Epigenetic Control of the Vasopressin Promoter Explains Physiological Ability to Regulate Vasopressin Transcription in Dehydration and Salt Loading States in the Rat.
Epigenetic Control of the Vasopressin Promoter Explains Physiological Ability to Regulate Vasopressin Transcription in Dehydration and Salt Loading States in the Rat.
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DOI：
10.1111/jne.12371
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发表时间：
2016-04
影响因子：
3.2
通讯作者：
Murphy D
中科院分区：
文献类型：
--
作者：
Greenwood MP;Greenwood M;Gillard BT;Loh SY;Paton JF;Murphy D
下丘脑视上核（SON）和室旁核（PVN）中精氨酸加压素（AVP）的合成对增加的血浆渗透压和减少的血容量敏感，并且因此通过脱水（增加的血浆渗透压和减少的血容量）和盐负荷（增加的血浆渗透压）两者稳健地增加。这两种刺激都会导致SON和PVN的功能重塑，这一过程被称为功能相关可塑性。最近，大脑中的这种可塑性变化与CpG（胞嘧啶-磷酸-鸟嘌呤）残基的DNA甲基化模式改变有关，这一过程被认为对基因转录的调节很重要。在这方面，近端Avp启动子含有许多CpG位点，并被认为是Avp基因的四个CpG岛之一，这表明甲基化可能调节Avp转录。在本研究中，我们发现，在永生化下丘脑细胞系4 B中，近端Avp启动子高度甲基化，用DNA甲基转移酶抑制剂5-Aza-2′-脱氧胞苷处理这些细胞以使DNA去甲基化，从而显著增加基础和刺激的Avp生物合成。我们报告DNA甲基转移酶Dnmt 1和Dnmt 3a的表达没有变化，而脱甲基酶ten-11-易位2 Tet 2在SON中通过脱水和盐负荷的表达降低。我们发现，在脱水大鼠中SON Avp启动子的甲基化程度更高，但在盐负荷大鼠中则没有。通过对单个CpG位点的分析，我们观察到脱水大鼠SON Avp启动子中特定CpG的低甲基化、高甲基化和甲基化没有变化。使用报告基因测定，我们表明，个别CpG的突变可以导致改变Avp启动子活性。我们认为，SON Avp启动子的甲基化对于协调慢性脱水大鼠血浆渗透压升高和血容量减少对Avp转录的双重输入是必要的。
The synthesis of arginine vasopressin (AVP) in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus is sensitive to increased plasma osmolality and a decreased blood volume, and thus is robustly increased by both dehydration (increased plasma osmolality and decreased blood volume) and salt loading (increased plasma osmolality). Both stimuli result in functional remodelling of the SON and PVN, a process referred to as functional‐related plasticity. Such plastic changes in the brain have recently been associated with altered patterns of DNA methylation at CpG (cytosine‐phosphate‐guanine) residues, a process considered to be important for the regulation of gene transcription. In this regard, the proximal Avp promoter contains a number of CpG sites and is recognised as one of four CpG islands for the Avp gene, suggesting that methylation may be regulating Avp transcription. In the present study, we show that, in an immortalised hypothalamic cell line 4B, the proximal Avp promoter is highly methylated, and treatment of these cells with the DNA methyltransferase inhibitor 5‐Aza‐2′‐deoxycytidine to demethylate DNA dramatically increases basal and stimulated Avp biosynthesis. We report no changes in the expression of DNA methyltransferases, Dnmt1 and Dnmt3a, whereas there is decreased expression of the demethylating enzyme ten‐eleven‐translocation 2, Tet2, in the SON by dehydration and salt loading. We found higher methylation of the SON Avp promoter in dehydrated but not salt‐loaded rats. By analysis of individual CpG sites, we observed hypomethylation, hypermethylation and no change in methylation of specific CpGs in the SON Avp promoter of the dehydrated rat. Using reporter gene assays, we show that mutation of individual CpGs can result in altered Avp promoter activity. We propose that methylation of the SON Avp promoter is necessary to co‐ordinate the duel inputs of increased plasma osmolality and decreased blood volume on Avp transcription in the chronically dehydrated rat.