環境汙染影響鰻魚卵巢發育

Environ Sci Technol. 2014 Sep 9. [Epub ahead of print]

Abnormal ovarian DNA methylation programming during gonad maturation in wild contaminated fish.

Pierron F, Bureau du Colombier S, Moffett A, Caron A, Peluhet L, Daffe G, Lambert P, Elie P, Labadie P, Budzinski H, Dufour S, Couture P, Baudrimont M.

Abstract

There is increasing evidence that pollutants may cause diseases via epigenetic modifications. Epigenetic mechanisms such as DNA methylation participate in the regulation of gene transcription. Surprisingly, epigenetics research is still limited in ecotoxicology. In this study, we investigated whether chronic exposure to contaminants experienced by wild female fish (Anguilla anguilla) throughout their juvenile phase can affect the DNA methylation status of their oocytes during gonad maturation. Thus, fish were sampled in two locations presenting a low or a high contamination level. Then, fish were transferred to the laboratory and artificially matured. Before hormonal treatment, the DNA methylation levels of the genes encoding for the aromatase and the receptor of the follicle stimulating hormone were higher in contaminated fish than in fish from the clean site. For the hormone receptor, this hypermethylation was positively correlated with the contamination level of fish and was associated with a decrease in its transcription level. In addition, whereas gonad growth was associated with an increase in DNA methylation in fish from the clean site, no changes were observed in contaminated fish in response to hormonal treatment. Finally, a higher gonad growth was observed in fish from the reference site in comparison to contaminated fish.

有越來越多的證據顯示，污染物可通過表觀遺傳修飾引發疾病。表觀遺傳機制利用DNA甲基化參與調節基因的轉錄。出人意料的是，表觀遺傳學的研究仍局限於生態毒理學。在這項研究中，作者調查從幼年階段就長期接觸污染物的野生母鰻魚（Anguilla anguilla），研究卵母細胞的DNA甲基化狀態是否影響其性腺成熟。鰻魚分別取樣自低或高污染的地區。然後，魚被移到實驗室進行人工催熟。激素處理前，被污染的魚其芳香酶和促卵泡激素的受體編碼基因的DNA甲基化的程度較高。所以激素受體基因的甲基化和污染程度有密切相關，其轉錄水平也下降。此外，儘管乾淨地區的魚其性腺生長也增加DNA的甲基化，但污染的魚就無此變化。在人工催熟下，受污染的鰻魚性腺發育較慢。