Cumulative lifetime maternal stress and epigenome-wide placental DNA methylation in the PRISM cohort

Evolving evidence links maternal stress exposure to changes in placental DNA methylation of specific genes regulating placental function that may have implications for the programming of a host of chronic disorders. Few studies have implemented an epigenome-wide approach. Using the Infinium HumanMethylation450 BeadChip (450K), we investigated epigenome-wide placental DNA methylation in relation to maternal experiences of traumatic and non-traumatic stressors over her lifetime assessed using the Life Stressor Checklist-Revised (LSC-R) survey (n = 207). We found differential DNA methylation at epigenome-wide statistical significance (FDR = 0.05) for 112 CpGs. Additionally, we observed three clusters that exhibited differential methylation in response to high maternal lifetime stress. Enrichment analyses, conducted at an FDR = 0.20, revealed lysine degradation to be the most significant pathway associated with maternal lifetimes stress exposure. Targeted enrichment analyses of the three largest clusters of probes, identified using the gap statistic, were enriched for genes associated with endocytosis (i.e., <i>SMAP1, ANKFY1</i>), tight junctions (i.e., <i>EPB41L4B</i>), and metabolic pathways (i.e., <i>INPP5E, EEF1B2</i>). These pathways, also identified in the top 10 KEGG pathways associated with maternal lifetime stress exposure, play important roles in multiple physiological functions necessary for proper fetal development. Further, two genes were identified to exhibit multiple probes associated with maternal lifetime stress (i.e., <i>ANKFY1, TM6SF1</i>). The methylation status of the probes belonging to each cluster and/or genes exhibiting multiple hits, may play a role in the pathogenesis of adverse health outcomes in children born to mothers with increased lifetime stress exposure.

日益增多的研究证据表明，母体应激暴露可改变调控胎盘功能的特定基因的胎盘DNA甲基化状态，或对多种慢性疾病的发育程序化过程产生潜在影响。目前采用表观全基因组（epigenome-wide）方法开展的相关研究仍较为有限。本研究依托Infinium人类甲基化450K芯片（Infinium HumanMethylation450 BeadChip，450K），采用生活应激检查表修订版（Life Stressor Checklist-Revised, LSC-R）对207名孕妇终身经历的创伤性与非创伤性应激事件进行评估，进而探究胎盘表观全基因组DNA甲基化与母体终身应激体验的关联。研究发现，有112个CpG位点（CpGs）达到表观全基因组水平的统计学显著性差异（错误发现率（False Discovery Rate, FDR）=0.05）。此外，本研究还观察到三个基因簇在母体终身高应激暴露下呈现显著甲基化差异。以错误发现率FDR=0.20进行富集分析后发现，赖氨酸降解通路是与母体终身应激暴露关联最显著的通路。通过间隙统计法识别的三个最大探针簇的靶向富集分析显示，其富集的基因分别与内吞作用（如SMAP1、ANKFY1）、紧密连接（如EPB41L4B）以及代谢通路（如INPP5E、EEF1B2）相关。上述通路同时位列与母体终身应激暴露相关的前十条京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）通路之中，在胎儿正常发育所需的多项生理功能中发挥关键作用。进一步分析显示，有两个基因（ANKFY1、TM6SF1）存在多个与母体终身应激暴露相关的探针位点。隶属于各基因簇的探针以及存在多个关联位点的基因的甲基化状态，或在终身应激暴露水平较高的母亲所生育子女的不良健康结局发病机制中发挥潜在作用。