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Impact of conditional uterine deletion of Esr1, Foxa2 or Foxo1 on DES-induced gene expression

ABSTRACT: Neonatal exposure to diethylstilbestrol (DES) results in abnormal reproductive tract morphology, female infertility and uterine cancer in mice. This exposure also causes altered gene expression in the female reproductive tract that persists into adulthood. To further explore on a genome-wide basis how neonatal estrogen exposure results in permanent epigenetic changes, we performed RNA-seq and ChIP-seq analyses of DES-treated and control mice. CD-1 mice were treated on postnatal days (PND) 1-5 with DES (2 µg/pup/day) or corn oil as a control; uterine tissues were collected on PND5. RNA-seq analysis resulted in 4,498 differentially expressed genes (>1.5 fold difference; RPKM >1; FDR <0.05). ChIP-seq was performed on uterine samples using H3K4me3, H3K27me3, H3K27acetyl and H3K4me1 as the precipitating antibodies. The most significant findings at the TSS were increased H3K4me3 at up-regulated genes (22%), increased H3K27ac at up-regulated genes (55%) and differential H3K27ac at down-regulated genes (33%). The most striking finding was differential association of H3K27ac at presumed enhancer regions; 3,012 out of 4498 altered genes (67%) had a differential H3K27ac peak associated with them and 2,962 out of 4,498 (66%) had differential H3K4me1. These differences were generally coordinated with gene expression with increased gene expression having more H3K27ac associated although a small subset of genes showed the opposite. To further investigate the mechanism of differential H3K27ac binding in enhancer regions near estrogen regulated genes, we overlapped these enhancers to Esr1 ChIP seq data; a large percentage of them overlap with Esr1 peaks (39%). We also performed motif analysis where ERE was enriched in the differential H3K27ac peaks. We further investigated Esr1’s role in differential H3K27ac enhancer binding by using a conditional uterine deletion of Esr1 by crossing Esr1 floxed mice with PgR-cre and then treating with vehicle or DES and collecting uteri on day 5. We performed a microarray and pattern analysis and determined there were 4,073 out of 4,617 altered genes (88%) protected by conditional uterine deletion of Esr1. We also performed H3K27ac ChIP seq on these samples and found a large number of these protected genes have a differential H3K27ac enhancer. Several Fox genes were up-regulated following DES treatment and Fox binding motifs were found to be enriched in both H3K27ac and H3K4me1 differential enhancer peaks. To further study the impact of Foxa2 or Foxo1, we conditionally deleted each of these using PgR-cre. There were far fewer genes impacted by deletion of either Foxa2 or Foxo1 suggesting these Fox genes are not responsible for DES induced gene expression and these two lines were not followed further. Taken together, these data suggest estrogen regulates gene expression in the neonatal mouse uterus by H3K27ac association at Esr1 binding sites near estrogen regulated genes. Changes in the epigenome during the time of treatment may contribute to the permanent alterations in gene expression observed in aged DES treated mice.

ORGANISM(S): Mus musculus

PROVIDER: GSE97073 | GEO | 2018/03/27

REPOSITORIES: GEO

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Project description:Estrogen Receptor (ESR1) drives growth in the majority of human breast cancers by binding to regulatory elements and inducing transcription events that promote tumor growth. Differences in enhancer occupancy by ESR1, contribute to the diverse expression profiles and clinical outcome observed in breast cancer patients. GATA3 is an ESR1 co-operating transcription factor mutated in breast tumors, however its genomic properties are not fully defined. In order to investigate the composition of enhancers involved in estrogen-induced transcription and the potential role of GATA3, we performed extensive ChIP-sequencing in unstimulated breast cancer cells and following estrogen treatment. We find that GATA3 is pivotal in mediating enhancer accessibility at regulatory regions involved in ESR1-mediated transcription. GATA3 silencing resulted in a global redistribution of co-factors and active histone marks prior to estrogen stimulation. These global genomic changes altered the ESR1 binding profile that subsequently occurred following estrogen, with events exhibiting both loss and gain in binding affinity, implying a GATA3 mediated re-distribution of ESR1 binding. The GATA3-mediated re-distributed ESR1 profile correlated with changes in gene expression, suggestive of its functionality. Chromatin loops at the TFF locus involving ESR1 bound enhancers occurred independently of ESR1 when GATA3 was silenced, indicating that GATA3, when present on the chromatin, may serve as a licensing factor for estrogen- ESR1 mediated interactions between cis-regulatory elements. Together these experiments suggest that GATA3 directly impacts ESR1 enhancer accessibility and may potentially explain the contribution of mutant-GATA3 in the heterogeneity of ESR1+ breast cancer. MCF7 cells were transfected with siRNA and cultured in hormone deprived conditions for a further 3 days. Cells were subsequently treated with 100nM estrogen (E2) or control (Veh) for 6 hrs. We performed two independent biological experiments each using three different siRNAs against GATA3 individually (six siGATA3 replicates in total). For siControl we used RNA from five biological replicates.

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Impact of conditional uterine deletion of Esr1, Foxa2 or Foxo1 on DES-induced gene expression

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