Project description:Changes in the activating histone-H3 chromatin marks K4me1, K4me3, and K27ac were assayed in male mouse liver following exposure to TCPOBOP, an agonist ligand of the nuclear receptor CAR (constitutive androstane receptor). This work is part of a larger study, entitled: "Widespread Epigenetic Changes to the Enhancer Landscape of Mouse Liver Induced by a Specific Xenobiotic Agonist Ligand of the Nuclear Receptor CAR" (Tox Sci, 2019).
Project description:This work is part of a larger study where we investigated activation of the nuclear receptor and transcription factor CAR (Nr1i3) by its specific agonist ligand TCPOBOP (1,4-bis[2-(3,5-dichloropyridyloxy)]benzene), which dysregulates hundreds of genes in mouse liver and is linked to male-biased hepatocarcinogenesis. We used DNase-seq and DNase hypersensitivity site (DHS) analysis to identify several thousand genomic regions (∆DHS) where short-term exposure to TCPOBOP induces localized changes (increases or decreases) in mouse liver chromatin accessibility, many of which cluster together with TCPOBOP-responsive genes. Sites of chromatin opening were highly enriched nearby genes induced by TCPOBOP and chromatin closing was highly enriched nearby genes repressed by TCPOBOP, consistent with TCPOBOP-responsive ∆DHS serving as enhancers and promoters that positively regulate CAR-responsive genes. Gene expression changes lagged behind chromatin opening or closing for a subset of TCPOBOP-responsive ∆DHS. DHS that were specifically responsive to TCPOBOP in male liver were significantly enriched for genomic regions with a basal male bias in chromatin accessibility; however, the male-biased response of hepatocellular carcinoma-related genes to TCPOBOP was not associated with a correspondingly male-biased ∆DHS response. These studies elucidate the genome-wide organization of CAR-responsive genes and of the thousands of associated genomic sites where TCPOBOP exposure induces both rapid and persistent changes in chromatin accessibility.
Project description:Changes in gene expression were assayed in mouse liver nuclear RNA following a single injection of the CAR agonist TCPOBOP (1,4-Bis-[2-(3,5-dichloropyridyloxy)]benzene) or the PXR agonist PCN (pregnenolone 16α-carbonitrile) in 7-week old mice. This study is part of a larger study entitled Sex-Differential Responses of Tumor Promotion-Associated Genes and Dysregulation of Novel Long Noncoding RNAs in Constitutive Androstane Receptor-Activated Mouse Liver (PMID: 28903501).
Project description:PolyA-selected RNA was isolated from the nuclear fraction of frozen liver tissue from adult male and female ICR/CD1 mice that were treated with a TCPOBOP delivered using either a Low Corn Oil vehice or a High Corn Oil vehicle regimen. Livers were collected and nuclear RNA purified and analyzed either 2 week or 8 weeks after initiating TCPOBOP treatment. These samples are part of a study designed to elucidate genes and gene-based mechanisms underlying TCPOBOP-disrupted liver metabolic dysfunction, including the pericentral steatosis seen within 2 weeks of the initial TCPOBOP exposure. Major findings of this work included the following: Early (1-day) TCPOBOP transcriptional responses were enriched for CAR-bound primary response genes, and for lipogenesis and xenobiotic metabolism and oxidative stress protection pathways; late (2-wk) TCPOBOP responses included many CAR binding-independent secondary response genes, with enrichment for macrophage activation, immune response and cytokine and reactive oxygen species production. Late upstream regulators specific to TCPOBOP-exposed male liver were linked to pro-inflammatory responses and hepatocellular carcinoma progression. TCPOBOP administered weekly to male mice using a high corn oil vehicle activated carbohydrate-responsive transcription factor (MLXIPL)-regulated target genes, dysregulated mitochondrial respiratory and translation regulatory pathways, and induced more advanced liver pathology. Overall, TCPOBOP exposure recapitulated histological and gene expression changes characteristic of emerging steatotic liver disease, including secondary gene responses in liver non-parenchymal cells indicative of transition to a more advanced disease state.
Project description:Chromatin immunoprecipitation and sequencing for three transcription factors (RXRa, CEBPa, CEBPb) was performed on livers of male mice treated with vehicle or with TCPOBOP for either 3 h or 27 h. This dataset is part of a larger study, entitled “Widespread epigenetic changes to the enhancer landscape of mouse liver induced by a specific xenobiotic agonist ligand of the nuclear receptor CAR”, which found that active enhancer and promoter histone marks induced by TCPOBOP were enriched at opening DNase hypersensitive sites (DHS) and TCPOBOP-inducible genes. Enrichment of CAR binding and CAR motifs was seen at opening DHS and their inducible drug/lipid metabolism gene targets, and at many constitutively open DHS located nearby. TCPOBOP-responsive cell cycle and DNA replication genes co-dependent on MET/EGFR signaling for induction were also enriched for CAR binding. A subset of opening DHS and many closing DHS mapping to TCPOBOP-responsive target genes did not bind CAR, indicating an indirect mechanism for their changes in chromatin accessibility. TCPOBOP-responsive DHS were also enriched for induced binding of RXRA, CEBPA and CEBPB, and for motifs for liver-enriched factors that may contribute to liver-specific transcriptional responses to TCPOBOP exposure. These studies elucidate the enhancer landscape of TCPOBOP-exposed liver and the widespread epigenetic changes that are induced by both direct and indirect mechanisms linked to CAR activation.
Project description:This SuperSeries is composed of the following subset Series: GSE13688: Effect of TCPOBOP and PCN in combination with high-cholesterol diet on genes involved in cholesterol homeostasis GSE13689: Effect of rosuvastatin and atorvastatin in combination with high-cholesterol diet on cholesterol homeostasis Refer to individual Series
Project description:TCPOBOP (1,4-Bis [2-(3,5-Dichloropyridyloxy)] benzene) is a constitutive androstane receptor (CAR) agonist that induces robust hepatocyte proliferation and hepatomegaly without any liver injury or tissue loss. TCPOBOP-induced direct hyperplasia has been considered to be CAR-dependent with no evidence of involvement of cytokines or growth factor signaling. Receptor tyrosine kinases (RTKs), MET and EGFR, are known to play a critical role in liver regeneration after partial hepatectomy, but their role in TCPOBOP-induced direct hyperplasia, not yet explored, is investigated in the current study. Disruption of the RTK-mediated signaling was achieved utilizing MET KO mice along with Canertinib treatment for EGFR inhibition. Combined elimination of MET and EGFR signaling [MET KO + EGFRi], but not individual disruption, dramatically reduced TCPOBOP-induced hepatomegaly and hepatocyte proliferation. TCPOBOP-driven CAR activation was not altered in [MET KO + EGFRi] mice, as measured by nuclear CAR translocation and analysis of typical CAR target genes. However, TCPOBOP induced cell cycle activation was impaired in [MET KO + EGFRi] mice due to defective induction of cyclins, which regulate cell cycle initiation and progression. TCPOBOP-driven induction of FOXM1, a key transcriptional regulator of cell cycle progression during TCPOBOP-mediated hepatocyte proliferation, was greatly attenuated in [MET KO + EGFRi] mice. Interestingly, TCPOBOP treatment caused transient decline in HNF4α expression concomitant to proliferative response; this was not seen in [MET KO + EGFRi] mice. Transcriptomic profiling revealed vast majority (~40%) of TCPOBOP-dependent genes mainly related to proliferative response, but not to drug metabolism, were differentially expressed in [MET KO + EGFRi] mice. Conclusion: Taken together, combined disruption of EGFR and MET signaling lead to dramatic impairment of TCPOBOP-induced proliferative response without altering CAR activation. We used microarrays to detail the global programme of gene expression in [METKO + EGFRi] mice liver following TCPOBOP treatment
Project description:Chromatin immunoprecipitation and sequencing for the H3K27me3 histone mark was performed on livers of male mice either treated with vehicle or with TCPOBOP for 27 h. This dataset is part of a larger study, entitled “Widespread epigenetic changes to the enhancer landscape of mouse liver induced by a specific xenobiotic agonist ligand of the nuclear receptor CAR”, which found that active enhancer and promoter histone marks induced by TCPOBOP were enriched at opening DNase hypersensitive sites (DHS) and TCPOBOP-inducible genes. Enrichment of CAR binding and CAR motifs was seen at opening DHS and their inducible drug/lipid metabolism gene targets, and at many constitutively open DHS located nearby. TCPOBOP-responsive cell cycle and DNA replication genes co-dependent on MET/EGFR signaling for induction were also enriched for CAR binding. A subset of opening DHS and many closing DHS mapping to TCPOBOP-responsive target genes did not bind CAR, indicating an indirect mechanism for their changes in chromatin accessibility. TCPOBOP-responsive DHS were also enriched for induced binding of RXRA, CEBPA and CEBPB, and for motifs for liver-enriched factors that may contribute to liver-specific transcriptional responses to TCPOBOP exposure. These studies elucidate the enhancer landscape of TCPOBOP-exposed liver and the widespread epigenetic changes that are induced by both direct and indirect mechanisms linked to CAR activation.