Epigenetic Effect of Cadmium on Global De Novo DNA Hypomethylation in the Cadmium-Induced Ventral Body Wall Defect (VBWD) in the Chick Model
Epigenetic Effect of Cadmium on Global De Novo DNA Hypomethylation in the Cadmium-Induced Ventral Body Wall Defect (VBWD) in the Chick Model
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DOI：
10.1093/toxsci/kfr022
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发表时间：
2011-04-01
影响因子：
3.8
通讯作者：
Thompson, Jennifer
中科院分区：
文献类型：
--
作者：
Doi, Takashi;Puri, Prem;Thompson, Jennifer
重金属镉（Cd）的施用会诱导鸡胚腹侧体壁缺陷（VBWD）。在该模型中，大多数参与体壁形成的基因的表达在治疗后 4 小时发生改变。然而，镉导致基因表达改变的机制仍不清楚。表观遗传机制可以在外源影响下改变基因组功能。此外，Cd 是影响表观基因组编程的环境因素之一。 DNA 从头甲基化对于正常胚胎发生至关重要，并受到 DNA 甲基转移酶 (DNMT)3A 和 DNMT3B 的调节。本研究的目的是调查这样的假设：DNMT3A/3B 基因表达水平发生改变，导致镉鸡模型胚胎发生关键时期整体 DNA 甲基化发生变化。孵育 60 小时后，在用盐水或 Cd 处理后 1、4 和 8 小时收获鸡胚 (n = 48)，并将其分为对照组和 Cd 组。进行定量逆转录PCR以评估鸡胚胎中DNMT3A/3B的基因表达水平，并使用Student's t检验进行统计分析。使用针对 5-甲基胞苷 (5'MeC) 的单克隆抗体进行免疫组织化学分析，该抗体标记细胞核内富含甲基的区域。与对照组相比，Cd 组 4 小时时的 DNMT3A/3B 基因表达水平显着下调（分别为 p < 0.005/p < 0.00001）。 4 小时后，Cd 组中 5'MeC 的免疫反应性显着降低。我们的研究结果首次证明，镉会影响 DNMT3A/3B 的表达水平，这可能是镉雏鸡模型中 VBWD 发病机制的基础。
Administration of the heavy metal cadmium (Cd) induces ventral body wall defects (VBWD) in the chick embryo. In this model, the expression of most genes involved in body wall formation is altered 4h-posttreatment. However, the mechanism by which Cd results in the initiation of altered gene expression remains unclear. Epigenetic mechanisms can change genome function under exogenous influences. Moreover, Cd is one of the environmental factors that can affect epigenomic programming. De novo DNA methylation is essential for normal embryogenesis and is regulated by the DNA methyltransferases (DNMT)3A and DNMT3B. The objective of this study was to investigate the hypothesis that gene expression levels of DNMT3A/3B were altered, resulting in global DNA methylation changes during the critical period of embryogenesis in the Cd chick model. After 60-h incubation, chick embryos (n = 48) were harvested at 1, 4, and 8 h after treatment with saline or Cd, and divided into controls and Cd groups. Quantitative reverse transcription PCR was performed to evaluate the gene expression levels of DNMT3A/3B in the chick embryos and was statistically analyzed using Student's t-test. Immunohistochemistry was performed using a monoclonal antibody against 5-methylcytidine (5'MeC), which labels methyl-rich regions within the nucleus. DNMT3A/3B gene expression levels at 4 h were significantly downregulated in the Cd group compared with controls (p < 0.005/p < 0.00001, respectively). Immunoreactivity of 5'MeC was markedly diminished in the Cd group at 4 h. Our findings demonstrates for the first time that Cd impacts on the expression levels of DNMT3A/3B, which may underlie the pathogenesis of VBWD in the Cd chick model.