Project description:Aging is accompanied by physiological impairments, which, in insulin-responsive tissues, including the liver, predispose individuals to metabolic disease. However, the molecular mechanisms underlying these changes remain largely unknown. Here, we analyze genome-wide profiles of RNA and chromatin organization in the liver of young (3 months) and old (21 months) mice. Transcriptional changes suggest that de-repression of the nuclear receptors PPARM-NM-1, PPARM-NM-3, and LXRM-NM-1 in aged mouse liver leads to activation of targets regulating lipid synthesis and storage, whereas age-dependent changes in nucleosome occupancy are associated with binding sites for both known regulators (forkhead factors and nuclear receptors) and for novel candidates associated with nuclear lamina (Hdac3 and Srf) implicated to govern metabolic function of aging liver. Winged-helix factor Foxa2 and nuclear receptor co-repressor Hdac3 exhibit reciprocal binding pattern at PPARM-NM-1 targets contributing to gene expression changes that lead to steatosis in aged liver. Genome-wide nucleosome profiles (MNase-Seq) from young (3 months) and old (21 months) mouse livers
Project description:Aging is accompanied by physiological impairments, which, in insulin-responsive tissues, including the liver, predispose individuals to metabolic disease. However, the molecular mechanisms underlying these changes remain largely unknown. Here, we analyze genome-wide profiles of RNA and chromatin organization in the liver of young (3 months) and old (21 months) mice. Transcriptional changes suggest that de-repression of the nuclear receptors PPARα, PPARγ, and LXRα in aged mouse liver leads to activation of targets regulating lipid synthesis and storage, whereas age-dependent changes in nucleosome occupancy are associated with binding sites for both known regulators (forkhead factors and nuclear receptors) and for novel candidates associated with nuclear lamina (Hdac3 and Srf) implicated to govern metabolic function of aging liver. Winged-helix factor Foxa2 and nuclear receptor co-repressor Hdac3 exhibit reciprocal binding pattern at PPARα targets contributing to gene expression changes that lead to steatosis in aged liver. Genome-wide expression profiles (RNA-Seq) from young (3 months) and old (21 months) mouse livers
Project description:To describe the protein profile in hippocampus, colon and ileum tissue’ changing after the old faeces transplants, we adopted a quantitative label free proteomics approach.
Project description:All eukaryotic cells divide a finite number of times, termed replicative aging, but the reason for this is not clear. Consistent with the decreased total histone protein levels in aged Saccharomyces cerevisiae, which is a cause of aging (1), we find that nucleosome occupancy decreases 50% across the whole genome during replicative aging by spike-in controlled MNase sequencing. Nucleosomes become fuzzier or move to sequences predicted to better accommodate histone octamers. All yeast genes are induced during aging. Genes that are repressed in young cells are most induced, accompanied by nucleosome loss from their promoters that have unique chromatin organization. Contrary to the loss of mitochondrial function during aging, mitochondrial DNA content increases and unprecedented levels of large-scale chromosomal alterations and increased retrotransposition are observed. Mnase-Seq experiments were carried out for young yeast, old yeast, and old yeast with histone over expression, 3 replicates were done for each category. RNA-Seq were carried out for the same categories of yeast cells but with 2 replicates for each. Genome-Seq were done for the young and old yeast with 2 replicates for each.
Project description:Aging is accompanied by physiological impairments, which, in insulin-responsive tissues, including the liver, predispose individuals to metabolic disease. However, the molecular mechanisms underlying these changes remain largely unknown. Here, we analyze genome-wide profiles of RNA and chromatin organization in the liver of young (3 months) and old (21 months) mice. Transcriptional changes suggest that de-repression of the nuclear receptors PPARα, PPARγ, and LXRα in aged mouse liver leads to activation of targets regulating lipid synthesis and storage, whereas age-dependent changes in nucleosome occupancy are associated with binding sites for both known regulators (forkhead factors and nuclear receptors) and for novel candidates associated with nuclear lamina (Hdac3 and Srf) implicated to govern metabolic function of aging liver. Winged-helix factor Foxa2 and nuclear receptor co-repressor Hdac3 exhibit reciprocal binding pattern at PPARα targets contributing to gene expression changes that lead to steatosis in aged liver. Genome-wide location analysis (ChIP-Seq) of Foxa2 and Hdac3 from young (3 months) and old (21 months) mouse livers
Project description:Nucleosome remodeling factors regulate the occupancy and positioning of nucleosomes genome-wide through ATP-driven DNA translocation. While many nucleosomes are well- and consistently positioned, some nucleosomes and nucleosome-like structures are more sensitive to nuclease digestion or transitory in nature. To better understand the role of nucleosome remodeling factors in generating and clearing these alternative nucleosome structures, we depleted murine embryonic stem cells of the remodeler ATPases BRG1 and SNF2H then performed MNase-seq in murine embryonic stem cells. We performed MNase-seq under high- and low-MNase conditions to assess the effects of nucleosome remodeling factors on nuclease-sensitive or “fragile” nucleosome occupancy. In parallel, we gel-extracted MNase-digested fragments to enrich for another alternative nucleosome structure, the overlapping dinucleosome. Overlapping dinucleosomes are composed of two canonical nucleosomes, asymmetrically lacking one H2A:H2B dimer and wrapped by ~250 bp of DNA. In vitro studies of nucleosome remodeling have suggested that the collision of adjacent nucleosomes by nucleosome sliding can stimulate formation of overlapping dinucleosomes. Using these methods, we were able to identify fragile nucleosomes and overlapping dinucleosomes near transcription start sites and gene-distal DNaseI hypersensitive sites in mouse embryonic stem cells, among other loci. We find that BRG1 consistently stimulates occupancy of fragile nucleosomes but represses occupancy of overlapping dinucleosomes through its nucleosome remodeling function, while SNF2H expression slightly increases fragile nucleosome occupancy.