Persistent chromatin modifications induced by high fat diet
ABSTRACT: Obesity is a highly heritable complex disease that results from the interaction of multiple genetic and environmental factors. Formerly obese individuals are susceptible to metabolic disorders later in life, even after lifestyle changes are made to mitigate the obese state. This is reminiscent of the metabolic memory phenomenon originally observed for persistent complications in diabetic patients, despite subsequent glycemic control. Epigenetic modifications represent a potential mediator of this observed memory. We previously demonstrated that a high fat (HF) diet leads to changes in chromatin accessibility in the mouse liver. The regions of greatest chromatin changes in accessibility are largely strain dependent, indicating a genetic component in diet-induced chromatin alterations. We have now examined the persistence of diet-induced chromatin accessibility changes upon diet reversal in two strains of mice. We find that a substantial fraction of loci that undergo chromatin accessibility changes with HF diet remain in the remodeled state after diet reversal in C57BL/6J mice. In contrast, the vast majority of diet-induced chromatin accessibility changes in A/J mice are transient. Our data also indicate that the persistent chromatin accessibility changes observed in C57BL/6J are associated with specific transcription factors and histone posttranslational modifications. The persistent loci identified here are likely to be contributing to the overall phenotype and are attractive targets for therapeutic intervention. Examination of chromatin remodeling with FAIRE-seq in livers of C57BL/6J and A/J mice on three diet regimen: 1) control diet for 16 weeks, 2) high fat diet for 16 weeks, or 3) high fat diet for 8 weeks with control diet for 8 weeks. These chromatin profiles were complemented with gene expression data (RNA-seq)
Project description:Chromatin accessibility is a hallmark of active regulatory function in the genome and variation of chromatin accessibility across individuals has been shown to contribute to complex traits and disease susceptibility. However, the mechanisms responsible for chromatin variation among different individuals and how this variation contributes to phenotypic diversity remain poorly understood. We examined chromatin accessibility variation in liver tissue from seven strains of adult mice that have phenotypic diversity in response to a high-fat/high-sucrose diet. Remarkably, nearly 40% of the loci with the greatest degree of chromatin variability across the strains are associated with transposable elements (TEs), with evolutionarily younger TEs being particularly enriched for regions of chromatin variation. We found that evolutionary younger and older TEs have differential chromatin accessibility profiles and are enriched for binding sites of different transcription factors, indicating the role of TEs in the evolution of regulatory networks in the liver. We also demonstrate that TE polymorphisms and epigenetic regulation of TEs contribute to regulatory variation across different strains through providing binding sites for liver transcription factors. Intriguingly, variable chromatin loci that are associated with liver metabolism are primarily TE-associated. We demonstrate that TEs contribute to regulatory variation in liver and have downstream effects on metabolism. Our data reveal TEs as a novel and important contributor to regulatory and phenotypic variation in the liver and suggest that regulatory variation at TEs is a major contributor to phenotypic variation in populations. Examination of chromatin accessibility with FAIRE-seq in livers of male mice (A/J, AKR/J, BALB/cJ, C57BL/6J, C3H/HeJ, CBA/J, DBA/2J, BXH2/TyJ, and BXH19/TyJ) fed a high-fat, high-sucrose diet.
Project description:The tissue-specific packaging of the genome into the nucleus through chromatin is fundamentally involved in gene regulation, and aberrant modifications to chromatin are a hallmark of many diseases. We show here that a high fat (HF) diet leads to substantial chromatin remodeling in the livers of C57BL/6J mice, as compared to mice fed a control diet. Regions of the genome that display the greatest variation in chromatin accessibility between HF and control regions are targeted by transcription factors with known roles in the liver including HNF4α, CEBP/α, and FOXA1. Whereas livers of DBA/2J mice fed a HF or control diet also demonstrate diet-induced chromatin remodeling, the regions displaying the greatest variation are largely distinct from those observed in B6 livers, indicating a crosstalk between genetic and epigenetic components in determining how diet-induced chromatin remodeling is associated with metabolic disease progression. Examination of chromatin remodeling with FAIRE-seq in livers of mice (C57BL/6J and DBA/2J) fed a high fat or control diet. Complemented with gene expression and H3K4me1 analyses
Project description:We profiled chromatin accessibility across the genome of HSPCs treated with either a small molecule inhibitor of G9a/GLP or DMSO. We observed that chromatin accessibility is dramatically altered at the regions of H3K9me2 nucleation. We have characterized the regions of H3K9me2 nucleation, revealing that H3K9me2 is nucleated in HSPCs at CpG islands (CGIs) and CGI-like sequences across the genome. Our analysis furthermore revealed a bias of H3K9me2 nucleation towards regions with low rates of C->T deamination, which typically lack DNA methylation. Lastly we examined the interaction of H3K9me2 and DNA methylation and determined that chromatin accessibility changes upon loss of H3K9me2 are dependent on the presence of DNA methylation. Examination of chromatin remodeling with FAIRE-seq in HSPCs treated with either a small molecule inhibitor of G9a/GLP or DMSO
Project description:We studied the effect of dietary fat type, varying in polyunsaturated/saturated fatty acid ratio's (P/S) on development of metabolic syndrome. C57Bl/6J mice were fed purified high-fat diets (45E% fat) containing palm oil (HF-PO; P/S 0.4), olive oil (HF-OO; P/S 1.1) or safflower oil (HF-SO; P/S 7.8) for 8 weeks. A low-fat palm oil diet (LF-PO; 10E% fat) was used as a reference. Additionally, we analyzed diet-induced changes in gut microbiota composition and mucosal gene expression. The HF-PO diet induced a higher body weight gain and liver triglyceride content compared to the HF-OO, HF-SO or LF-PO diet. In the intestine, the HF-PO diet reduced microbial diversity and increased the Firmicutes/Bacteroidetes ratio. Although this fits a typical obesity profile, our data clearly indicate that an overflow of the HF-PO diet to the distal intestine, rather than obesity itself, is the main trigger for these gut microbiota changes. A HF-PO diet-induced elevation of lipid metabolism-related genes in the distal small intestine confirmed the overflow of palm oil to the distal intestine. Some of these lipid metabolism-related genes were previously already associated with the metabolic syndrome. In conclusion, our data indicate that saturated fat (HF-PO) has a more stimulatory effect on weight gain and hepatic lipid accumulation than unsaturated fat (HF-OO and HF-SO). The overflow of fat to the distal intestine on the HF-PO diet induced changes in gut microbiota composition and mucosal gene expression. We speculate that both are directly or indirectly contributive to the saturated fat-induced development of obesity and hepatic steatosis. Keywords: Diet intervention study Nine-week-old C57Bl/6J mice were fed a low-fat diet (LF-PO) and three different types of high-fat diet, based on palm oil (HF-PO; P/S1.0), olive oil (HF-OO; P/S4.6) and safflower oil (HF-SO; P/S10.1) for 8 weeks. Body weight was recorded weekly and after 7 weeks of diet intervention an oral glucose tolerance test was performed. After 2 weeks of diet intervention, 6 mice per high-fat diet group were anaesthetized with a mixture of isofluorane (1.5%), nitrous oxide (70%) and oxygen (30%) and the small intestines were excised. Adhering fat and pancreatic tissue were carefully removed. The small intestines were divided in three equal parts along the proximal to distal axis (SI 1, SI 2 and SI 3) and microarray analysis was performed on mucosal scrapings.
Project description:Background: Consumption of high fat diets has negative impacts on health and well-being, some of which may be epigenetically regulated. Selenium and folate are two compounds which influence epigenetic mechanisms. We investigated the hypothesis that post-weaning supplementation with adequate levels of selenium and folate in mouse offspring fed a high fat, low selenium and folate diet during gestation and lactation will lead to epigenetic changes of potential importance for long-term health. Female offspring of mothers fed the experimental diet were either maintained on this diet (HF-low-low), or weaned onto a high-fat diet with sufficient levels of selenium and folate (HF-low-suf), for 8 weeks. Gene and protein expression, DNA methylation, and histone modifications were measured in colon and liver of female offspring. Results: Adequate levels of selenium and folate post-weaning affected gene expression in colon and liver of offspring, including decreasing Slc2a4 gene expression. Protein expression was only altered in the liver. There was no effect of adequate levels of selenium and folate on global histone modifications in the liver. Global liver DNA methylation was decreased in mice switched to adequate levels of selenium and folate, but there was no effect on methylation of specific CpG sites within the Slc2a4 gene in liver. Conclusions: Post-weaning supplementation with adequate levels of selenium and folate in female offspring of mice fed high-fat diets during gestation and lactation can alter global DNA methylation in liver. This may be one mechanism by which the negative effects of a poor diet during early life can be ameliorated. Further research is required to establish what role epigenetic changes play in mediating observed changes in gene and protein expression, and the relevance of these changes to health. Female wild type C57BL/6 mice (Animal Resource Centre, Western Australia) were fed a High Fat diet containing low levels of selenium and folate (HF-Low) for 7 days prior to mating with male C57BL/6 mice (Ruakura Small Animal Facility, Hamilton, New Zealand). Mothers were maintained on the HF-Low diet throughout gestation and lactation. Offspring of these female mice were randomly assigned to one of two different dietary treatments: either the same diet as the mothers (HF-Low), or a High Fat diet containing adequate selenium and folate (HF-Suf). At 12 weeks of age, mice were euthanized and colon and liver samples taken for microarray, proteomics, and DNA methylation analyses. Genomic DNA, total RNA and protein from whole colon and liver tissue was extracted using an AllPrep® DNA/RNA/Protein mini kit (Qiagen, Cat number 80004). Colon and liver RNA from six female offspring on the HF-Low diet was compared with colon and liver RNA from six female offspring on the HF-Suf diet. All individual RNA samples were hybridized against a common reference RNA on separate arrays. The reference RNA was prepared by pooling in equimolar proportions RNA extracted from the intestine and liver of twelve female C57BL/6 mice, these being all of the mice from which samples were derived for microarray analysis in the current study.
Project description:Comprehensive sequencing of human cancers has identified recurrent mutations in genes encoding chromatin regulatory proteins. For clear cell renal cell carcinoma (ccRCC), three of the five commonly mutated genes encode the chromatin regulators PBRM1, SETD2, and BAP1. How these mutations alter the chromatin landscape and transcriptional program in ccRCC or other cancers is not understood. Here, we identified alterations in chromatin organization and transcript profiles associated with mutations in chromatin regulators in a large cohort of primary human kidney tumors. By associating variation in chromatin organization with mutations in SETD2, which encodes the enzyme responsible for H3K36 trimethylation, we found that changes in chromatin accessibility occurred primarily within actively transcribed genes. This increase in chromatin accessibility was linked with widespread alterations in RNA processing, including intron retention and aberrant splicing, affecting approximately 25% of all expressed genes. Further, decreased nucleosome occupancy proximal to misspliced exons was observed in tumors lacking H3K36me3. These results directly link mutations in SETD2 to chromatin accessibility changes and RNA processing defects in cancer. Detecting the functional consequences of specific mutations in chromatin regulatory proteins in primary human samples could ultimately inform the therapeutic application of an emerging class of chromatin-targeted compounds. Additional file: MutationAnnotation.txt- contains sample ID, location of variant on hg19, reference allele, alternate allele, reference depth, alternate depth, frequency, confidence score, gene symbol, mutation type, mutation location (transcript ID and exon number, if applicable), and amino acid change.
Project description:Epithelial-mesenchymal transition (EMT), the process whereby cells gain migratory and invasive properties characteristic of mesenchymal cells, plays a central role in embryogenesis and wound healing in a wide range of tissues. However, EMT has also been linked to the formation of cancer stem cells (CSCs). Many of the signaling pathways involved in EMT have also been implicated in CSC formation but the processes that contribute uniquely to CSC formation remain elusive. We have previously demonstrated that PKCθ activation is critical for EMT induction and concomitant CSC formation in the breast cancer luminal epithelial cell line, MCF7. To discover how PKC-induced alterations in the epigenome influence the EMT and CSC formation in MCF-7 cells, we employed a combination of expression profiling and Formaldehyde Assisted Regulatory Elements (FAIRE)-sequencing in order to reveal novel links between gene expression and DNA accessibility changes after PKCθ activation. We found that, during EMT, increases in accessibility generally occurred in regions away from transcription start sites, low in CpG, enriched with chromatin marks of enhancer elements and motifs for FOX, AP1, TEAD and AP2. Increases in FOX and AP-1 motif accessibility were associated with genes that exhibited increased expression in CSC, while increased AP-2 accessibility was associated with genes that had higher expression in non-CSCs. This study revealed novel regions of DNA accessibility induced by PKC that contribute to the understanding of how epigenomic plasticity of cells undergoing EMT leads to the activation of genes that drive the CSC program. 2 biological samples were analysed with 2 biological replicates each and a mixed total input.
Project description:Chromatin accessibility is an important functional genomics phenotype that influences transcription factor binding and gene expression. Genome-scale technologies allow chromatin accessibility to be mapped with high-resolution, facilitating detailed analyses into the genetic architecture and evolution of chromatin structure within and between species. We performed Formaldehyde-Assisted Isolation of Regulatory Elements sequencing (FAIRE-Seq) to map chromatin accessibility in two parental haploid yeast species, Saccharomyces cerevisiae and Saccharomyces paradoxus and their diploid hybrid. We show that although broad-scale characteristics of the chromatin landscape are well conserved between these species, accessibility is significantly different for 947 regions upstream of genes that are enriched for GO terms such as intracellular transport and protein localization exhibit. We also develop new statistical methods to investigate the genetic architecture of variation in chromatin accessibility between species, and find that cis effects are more common and of greater magnitude than trans effects. Interestingly, we find that cis and trans effects at individual genes are often negatively correlated, suggesting widespread compensatory evolution to stabilize levels of chromatin accessibility. Finally, we demonstrate that the relationship between chromatin accessibility and gene expression levels is complex, and a significant proportion of differences in chromatin accessibility might be functionally benign. There are 20 samples in total. These consist of 10 FAIRE-seq samples, specifically 6 haploid samples, S. cerevisiae strain UWOPS05_217_3 replicates 1 and 2, S. cerevisiae strain DBVPG1373 replicates 1 and 2, and S. paradoxus strain CBS432 replicates 1 and 2. There are also 4 diploid hybrid samples, hybrid between S. cerevisiae strain UWOPS05_217_3 and S. paradoxus strain CBS432 replicates 1 and 2, and the hybrid between S. cerevisiae strain DBVPG1373 and S. paradoxus strain CBS432 replicates 1 and 2. There are also RNA-seq samples for each of these 10 samples.
Project description:These mouse strains differ in absolute numbers of hematopoietic stem cells but differ genetically only at the Chr 5 congenic locus. We used microarray analysis to identify candidate regulators of hematopoietic stem cells based on differential gene expression patterns. Triplicate RNA samples, except for duplicate DBA/2J samples, were isolated from 80,00-137,000 LSK cells from each strain. Each of the 11 samples were analyzed on individual microarrays on two Illumina Sentrix-Mouse 6 Whole Genome Expression Beadhips.
Project description:In this study we use RNAseq to explore allele specific expression (ASE) in adipose tissue of male and female F1 mice, produced from reciprocal crosses of C57BL/6J and DBA/2J strains. Comparison of the identified cis-eQTLs, to local-eQTLs, that were obtained from adipose tissue expression in two previous population based studies in our laboratory, yields poor overlap between the two mapping approaches, while both local-eQTL studies show highly concordant results. Specifically, local-eQTL studies show ~60% overlap between themselves, while only 15-20% of local-eQTLs are identified as cis by ASE, and less than 50% of ASE genes are recovered in local-eQTL studies. Utilizing recently published ENCODE data, we also find that ASE genes show significant bias for SNPs prevalence in DNase I hypersensitive sites that is ASE direction specific. We suggest a new approach to analysis of allele specific expression that is more sensitive and accurate than the commonly used fisher or chi-square statistics. Our analysis indicates that technical differences between the cis and local-eQTL approaches, such as differences in genomic background or sex specificity, account for relatively small fraction of the discrepancy. Therefore, we suggest that the differences between two eQTL mapping approaches may facilitate sorting of SNP-eQTL interactions into true cis and trans, and that a considerable portion of local-eQTL may actually represent trans interactions. 4 samples - male and female, BxD and DxB adipose of pooled RNA (3 animals per pool) were analyzed with high coverage RNAseq data.