Okhovat M, Maguire S M, Phelps S M
Department of Integrative Biology , University of Texas at Austin , Austin, TX , USA.
R Soc Open Sci. 2017 Jan 18;4(1):160646. doi: 10.1098/rsos.160646. eCollection 2017 Jan.
DNA methylation can cause stable changes in neuronal gene expression, but we know little about its role in individual differences in the wild. In this study, we focus on the vasopressin 1a receptor (), a gene extensively implicated in vertebrate social behaviour, and explore natural variation in DNA methylation, genetic polymorphism and neuronal gene expression among 30 wild prairie voles (). Examination of CpG density across 8 kb of the locus revealed two distinct CpG islands overlapping promoter and first exon, characterized by few CpG polymorphisms. We used a targeted bisulfite sequencing approach to measure DNA methylation across approximately 3 kb of in the retrosplenial cortex, a brain region implicated in male space use and sexual fidelity. We find dramatic variation in methylation across the locus, with pronounced diversity near the exon-intron boundary and in a genetically variable putative enhancer within the intron. Among our wild voles, differences in cortical expression correlate with DNA methylation in this putative enhancer, but not with the methylation status of the promoter. We also find an unusually high number of polymorphic CpG sites (polyCpGs) in this focal enhancer. One polyCpG within this enhancer (polyCpG 2170) may drive variation in expression either by disrupting transcription factor binding motifs or by changing local DNA methylation and chromatin silencing. Our results contradict some assumptions made within behavioural epigenetics, but are remarkably concordant with genome-wide studies of gene regulation.
DNA甲基化可导致神经元基因表达发生稳定变化，但我们对其在野生动物个体差异中的作用知之甚少。在本研究中，我们聚焦于血管加压素1a受体（V1aR），该基因广泛涉及脊椎动物的社会行为，并探究了30只野生草原田鼠中DNA甲基化、基因多态性和神经元基因表达的自然变异。对该基因座8 kb范围内的CpG密度进行检测，发现有两个不同的CpG岛与启动子和第一个外显子重叠，其特征是CpG多态性较少。我们采用靶向亚硫酸氢盐测序方法，测量了脾后皮质中约3 kb的V1aR区域的DNA甲基化情况，该脑区与雄性空间利用和性忠诚度有关。我们发现V1aR基因座的甲基化存在显著差异，在外显子 - 内含子边界附近以及内含子内一个基因可变的假定增强子区域有明显的多样性。在我们的野生田鼠中，皮质V1aR表达的差异与该假定增强子中的DNA甲基化相关，但与启动子的甲基化状态无关。我们还在这个重点增强子中发现了异常多的多态性CpG位点（polyCpGs）。该增强子内的一个多态性CpG位点（polyCpG 2170）可能通过破坏转录因子结合基序或改变局部DNA甲基化和染色质沉默来驱动表达变化。我们的结果与行为表观遗传学中的一些假设相矛盾，但与全基因组基因调控研究结果非常一致。
