Fellous Alexandre, Favrel Pascal, Riviere Guillaume
UMR BOREA Biologie des Organismes et Ecosystèmes Aquatiques, MNHN, UPMC, UCBN, CNRS-7208, IRD-207, Institut de Biologie Fondamentale et Appliquée, Université de Caen Basse-Normandie, Esplanade de la Paix, CS 14032, 14032 Caen cedex 5, France.
UMR BOREA Biologie des Organismes et Ecosystèmes Aquatiques, MNHN, UPMC, UCBN, CNRS-7208, IRD-207, Institut de Biologie Fondamentale et Appliquée, Université de Caen Basse-Normandie, Esplanade de la Paix, CS 14032, 14032 Caen cedex 5, France.
Mar Genomics. 2015 Feb;19:23-30. doi: 10.1016/j.margen.2014.09.002. Epub 2014 Sep 16.
In many groups, epigenetic mechanisms influence developmental gene regulation under environmental inputs. The Pacific oyster Crassostrea gigas belongs to lophotrochozoans and its larval development is highly dependent on temperature, but the role of epigenetic mechanisms in this context is unknown despite high levels of the recently characterized Jumonji histone demethylase (JHDM) orthologues (Cg_Jumonji) suggesting a physiological relevance of histone methylation in the oyster development. Because in other species alterations of the histone methylation pattern have deleterious outcomes, we investigated the influence of temperature during the oyster larval life on histone methylation and JHDM expression. To shed light on this point, oyster embryonic and early larval development experiments were carried out at different temperatures (18 °C, 25 °C and 32 °C). Histone methylation levels were investigated using fluorescent ELISA at 6 and 24h post-fertilization. When compared to the 25 °C group, at 18 °C H3K4, H3K9 and H3K27 residues were hypomethylated at 6h post fertilization (hpf) and hypermethylated at 24 hpf. In contrast, at 32 °C, 6hpf animals present a dramatic hypermethylation (ca. 4-fold) of all examined residues, which is minored but sustained at 24 hpf. RT-qPCR investigations of the mRNA expression of the nine oyster JHDMs, showed gene- and stage-specific temperature sensitivities throughout the early life of oysters. This study provides evidence of the biological significance of histone methylation during development in a lophotrochozoan species. Our results also indicate that temperature influences histone methylation, possibly through the expression level of putative actors of its regulation, which might participate in developmental control. To our knowledge, this is the first report indicating a direct relationship between an epigenetic mark and an environmental parameter in marine molluscs. Such investigations could help better understand the molecular mechanisms of development and adaptation in lophotrochozoans.
在许多生物群体中，表观遗传机制在环境输入的影响下调控发育基因。太平洋牡蛎（Crassostrea gigas）属于冠轮动物，其幼体发育高度依赖温度。尽管最近鉴定出的高水平Jumonji组蛋白去甲基化酶（JHDM）直系同源物（Cg_Jumonji）表明组蛋白甲基化在牡蛎发育中具有生理相关性，但表观遗传机制在这一过程中的作用尚不清楚。由于在其他物种中组蛋白甲基化模式的改变会产生有害后果，我们研究了牡蛎幼体期温度对组蛋白甲基化和JHDM表达的影响。为阐明这一点，在不同温度（18℃、25℃和32℃）下进行了牡蛎胚胎和幼体早期发育实验。在受精后6小时和24小时，使用荧光ELISA法研究组蛋白甲基化水平。与25℃组相比，在18℃时，受精后6小时（hpf）H3K4、H3K9和H3K27残基发生低甲基化，而在24 hpf时发生高甲基化。相反，在32℃时，6hpf的动物所有检测残基均出现显著的高甲基化（约4倍），在24 hpf时虽有所减弱但仍持续存在。对9种牡蛎JHDM的mRNA表达进行RT-qPCR研究，结果表明在牡蛎的早期生命过程中，基因和阶段对温度具有特异性敏感性。本研究提供了冠轮动物发育过程中组蛋白甲基化生物学意义的证据。我们的结果还表明，温度可能通过其调控相关假定因子的表达水平影响组蛋白甲基化，这可能参与发育控制。据我们所知，这是第一份表明海洋软体动物中表观遗传标记与环境参数之间存在直接关系的报告。此类研究有助于更好地理解冠轮动物发育和适应的分子机制。
