Gonzalez-Romero Rodrigo, Suarez-Ulloa Victoria, Rodriguez-Casariego Javier, Garcia-Souto Daniel, Diaz Gabriel, Smith Abraham, Pasantes Juan Jose, Rand Gary, Eirin-Lopez Jose M
Environmental Epigenetics Group, Department of Biological Sciences, Florida International University, North Miami, FL 33181, USA.
Environmental Epigenetics Group, Department of Biological Sciences, Florida International University, North Miami, FL 33181, USA; Ecotoxicology and Risk Assessment Laboratory, Southeast Environmental Research Center, Florida International University, North Miami, FL 33181, USA.
Aquat Toxicol. 2017 May;186:196-204. doi: 10.1016/j.aquatox.2017.03.006. Epub 2017 Mar 7.
Massive algal proliferations known as Harmful Algal Blooms (HABs) represent one of the most important threats to coastal areas. Among them, the so-called Florida Red Tides (FRTs, caused by blooms of the dinoflagellate Karenia brevis and associated brevetoxins) are particularly detrimental in the southeastern U.S., causing high mortality rates and annual losses in excess of $40 million. The ability of marine organisms to cope with environmental stressors (including those produced during HABs) is influenced by genetic and epigenetic mechanisms, the latter resulting in phenotypic changes caused by heritable modifications in gene expression, without involving changes in the genetic (DNA) sequence. Yet, studies examining cause-effect relationships between environmental stressors, specific epigenetic mechanisms and subsequent responses are still lacking. The present work contributes to increase this knowledge by investigating the effects of Florida Red Tides on two types of mechanisms participating in the epigenetic memory of Eastern oysters: histone variants and DNA methylation. For that purpose, a HAB simulation was conducted in laboratory conditions, exposing oysters to increasing concentrations of K. brevis. The obtained results revealed, for the first time, the existence of H2A.X, H2A.Z and macroH2A genes in this organism, encoding histone variants potentially involved in the maintenance of genome integrity during responses to the genotoxic effect of brevetoxins. Additionally, an increase in H2A.X phosphorylation (γH2A.X, a marker of DNA damage) and a decrease in global DNA methylation were observed as the HAB simulation progressed. Overall, the present work provides a basis to better understand how epigenetic mechanisms participate in responses to environmental stress in marine invertebrates, opening new avenues to incorporate environmental epigenetics approaches into management and conservation programs.
大规模藻类增殖，即有害藻华（HABs），是沿海地区面临的最重要威胁之一。其中，所谓的佛罗里达红潮（FRTs，由双鞭毛藻短裸甲藻大量繁殖及其产生的短裸甲藻毒素引起）在美国东南部尤其有害，导致高死亡率以及每年超过4000万美元的损失。海洋生物应对环境应激源（包括有害藻华期间产生的应激源）的能力受到遗传和表观遗传机制的影响，后者导致由基因表达的可遗传修饰引起的表型变化，而不涉及遗传（DNA）序列的改变。然而，关于环境应激源、特定表观遗传机制与后续反应之间因果关系的研究仍然缺乏。本研究通过调查佛罗里达红潮对参与东部牡蛎表观遗传记忆的两种机制的影响，即组蛋白变体和DNA甲基化，为增加这方面的知识做出了贡献。为此，在实验室条件下进行了有害藻华模拟，让牡蛎暴露于浓度不断增加的短裸甲藻中。获得的结果首次揭示了该生物中存在H2A.X、H2A.Z和macroH2A基因，这些基因编码的组蛋白变体可能参与了对短裸甲藻毒素遗传毒性效应反应期间基因组完整性的维持。此外，随着有害藻华模拟的进行，观察到H2A.X磷酸化（γH2A.X，DNA损伤的标志物）增加，整体DNA甲基化减少。总体而言，本研究为更好地理解表观遗传机制如何参与海洋无脊椎动物对环境应激的反应提供了基础，为将环境表观遗传学方法纳入管理和保护计划开辟了新途径。
