Single Cell Transcriptomics Reveals TGF-Beta and HMGA1 as Global Markers of Transcriptional Diversity in Cellular Senescence
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ABSTRACT: Here, through single-cell transcriptional profiling of genetically homogenous clonal cell lines, we analyzed subpopulations in all three major forms of senescence, namely Oncogene Induced Senescence (OIS), Replicative Senescence (RS), and DNA Damage Induced Senescence (DDIS).
Project description:By transcriptome analysis of IMR-90 human fibroblasts following oncogene-induced senescence (OIS) and replicative senescence (RS), we identified commonly regulated genes in both conditions.
Project description:While, transcriptional and epigenetic changes associated senescence processes are well studied, the 3D chromatin changes associated with it remains elusive. In this study, we have generated genome wide chromatin interaction maps (Hi-C), epigenetic (ChIP-Seq), replication-timing and gene expression (RNA-Seq) profiles from replication induced (RS) and oncogene induced (OIS) senescent cells. As senescence associated heterochromatin foci (SAHFs) differentiates both RS and OIS nuclei, we identified the regions that constitute SAHFs and called them Senescence Associated Heterochromatin Domains (SAHDs). Further, screening of candidate factors for SAHF induction allowed us to identify DNMT1 as a novel component that induces SAHFs by stimulation of HMGA2 expression. DNMT1 depletion does not reverse the senescence process, however, instead, depleted cells transition to a 3D genome conformation akin to that of cells in replicative senescence, suggesting that acute senescence induction (OIS) involves SAHF formation in addition to the RS-dependent 3D genome rewiring.
Project description:H3K9me3 ChIPseq in Proliferating and Senescent IMR90s We used ChIP-seq to examine the global binding of H3K9me3 in human IMR90 replicative senescence (RS) and oncogene-induced (OIS)
Project description:Cellular senescence is a state of stable cell growth arrest induced by various stimuli such as oncogene expression and telomere shortening, referred to as oncogene-induced senescence (OIS) and replicative senescence (RS), respectively. Senescence is accompanied not only by global transcriptional alterations but also by 3D genome reorganization. Here we demonstrate that the human condensin II complex participates in cellular senescence via gene regulation and reorganization of euchromatic A and heterochromatic B chromatin compartments. OIS and RS are accompanied by A-to-B and B-to-A compartmental transitions, the latter of which occur more frequently and account for 15% of the human genome. Mechanistically, condensin is enriched at A compartments, especially at gene promoters and typical/super enhancers, and implicated in the B-to-A transitions. Genes present at B-to-A-switching regions tend to be up-regulated. The full activation of senescence genes (SASP genes and p53 targets) requires condensin; its depletion impairs senescence markers such as the activity of senescence-associated beta-galactosidase (SA-beta-gal) and senescence-associated heterochromatic foci (SAHF). This study describes that condensin reinforces euchromatic A compartments and is required for optimal expression of senescence genes, thereby contributing to the establishment and maintenance of the senescent state.
Project description:Cellular senescence constitutes a generally irreversible proliferation barrier, accompanied by macromolecular damage and metabolic rewiring. Several senescence types have been identified based on the initiating stimulus, such as replicative (RS), stress-induced (SIS) and oncogene-induced senescence (OIS). Reduced protein synthesis is considered a senescence hallmark, but whether this trait pertains to various senescence subtypes and if distinct molecular mechanisms are involved remain largely unknown. Here, we analyze large published or experimentally produced RNA-seq and Ribo-seq datasets to determine whether major translation-regulating entities such as ribosome stalling, the presence of uORFs/dORFs and IRES elements may differentially contribute to translation deficiency in senescence subsets. We show that translation-regulating mechanisms may not be directly relevant to RS, however uORFs are significantly enriched in SIS. Interestingly, ribosome stalling, uORF/dORF patterns and IRES elements comprise predominant mechanisms upon OIS, strongly correlating with Notch pathway activation. Our study provides for the first time evidence that major translation dysregulation mechanisms/patterns occur during cellular senescence, but at different rates depending on the stimulus type. The degree at which those mechanisms accumulate directly correlates with translation deficiency levels. Our thorough analysis contributes to elucidating crucial and so far unknown differences in the translation machinery and ribosome biogenesis between senescence subsets.
Project description:Cellular senescence is a stable proliferation arrest associated with an altered secretory pathway, the Senescence-Associated Secretory Phenotype (SASP). However, cellular senescence is initiated by diverse molecular triggers, such as activated oncogenes and shortened telomeres, and is associated with varied and complex physiological endpoints, such as tumor suppression and tissue aging. The extent to which distinct triggers activate divergent modes of senescence that might be associated with different physiological endpoints is largely unknown. To begin to address this, we performed gene expression profiling to compare the senescence programs associated with two different modes of senescence, oncogene-induced senescence (OIS) and replicative senescence (RS [in part caused by shortened telomeres]). While both OIS and RS are associated with many common changes in gene expression compared to control proliferating cells, they also exhibit substantial differences. These results are discussed in light of potential physiological consequences, tumor suppression and aging. We used microarrays to detail the global programme of gene expression after oncogene induced senescence.
Project description:Cellular senescence is a stable proliferation arrest associated with an altered secretory pathway, the Senescence-Associated Secretory Phenotype (SASP). However, cellular senescence is initiated by diverse molecular triggers, such as activated oncogenes and shortened telomeres, and is associated with varied and complex physiological endpoints, such as tumor suppression and tissue aging. The extent to which distinct triggers activate divergent modes of senescence that might be associated with different physiological endpoints is largely unknown. To begin to address this, we performed gene expression profiling to compare the senescence programs associated with two different modes of senescence, oncogene-induced senescence (OIS) and replicative senescence (RS [in part caused by shortened telomeres]). While both OIS and RS are associated with many common changes in gene expression compared to control proliferating cells, they also exhibit substantial differences. These results are discussed in light of potential physiological consequences, tumor suppression and aging.
Project description:Blocking of nucleocytoplasmic trafficking is an essential feature of replicative senescence (RS). However, whether nuclear barrier per se causes cellular senescence still remains elusive. Here, we show that nuclear barrier induced by blocking nucleocytoplasmic trafficking, especially nuclear export, elicits RS-like changes in SA-β-gal activity, DNA damage, and expression of cell cycle regulators. Comparative transcriptome analysis revealed that nuclear barrier-induced senescence (NBIS) was most similar in gene expression changes to RS compared to senescence induced by stresses (oxidative stress, DNA damage and oncogene), implying that nuclear barrier induces RS-like physiological senescence-associated changes. Shared senescence-related processes between NBIS and RS included lysosomal degradation, nuclear transport, and translation, resulting in coordinated reduction in transmission of extrinsic signals to nucleus and intracellular protein supply from nucleus. Notably, these processes were conserved in yeast aging. Therefore, we propose NBIS as a novel modality of cellular senescence, representing the fundamental nature of physiological aging in eukaryotes.
Project description:Senescent cells exhibit a reduced response to intrinsic and extrinsic stimuli. This reduction could be explained by disrupted nuclear transmission of signals. However, this hypothesis required more evidence to complete as a new modality of cellular senescence. Proteomic analysis of the cytoplasmic and nuclear fractions from young and senescent cells revealed disruption of nucleocytoplasmic trafficking (NCT) as an essential feature of replicative senescence (RS) at the global level. Blocking NCT either chemically or genetically induced RS-like senescence phenotypes, named as nuclear barrier-induced senescence (NBIS). Transcriptomic analysis revealed that NBIS had the most similar gene expression pattern to RS, compared with other stress-induced types of cellular senescence. Core proteomic and transcriptomic shared patterns between RS and NBIS included upregulation of endocytosis-lysosome network and downregulation of NCT in senescent cells, which were also conserved in yeast aging model. These results implicate an aging-dependent coordinated reduction in the transmission of extrinsic signals to the nucleus and in the nucleus-to-cytoplasm supply of proteins/RNAs. We further showed that the aging-associated decrease in Sp1 transcription factor expression was responsible for downregulation of NCT. Our results suggest that NBIS is a modality of cellular senescence that can represent the nature of physiological aging in eukaryotes.
Project description:we attempted to identify the genetic changes in the remaining MSCs after BPTES treatment and identified senescence-related candidate genes that recovered after BPTES treatment. The transcriptomes of U-MSCs and rS-MSCs were analyzed to determine the genetic significance of replicative senescence in WJ-MSCs