Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

In situ visualization of telomere elongation patterns in human cells.

ABSTRACT: The telomerase enzyme plays a critical role in human aging and cancer biology by maintaining telomere length and extending the proliferative lifespan of most stem cells and cancer cells. Despite the importance of this enzyme, our understanding of the mechanisms that regulate its activity and establish telomere length homeostasis in mammalian cells is incomplete, in part because the perfect repetitive nature of telomeric sequence hampers in situ detection of telomere elongation patterns. Here, we describe a novel assay using a mutant telomerase that adds a well-tolerated variant telomeric repeat sequence to telomere ends. By specifically detecting the addition of these variant repeats, we can directly visualize telomere elongation events in human cells. We validate this approach by in situ mapping of telomere elongation patterns within individual nuclei and across a population of cells.

SUBMITTER: Diolaiti ME

PROVIDER: S-EPMC3794614 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

In situ visualization of telomere elongation patterns in human cells.

Diolaiti Morgan E ME Cimini Beth A BA Kageyama Robin R Charles Florie A FA Stohr Bradley A BA

Nucleic acids research 20130819 18

The telomerase enzyme plays a critical role in human aging and cancer biology by maintaining telomere length and extending the proliferative lifespan of most stem cells and cancer cells. Despite the importance of this enzyme, our understanding of the mechanisms that regulate its activity and establish telomere length homeostasis in mammalian cells is incomplete, in part because the perfect repetitive nature of telomeric sequence hampers in situ detection of telomere elongation patterns. Here, we ...[more]

PMID: 23963699

Similar Datasets

Telomere elongation in parthenogenetic stem cells.

Project description: Not available

| S-EPMC3938844 | biostudies-literature

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

Project description: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.

| S-EPMC4663052 | biostudies-literature

Zscan4 regulates telomere elongation and genomic stability in ES cells.

Project description:Exceptional genomic stability is one of the hallmarks of mouse embryonic stem (ES) cells. However, the genes contributing to this stability remain obscure. We previously identified Zscan4 as a specific marker for two-cell embryo and ES cells. Here we show that Zscan4 is involved in telomere maintenance and long-term genomic stability in ES cells. Only 5% of ES cells express Zscan4 at a given time, but nearly all ES cells activate Zscan4 at least once during nine passages. The transient Zscan4-positive state is associated with rapid telomere extension by telomere recombination and upregulation of meiosis-specific homologous recombination genes, which encode proteins that are colocalized with ZSCAN4 on telomeres. Furthermore, Zscan4 knockdown shortens telomeres, increases karyotype abnormalities and spontaneous sister chromatid exchange, and slows down cell proliferation until reaching crisis by passage eight. Together, our data show a unique mode of genome maintenance in ES cells.

| S-EPMC2851843 | biostudies-literature

Visualization and quantitative analysis of extrachromosomal telomere-repeat DNA in individual human cells by Halo-FISH.

Project description:Current methods for characterizing extrachromosomal nuclear DNA in mammalian cells do not permit single-cell analysis, are often semi-quantitative and frequently biased toward the detection of circular species. To overcome these limitations, we developed Halo-FISH to visualize and quantitatively analyze extrachromosomal DNA in single cells. We demonstrate Halo-FISH by using it to analyze extrachromosomal telomere-repeat (ECTR) in human cells that use the Alternative Lengthening of Telomeres (ALT) pathway(s) to maintain telomere lengths. We find that GM847 and VA13 ALT cells average ?80 detectable G/C-strand ECTR DNA molecules/nucleus, while U2OS ALT cells average ?18 molecules/nucleus. In comparison, human primary and telomerase-positive cells contain <5 ECTR DNA molecules/nucleus. ECTR DNA in ALT cells exhibit striking cell-to-cell variations in number (<20 to >300), range widely in length (<1 to >200 kb) and are composed of primarily G- or C-strand telomere-repeat DNA. Halo-FISH enables, for the first time, the simultaneous analysis of ECTR DNA and chromosomal telomeres in a single cell. We find that ECTR DNA comprises ?15% of telomere-repeat DNA in GM847 and VA13 cells, but <4% in U2OS cells. In addition to its use in ALT cell analysis, Halo-FISH can facilitate the study of a wide variety of extrachromosomal DNA in mammalian cells.

| S-EPMC4344523 | biostudies-literature

Expression data by telomere elongation

Project description:Limitless reproductive potential is one of the hallmarks of cancer cells1. This ability is accomplished by maintaining telomeres, which erosion otherwise causes cellular senescence or death. Human cancer cells often maintain shorter telomeres than do cells in surrounding normal tissues2-5. While most cancer cells activate telomerase, which can elongate telomeres6, it remains elusive why cancer cells keep telomeres short. Here we show that forced elongation of telomeres in cancer cells promotes their differentiation in a tumor microenvironment in vivo. We elongated telomeres of human prostate cancer PC-3 cells, which possess short telomeres7, by enhancing their telomerase activity. The resulting cells with long telomeres retain an ability to form tumors in a mouse xenograft model. Strikingly, these tumors exhibit many duct-like structures and reduced N-cadherin expression, reminiscent of well-differentiated adenocarcinoma. These phenotypic changes are caused by telomere elongation per se but not enhanced telomerase activity. Gene expression profiling revealed that telomere elongation correlates with inhibition of cell-cycle processes. Together, our results suggest a functional contribution of short telomeres to tumor malignancy by regulating cancer cell differentiation. Two samples are telomere-elongated cells, both in the presence and absence of the exogenous hTERT. The other two samples are control cell lines.

2013-05-31 | E-GEOD-36649 | biostudies-arrayexpress

BRD4 inhibitors block telomere elongation.

Project description:Cancer cells maintain telomere length equilibrium to avoid senescence and apoptosis induced by short telomeres, which trigger the DNA damage response. Limiting the potential for telomere maintenance in cancer cells has been long been proposed as a therapeutic target. Using an unbiased shRNA screen targeting known kinases, we identified bromodomain-containing protein 4 (BRD4) as a telomere length regulator. Four independent BRD4 inhibitors blocked telomere elongation, in a dose-dependent manner, in mouse cells overexpressing telomerase. Long-term treatment with BRD4 inhibitors caused telomere shortening in both mouse and human cells, suggesting BRD4 plays a role in telomere maintenance in vivo. Telomerase enzymatic activity was not directly affected by BRD4 inhibition. BRD4 is in clinical trials for a number of cancers, but its effects on telomere maintenance have not been previously investigated.

| S-EPMC5737673 | biostudies-literature

In situ autofluorescence visualization of human trabecular meshwork structure.

Project description:PURPOSE:To characterize the three-dimensional (3-D) structure of the human trabecular meshwork (TM) by two-photon excited (TPEF) autofluorescence (AF) and optical sectioning without conventional histologic embedding and sectioning. METHODS:Viable human ex vivo explants of the anterior chamber angle containing the aqueous humor drainage tissue in situ were imaged by TPEF to localize AF and Hoechst 33342 nuclear fluorescence. An autofluorescent marker in Schlemm's Canal (SC) aided SC situ visualization. En face and orthogonal views of the TM were generated. RESULTS:In the innermost uveal TM, AF signals outlined an intricate 3-D network of fine branching beams with large openings between the beams. In the adjacent corneoscleral TM, beams were thicker and coalesced as plate-like structures with pore-like openings. Linear and coiled AF fibers were visible on the background AF of beams. Deeper, in the external TM, this organization changed to fine fiber arrays orientated in the tissue's longitudinal axis, reminiscent of the cribriform plexus of the juxtacanalicular TM (JCT). In the outermost JCT, AF of fine fibers was sparse, then undetectable as optical sections approached the inner wall of SC. Cell nuclei were closely associated with the TM structural extracellular matrix. CONCLUSIONS:We have used TPEF and optical sectioning to exploit AF as a useful method to visualize the structure of the human conventional aqueous drainage pathway in situ. Ancillary nuclear staining allowed cell association with the AF structures to be seen. This approach revealed a unique 3-D perspective of the TM that is consistent with known TM structural characteristics.

| S-EPMC3995572 | biostudies-literature

Telomere elongation in induced pluripotent stem cells from dyskeratosis congenita patients.

Project description:Patients with dyskeratosis congenita (DC), a disorder of telomere maintenance, suffer degeneration of multiple tissues. Patient-specific induced pluripotent stem (iPS) cells represent invaluable in vitro models for human degenerative disorders like DC. A cardinal feature of iPS cells is acquisition of indefinite self-renewal capacity, which is accompanied by induction of the telomerase reverse transcriptase gene (TERT). We investigated whether defects in telomerase function would limit derivation and maintenance of iPS cells from patients with DC. Here we show that reprogrammed DC cells overcome a critical limitation in telomerase RNA component (TERC) levels to restore telomere maintenance and self-renewal. We discovered that TERC upregulation is a feature of the pluripotent state, that several telomerase components are targeted by pluripotency-associated transcription factors, and that in autosomal dominant DC, transcriptional silencing accompanies a 3' deletion at the TERC locus. Our results demonstrate that reprogramming restores telomere elongation in DC cells despite genetic lesions affecting telomerase, and show that strategies to increase TERC expression may be therapeutically beneficial in DC patients.

| S-EPMC3058620 | biostudies-literature

Visualization of long human telomere mimics by single-molecule fluorescence imaging.

Project description:Study of long single-stranded telomeric DNA is important for a variety of basic science and biotechnological applications, yet few methods exist for synthesis and visualization of single copies of this DNA in solution at biologically relevant length scales necessary for assessment of heterogeneity in its structure and behavior. We have synthesized kilobase-long single-stranded human telomere mimics in situ by rolling circle replication (RCR) on a microscope coverslip surface and visualized individual strands by staining with SYBR Gold. Under buffer flow, differential extensibility and varying morphology of these long telomere-mimicking DNA sequences were observed at the single-molecule level in real time. Using this procedure, we detected striking differences in the extensibility of individual RCR products based on the human G-rich telomeric sequence in the presence and absence of short, complementary single-stranded oligonucleotides. We also apply this new mode of single-stranded DNA characterization to probe the interaction of kilobase-length telomere mimics with the small-molecule G-quadruplex-binding agent TMPyP4.

| S-EPMC2688642 | biostudies-literature

Loss of Human TGS1 Hypermethylase Promotes Increased Telomerase RNA and Telomere Elongation.

Project description:Biogenesis of the human telomerase RNA (hTR) involves a complex series of posttranscriptional modifications, including hypermethylation of the 5' mono-methylguanosine cap to a tri-methylguanosine cap (TMG). How the TMG cap affects hTR maturation is unknown. Here, we show that depletion of trimethylguanosine synthase 1 (TGS1), the enzyme responsible for cap hypermethylation, increases levels of hTR and telomerase. Diminished trimethylation increases hTR association with the cap-binding complex (CBC) and with Sm chaperone proteins. Loss of TGS1 causes an increase in accumulation of mature hTR in both the nucleus and the cytoplasm compared with controls. In TGS1 mutant cells, increased hTR assembles with telomerase reverse transcriptase (TERT) protein to yield elevated active telomerase complexes and increased telomerase activity, resulting in telomere elongation in cultured human cells. Our results show that TGS1-mediated hypermethylation of the hTR cap inhibits hTR accumulation, restrains levels of assembled telomerase, and limits telomere elongation.

| S-EPMC7156301 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data