Understanding the causes of DNA methylation response to methylmercury: a novel approach to quantify genetic, environmental, and stochastic factors

项目总结 环境毒物暴露与DNA甲基化的变化或DNA的化学修饰有关 调控基因表达，但这些相关性背后的机制尚不清楚。DNA甲基化 可以在基因相同的个体中不同，允许不同的表型从相同的基因类型发展而来 在暴露之后。这些结果表明，细胞对导致环境污染的化学物质有特定的反应。 表型差异。此外，未经暴露的基因相同的个体在DNA中表现出变异性 甲基化，表明某些差异是随机的(即，概率)。在基因不同的个体中， DNA甲基化模式与基因高度相关，在没有或存在化学物质的情况下 暴露，表明一些DNA甲基化处于基因控制之下，而一些DNA甲基化 对化学物质的反应在某些基因类型中比在其他基因类型中发生得更多(基因-环境相互作用)。在这里，我会 检验中心假设，即这四个来源各自解释了总DNA甲基化的相同比例 发育过程中暴露于模型化学物质--重金属--的不同基因类型的小鼠的反应 甲基汞(MeHg)。甲基汞是一种理想的模型化学品，因为它对公共卫生有强烈的关注，有 暴露在人类和啮齿动物中的已知表型差异，甲基汞不会造成DNA损伤，这 独立影响DNA甲基化。我的职业发展目标是整合统计方面的新培训 以我在环境表观遗传学方面的背景，我从事的研究既是机械性的，也是 可翻译给人类的。我将利用两只近交系小鼠之间的经典F2杂交设计 一株对甲基汞神经毒性敏感(CAST/EIJ)，一株对甲基汞耐药(C57BL/6J)。F1杂交鼠是 由亲本品系之间的正反交产生，以及由F1小鼠与相反的小鼠杂交产生的F2杂交小鼠 亲子关系。F1小鼠在基因上是相同的。F2小鼠的基因不同，但没有携带DNA序列 在F1小鼠中不存在。我将测量F1和F2小鼠海马区DNA甲基化水平，这两只小鼠都是 而且在母亲的饮食中没有发育阶段暴露于与环境相关的剂量(500 ng/g)的甲基汞。 暴露于F1的小鼠与对照小鼠的DNA甲基化差异将代表环境影响；高变数 F1对照组小鼠的DNA甲基化将呈现随机效应。预测DNA的基因序列变异 F2对照组小鼠的甲基化将代表遗传效应；预测差异的序列变异 与对照相比，暴露在F2中的甲基化将代表基因与环境的相互作用。这些结果将提供 洞察甲基汞神经毒性个体差异的原因。重要的是，这项工作将提高我们的 毒物对DNA甲基化反应的机制理解。 好了！ 好了！

PROJECT SUMMARY Environmental toxicant exposures correlate with changes to DNA methylation, or chemical modifications to DNA that regulate gene expression, but the mechanisms underlying these correlations are unknown. DNA methylation can differ in genetically identical individuals, allowing different phenotypes to develop from identical genotypes following exposure. These results suggest specific cellular responses to chemicals that lead to environmental differences in phenotype. In addition, unexposed genetically identical individuals show variability in DNA methylation, indicating that some differences are stochastic (i.e., probabilistic). In genetically different individuals, DNA methylation patterns correlate highly with genotype, both in the absence and presence of chemical exposure, indicating that some DNA methylation is under genetic control, and that some DNA methylation responses to chemicals occur in some genotypes more than others (gene-environment interactions). Here, I will test the central hypothesis that these four sources each explain equal proportions of the total DNA methylation response in genotypically different mice with developmental exposure to a model chemical, the heavy metal methylmercury (MeHg). MeHg is an ideal model chemical because it is of strong public health concern, there are known phenotypic differences in exposed humans and rodents, and MeHg does not cause DNA damage, which independently affects DNA methylation. My career development goal is to integrate new training in statistical genetics with my background in environmental epigenetics to do research that is both mechanistic and translatable to human populations. I will leverage a classic F2 intercross design between two inbred mouse strains, one susceptible (CAST/EiJ) and one resistant (C57BL/6J) to MeHg neurotoxicity. F1 hybrid mice are generated with reciprocal crosses between parent strains, and F2 hybrid mice by crossing F1 mice with opposite parentage. F1 mice are genotypically identical. F2 mice are genotypically different but carry no DNA sequence not also present in F1 mice. I will measure DNA methylation levels in hippocampus from F1 and F2 mice both with and without developmental exposure to an environmentally relevant dose (500 ng/g) of MeHg in maternal diet. DNA methylation differences in F1 exposed vs. control mice will represent environmental effects; hypervariable DNA methylation in F1 control mice will represent stochastic effects. Genetic sequence variants that predict DNA methylation in F2 control mice will represent genetic effects; sequence variants that predict differential methylation in F2 exposed vs. control will represent gene-environment interactions. These results will provide insight into causes of inter-individual differences in MeHg neurotoxicity. Critically, this work will improve our mechanistic understanding of DNA methylation response to toxicants. ! !