Cellular senescence is a program of irreversible cell cycle arrest that normal cells undergo in response to progressive shortening of telomeres, changes in telomeric structure, oncogene activation or oxidative stress. The underlying signalling pathways, potentially of major clinicopathological relevance, are unknown. A major stumbling block to studying senescence has been the absence of suitable model systems because of the asynchrony of this process in heterogeneous cell populations. To simplify this process many investigators study oncogene-induced senescence due to expression of activated oncogenes where senescence occurs prematurely without telomere attrition and can be induced acutely in a variety of cell types. We have taken a different approach by making use of the finding that reconstitution of telomerase activity by introduction of the catalytic subunit of human telomerase alone is incapable of immortalising all human somatic cells, but inactivation of the p16-pRB and p53-p21 pathways are required in addition. The ability of SV40 large T antigen to inactivate the p16-pRB and p53-p21 pathways has enabled us to use a thermolabile mutant of LT antigen, in conjunction with hTERT, to develop conditionally immortalised human (HMF3A) fibroblasts that are immortal but undergo an irreversible growth arrest when the thermolabile LT antigen is inactivated leading to activation of pRB and p53. When these cells cease dividing, senescence-associated- b-galactosidase activity is induced and the growth-arrested cells have morphological features and express genes in common with senescent cells. Since these cells growth arrest in a synchronous manner they are an excellent starting point for dissecting the pathways that underlie cellular senescence and act downstream of p16-pRB and p53-p21 pathways. We have combined genome-wide expression profiling with genetic complementation to undertake identification of genes that are differentially expressed when these conditionally immortalised human fibroblasts undergo senescence upon activation of the p16-pRB and p53-p21 tumour suppressor pathways.
Activation of nuclear factor-kappa B signalling promotes cellular senescence.
Cell line, Treatment
View SamplesThe goal of this experiment is to analyze global gene expression profiles during the cell cycle after acute depletion of E2F7. Overall design: RNA was isolated at three time-points following exit from cell cycle arrest, which represent G1/S transition (0h), S phase (3h) and G2/M boundary (12h) of the cell cycle in cells transfected with siRNAs specific for E2F7 (siE2F7) or with non-target control siRNAs (siNT)
An E2F7-dependent transcriptional program modulates DNA damage repair and genomic stability.
Cell line, Subject
View SamplesMultiple Myeloma (MM) remains incurable, and new drugs with novel mechanisms of action are still needed. In this report, we have analyzed the action of Zalypsis, an alkaloid analogous to certain natural marine compounds, in MM. Zalypsis turned out to be the most potent antimyeloma agent we have tested so far, with IC50s from picomolar to low nanomolar ranges. It also showed remarkable ex vivo potency in plasma cells from patients and in MM cells in vivo xenografted in mice. Besides the induction of apoptosis and cell cycle arrest, Zalypsis provoked DNA double-strand-breaks (DSB), evidenced by an increase in phospho-Histone-H2AX and phospho-CHK2, followed by a striking overexpression of p53 in p53-wild type cell lines. In addition, in those cell lines in which p53 was mutated, Zalypsis also provoked DSB and induced cell death, although higher concentrations were required. Immunohistochemical studies in tumours also demonstrated Histone-H2AX phosphorylation and p53 overexpression. Gene expression profile studies were concordant with these results, revealing an important deregulation of genes involved in DNA-damage response. The potent in vitro and in vivo antimyeloma activity of Zalypsis uncovers the high sensitivity of tumour plasma cells to DSB, and strongly supports the use of this compound in MM patients.
Zalypsis: a novel marine-derived compound with potent antimyeloma activity that reveals high sensitivity of malignant plasma cells to DNA double-strand breaks.
No sample metadata fields
View SamplesIn order to understand how Pseudomonas aeruginosa responds to low oxygen we grew strain PAO1 with 3 different oxygen concentrations: 2%, 0.4% and 0% supplemented with nitrate as an electron acceptor. Gene expression under these conditions was compared to that of cells grown with 20% oxygen.
Responses of Pseudomonas aeruginosa to low oxygen indicate that growth in the cystic fibrosis lung is by aerobic respiration.
No sample metadata fields
View SamplesThe dentate gyrus of the hippocampus continues generating new neurons throughout life. These nerve cells originate from radial astrocytes within the subgranular zone (SGZ). We find that Sox1, a member of the SoxB1 family of transcription factors, is expressed in a subset of radial astrocytes. Lineage tracing using Sox1 driven reporter mice shows that the Sox1-expressing cells represent an activated neural stem/progenitor population.
Sox1 marks an activated neural stem/progenitor cell in the hippocampus.
Age, Specimen part
View SamplesPlants regulate their time to flowering by gathering information from the environment. Photoperiod and temperature are among the most important environmental variables. Suboptimal, but not near-freezing, temperatures regulate flowering through the thermosensory pathway, which overlaps with the autonomous pathway. Here we show that ambient temperature regulates flowering by two genetically distinguishable pathways, one that requires TFL1 and another that requires ELF3. The delay in flowering time observed at lower temperatures was partially suppressed in single elf3 and tfl1 mutants, whereas double elf3 tfl1 mutants were insensitive to temperature. tfl1 mutations abolished the temperature response in cryptochrome mutants that are deficient in photoperiod perception, but not in phyB mutants that have a constitutive photoperiodic response. Contrary to tfl1, elf3 mutations were able to suppress the temperature response in phyB mutants, but not in cryptochrome mutants. The gene expression profile revealed that the tfl1 and elf3 effects are due to the activation of different sets of genes and identified CCA1 and SOC1/AGL20 as being important cross talk points. Finally, genome-wide gene expression analysis strongly suggests a general and complementary role for ELF3 and TFL1 in temperature signalling.
A complementary role for ELF3 and TFL1 in the regulation of flowering time by ambient temperature.
No sample metadata fields
View SamplesHuman Burkitt's lymphoma ST486 cells were transduced with non-target control shRNA lentiviral vectors, FOXM1 shRNA, and MYB shRNA lentiviral vectors. Total RNA was isolated 24h later. cRNA was produced with the standard one-step IVT protocol (Affymetix) and hybridized in U95Av2 gene chips (Affymetrix).
Correlating measurements across samples improves accuracy of large-scale expression profile experiments.
Cell line, Time
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Lhx5 controls mamillary differentiation in the developing hypothalamus of the mouse.
Specimen part, Treatment
View SamplesLhx5 mutant mouse embryos show loss of a neuronal nucleus of the brain called the mamillary body and essential for the formation of memories. We wanted to identify the genes that are responsible for the normal development of the mammillary body.
Lhx5 controls mamillary differentiation in the developing hypothalamus of the mouse.
Specimen part
View SamplesIn this data, we examined Transcriptome detection and expression in 8 samples of Retinoblastoma. We found a central core shared by all samples .
Discovery of a transcriptomic core of genes shared in 8 primary retinoblastoma with a novel detection score analysis.
Disease
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