

    Hohensinner, P J; Kaun, C; Buchberger, E; Ebenbauer, B; Demyanets, S; Huk, I; Eppel, W; Maurer, G; Huber, K; Wojta, J

    2016-02-01

    Aging is a major factor predisposing for multiple diseases. Telomeres at the ends of chromosomes protect the integrity of chromosomal DNA. A specialized six-protein complex termed shelterin protects the telomere from unwanted interaction with DNA damage pathways. The aim of our study was to evaluate the integrity of telomeres and the stability of telomere protection during aging in endothelial cells (EC). We describe that aging EC can be characterized by an increased cell size (40%, p=0.02) and increased expression of PAI 1 (4 fold, p=0.02), MCP1 (10 fold, p=0.001) and GMCSF (15 fold, p=0.004). Telomeric state in aging cells is defined by an increased telomere oxidation (27%, p=0.01), reduced telomere length (62%, p=0.02), and increased DNA damage foci formation (5% in young EC versus 16% in aged EC, p=0.003). This telomeric dysfunction is accompanied by a reduction in the shelterin component TRF1 (33% mRNA, p=0.001; 24% protein, p=0.007). Overexpression of TRF1 in aging EC reduced telomere-associated DNA damage foci to 5% (p=0.02) and reduced expression levels of MCP1 (18% reduction, p=0.008). Aged EC have increased telomere damage and an intrinsic loss of telomere protection. Reestablishing telomere integrity could therefore be a target for rejuvenating endothelial cell function.

  15. Age-related arterial telomere uncapping and senescence is greater in women compared with men.

    PubMed

    Walker, Ashley E; Morgan, R Garrett; Ives, Stephen J; Cawthon, Richard M; Andtbacka, Robert H I; Noyes, Dirk; Lesniewski, Lisa A; Richardson, Russell S; Donato, Anthony J

    2016-01-01

    Telomere uncapping increases with advancing age in human arteries and this telomere uncapping is associated with increased markers of senescence, independent of mean telomere length. However, whether there are sex specific differences in arterial telomere uncapping is unknown. We found that telomere uncapping (serine 139 phosphorylated histone γ-H2A.X in telomeres) in arteries was ~2.5 fold greater in post-menopausal women (n=17, 63±2 years) compared with pre-menopausal women (n=11, 30±2 years, p=0.02), while there was only a trend towards greater telomere uncapping in older men (n=26, 66±2 years) compared with young men (n=11, 31±2, p=0.11). Senescence markers, p53 bound to the p21 gene promoter and p21 gene expression, were 3-4 fold greater in post-menopausal compared with pre-menopausal women (p=0.01-0.02), but only 1.5-2 fold greater in older compared with young men (p=0.02-0.08). Blood glucose was related to telomere uncapping in women, while systolic blood pressure, pulse pressure and serum creatinine were related to telomere uncapping in men. Mean arterial telomere length decreased similarly in women and men with age (p<0.01). Thus, the age-related increase in arterial telomere uncapping and senescence is greater in women than men, despite similar age-related reductions in mean telomere length in both sexes.

  16. The OB-fold domain 1 of human POT1 recognizes both telomeric and non-telomeric DNA motifs

    PubMed Central

    Kolar, Carol; Yan, Ying; Borgstahl, Gloria E.O.; Ouellette, Michel M.

    2015-01-01

    The POT1 protein plays a critical role in telomere protection and telomerase regulation. POT1 binds single-stranded 5’-TTAGGGTTAG-3’ and forms a dimer with the TPP1 protein. The dimer is recruited to telomeres, either directly or as part of the Shelterin complex. Human POT1 contains two Oligonucleotide/Oligosaccharide Binding (OB) fold domains, OB1 and OB2, which make physical contact with the DNA. OB1 recognizes 5’-TTAGGG whereas OB2 binds to the downstream TTAG-3’. Studies of POT1 proteins from other species have shown that some of these proteins are able to recognize a broader variety of DNA ligands than expected. To explore this possibility in humans, we have used SELEX to reexamine the sequence-specificity of the protein. Using human POT1 as a selection matrix, high-affinity DNA ligands were selected from a pool of randomized single-stranded oligonucleotides. After six successive rounds of selection, two classes of high-affinity targets were obtained. The first class was composed of oligonucleotides containing a cognate POT1 binding sites (5’-TTAGGGTTAG-3’). The second and more abundant class was made of molecules that carried a novel non-telomeric consensus: 5’-TNCANNAGKKKTTAGG-3’ (where K=G/T and N=any base). Binding studies showed that these non-telomeric sites were made of an OB1-binding motif (TTAGG) and a non-telomeric motif (NT motif), with the two motifs recognized by distinct regions of the OB1 domain. POT1 interacted with these non-telomeric binding sites with high affinity and specificity, even when bound to its dimerization partner TPP1. This intrinsic ability of POT1 to recognize NT motifs raises the possibility that the protein may fulfill additional functions at certain non-telomeric locations of the genome, in perhaps gene transcription, replication, or repair. PMID:25934589

  17. Adipocyte telomere length associates negatively with adipocyte size, whereas adipose tissue telomere length associates negatively with the extent of fibrosis in severely obese women.

    PubMed

    el Bouazzaoui, F; Henneman, P; Thijssen, P; Visser, A; Koning, F; Lips, M A; Janssen, I; Pijl, H; Willems van Dijk, K; van Harmelen, V

    2014-05-01

    Telomere length can be considered as a biological marker for cell proliferation and aging. Obesity is associated with adipocyte hypertrophy and proliferation as well as with shorter telomeres in adipose tissue. As adipose tissue is a mixture of different cell types and the cellular composition of adipose tissue changes with obesity, it is unclear what determines telomere length of whole adipose tissue. We aimed to investigate telomere length in whole adipose tissue and isolated adipocytes in relation to adiposity, adipocyte hypertrophy and adipose tissue inflammation and fibrosis. Telomere length was measured by real-time PCR in visceral adipose tissue, and isolated adipocytes of 21 obese women with a waist ranging from 110 to 147 cm and age from 31 to 61 years. Telomere length in adipocytes was shorter than in whole adipose tissue. Telomere length of adipocytes but not whole adipose tissue correlated negatively with waist and adipocyte size, which was still significant after correction for age. Telomere length of whole adipose tissue associated negatively with fibrosis as determined by collagen content. Thus, in extremely obese individuals, adipocyte telomere length is a marker of adiposity, whereas whole adipose tissue telomere length reflects the extent of fibrosis and may indicate adipose tissue dysfunction.

  18. Genome-wide meta-analysis points to CTC1 and ZNF676 as genes regulating telomere homeostasis in humans

    PubMed Central

    Mangino, Massimo; Hwang, Shih-Jen; Spector, Timothy D.; Hunt, Steven C.; Kimura, Masayuki; Fitzpatrick, Annette L.; Christiansen, Lene; Petersen, Inge; Elbers, Clara C.; Harris, Tamara; Chen, Wei; Srinivasan, Sathanur R.; Kark, Jeremy D.; Benetos, Athanase; El Shamieh, Said; Visvikis-Siest, Sophie; Christensen, Kaare; Berenson, Gerald S.; Valdes, Ana M.; Viñuela, Ana; Garcia, Melissa; Arnett, Donna K.; Broeckel, Ulrich; Province, Michael A.; Pankow, James S.; Kammerer, Candace; Liu, Yongmei; Nalls, Michael; Tishkoff, Sarah; Thomas, Fridtjof; Ziv, Elad; Psaty, Bruce M.; Bis, Joshua C.; Rotter, Jerome I.; Taylor, Kent D.; Smith, Erin; Schork, Nicholas J.; Levy, Daniel; Aviv, Abraham

    2012-01-01

    Leukocyte telomere length (LTL) is associated with a number of common age-related diseases and is a heritable trait. Previous genome-wide association studies (GWASs) identified two loci on chromosomes 3q26.2 (TERC) and 10q24.33 (OBFC1) that are associated with the inter-individual LTL variation. We performed a meta-analysis of 9190 individuals from six independent GWAS and validated our findings in 2226 individuals from four additional studies. We confirmed previously reported associations with OBFC1 (rs9419958 P = 9.1 × 10−11) and with the telomerase RNA component TERC (rs1317082, P = 1.1 × 10−8). We also identified two novel genomic regions associated with LTL variation that map near a conserved telomere maintenance complex component 1 (CTC1; rs3027234, P = 3.6 × 10−8) on chromosome17p13.1 and zinc finger protein 676 (ZNF676; rs412658, P = 3.3 × 10−8) on 19p12. The minor allele of rs3027234 was associated with both shorter LTL and lower expression of CTC1. Our findings are consistent with the recent observations that point mutations in CTC1 cause short telomeres in both Arabidopsis and humans affected by a rare Mendelian syndrome. Overall, our results provide novel insights into the genetic architecture of inter-individual LTL variation in the general population. PMID:23001564

  19. Genetic map of the human pseudoautosomal region reveals a high rate of recombination in female meiosis at the Xp telomere

    SciTech Connect

    Henke, A.; Fischer, C.; Rappold, G.A. )

    1993-12-01

    This paper describes the genetic map of the pseudoautosomal region bounded by the telomere of the short arms of the X and Y chromosomes. In males, meiotic exchange on Xp/Yp is confined to this region, leading to highly elevated recombination rates. The map was constructed using 11 pseudoautosomal probes (six of which are new) and typing individuals from 38 CEPH families. All markers have been physically mapped, thus providing the opportunity to compare genetic distance to physical distance through all intervals of the map. This comparison reveals an unexpected high rate of recombination in female meiosis between loci DXYS20 and DXYS78, within 20-80 kb from the telomere. Within this telemore-adjacent region no differences in male and female recombination rates are seen. Furthermore, data from this genetic map support the hypothesis of a linear gradient of recombination across most of the region in male meiosis and provide densely spaced anchor points for linkage studies especially in the telomeric portion of the pseudoautosomal region. 34 refs., 4 figs., 4 tabs.

  20. Mechanical unfolding of human telomere G-quadruplex DNA probed by integrated fluorescence and magnetic tweezers spectroscopy.

    PubMed

    Long, Xi; Parks, Joseph W; Bagshaw, Clive R; Stone, Michael D

    2013-02-01

    Single-molecule techniques facilitate analysis of mechanical transitions within nucleic acids and proteins. Here, we describe an integrated fluorescence and magnetic tweezers instrument that permits detection of nanometer-scale DNA structural rearrangements together with the application of a wide range of stretching forces to individual DNA molecules. We have analyzed the force-dependent equilibrium and rate constants for telomere DNA G-quadruplex (GQ) folding and unfolding, and have determined the location of the transition state barrier along the well-defined DNA-stretching reaction coordinate. Our results reveal the mechanical unfolding pathway of the telomere DNA GQ is characterized by a short distance (<1 nm) to the transition state for the unfolding reaction. This mechanical unfolding response reflects a critical contribution of long-range interactions to the global stability of the GQ fold, and suggests that telomere-associated proteins need only disrupt a few base pairs to destabilize GQ structures. Comparison of the GQ unfolded state with a single-stranded polyT DNA revealed the unfolded GQ exhibits a compacted non-native conformation reminiscent of the protein molten globule. We expect the capacity to interrogate macromolecular structural transitions with high spatial resolution under conditions of low forces will have broad application in analyses of nucleic acid and protein folding. PMID:23303789

  1. Flap Endonuclease 1 Limits Telomere Fragility on the Leading Strand*

    PubMed Central

    Teasley, Daniel C.; Parajuli, Shankar; Nguyen, Mai; Moore, Hayley R.; Alspach, Elise; Lock, Ying Jie; Honaker, Yuchi; Saharia, Abhishek; Piwnica-Worms, Helen; Stewart, Sheila A.

    2015-01-01

    The existence of redundant replication and repair systems that ensure genome stability underscores the importance of faithful DNA replication. Nowhere is this complexity more evident than in challenging DNA templates, including highly repetitive or transcribed sequences. Here, we demonstrate that flap endonuclease 1 (FEN1), a canonical lagging strand DNA replication protein, is required for normal, complete leading strand replication at telomeres. We find that the loss of FEN1 nuclease activity, but not DNA repair activities, results in leading strand-specific telomere fragility. Furthermore, we show that FEN1 depletion-induced telomere fragility is increased by RNA polymerase II inhibition and is rescued by ectopic RNase H1 expression. These data suggest that FEN1 limits leading strand-specific telomere fragility by processing RNA:DNA hybrid/flap intermediates that arise from co-directional collisions occurring between the replisome and RNA polymerase. Our data reveal the first molecular mechanism for leading strand-specific telomere fragility and the first known role for FEN1 in leading strand DNA replication. Because FEN1 mutations have been identified in human cancers, our findings raise the possibility that unresolved RNA:DNA hybrid structures contribute to the genomic instability associated with cancer. PMID:25922071

  2. Covalent ligation studies on the human telomere quadruplex

    PubMed Central

    Qi, Jianying; Shafer, Richard H.

    2005-01-01

    Recent X-ray crystallographic studies on the human telomere sequence d[AGGG(TTAGGG)3] revealed a unimolecular, parallel quadruplex structure in the presence of potassium ions, while earlier NMR results in the presence of sodium ions indicated a unimolecular, antiparallel quadruplex. In an effort to identify and isolate the parallel form in solution, we have successfully ligated into circular products the single-stranded human telomere and several modified human telomere sequences in potassium-containing solutions. Using these sequences with one or two terminal phosphates, we have made chemically ligated products via creation of an additional loop. Circular products have been identified by polyacrylamide gel electrophoresis, enzymatic digestion with exonuclease VII and electrospray mass spectrometry in negative ion mode. Optimum pH for the ligation reaction of the human telomere sequence ranges from 4.5 to 6.0. Several buffers were also examined, with MES yielding the greatest ligation efficiency. Human telomere sequences with two phosphate groups, one each at the 3′ and 5′ ends, were more efficient at ligation, via pyrophosphate bond formation, than the corresponding sequences with only one phosphate group, at the 5′ end. Circular dichroism spectra showed that the ligation product was derived from an antiparallel, single-stranded guanine quadruplex rather than a parallel single-stranded guanine quadruplex structure. PMID:15933211

  3. Two 22q telomere deletions serendipitously detected by FISH.

    PubMed

    Precht, K S; Lese, C M; Spiro, R P; Huttenlocher, P R; Johnston, K M; Baker, J C; Christian, S L; Kittikamron, K; Ledbetter, D H

    1998-11-01

    Cryptic telomere deletions have been proposed to be a significant cause of idiopathic mental retardation. We present two unrelated subjects, with normal G banding analysis, in whom 22q telomere deletions were serendipitously detected at two different institutions using fluorescence in situ hybridisation (FISH). Both probands presented with several of the previously described features associated with 22q deletions, including hypotonia, developmental delay, and absence of speech. Our two cases increase the total number of reported 22q telomere deletions to 19, the majority of which were identified by cytogenetic banding analysis. With the limited sensitivity of routine cytogenetic studies (approximately 2-5 Mb), these two new cases suggest that the actual prevalence of 22q telomere deletions may be higher than currently documented. Of additional interest is the phenotypic overlap with Angelman syndrome (AS) as it raises the possibility of a 22q deletion in patients in whom AS has been ruled out. The use of telomeric probes as diagnostic reagents would be useful in determining an accurate prevalence of chromosome 22q deletions and could result in a significantly higher detection rate of subtelomeric rearrangements.

  4. Interactions of TRF2 with model telomeric ends

    SciTech Connect

    Khan, Sheik J.; Yanez, Giscard; Seldeen, Kenneth; Wang, Hongda; Lindsay, Stuart M.; Fletcher, Terace M.

    2007-11-09

    Telomeres are DNA-protein complexes at the ends of eukaryotic chromosomes, the integrity of which is essential for chromosome stability. An important telomere binding protein, TTAGGG repeat factor 2 (TRF2), is thought to protect telomere ends by remodeling them into T-loops. We show that TRF2 specifically interacts with telomeric ss/ds DNA junctions and binding is sensitive to the sequence of the 3', guanine-strand (G-strand) overhang and double-stranded DNA sequence at the junction. Association of TRF2 with DNA junctions hinders cleavage by exonuclease T. TRF2 interactions with the G-strand overhang do not involve the TRF2 DNA binding domain or the linker region. However, mobility shifts and atomic force microscopy show that the previously uncharacterized linker region is involved in DNA-specific, TRF2 oligomerization. We suggest that T-loop formation at telomere ends involves TRF2 binding to the G-strand overhang and oligomerization through both the known TRFH domain and the linker region.

  5. Transposition as a mechanism for maintaining telomere length in Drosophila

    SciTech Connect

    Mason, J.M.; Biessmann, H.

    1993-12-31

    Telomeres are structures at the termini of linear chromosomes that serve to maintain the stability of those ends. Several functions have been attributed to telomeres, at least two of these are vital. The vital functions are (a) to {open_quotes}cap{close_quotes} the natural chromosome ends in order to distinguish them from broken ends and, thus, to protect them from recombination, repair, and degradation, and (b) to maintain chromosome length by periodic elongation and, thus, to counteract the inability of DNA polymerases to replicate linear chromosomes completely. While very little is known about capping, the mechanisms of telomere elongation in a number of organisms are being elucidated. Several models for elongation have been proposed. Recent evidence suggests that two of these may operate in different organisms or under different conditions. In many species elongation is accomplished by the interaction of two telomeric DNA repeats. The repeating unit is generally 6-8 basepairs (bp) long and guanine-rich on one strand. The sequence of the repeating unit is evolutionarily conserved, being very similar in ciliated protozoa, flowering plants and vertebrates. The second component is an enzyme, telomerase, that adds more copies of the repeating unit at the terminus. Telomerase resembles reverse transcriptases in structure and carries an associated RNA that is used as a template for the telomere extension.

  6. Immunosenescence and Rheumatoid Arthritis: Does Telomere Shortening Predict Impending Disease?

    PubMed Central

    Costenbader, Karen H.; Prescott, Jennifer; Zee, Robert Y.; De Vivo, Immaculata

    2011-01-01

    The pathogenesis of RA, a disabling autoimmune disease, is incompletely understood. Early in the development of RA there appears to be loss of immune homeostasis and regulation, and premature immunosenescence. While identification of risk factors and understanding of the phases of RA pathogenesis are advancing, means of accurately predicting an individual’s risk of developing RA are currently lacking. Telomere length has been proposed as a potential new biomarker for the development of RA that could enhance prediction of this serious disease. Studies examining telomere length in relation to RA have found that telomere erosion appears to proceed more rapidly in subjects with RA than in healthy controls, and that telomere lengths are shorter in those with the RA-risk HLA-shared epitope genes. These studies have been small, however, with retrospective or cross-sectional designs. The potential role of telomere shortening as an independent biomarker for future RA risk, perhaps strongly genetically determined by HLA-SE genes, after controlling for known risk factors such as smoking, body mass index and immunosuppressant medication use, as well as systemic inflammation, is an unanswered question. PMID:21575746

  7. Abnormal uterine bleeding.

    PubMed

    Jennings, J C

    1995-11-01

    Physicians who care for female patients cannot avoid the frequent complaint of abnormal uterine bleeding. Knowledge of the disorders that cause this problem can prevent serious consequences in many patients and improve the quality of life for many others. The availability of noninvasive and minimally invasive diagnostic studies and minimally invasive surgical treatment has revolutionized management of abnormal uterine bleeding. Similar to any other disorder, the extent to which a physician manages abnormal uterine bleeding depends on his or her own level of comfort. When limitations of either diagnostic or therapeutic capability are encountered, consultation and referral should be used to the best interest of patients.

  8. Genetic Heterogeneity of HER2 Amplification and Telomere Shortening in Papillary Thyroid Carcinoma

    PubMed Central

    Caria, Paola; Cantara, Silvia; Frau, Daniela Virginia; Pacini, Furio; Vanni, Roberta; Dettori, Tinuccia

    2016-01-01

    Extensive research is dedicated to understanding if sporadic and familial papillary thyroid carcinoma are distinct biological entities. We have previously demonstrated that familial papillary thyroid cancer (fPTC) cells exhibit short relative telomere length (RTL) in both blood and tissues and that these features may be associated with chromosome instability. Here, we investigated the frequency of HER2 (Human Epidermal Growth Factor Receptor 2) amplification, and other recently reported genetic alterations in sporadic PTC (sPTC) and fPTC, and assessed correlations with RTL and BRAF mutational status. We analyzed HER2 gene amplification and the integrity of ALK, ETV6, RET, and BRAF genes by fluorescence in situ hybridization in isolated nuclei and paraffin-embedded formalin-fixed sections of 13 fPTC and 18 sPTC patients. We analyzed BRAFV600E mutation and RTL by qRT-PCR. Significant HER2 amplification (p = 0.0076), which was restricted to scattered groups of cells, was found in fPTC samples. HER2 amplification in fPTCs was invariably associated with BRAFV600E mutation. RTL was shorter in fPTCs than sPTCs (p < 0.001). No rearrangements of other tested genes were observed. These findings suggest that the association of HER2 amplification with BRAFV600E mutation and telomere shortening may represent a marker of tumor aggressiveness, and, in refractory thyroid cancer, may warrant exploration as a site for targeted therapy. PMID:27775641

  9. Daily torpor is associated with telomere length change over winter in Djungarian hamsters.

    PubMed

    Turbill, Christopher; Smith, Steve; Deimel, Caroline; Ruf, Thomas

    2012-04-23

    Ageing can progress at different rates according to an individual's physiological state. Natural hypothermia, including torpor and hibernation, is a common adaptation of small mammals to survive intermittent or seasonal declines in environmental conditions. In addition to allowing energy savings, hypothermia and torpor have been associated with retarded ageing and increased longevity. We tested the hypothesis that torpor use slows ageing by measuring changes in the relative telomere length (RTL) of Djungarian hamsters, Phodopus sungorus, a highly seasonal rodent using spontaneous daily torpor, over 180 days of exposure to a short-day photoperiod and warm (approx. 20°C) or cold (approx. 9°C) air temperatures. Multi-model inference showed that change in RTL within individuals was best explained by positive effects of frequency of torpor use, particularly at low body temperatures, as well as the change in body mass and initial RTL. Telomere dynamics have been linked to future survival and proposed as an index of rates of biological ageing. Our results therefore support the hypothesis that daily torpor is associated with physiological changes that increase somatic maintenance and slow the processes of ageing. PMID:21920955

  10. Daily torpor is associated with telomere length change over winter in Djungarian hamsters.

    PubMed

    Turbill, Christopher; Smith, Steve; Deimel, Caroline; Ruf, Thomas

    2012-04-23

    Ageing can progress at different rates according to an individual's physiological state. Natural hypothermia, including torpor and hibernation, is a common adaptation of small mammals to survive intermittent or seasonal declines in environmental conditions. In addition to allowing energy savings, hypothermia and torpor have been associated with retarded ageing and increased longevity. We tested the hypothesis that torpor use slows ageing by measuring changes in the relative telomere length (RTL) of Djungarian hamsters, Phodopus sungorus, a highly seasonal rodent using spontaneous daily torpor, over 180 days of exposure to a short-day photoperiod and warm (approx. 20°C) or cold (approx. 9°C) air temperatures. Multi-model inference showed that change in RTL within individuals was best explained by positive effects of frequency of torpor use, particularly at low body temperatures, as well as the change in body mass and initial RTL. Telomere dynamics have been linked to future survival and proposed as an index of rates of biological ageing. Our results therefore support the hypothesis that daily torpor is associated with physiological changes that increase somatic maintenance and slow the processes of ageing.

  11. Comprehensive screening of alternative lengthening of telomeres phenotype and loss of ATRX expression in sarcomas.

    PubMed

    Liau, Jau-Yu; Lee, Jen-Chieh; Tsai, Jia-Huei; Yang, Ching-Yao; Liu, Tsung-Lin; Ke, Zhi-Long; Hsu, Hung-Han; Jeng, Yung-Ming

    2015-12-01

    According to cytogenetic aberrations, sarcomas can be categorized as complex or simple karyotype tumors. Alternative lengthening of telomeres is a telomere-maintenance mechanism common in sarcomas. Recently, this mechanism was found to be associated with loss of either α-thalassemia/mental retardation syndrome X-linked (ATRX) or death domain-associated (DAXX) protein. We previously reported that alternative lengthening of telomeres and loss of ATRX expression were common in leiomyosarcoma, angiosarcoma, pleomorphic liposarcoma, and dedifferentiated liposarcoma. In the present study, we screened an additional 245 sarcomas of other types to determine the prevalence of alternative lengthening of telomeres, loss of ATRX/DAXX expression, and their relationship. Undifferentiated pleomorphic sarcomas were frequently alternative lengthening of telomeres positive (65%) and loss of ATRX was seen in approximately half of the alternative lengthening of telomeres-positive tumors. Nineteen of 25 myxofibrosarcomas were alternative lengthening of telomeres-positive, but only one was ATRX deficient. Three of 15 radiation-associated sarcomas were alternative lengthening of telomeres positive, but none of them was ATRX deficient. Alternative lengthening of telomeres and/or loss of ATRX were uncommon in malignant peripheral nerve sheath tumors, gastrointestinal stromal tumors, and embryonal rhabdomyosarcomas. By contrast, none of the 71 gene fusion-associated sarcomas was ATRX deficient or alternative lengthening of telomeres positive. All tumors exhibited preserved DAXX expression. Combining our previous studies and this study, a total of 384 sarcomas with complex karyotypes were examined, 83 of which were ATRX deficient (22%). By telomere-specific fluorescence in situ hybridization, 45% (138/308) were alternative lengthening of telomeres positive, 55% (76/138) of which were ATRX deficient. Loss of ATRX was highly associated with alternative lengthening of telomeres (P<0.001). We

  12. "Jeopardy" in Abnormal Psychology.

    ERIC Educational Resources Information Center

    Keutzer, Carolin S.

    1993-01-01

    Describes the use of the board game, Jeopardy, in a college level abnormal psychology course. Finds increased student interaction and improved application of information. Reports generally favorable student evaluation of the technique. (CFR)

  13. Abnormal Uterine Bleeding

    MedlinePlus

    ... Abnormal uterine bleeding is any bleeding from the uterus (through your vagina) other than your normal monthly ... or fibroids (small and large growths) in the uterus can also cause bleeding. Rarely, a thyroid problem, ...

  14. Abnormal Uterine Bleeding FAQ

    MedlinePlus

    ... as cancer of the uterus, cervix, or vagina • Polycystic ovary syndrome How is abnormal bleeding diagnosed? Your health care ... before the fetus can survive outside the uterus. Polycystic Ovary Syndrome: A condition characterized by two of the following ...

  15. Religious Involvement and Telomere Length in Women Family Caregivers.

    PubMed

    Koenig, Harold G; Nelson, Bruce; Shaw, Sally F; Saxena, Salil; Cohen, Harvey Jay

    2016-01-01

    Telomere length (TL) is an indicator of cellular aging associated with longevity and psychosocial stress. We examine here the relationship between religious involvement and TL in 251 stressed female family caregivers recruited into a 2-site study. Religious involvement, perceived stress, caregiver burden, depressive symptoms, and social support were measured and correlated with TL in whole blood leukocytes. Results indicated a U-shaped relationship between religiosity and TL. Those scoring in the lowest 10% on religiosity tended to have the longest telomeres (5743 bp ± 367 vs. 5595 ± 383, p = 0.069). However, among the 90% of caregivers who were at least somewhat religious, religiosity was significantly and positively related to TL after controlling for covariates (B = 1.74, SE = 0.82, p = 0.034). Whereas nonreligious caregivers have relatively long telomeres, we found a positive relationship between religiosity and TL among those who are at least somewhat religious.

  16. Genome rearrangements caused by interstitial telomeric sequences in yeast

    PubMed Central

    Aksenova, Anna Y.; Greenwell, Patricia W.; Dominska, Margaret; Shishkin, Alexander A.; Kim, Jane C.; Petes, Thomas D.; Mirkin, Sergei M.

    2013-01-01

    Interstitial telomeric sequences (ITSs) are present in many eukaryotic genomes and are linked to genome instabilities and disease in humans. The mechanisms responsible for ITS-mediated genome instability are not understood in molecular detail. Here, we use a model Saccharomyces cerevisiae system to characterize genome instability mediated by yeast telomeric (Ytel) repeats embedded within an intron of a reporter gene inside a yeast chromosome. We observed a very high rate of small insertions and deletions within the repeats. We also found frequent gross chromosome rearrangements, including deletions, duplications, inversions, translocations, and formation of acentric minichromosomes. The inversions are a unique class of chromosome rearrangement involving an interaction between the ITS and the true telomere of the chromosome. Because we previously found that Ytel repeats cause strong replication fork stalling, we suggest that formation of double-stranded DNA breaks within the Ytel sequences might be responsible for these gross chromosome rearrangements. PMID:24191060

  17. Tying up loose ends: telomeres, genomic instability and lamins.

    PubMed

    Gonzalo, Susana; Eissenberg, Joel C

    2016-04-01

    On casual inspection, the eukaryotic nucleus is a deceptively simple organelle. Far from being a bag of chromatin, the nucleus is, in some ways, a structural and functional extension of the chromosomes it contains. Recently, interest has intensified in how chromosome compartmentalization and dynamics affect nuclear function. Different studies uncovered functional interactions between chromosomes and the filamentous nuclear meshwork comprised of lamin proteins. Here, we summarize recent research suggesting that telomeres, the capping structures that protect chromosome ends, are stabilized by lamin-binding and that alterations in nuclear lamins lead to defects in telomere compartmentalization, homeostasis and function. Telomere dysfunction contributes to the genomic instability that characterizes aging-related diseases, and might be an important factor in the pathophysiology of lamin-related diseases. PMID:27010504

  18. Production of Engineered Minichromosome Vectors via the Introduction of Telomere Sequences.

    PubMed

    Graham, Nathaniel; Swyers, Nathan; Cody, Jon; McCaw, Morgan; Zhao, Changzeng; Birchler, James A

    2016-01-01

    Artificial minichromosomes are non-integrating vectors capable of stably maintaining transgenes outside of the main chromosome set. The production of minichromosomes relies on telomere-mediated chromosomal truncation, which involves introducing transgenes and telomere sequences concurrently to the cell to truncate an endogenous chromosomal target. Two methods can be utilized; either the telomere sequences can be incorporated into a binary vector for transformation with Agrobacterium tumefaciens, or the telomere sequences can be co-introduced with transgenes during particle bombardment. In this protocol, the methods required to isolate and introduce telomere sequences are presented. Following the methods presented, standard transformation procedures can be followed to produce minichromosome containing plants. PMID:27557682

  19. Regulating telomere length from the inside out: the replication fork model

    PubMed Central

    2016-01-01

    Telomere length is regulated around an equilibrium set point. Telomeres shorten during replication and are lengthened by telomerase. Disruption of the length equilibrium leads to disease; thus, it is important to understand the mechanisms that regulate length at the molecular level. The prevailing protein-counting model for regulating telomerase access to elongate the telomere does not explain accumulating evidence of a role of DNA replication in telomere length regulation. Here I present an alternative model: the replication fork model that can explain how passage of a replication fork and re