Data from: Genetic variation in the developmental regulation of cortical avpr1a among prairie voles

Early experiences can have enduring impacts on brain and behavior, but the strength of these effects can be influenced by genetic variation. In principle, polymorphic CpGs (polyCpGs) may contribute to gene-by-environment interactions (GxE) by altering DNA methylation. In this study, we investigate the influence of polyCpGs on the development of vasopressin receptor 1a abundance in the retrosplenial cortex (RSC-V1aR) of prairie voles (Microtus ochrogaster). Two alternative alleles (HI/LO) predict RSC avpr1a expression, V1aR abundance and sexual fidelity in adulthood; these alleles differ in the frequency of CpG sites and in methylation at a putative intron enhancer. We hypothesized that the elevated CpG abundance in LO alleles would make homozygous LO/LO voles more sensitive to developmental perturbations. We found that genotype differences in RSC-V1aR abundance emerged early in ontogeny and were accompanied by differences in methylation of the putative enhancer. As predicted, postnatal treatment with an oxytocin receptor antagonist (OTA) reduced RSC-V1aR abundance in LO/LO adults but not their HI/HI siblings. Similarly, methylation inhibition by zebularine increased RSC-V1aR in LO/LO adults, but not in HI/HI siblings. These data demonstrate a gene-by-environment interaction in RSC-V1aR. Surprisingly, however, neither OTA nor zebularine altered adult methylation of the intronic enhancer, suggesting that differences in sensitivity could not be explained by CpG density at the enhancer alone. Methylated DNA immunoprecipiation-sequencing (MeDIP-seq) revealed additional differentially methylated regions between HI/HI and LO/LO voles. Future research should examine the role of these regions and other regulatory elements in the ontogeny of RSC-V1aR and its developmentally induced changes.早期经历可对大脑及行为产生持久影响，而此类效应的强度可受遗传变异调控。理论上，多态性CpG位点（polymorphic CpGs, polyCpGs）可通过改变DNA甲基化，参与基因-环境交互作用（gene-by-environment interactions, GxE）。本研究旨在探讨多态性CpG位点对草原田鼠（Microtus ochrogaster）后压部皮层加压素1a受体（RSC-V1aR）丰度发育的影响。本研究中存在两种可预测成年个体后压部皮层avpr1a基因表达、V1aR丰度及性忠诚行为的等位基因（高型HI/低型LO）；这两类等位基因在CpG位点频率以及推定内含子增强子的甲基化水平上存在差异。我们提出假说：低型（LO）等位基因中更高的CpG富集度，会使纯合LO/LO型草原田鼠对发育扰动更为敏感。研究发现，后压部皮层V1aR丰度的基因型差异在发育早期即可显现，并伴随推定内含子增强子的甲基化差异。如所预测，产后给予催产素受体拮抗剂（oxytocin receptor antagonist, OTA）可降低LO/LO型成年个体的RSC-V1aR丰度，但对其HI/HI型同窝个体无此效应。同理，通过阿扎胞苷（zebularine，一种甲基化抑制剂）抑制甲基化，可提升LO/LO型成年个体的RSC-V1aR水平，但对HI/HI型同窝个体无此作用。上述数据证实了RSC-V1aR存在基因-环境交互作用。但令人意外的是，OTA与阿扎胞苷均未改变成年个体内含子增强子的甲基化水平，这提示敏感性差异无法仅通过增强子区域的CpG密度来解释。甲基化DNA免疫沉淀测序（methylated DNA immunoprecipitation sequencing, MeDIP-seq）结果显示，HI/HI与LO/LO型草原田鼠之间还存在其他差异甲基化区域。未来研究可进一步探讨这些区域及其他调控元件在RSC-V1aR发育过程及其发育诱导变化中的作用。