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Activation of the aryl hydrocarbon receptor by dioxin during embryonic stem cell differentiation disrupts the expression of homeobox transcription factors that control cardiomyogenesis

ABSTRACT: The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that regulates the expression of xenobiotic detoxification genes and is a critical mediator of gene-environment interactions. In addition, many AHR target genes that have been identified by genome-wide profiling have morphogenetic functions, suggesting that AHR activation may play a role in embryonic development. To address this hypothesis, we studied the consequences of AHR activation by TCDD, its prototypical ligand, during spontaneous mouse ES cell differentiation into contractile cardiomyocytes. Treatment with TCDD or shRNA-mediated AHR knockdown significantly decreased the ability of cardiomyocytes to contract and the expression of cardiac markers in these cells. An AHR-positive embryonic stem cell lineage was generated that expressed puromycin resistance and eGFP under the control of the AHR-responsive Cyp1a1 promoter. Cells of this lineage were over 90% pure and expressed AHR as well as cardiomyocyte markers. Analysis of temporal trajectories of global gene expression in these cells shows that activation of the AHR/TCDD axis disrupts the concerted expression of genes that regulate multiple signaling pathways involved in cardiac and neural morphogenesis and differentiation, including dozens of genes encoding homeobox transcription factors and Polycomb and Trithorax Group genes. More than 50% of the homeobox factors so regulated do not have AhRE sites in their promoters, indicating that AHR activation may establish a complex regulatory network that reaches beyond direct AHR signaling and is capable of disrupting various aspects of embryonic development, including cardiomyocyte differentiation.

ORGANISM(S): Mus musculus

PROVIDER: GSE47964 | GEO | 2013/06/15

SECONDARY ACCESSION(S): PRJNA208492

REPOSITORIES: GEO

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Project description:Background: Estrogen receptor (ERα) and aryl hydrocarbon receptor (AHR) are two nuclear receptors involved in regulating gene expression. ERα and AHR are regulated by estradiol(E2) and TCDD respectively. They are also regulated by dietary ligands including 3,3´diindolylmethane (DIM) and resveratrol (RES). DIM is an ERα and AHR agonist, while RES is an ERα agonist and AHR antagonist. Few studies have investigated the impact of RES and DIM on ERα and AHR signaling at a genome-wide level. This study assessed ERα and AHR binding and associated gene expression changes after treatment of MCF-7 human breast cancer cells with DIM, RES, E2, TCDD, and E2+TCDD for 1 hour and 6 hours before ChIP and RNA sequencing respectively. Results: 88% and 86% of the ERα bound sites after RES and DIM overlapped with E2 ERα sites. RES and DIM resulted in 577 and 446 differentially expressed genes (DEGs) respectively compared to 866 after E2. 68% and 62.3% of the DEGs after RES and DIM were closest to an ERα binding site. Motif analysis indicated enrichment for AHRE motif among DIM ERα sites but not among E2 or RES ERα sites. Both DIM and E2+TCDD resulted in greater genome wide binding of AHR than TCDD. DIM and E2+TCDD resulted in 10546 and 8904 AHR and ERα co-occupied sites respectively. While co-occupied sites for both enriched for the AHR and ERE motif among others, DIM mediated co-occupied sites enriched for Tcfcp2l1, Tgif1, Gata3 motifs while E2+TCDD mediated ones enriched for the NF1 and Ppara motifs. Overlap of coregulated DEGs after DIM and E2+TCDD indicated 123 were the same among both with 81 and 85 unique coregulated DEGs respectively. Enrichment analysis indicated that more enrichment terms were different than similar for coregulated genes after E2+TCDD and DIM. Conclusions: AHR activation is responsible for DIM mediated reduced regulation of gene expression by ERα relative to E2 and only a subset of the DEG’s after DIM and RES are ERα targets indicating future studies into other transcription factors regulated by DIM and RES are needed for insights into the regulation of gene expression by these ligands.

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Activation of the aryl hydrocarbon receptor by dioxin during embryonic stem cell differentiation disrupts the expression of homeobox transcription factors that control cardiomyogenesis

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