BACKGROUND Maternal exposure to environmental chemicals can cause adverse health effects in offspring. Mounting evidence supports that these effects are influenced, at least in part, by epigenetic modifications. It is unknown whether epigenetic changes in surrogate tissues such as the blood are reflective of similar changes in target tissues such as cortex or liver. OBJECTIVE We examined tissue- and sex-specific changes in DNA methylation (DNAm) associated with human-relevant lead (Pb) and di(2-ethylhexyl) phthalate (DEHP) exposure during perinatal development in cerebral cortex, blood, and liver. METHODS Female mice were exposed to human relevant doses of either Pb (32 ppm) via drinking water or DEHP (5mg/kg-day) via chow for 2 weeks prior to mating through offspring weaning. Whole genome bisulfite sequencing (WGBS) was utilized to examine DNAm changes in offspring cortex, blood, and liver at 5 months of age. Metilene and methylSig were used to identify differentially methylated regions (DMRs). Annotatr and ChIP-enrich were used for genomic annotations and gene set enrichment tests of DMRs, respectively. RESULTS The cortex contained the majority of DMRs associated with Pb (66%) and DEHP (57%) exposure. The cortex also contained the greatest degree of overlap in DMR signatures between sexes (n=13 and 8 DMRs with Pb and DEHP exposure, respectively) and exposure types (n=55 and 39 DMRs in males and females, respectively). In all tissues, detected DMRs were preferentially found at genomic regions associated with gene expression regulation (e.g., CpG islands and shores, 5' UTRs, promoters, and exons). An analysis of GO terms associated with DMR-containing genes identified imprinted genes to be impacted by both Pb and DEHP exposure. Of these, Gnas and Grb10 contained DMRs across tissues, sexes, and exposures, with some signatures replicated between target and surrogate tissues. DMRs were enriched in the imprinting control regions (ICRs) of Gnas and Grb10, and we again observed a replication of DMR signatures between blood and target tissues. Specifically, we observed hypermethylation of the Grb10 ICR in both blood and liver of Pb-exposed male animals. CONCLUSIONS These data provide preliminary evidence that imprinted genes may be viable candidates in the search for epigenetic biomarkers of toxicant exposure in target tissues. Additional research is needed on allele- and developmental stage-specific effects, as well as whether other imprinted genes provide additional examples of this relationship. https://doi.org/10.1289/EHP14074.

中文翻译：

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发育期铅和邻苯二甲酸盐暴露对成年小鼠血液、大脑和肝脏 DNA 甲基化的影响：关注组织和性别的基因组印记。


背景技术母亲接触环境化学物质会对后代的健康造成不利影响。越来越多的证据表明，这些效应至少部分受到表观遗传修饰的影响。目前尚不清楚血液等替代组织中的表观遗传变化是否反映了皮质或肝脏等目标组织中的类似变化。目的 我们检查了大脑皮层、血液和肝脏围产期发育过程中与人类相关铅 (Pb) 和邻苯二甲酸二(2-乙基己基)酯 (DEHP) 暴露相关的 DNA 甲基化 (DNAm) 的组织和性别特异性变化。方法 雌性小鼠在交配至后代断奶前两周，通过饮用水暴露于人类相关剂量的 Pb（32 ppm）或通过食物暴露于 DEHP（5 毫克/公斤-天）。全基因组亚硫酸氢盐测序 (WGBS) 用于检查 5 个月大的后代皮质、血液和肝脏中的 DNAm 变化。 Metilene 和methylSig 用于识别差异甲基化区域（DMR）。 Annotatr 和 ChIP-enrich 分别用于 DMR 的基因组注释和基因集富集测试。结果 皮质中含有大部分与 Pb (66%) 和 DEHP (57%) 暴露相关的 DMR。皮质中的 DMR 特征在性别（Pb 和 DEHP 暴露分别为 13 和 8 个 DMR）和暴露类型（男性和女性中分别为 55 和 39 个 DMR）之间也存在最大程度的重叠。在所有组织中，检测到的 DMR 优先发现于与基因表达调控相关的基因组区域（例如 CpG 岛和海岸、5' UTR、启动子和外显子）。对与含有 DMR 的基因相关的 GO 术语的分析确定了受 Pb 和 DEHP 暴露影响的印记基因。 其中，Gnas 和 Grb10 包含跨组织、性别和暴露的 DMR，并且一些特征在目标组织和替代组织之间复制。 DMR 在 Gnas 和 Grb10 的印记控制区 (ICR) 中富集，我们再次观察到 DMR 特征在血液和靶组织之间复制。具体来说，我们在暴露于铅的雄性动物的血液和肝脏中观察到 Grb10 ICR 的高度甲基化。结论 这些数据提供了初步证据，表明印迹基因可能是寻找目标组织中有毒物质暴露的表观遗传生物标志物的可行候选者。需要对等位基因和发育阶段的特异性效应以及其他印记基因是否提供这种关系的更多例子进行进一步的研究。 https://doi.org/10.1289/EHP14074。