Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
Environmental and Marine Biology, Faculty of Science and Engineering, Åbo Akademi University, Åbo, Finland.
Mol Ecol. 2019 Apr;28(8):1975-1993. doi: 10.1111/mec.15062. Epub 2019 Apr 29.
Social insects provide systems for studying epigenetic regulation of phenotypes, particularly with respect to differentiation of reproductive and worker castes, which typically arise from a common genetic background. The role of gene expression in caste specialization has been extensively studied, but the role of DNA methylation remains controversial. Here, we perform well replicated, integrated analyses of DNA methylation and gene expression in brains of an ant (Formica exsecta) with distinct female castes using traditional approaches (tests of differential methylation) combined with a novel approach (analysis of co-expression and co-methylation networks). We found differences in expression and methylation profiles between workers and queens at different life stages, as well as some overlap between DNA methylation and expression at the functional level. Large portions of the transcriptome and methylome are organized into "modules" of genes, some significantly associated with phenotypic traits of castes and developmental stages. Several gene co-expression modules are preserved in co-methylation networks, consistent with possible regulation of caste-specific gene expression by DNA methylation. Surprisingly, brain co-expression modules were highly preserved when compared with a previous study that examined whole-body co-expression patterns in 16 ant species, suggesting that these modules are evolutionarily conserved and for specific functions in various tissues. Altogether, these results suggest that DNA methylation participates in regulation of caste specialization and age-related physiological changes in social insects.
社会性昆虫为研究表型的表观遗传调控提供了系统，特别是在研究生殖和工蚁等级的分化方面，这些等级通常起源于共同的遗传背景。基因表达在等级特化中的作用已经得到了广泛的研究，但 DNA 甲基化的作用仍存在争议。在这里，我们使用传统方法（差异甲基化测试）结合新方法（共表达和共甲基化网络分析），对具有明显雌性等级的蚂蚁（Formica exsecta）的大脑中的 DNA 甲基化和基因表达进行了可重复的综合分析。我们发现，在不同的生命阶段，工蚁和蚁后之间的表达和甲基化谱存在差异，并且在功能水平上 DNA 甲基化和表达之间存在一些重叠。转录组和甲基组的大部分被组织成“模块”的基因，其中一些与等级和发育阶段的表型特征显著相关。几个基因共表达模块被保存在共甲基化网络中，这与 DNA 甲基化可能对特定等级的基因表达的调控一致。令人惊讶的是，与之前研究 16 种蚂蚁物种的全身共表达模式的研究相比，大脑的共表达模块高度保守，这表明这些模块在进化上是保守的，并且在各种组织中具有特定的功能。总的来说，这些结果表明 DNA 甲基化参与了社会性昆虫的等级特化和与年龄相关的生理变化的调节。
