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Genome-wide profiling of PPARγ:RXR and RNA polymerase II

ABSTRACT: Genome-wide profiling of PPARγ:RXR and RNA polymerase II reveals temporal activation of distinct metabolic pathways in RXR dimer composition during adipogenesis. Chromatin immunoprecipitation combined with deep sequencing was performed to generate genome-wide maps of peroxisome prolifelator-activated receptor gamma (PPARg) and retinoid X receptor (RXR) binding sites, and RNA polymerase II (RNAPII) occupancy at high resolution throughout adipocyte differentiation of 3T3-L1 cells. The data provides the first positional and temporal map PPARγ and RXR occupancy during adipocyte differentiation at a global scale. The number of PPARγ:RXR shared binding sites is steadily increasing from D0 to D6. At Day6 there are over 5000 high confidence shared PPARy:RXR binding sites. We show that at the early days of differentiation several of these sites bind not only PPARγ:RXR but also other RXR dimers. The data also provides a comprehensive temporal map of RNAPII occupancy at genes throughout 3T3-L1 adipogenesis thereby uncovering groups of similarly regulated genes belonging to glucose and lipid metabolic pathways. The majority of the upregulated but very few downregulated genes have assigned PPARγ:RXR target sites, thereby underscoring the importance of PPARγ:RXR in gene activation during adipogenesis and indicating that a hitherto unrecognized high number of adipocyte genes are directly activated by PPARγ:RXR

ORGANISM(S): Mus musculus

PROVIDER: GSE13511 | GEO | 2008/12/10

SECONDARY ACCESSION(S): PRJNA110113

REPOSITORIES: GEO

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Project description:Metabolic syndrome is an important public concern and demand for effective therapeutic strategies. Abdominal obesity, especially an increase in the visceral adipose tissue, is the main cause of this syndrome. Flavonoids are expected to improve risk factors for metabolic syndrome. Bilberry, original species of blueberry containing anthocyanidin flavonoids have been used for centuries in Europe to ameliorate the symptoms of diabetes, but their effects and the mechanisms on lipid accumulation of adipocyte cells are not well defined. In the present study, we investigated effects of the Bilberry extract on differentiation of adipocytes using 3T3-L1 adipocyte cell line. Exposure to Bilberry extract during the early period of adipogenesis (6 days) was significantly inhibited adipocyte differentiation of 3T3-L1. During this period, Bilberry extract greatly down-regulated the mRNA levels of the key adipogenesis-associated markers peroxisome proliferator-activated receptor-γ (PPARγ). Furthermore, Bilberry extract significantly decreased expression of the transcription factor Sterol Regulatory Element Binding Protein 1c (SREBP1c), which plays a central role in adipocyte differentiation including the induction of PPARγ. The expression of SREBP1c is remarkably enhanced in response to insulin, thus raises the possibility that Bilberry extract might inhibit the Insulin pathway. So, We investigated whether Billberry extract and anthocyanidines turned the insulin signaling pathway using microarray. As a result, Gene Set Enrichment Analysis (GSEA) shows that these additives turned insulin signaling pathway certainly. We quantified expression profiles of whole mRNAs by microarray in the adipocyte from 3T3-L1 with or without additives. 3T3-L1 preadipocytes (American Type Culture Collection, Manassas, VA) were grown to confluence in DMEM media (Sigma Aldrich, Tokyo, Japan) with 10% calf serum and penicillin (100 U/ml)/streptomycin (100 ug/ml). Adipogenesis was induced using an adipogenesis assay kit (Chemicon International, Temecula, CA). On day 0, cells were induced with initiation media (10 ug/ml insulin, 1 uM dexamethasone and 0.5 uM IBMX in DMEM media added with 1: 0.1% DMSO, 2: 100 ug/ml Bilberry extract, 3: 100 nM Delphinidin or 4: 100 nM Cyanidin (total 4 samples). On day 2, harvested the cells, extracted total RNA and did microarray experiments.

Project description:Growing evidence suggests that chemicals in disparate structural classes activate specific subsets of PPARγ’s transcriptional programs to generate adipocytes with distinct phenotypes. Our objectives were to 1) establish a novel classification method to predict PPARγ-interacting and modifying chemicals and 2) create taxonomy labels to group chemicals based on their effects on PPARγ’s transcriptome and downstream metabolic functions. We tested the hypothesis that an environmental ligand highly ranked by the taxonomy, but that segregated from the therapeutic ligands, would induce white but not brite adipogensis. 3T3-L1 cells were differentiated in the presence of 76 chemicals (negative controls, synthetic nuclear receptor ligands known to influence adipocyte biology, suspected environmental PPARγ ligands). Differentiation was assessed by measuring lipid accumulation. mRNA expression was determined by highly multiplexed RNA-Seq and validated by RT-qPCR. A novel classification model was developed using an amended random forest procedure. A subset of environmental contaminants identified as strong PPARγ agonists were characterized further for lipid handling, mitochondrial biogenesis and cellular respiration in 3T3-L1 cells and primary human preadipocytes. The 76 chemicals generated a spectrum of adipogenic differentiation. We used lipid accumulation and RNA sequencing data to develop a classification system that 1) identified PPARγ agonists and 2) sorted agonists into likely white or brite adipocyte inducers. Expression of Cidec, was the most efficacious indicator for strong PPARγ activation. Two known environmental PPARγ ligands, tetrabromobisphenol A, and triphenyl phosphate, which sorted distinctly from therapeutic ligands, induced white but not brite adipocyte genes and induced fatty acid uptake but not mitochondrial biogenesis in 3T3-L1 cells. The highly ranked agonists, tonalid and quinoxyfen, also induced white adipogenesis in 3T3-L1 cells and primary human preadipocytes. A novel classification procedure accurately identified environmental chemicals as PPARγ-modifying chemicals distinct from known PPARγ-modifying therapeutics.

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Genome-wide profiling of PPARγ:RXR and RNA polymerase II

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