Fibroblast Growth Factor 8 Expression in GT1-7 GnRH-Secreting Neurons Is Androgen-Independent, but Can Be Upregulated by the Inhibition of DNA Methyltransferases.
Fibroblast Growth Factor 8 Expression in GT1-7 GnRH-Secreting Neurons Is Androgen-Independent, but Can Be Upregulated by the Inhibition of DNA Methyltransferases.
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DOI：
10.3389/fcell.2016.00034
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发表时间：
2016
影响因子：
5.5
通讯作者：
Chung WC
中科院分区：
文献类型：
--
作者：
Linscott ML;Chung WC
成纤维细胞生长因子8（FGF 8）是一种有效的形态发生因子，调节下丘脑神经内分泌细胞的胚胎发育。事实上，使用Fgf 8亚型小鼠，我们发现Fgf 8 mRNA表达减少完全消除了促性腺激素释放激素（GnRH）神经元的存在。这些发现表明，在小鼠GnRH神经元的胚胎发育过程中需要FGF 8信号。此外，原位杂交研究表明，胚胎原始出生的地方GnRH神经元，嗅基板，是高度富集Fgf 8 mRNA的表达。总之，这些数据强调了FGF 8信号对GnRH出现的重要性。然而，一个重要的问题仍然没有答案：Fgf 8基因表达在发育中的胚胎小鼠大脑中是如何调节的？一个主要的候选者是雄激素受体（AR），其已显示在60-70%的新诊断的前列腺癌中上调Fgf 8 mRNA。因此，我们假设AR可能参与发育中小鼠大脑Fgf 8转录的调节。为了验证这一假设，我们使用染色质免疫沉淀（ChIP）分析来阐明AR是否与永生化小鼠GnRH神经元（GT 1 -7）和鼻外植体中Fgf 8基因翻译起始位点上游的5′UTR区域相互作用。我们的数据显示，虽然AR与Fgf 8启动子区域相互作用，但这种相互作用是雄激素非依赖性的，并且雄激素处理不影响Fgf 8 mRNA水平，表明雄激素信号传导不诱导Fgf 8转录。相反，DNA甲基转移酶（DNMT）的抑制显著上调Fgf 8 mRNA水平，表明Fgf 8转录活性可能依赖于DNA甲基化状态。
Fibroblast growth factor 8 (FGF8) is a potent morphogen that regulates the embryonic development of hypothalamic neuroendocrine cells. Indeed, using Fgf8 hypomorphic mice, we showed that reduced Fgf8 mRNA expression completely eliminated the presence of gonadotropin-releasing hormone (GnRH) neurons. These findings suggest that FGF8 signaling is required during the embryonic development of mouse GnRH neurons. Additionally, in situ hybridization studies showed that the embryonic primordial birth place of GnRH neurons, the olfactory placode, is highly enriched for Fgf8 mRNA expression. Taken together these data underscore the importance of FGF8 signaling for GnRH emergence. However, an important question remains unanswered: How is Fgf8 gene expression regulated in the developing embryonic mouse brain? One major candidate is the androgen receptor (AR), which has been shown to upregulate Fgf8 mRNA in 60–70% of newly diagnosed prostate cancers. Therefore, we hypothesized that ARs may be involved in the regulation of Fgf8 transcription in the developing mouse brain. To test this hypothesis, we used chromatin-immunoprecipitation (ChIP) assays to elucidate whether ARs interact with the 5′UTR region upstream of the translational start site of the Fgf8 gene in immortalized mouse GnRH neurons (GT1-7) and nasal explants. Our data showed that while AR interacts with the Fgf8 promoter region, this interaction was androgen-independent, and that androgen treatment did not affect Fgf8 mRNA levels, indicating that androgen signaling does not induce Fgf8 transcription. In contrast, inhibition of DNA methyltransferases (DNMT) significantly upregulated Fgf8 mRNA levels indicating that Fgf8 transcriptional activity may be dependent on DNA methylation status.