Overlapping and distinct functions between ERa and ERÃ homodimers and corresponding transcriptomes in the same cellular context
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The two estrogen receptors, ERa and ERÃ function as ligand-inducible transcription factors. Most in vitro studies have reported that ERa drives breast cancer growth whereas ERÃ, if expressed, suppresses growth. To dissect function and gene expression profile regulated by ERa or ERÃ, respectively, we generated a novel cell model expressing only ERÃ, by applying CRISPR-cas9 to delete ERa in MCF7 cells with stable Tet-Off-inducible ERÃ expression. This model with ERÃ expression only, exhibited regulation of known estrogen responsive genes in a ligand-dependent manner. By cell proliferation assay, we found that either ER was required for proliferation, and that while E2 increased proliferation of ERa (only) MCF7, it reduced proliferation of ERÃ (only) MCF7 cells. RNA-Seq analysis revealed 768 and 984 specific target genes regulated by ERa and ERÃ in response to E2, respectively. Furthermore, functional enrichment analysis showed that the two ER isoforms regulated cell proliferation in opposite direction. In conclusion, within the same cellular context the two ERs regulated cell proliferation in opposite manner by regulating distinct sets of target genes in response to E2. The novel developed cell model provides a novel and valuable resource to further complement the mechanistic understanding of the two different ER isoforms. Overall design: mRNA profiles of MCF7 tetoff cell model upon E2/vehicle treatment
两种雌激素受体（estrogen receptor, ER）α与β均作为配体诱导型转录因子发挥功能。多数体外研究显示，ERα可促进乳腺癌细胞增殖，而ERβ若有表达则会抑制细胞增殖。为分别解析ERα与ERβ所调控的细胞功能及基因表达谱，我们通过CRISPR-Cas9技术在稳定表达Tet-Off诱导型ERβ的MCF7细胞中敲除ERα，构建了仅表达ERβ的全新细胞模型。该仅表达ERβ的细胞模型可通过配体依赖性方式调控已知的雌激素应答基因。通过细胞增殖实验，我们发现两种ER亚型均为细胞增殖所必需；且雌二醇（estradiol, E2）可促进仅表达ERα的MCF7细胞增殖，却抑制仅表达ERβ的MCF7细胞增殖。RNA测序（RNA-Seq）分析显示，ERα与ERβ分别在响应E2的过程中调控768个和984个特异性靶基因。进一步的功能富集分析表明，两种ER亚型对细胞增殖的调控方向截然相反。综上，在相同细胞背景下，两种ER通过调控不同的靶基因集合响应E2，进而对细胞增殖产生相反的调控效应。本研究构建的全新细胞模型，可为进一步阐明两种不同ER亚型的作用机制提供宝贵的新型研究资源。实验设计概况：经E2/溶剂对照处理的MCF7 Tet-Off细胞模型的mRNA表达谱
