Project description:Gene expression programs are regulated by enhancers which act in a context-specific manner, and can reside at great distances from their target genes. Extensive three-dimensional (3D) genome reorganization occurs in senescence, but how enhancer interactomes are reconfigured during this process is just beginning to be understood. Here we generated high-resolution contact maps of active enhancers and their target genes, assessed chromatin accessibility, and established one-dimensional maps of various histone modifications and transcription factors to comprehensively understand the regulation of enhancer configuration during senescence. Hyper-connected enhancer communities/cliques formed around genes that are highly expressed and within essential gene pathways in each cell state. In addition, motif analysis indicates the involvement of specific transcription factors in hyper-connected regulatory elements in each condition; importantly, MafK, a bZIP family transcription factor, was upregulated in senescence, and reduced expression of MafK ameliorated the senescence phenotypes. Because the accumulation of senescent cells is a key feature of aging, we further investigated enhancer connectomes in the liver of young and aged mice. Hyper-connected enhancer communities were identified during aging, which regulate essential genes that maintain cell differentiation and homeostasis. These findings reveal that hyper-connected enhancer communities correlate with high gene expression in senescence and aging and provide potential hotspots for therapeutic intervention in aging and age-associated diseases.
Project description:Gene expression programs are regulated by enhancers which act in a context-specific manner, and can reside at great distances from their target genes. Extensive three-dimensional (3D) genome reorganization occurs in senescence, but how enhancer interactomes are reconfigured during this process is just beginning to be understood. Here we generated high-resolution contact maps of active enhancers and their target genes, assessed chromatin accessibility, and established one-dimensional maps of various histone modifications and transcription factors to comprehensively understand the regulation of enhancer configuration during senescence. Hyper-connected enhancer communities/cliques formed around genes that are highly expressed and within essential gene pathways in each cell state. In addition, motif analysis indicates the involvement of specific transcription factors in hyper-connected regulatory elements in each condition; importantly, MafK, a bZIP family transcription factor, was upregulated in senescence, and reduced expression of MafK ameliorated the senescence phenotypes. Because the accumulation of senescent cells is a key feature of aging, we further investigated enhancer connectomes in the liver of young and aged mice. Hyper-connected enhancer communities were identified during aging, which regulate essential genes that maintain cell differentiation and homeostasis. These findings reveal that hyper-connected enhancer communities correlate with high gene expression in senescence and aging and provide potential hotspots for therapeutic intervention in aging and age-associated diseases.
Project description:Cellular senescence is an irreversible cell growth arrest state linked to loss of tissue function and aging in mammals. The cellular transition from proliferation to senescence is marked by increased expression of the cell-cycle inhibitor p16INK4A and formation of senescence-associated heterochromatin foci (SAHF). It is known that SAHF formation depends primarily on HIRA-mediated nucleosome assembly of H3.3, and that the serine/threonine protein kinase Pak2 regulates HIRA-mediated nucleosome assembly of histone H3.3. Here, we tested the role of Pak2 in the regulation of cellular senescence. Depletion of Pak2 delays premature cellular senescence in both oncogene-induced senescence in human fibroblasts IMR90 cells and in oxidative stress induced senescence of mouse embryonic fibroblasts. Furthermore, overexpression of Pak2 promotes senescence of IMR90 cells. Importantly, depletion of Pak2 in mice delays the onset of some of the aging-associated phenotypes and extend life span of a progeroid mouse model. Lastly, we showed that Pak2 is required for expression of a group of genes involved in cellular senescence and regulates the deposition of newly synthesized H3.3 onto chromatin in senescent cells. Together, our results demonstrate that Pak2 is an important regulator of cellular senescence and organismal aging, in part through the regulation of gene expression and H3.3 nucleosome assembly.
Project description:Cellular senescence can be transmitted to neighbouring cells in a paracrine manner through different mechanisms, including soluble factors released by senescent cells. To understand the dynamic regulation of paracrine senescence, here we investigated gene expression profiles in normal human fibroblasts (IMR90) exposed to conditioned medium generated by an inducible model of fibroblast Oncogene-Induced Senescence (IMR90-ER:RAS) at different time points after induction of senescence.
Project description: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.
Project description:Kidney is a vital organ responsible for homeostasis in the body. To retard kidney aging is of great importance for maintaining body health. Whereas the therapeutic strategies targeting against kidney aging are not elucidated. Recent studies show mitochondrial dysfunction is critical for renal tubular cell senescence and kidney aging, however, the underlying mechanisms of mitochondrial dysfunction in kidney aging have not been demonstrated. Herein, we found calcium overload, and the mitochondrial calcium uniporter (MCU) was induced in renal tubular cells and aged kidney. To activate MCU not only triggered mitochondrial calcium overload, but also induced reactive oxygen species (ROS) production and cellular senescence and age-related kidney fibrosis. Inversely, to block MCU or chelate calcium diminished ROS generation, restored mitochondrial homeostasis, and retarded cell senescence and protected against kidney aging. These results demonstrate MCU plays a key role in promote renal tubular cell senescence, which provides a new insight on the therapeutic strategy for fighting against kidney aging.