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High-resolution Hi-C reveals increased chromatin looping with senescence associated with hypomethylation and retrotransposon derepression [Long Read DNA-seq]

ABSTRACT: This study presents the highest-resolution chromatin map of cellular senescence to date, shedding light on how genomic architecture is altered with this damaging phenotype. Senescence, a driver of aging, is a pro-inflammatory state of proliferative arrest caused by DNA damage; it is associated with epigenetic changes, including those to chromatin organization. We created ~3kb Hi-C contact maps of proliferating, quiescent, and replicative senescent lung fibroblasts, and also compared these to oncogene-induced senescence. Our findings confirm a loss of heterochromatin, with a shift towards the A compartment and A subcompartments. We establish a novel loop analysis framework, revealing the ~six times more unique loops with senescence, which lose methylation at their anchors. Additionally, we present a custom long-read reference genome highlighting structural changes supporting retrotransposon derepression, particularly at a defined ‘hotspot’. These architectural changes contribute to senescence, as they promote cell cycle arrest and inflammation, as well as epigenetic drift.

ORGANISM(S): Homo sapiens

PROVIDER: GSE268488 | GEO | 2024/10/30

REPOSITORIES: GEO

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Project description:DallePazze2014 - Cellular senescene-induced mitochondrial dysfunction This model is described in the article: Dynamic modelling of pathways to cellular senescence reveals strategies for targeted interventions. Dalle Pezze P, Nelson G, Otten EG, Korolchuk VI, Kirkwood TB, von Zglinicki T, Shanley DP. PLoS Comput. Biol. 2014 Aug; 10(8): e1003728 Abstract: Cellular senescence, a state of irreversible cell cycle arrest, is thought to help protect an organism from cancer, yet also contributes to ageing. The changes which occur in senescence are controlled by networks of multiple signalling and feedback pathways at the cellular level, and the interplay between these is difficult to predict and understand. To unravel the intrinsic challenges of understanding such a highly networked system, we have taken a systems biology approach to cellular senescence. We report a detailed analysis of senescence signalling via DNA damage, insulin-TOR, FoxO3a transcription factors, oxidative stress response, mitochondrial regulation and mitophagy. We show in silico and in vitro that inhibition of reactive oxygen species can prevent loss of mitochondrial membrane potential, whilst inhibition of mTOR shows a partial rescue of mitochondrial mass changes during establishment of senescence. Dual inhibition of ROS and mTOR in vitro confirmed computational model predictions that it was possible to further reduce senescence-induced mitochondrial dysfunction and DNA double-strand breaks. However, these interventions were unable to abrogate the senescence-induced mitochondrial dysfunction completely, and we identified decreased mitochondrial fission as the potential driving force for increased mitochondrial mass via prevention of mitophagy. Dynamic sensitivity analysis of the model showed the network stabilised at a new late state of cellular senescence. This was characterised by poor network sensitivity, high signalling noise, low cellular energy, high inflammation and permanent cell cycle arrest suggesting an unsatisfactory outcome for treatments aiming to delay or reverse cellular senescence at late time points. Combinatorial targeted interventions are therefore possible for intervening in the cellular pathway to senescence, but in the cases identified here, are only capable of delaying senescence onset. This model is hosted on BioModels Database and identified by: BIOMD0000000582. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:BackgroundThe Cancer/Testis Antigens (CTAs) are a heterogeneous group of proteins whose expression is typically restricted to the testis. However, they are aberrantly expressed in most cancers that have been examined to date. Broadly speaking, the CTAs can be divided into two groups: the CTX antigens that are encoded by the X-linked genes and the non-X CT antigens that are encoded by the autosomes. Unlike the non-X CTAs, the CTX antigens form clusters of closely related gene families and their expression is frequently associated with advanced disease with poorer prognosis. Regardless however, the mechanism(s) underlying their selective derepression and stage-specific expression in cancer remain poorly understood, although promoter DNA demethylation is believed to be the major driver.MethodsHere, we report a systematic analysis of DNA methylation profiling data from various tissue types to elucidate the mechanism underlying the derepression of the CTAs in cancer. We analyzed the methylation profiles of 501 samples including sperm, several cancer types, and their corresponding normal somatic tissue types.ResultsWe found strong evidence for specific DNA hypomethylation of CTA promoters in the testis and cancer cells but not in their normal somatic counterparts. We also found that hypomethylation was clustered on the genome into domains that coincided with nuclear lamina-associated domains (LADs) and that these regions appeared to be insulated by CTCF sites. Interestingly, we did not observe any significant differences in the hypomethylation pattern between the CTAs without CpG islands and the CTAs with CpG islands in the proximal promoter.ConclusionOur results corroborate that widespread DNA hypomethylation appears to be the driver in the derepression of CTA expression in cancer and furthermore, demonstrate that these hypomethylated domains are associated with the nuclear lamina-associated domains (LADS). Taken together, our results suggest that wide-spread methylation changes in cancer are linked to derepression of germ-line-specific genes that is orchestrated by the three dimensional organization of the cancer genome.

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High-resolution Hi-C reveals increased chromatin looping with senescence associated with hypomethylation and retrotransposon derepression [Long Read DNA-seq]

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