Genome‐wide analysis of changes in early gene expression induced by oestrogen

Abstract

Background: The sex hormone 17β‐oestradiol (E2) has profound effects on many aspects of reproduction, development, as well as behaviour. Although the oestrogen receptor is well characterized on a molecular level, relatively few genes affected by E2 have been identified, and the mechanisms underlying the physiological changes caused by E2 are largely unknown. In order to identify oestrogen‐regulated genes in vivo, early uterine gene expression profiles were developed using DNA microarrays. Results: Ovariectomized mice were exposed to 17β‐oestradiol for 6 h, and mRNA expression analysis for 9977 genes was performed. Although a large number of genes was affected by oestrogen administration, the genes that showed higher reproducibility in repetitive experiments were selected and further examined. For most of the selected genes, expression was induced in a dose‐dependent manner, and gene expression was not altered following oestrogen treatment in oestrogen receptor‐α (ERα)‐deficient mice. In combination with the estimation of gene expression levels using quantitative PCR, it was revealed that multiple genes related to sterol biosynthesis, tRNA synthesis, RNA processing, and growth signalling were activated. Based on the microarray data, we selected additional genes related to sterol biosynthesis and tRNA synthesis and confirmed that these genes are also activated by oestrogen. Conclusion: Genes suggesting a basis for the drastic uterotrophic effect observed several days following oestrogen administration were identified. These findings not only reveal the diverse effect of oestrogen signalling on transcript levels in vivo but also demonstrate the ability of DNA microarrays to identify cellular pathways affected by oestrogen.

Similarities and differences in uterine gene expression patterns caused by treatment with physiological and non-physiological estrogens

“…Thus, the microarray data were highly reproducible. In a previous paper, we used Student's t-test with three sets of independent DNA microarray experiments to identify 46 estrogen-induced genes (Watanabe et al 2002). More than 80% of these genes were also found in this study (data not shown), which supports the reproducibility of these microarray experiments.…”

“…These transcription factors may be related to the activation of downstream genes. Also selected were two genes related to sterol synthesis, which we showed in an earlier study to be activated by estrogen (Watanabe et al 2002). When we compared the positivly-correlated genes with temporal changes of the expression pattern (Watanabe et al 2003), it was revealed that the expressions of the positively-correlated genes were not temporally correlated.…”

Estrogen-occupied Estrogen Receptor Represses Cyclin G2 Gene Expression and Recruits a Repressor Complex at the Cyclin G2 Promoter

“…MCF-7 cells were treated with 10 nM E2 for 45 min before harvest. The antibodies used were purchased from Santa Cruz Biotechnology (HDAC-1 (N- 19) 16 ), Sp1, Sin3A) or NeoMarkers (IgG). The primers used for PCR were: cyclin G2 fw (5Ј-TCAGGTGGGGCATAC-CGAG) and rev (5Ј-CAAGTGCTCTGCCCCCAAA), which produce an amplicon of 343 bp.…”

“…Gene expression profiling on breast cancer cells using cDNA microarrays, which has proved to be a powerful tool for identifying estrogen receptor target genes, has revealed that in ER-containing breast cancer cells estrogen is able to down-regulate as many genes as it up-regulates (7,(17)(18)(19). Intriguingly, these down-regulated genes include cell cycle inhibitory genes, such as cyclin G2, and proapoptic genes whose suppression by estradiol would enhance tumor cell growth and survival (7).…”

Estrogen Receptor Alpha Represses Transcription of Early Target Genes via p300 and CtBP1

“…Estrogen receptor alpha (ER␣) and ER␤, which are members of the nuclear receptor superfamily of ligand-activated transcription factors, play crucial roles in mammary gland development and also in breast cancer etiology, progression, and treatment (2,21,23). From genome-wide transcriptome studies of breast cancer cells, it is clear that hormone-bound ER␣ is a pivotal regulator that can both stimulate and repress gene transcription and influence, over time, a vast number of target gene mRNAs and proteins, thus creating a well-integrated hormonal response that affects numerous cell processes (6,14,42). Global gene expression profiling by microarray analysis has revealed that estradiol (E2), acting through ER␣, upregulates the expression of genes encoding positive proliferation regulators, including multiple growth factors, growth factor receptors, and proteins involved in cell cycle progression, and downregulates transcriptional repressors and antiproliferative and proapoptotic genes, these together contributing to the stimulation of proliferation and suppression of apoptosis by estradiol in breast cancer cells (14,15,23).…”