家雞由于人的馴養(yǎng)基因組功能產(chǎn)生了快速而廣泛的改變,。近日,，瑞典林雪平大學(xué)的一個(gè)研究團(tuán)隊(duì)證實(shí)這些改變是可遺傳的,，盡管它們并未影響到DNA結(jié)構(gòu)。相關(guān)論文發(fā)表在BMC Genomics雜志上,。
人類(lèi)把紅原雞(Red Junglefowl)作為家禽飼養(yǎng)已經(jīng)有8000的歷史,。從進(jìn)化上來(lái)看，數(shù)量巨大的,、各種不同顏色、外形,、大小的家禽幾乎是在某個(gè)有記錄的時(shí)間突然出現(xiàn)的,。傳統(tǒng)的達(dá)爾文進(jìn)化學(xué)說(shuō)解釋為，在幾千年的時(shí)間中,，人們通過(guò)在雞的基因上發(fā)生的隨機(jī),、自發(fā)的突變來(lái)選育各種不同品種。
林雪平大學(xué)的的動(dòng)物學(xué)家Daniel Nätt和Per Jensen作為一線的研究人員,，他們?cè)谧约旱难芯恐凶C實(shí),，表觀遺傳因子所發(fā)揮的作用要比此前人們想象的要大的多。他們的研究結(jié)果發(fā)表在BMC Genomics雜志上,。
他們對(duì)比現(xiàn)代蛋雞與這個(gè)品種的起源紅原雞之間在大腦中基因活性上的差異,。他們發(fā)現(xiàn)，數(shù)百個(gè)基因的活性存在顯著的差異,。
他們對(duì)幾千個(gè)基因上發(fā)生的一種表觀遺傳學(xué)修飾—DNA甲基化—程度進(jìn)行了測(cè)量,。DNA甲基化是DNA分子上發(fā)生的一種化學(xué)改變，可以影響基因的表達(dá),，但是與突變不同,，這種修飾并不出現(xiàn)在DNA結(jié)構(gòu)中。研究結(jié)果顯示,，在數(shù)百個(gè)基因中存在清晰的差異,。
研究人員對(duì)這些表觀遺傳差異是否具有遺傳性進(jìn)行了檢測(cè)。答案的肯定的,。小雞從他們的父代中遺傳得到了甲基化和基因活性,。即便對(duì)兩種類(lèi)型的雞進(jìn)行8代交叉繁殖，這些差異依然明顯,。
研究結(jié)果表明,，馴養(yǎng)導(dǎo)致了表觀遺傳的變化,。被馴養(yǎng)的雞有超過(guò)70%的基因保留著更高程度的甲基化。由于甲基化相比隨機(jī)突變來(lái)說(shuō)發(fā)生的更為快速,，并且可能是由于壓力或其他經(jīng)歷引發(fā),，這就可以解釋?zhuān)瑸槭裁丛诙虝r(shí)間內(nèi)一個(gè)品種中的變種數(shù)量會(huì)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.
