The phenotypic plasticity of many organisms is mediated in part by epigenetics, the heritable changes in gene activity that occur without any alterations to DNA sequence. A major mechanism in epigenetics is the DNA methylation (DNAm). Hypo- and hyper-methylation are generalized responses to control gene expression however recent studies have demonstrated that classes of contaminants could mark specific DNAm signatures, that could usefully signal prior environmental exposure.

We collected skin and blubber from 6 free-ranging fin whale (Balaenoptera physalus) individuals sampled as a part of a previous published study in the northern Mediterranean Sea. Genomic DNA extracted from the skin of the fin whales and levels of contaminants measured in the blubber of the same individuals were used for DNAm profiling through reduced representation bisulfite sequencing (RRBS).

We tested the hypothesis that differences in the methylation patterns could be related to environmental exposure to contaminants and load in the whale tissues.

The aims of this study were to determine the DNAm profiles of the methylation contexts (CpGs and non-CpGs) of differently contaminated groups using the RRBS, and to identify potential contaminant exposure related genes. Amount and proportion of methylcytosines in CpG and non-CpG regions (CHH and CHG) was very similar across the 6 samples. The proportion of methylcytosines sites in CpG was n = 32,682, the highest among all the sequence contexts (n = 3216 in CHH; n = 1743 in CHG). The majority of the methylcytosine occurred in the intron regions, followed by exon and promoter regions in CpG, CHH and CHG.

Gene Ontology results indicated that DNAm affected genes that take place in cell differentiation and function in cutaneous, vascular and nervous systems. The identification of cellular response pathways allows a better understanding of the organism biological reaction to a specific environmental challenge and the development of sensitive tools based on the predictive responses. Eco-epigenetics analyses have an extraordinary potential to address growing issues on pollution biomonitoring, ecotoxicity assessment, conservation and management planning.

许多生物体的表型可塑性部分是由表观遗传学介导的，即基因活性的可遗传变化，DNA 序列没有任何改变。表观遗传学的一个主要机制是 DNA 甲基化 (DNAm)。低甲基化和高甲基化是对控制基因表达的普遍反应，但最近的研究表明，污染物类别可以标记特定的 DNAm 特征，这可以有效地表明先前的环境暴露。

我们收集了 6 只自由放养的长须鲸 ( Balaenoptera physalus ) 个体的皮肤和鲸脂，这些个体是之前在地中海北部发表的一项研究的一部分。从长须鲸的皮肤中提取的基因组 DNA 和在相同个体的鲸脂中测量的污染物水平被用于通过减少代表性亚硫酸氢盐测序 (RRBS) 进行 DNAm 分析。

我们检验了甲基化模式的差异可能与环境暴露于污染物和鲸鱼组织中的负荷有关的假设。

本研究的目的是使用 RRBS 确定不同污染组的甲基化环境（CpG 和非 CpG）的 DNAm 谱，并确定潜在的污染物暴露相关基因。CpG 和非 CpG 区域（CHH 和 CHG）中甲基胞嘧啶的数量和比例在 6 个样品中非常相似。CpG 中甲基胞嘧啶位点的比例为n  = 32,682，在所有序列上下文中最高（ CHH 中n = 3216； CHG 中n = 1743）。大多数甲基胞嘧啶位于内含子区域，其次是 CpG、CHH 和 CHG 中的外显子和启动子区域。

基因本体论结果表明，DNAm 影响发生在皮肤、血管和神经系统中的细胞分化和功能的基因。细胞反应途径的识别可以更好地了解生物体对特定环境挑战的生物反应，以及基于预测反应的敏感工具的开发。生态表观遗传学分析在解决污染生物监测、生态毒性评估、保护和管理规划等日益严重的问题方面具有非凡的潜力。