家鸡由于人的驯养基因组功能产生了快速而广泛的改变。近日，瑞典林雪平大学的一个研究团队证实这些改变是可遗传的，尽管它们并未影响到DNA结构。相关论文发表在BMC Genomics杂志上。
人类把红原鸡(Red Junglefowl)作为家禽饲养已经有8000的历史。从进化上来看，数量巨大的、各种不同颜色、外形、大小的家禽几乎是在某个有记录的时间突然出现的。传统的达尔文进化学说解释为，在几千年的时间中，人们通过在鸡的基因上发生的随机、自发的突变来选育各种不同品种。
林雪平大学的的动物学家Daniel Nätt和Per Jensen作为一线的研究人员，他们在自己的研究中证实，表观遗传因子所发挥的作用要比此前人们想象的要大的多。他们的研究结果发表在BMC Genomics杂志上。
他们对比现代蛋鸡与这个品种的起源红原鸡之间在大脑中基因活性上的差异。他们发现，数百个基因的活性存在显著的差异。
他们对几千个基因上发生的一种表观遗传学修饰—DNA甲基化—程度进行了测量。DNA甲基化是DNA分子上发生的一种化学改变，可以影响基因的表达，但是与突变不同，这种修饰并不出现在DNA结构中。研究结果显示，在数百个基因中存在清晰的差异。
研究人员对这些表观遗传差异是否具有遗传性进行了检测。答案的肯定的。小鸡从他们的父代中遗传得到了甲基化和基因活性。即便对两种类型的鸡进行8代交叉繁殖，这些差异依然明显。
研究结果表明，驯养导致了表观遗传的变化。被驯养的鸡有超过70%的基因保留着更高程度的甲基化。由于甲基化相比随机突变来说发生的更为快速，并且可能是由于压力或其他经历引发，这就可以解释，为什么在短时间内一个品种中的变种数量会上升如此之快。（生物谷Bioon.com）
doi:10.1186/1471-2164-13-59
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Heritable genome-wide variation of gene expression and promoter methylation between wild and domesticated chickens
Daniel Natt, Carl-Johan Rubin, Dominic Wright, Martin Johnsson, Johan Belteky, Leif Andersson and Per Jensen
Background 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.
Results 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.
Conclusions 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.
