AVIAN Behavioural Physiology and Genomics Group, IFM Biology, Linköping University, 581 83, Linköping, Sweden.
Genet Sel Evol. 2018 Apr 2;50(1):13. doi: 10.1186/s12711-018-0384-z.
Domestication of animals leads to large phenotypic alterations within a short evolutionary time-period. Such alterations are caused by genomic variations, yet the prevalence of modified traits is higher than expected if they were caused only by classical genetics and mutations. Epigenetic mechanisms may also be important in driving domesticated phenotypes such as behavior traits. Gene expression can be modulated epigenetically by mechanisms such as DNA methylation, resulting in modifications that are not only variable and susceptible to environmental stimuli, but also sometimes transgenerationally stable. To study such mechanisms in early domestication, we used as model two selected lines of red junglefowl (ancestors of modern chickens) that were bred for either high or low fear of humans over five generations, and investigated differences in hypothalamic DNA methylation between the two populations.
Twenty-two 1-kb windows were differentially methylated between the two selected lines at p < 0.05 after false discovery rate correction. The annotated functions of the genes within these windows indicated epigenetic regulation of metabolic and signaling pathways, which agrees with the changes in gene expression that were previously reported for the same tissue and animals.
Our results show that selection for an important domestication-related behavioral trait such as tameness can cause divergent epigenetic patterns within only five generations, and that these changes could have an important role in chicken domestication.
动物的驯化导致在短时间内出现了大量的表型变化。这些变化是由基因组变异引起的，但如果仅由经典遗传学和突变引起，那么修饰特征的流行率就会高于预期。表观遗传机制也可能在驱动驯化表型方面发挥重要作用，如行为特征。基因表达可以通过 DNA 甲基化等机制进行表观遗传调控，从而产生不仅具有可变性且易受环境刺激影响的修饰，有时还具有跨代稳定性。为了研究早期驯化中的这些机制，我们使用了两个经过五代选择的红原鸡（现代鸡的祖先）品系作为模型，这些品系分别选择了对人类恐惧程度高或低的特征，研究了两个群体间下丘脑 DNA 甲基化的差异。
在经过假发现率校正后，两个选择品系之间有 22 个 1kb 窗口的甲基化存在差异，p<0.05。这些窗口内基因的注释功能表明，代谢和信号通路的表观遗传调控与之前报道的同一组织和动物的基因表达变化一致。
我们的研究结果表明，选择温顺等重要的驯化相关行为特征仅在五代内就可以导致不同的表观遗传模式，这些变化可能在鸡的驯化中发挥重要作用。
