BMC Genomics:瑞典研究發現表觀遺傳學變化具有可遺傳性

家雞由於人的馴養基因組功能產生了快速而廣泛的改變。近日，瑞典林雪平大學的一個研究團隊證實這些改變是可遺傳的，儘管它們並未影響到DNA結構。相關論文發表在BMC Genomics雜誌上。

人類把紅原雞(Red Junglefowl)作為家禽飼養已經有8000的歷史。從進化上來看，數量巨大的、各種不同顏色、外形、大小的家禽幾乎是在某個有記錄的時間突然出現的。傳統的達爾文進化學說解釋為，在幾千年的時間中，人們通過在雞的基因上發生的隨機、自發的突變來選育各種不同品種。

林雪平大學的的動物學家Daniel Nätt和Per Jensen作為一線的研究人員，他們在自己的研究中證實，表觀遺傳因子所發揮的作用要比此前人們想像的要大的多。他們的研究結果發表在BMC Genomics雜誌上。

他們對比現代蛋雞與這個品種的起源紅原雞之間在大腦中基因活性上的差異。他們發現，數百個基因的活性存在顯著的差異。

他們對幾千個基因上發生的一種表觀遺傳學修飾—DNA甲基化—程度進行了測量。DNA甲基化是DNA分子上發生的一種化學改變，可以影響基因的表達，但是與突變不同，這種修飾並不出現在DNA結構中。研究結果顯示，在數百個基因中存在清晰的差異。

研究人員對這些表觀遺傳差異是否具有遺傳性進行了檢測。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。即便對兩種類型的雞進行8代交叉繁殖，這些差異依然明顯。

研究結果表明，馴養導致了表觀遺傳的變化。被馴養的雞有超過70%的基因保留著更高程度的甲基化。由於甲基化相比隨機突變來說發生的更為快速，並且可能是由於壓力或其他經歷引發，這就可以解釋，為什麼在短時間內一個品種中的變種數量會上升如此之快。（生物谷Bioon.com）

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.