RNA profiling of p16ink4a-expressing pancreatic beta-cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE76992 | GEO | 2016/01/20
SECONDARY ACCESSION(S): PRJNA309188
REPOSITORIES: GEO
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Project description:p16INK4A inhibits the CDK4/6 kinases and is therefore an important cell cycle regulator. Accumulation of p16INK4A in response to oncogenic transformation leads to cellular senescence and it is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of cellular oxidative stress and therefore could potentially be regulated by redox signaling, which is a form of signal transduction that is mediated by the reversible oxidation of cysteine-thiol side chains in proteins. We found that oxidation of the single cysteine residue in p16INK4A in human cells occurs under relatively mild oxidizing conditions and that this leads to disulfide dependent dimerization. p16INK4A is a well-characterized all alpha-helical protein, but we find that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-β sheet structure, and typical dimensions found in electron microscopy. We find that p16INK4A amyloid formation abolishes its function as a CDK4/6 inhibitor in human cells. Taken together, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils.
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Project description:We collected freshly sorted mesenchyme (live CD45-Epcam-CD31-PDGFRa+GFP- or GFP+) from dissociated lung tissue of INKBRITE animals to characterize the transcriptome difference between p16INK4a+ vs p16INK4a- cells at homeostasis and during injury. We used fluorescence activated cell sorting (FACS) to exclude immune (CD45+), epithelial (Epcam+), and endothelial (CD31+) cells and positively select for PDGFRa+ mesenchyme. Cells were sequenced at a depth of average of 45 million reads/sample. The results revealed an increase of senescence associated secretory phenotype (SASP) signature in p16INK4+ cells that becomes refined after injury. We found the expression of an epithelial growth factor epiregulin (ereg) increased in p16INK4a+ cells after injury suggesting a possible role of p16INK4a+ senescence during regeneration of lung epithelium.
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Project description:P16Ink4a is a well-established marker of senescence. Although P16Ink4a is expressed in endothelial cells, little is known about its function in these cells. Using isolated liver endothelial cells with silencing or overexpression of P16Ink4a, we show here that dependent on P16Ink4a levels, different pathways and functions are affected. High levels of P16Ink4a reduce proliferation and induce senescence while low levels have the opposite effects. Only high P16Ink4a expression reduces in vitro angiogenesis. Expression profiling reveals an inflammatory phenotype upon silencing of P16Ink4a while P16Ink4a overexpression is associated with a profile associated to DNA damage, repair and senescence. Low levels of P16Ink4a induce reactive oxygen species (ROS) generation and increase endothelial cell leakage. Collectively, P16Ink4a represents an “antagonistic pleiotropy” gene, which is on the one hand required to prevent ROS generation and endothelial damage and on the other hand at high levels inhibits angiogenesis through induction of senescence.
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Project description:Using a mouse model of chronic myelogenous leukemia (CML), here we report that HIF1α plays a crucial role in survival maintenance of leukemia stem cells (LSCs). Deletion of HIF1α impairs the propagation of CML through impairing cell cycle progression and inducing apoptosis of LSCs. Deletion of HIF1α results in elevated expression of p16Ink4a and p19Arf in LSCs, and knockdown of p16Ink4a and p19Arf rescues the defective colony-forming ability of HIF1α-/- LSCs. To further identify the pathways in which Hif1a regulates function of LSCs, we performed a comparative DNA microarray analysis using total RNA isolated from BCR-ABL-expressing wild type LSCs and BCR-ABL-expressing Hif1a-/- LSCs. The result was validated by quantitative real-time PCR analysis of non-BCR-ABL-expressing Lin-Sca-1+c-Kit+ cells, BCR-ABL-expressing wild type LSCs, and BCR-ABL-expressing Hif1a-/- LSCs.
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Project description:In this study we examine the outcomes of p16INK4a activation in the adult epidermis. We found that prolonged expression of p16INK4a induces epidermal hyperplasia and dysplasia. We also found that continued p16INK4a expression increased the number of epidermal papillomas that developed after carcinogen treatment. Profling of p16INK4a- expressing cells showed elevated levels of Wnt-pathway ligands and targets, and pharmacologic or genetic Wnt inhibition suppressed p16-induced hyperplasia. In human actinic keratosis, a precursor of squamous cell carcinoma, p16-expressing cells are typically found adjacent to dividing cells, consistent with paracrine interaction. These findings reveal that in addition to its cell-autonomous role in blocking cell proliferation, p16 can induce hyperplasia through paracrine stimulation, suggesting that its activity contributes to the formation of early premalignant epidermal lesions.
2020-04-06 | GSE121728 | GEO
Project description:In this study we examine the outcomes of p16INK4a activation in the adult epidermis. We found that prolonged expression of p16INK4a induces epidermal hyperplasia and dysplasia. We also found that continued p16INK4a expression increased the number of epidermal papillomas that developed after carcinogen treatment. Profling of p16INK4a- expressing cells showed elevated levels of Wnt-pathway ligands and targets, and pharmacologic or genetic Wnt inhibition suppressed p16-induced hyperplasia. In human actinic keratosis, a precursor of squamous cell carcinoma, p16-expressing cells are typically found adjacent to dividing cells, consistent with paracrine interaction. These findings reveal that in addition to its cell-autonomous role in blocking cell proliferation, p16 can induce hyperplasia through paracrine stimulation, suggesting that its activity contributes to the formation of early premalignant epidermal lesions.
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Project description:Cellular senescence plays a causal role in ageing and, in mouse, depletion of p16INK4a-expressing senescent cells delays ageing-associated disorders. Adenosine deaminases acting on RNA (ADARs) RNA editing enzymes are also implicated as important regulators of human ageing and ADAR inactivation causes age-associated pathologies such as neurodegeneration in model organisms. However, the role, if any, of ADARs in cellular senescence is unknown. Here we show that ADAR1 is post-transcriptionally downregulated by autophagic degradation to promote senescence through upregulating p16INK4a. ADAR1 is downregulated during senescence post-transcriptionally by autophagy-lysosomal pathway and the downregulation is sufficient to drive senescence in both in vitro and in vivo models. Senescence induced by ADAR1 downregulation is p16INK4a dependent and independent of its RNA editing function. Mechanistically, ADAR1 promotes SIRT1 expression by affecting its RNA stability through HuR, an RNA binding protein that increases the half-life and steady state levels of its target mRNAs. And SIRT1, in turn, antagonizes translation of mRNA encoding p16INK4a. Hence, downregulation of ADAR1 and SIRT1 mediates p16INK4aupregulation by enhancing its mRNA translation. Finally, Adar1 is downregulated during ageing of mouse tissues such as brain, ovary, and intestine, and Adar1 expression correlates with Sirt1 expression in these tissues in mice. Together, our study reveals an RNA-editing independent role of ADAR1 in regulating senescence by post-transcriptionally controlling p16INK4a expression.
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Project description:In this study, we generated a novel nuclear-localized red fluorescence knock-in reporter allele (Ins2.Apple) for mouse pancreatic beta-cells. Beta-cells were isolated by FACS from 60-day-old mice, segregated by sex, and RNA-sequencing was performed to assess sex-specific differences in beta-cell gene expression profiles. We also isolated beta-cells (by FACS) from MIP-GFP mice at 60 days of age. RNA-sequencing was performed, and was compared to that of Ins2.Apple beta cells, to assess gene expression changes brought on by the presence of the MIP-GFP transgene.
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