IFM Biology, Division of Zoology, Avian Behavioural Genomics and Physiology Group, Linköping University, Sweden.
BMC Genomics. 2012 Feb 4;13:59. doi: 10.1186/1471-2164-13-59.
Variations in gene expression, mediated by epigenetic mechanisms, may cause broad phenotypic effects in animals. However, it has been debated to what extent expression variation and epigenetic modifications, such as patterns of DNA methylation, are transferred across generations, and therefore it is uncertain what role epigenetic variation may play in adaptation.
In Red Junglefowl, ancestor of domestic chickens, gene expression and methylation profiles in thalamus/hypothalamus differed substantially from that of a domesticated egg laying breed. Expression as well as methylation differences were largely maintained in the offspring, demonstrating reliable inheritance of epigenetic variation. Some of the inherited methylation differences were tissue-specific, and the differential methylation at specific loci were little changed after eight generations of intercrossing between Red Junglefowl and domesticated laying hens. There was an over-representation of differentially expressed and methylated genes in selective sweep regions associated with chicken domestication.
Our results show that epigenetic variation is inherited in chickens, and we suggest that selection of favourable epigenomes, either by selection of genotypes affecting epigenetic states, or by selection of methylation states which are inherited independently of sequence differences, may have been an important aspect of chicken domestication.
由表观遗传机制介导的基因表达变化可能会导致动物产生广泛的表型效应。然而，表达变异和表观遗传修饰（如 DNA 甲基化模式）在多大程度上跨代传递，以及因此，表观遗传变异在适应中可能扮演什么角色，这些问题一直存在争议。
在红原鸡（家鸡的祖先）中，丘脑/下丘脑的基因表达和甲基化谱与一个家养的产蛋品种有很大的不同。表达和甲基化差异在后代中基本保持不变，这表明表观遗传变异具有可靠的遗传性。一些遗传甲基化差异是组织特异性的，而且在红原鸡和家养产蛋鸡之间进行了八代杂交后，特定基因座的差异甲基化变化很小。与鸡驯化相关的选择清除区域中，差异表达和甲基化的基因数量过多。
我们的研究结果表明，表观遗传变异在鸡中是可以遗传的，我们认为，有利的表观基因组的选择，无论是通过影响表观遗传状态的基因型选择，还是通过独立于序列差异遗传的甲基化状态选择，都可能是鸡驯化的一个重要方面。
