Effect of Low-Dose Cadmium Exposure on DNA Methylation in the Endangered European Eel

Abstract

There is increasing evidence that epigenetics can play a key role in the etiology of diseases engendered by chronic pollutant exposure. Although epigenetics has received significant attention in the field of biomedicine during the last years, epigenetics research is surprisingly very limited in ecotoxicology. The aim of the present study was to investigate the possible effects of low-dose cadmium exposure on the DNA methylation profile in a critically endangered fish species, the European eel. Eels were exposed to environmentally realistic concentrations of cadmium (0.4 and 4 μg·L(-1)) during 45 days. The global CpG methylation status of eel liver was determined by means of a homemade ELISA assay. We then used a methylation-sensitive arbitrarily primed PCR method to identify genes that are differentially methylated between control and Cd-exposed eels. Our results show that cadmium exposure is associated with DNA hypermethylation and with a decrease in total RNA synthesis. Among hypermethylated sequences identified, several fragments presented high homologies with genes encoding for proteins involved in intracellular trafficking, lipid biosynthesis, and phosphatidic acid signaling pathway. In addition, few fragments presented high homologies with retrotransposon-like sequences. Our study illustrates how DNA methylation can be involved in the chronic stress response to Cd in fish.

Low levels of Cd induce persisting epigenetic modifications and acclimation mechanisms in the earthworm Lumbricus terrestris

“…A similar effect was also described in human prostate cell lines during Cd-induced malignant transformation [19]. Eels exposed to 0.4 and 4 μg/L Cd were associated with a significant increase in the global CpG methylation status [50] as well as human embryo lung fibroblast cells after long-term, low-dose Cd exposure [51]. DNA methylation levels and the gene expression of DNMT1 and DNMT3a in hens’ liver and kidney were significantly elevated by Cd treatment [52].…”

Transcriptional and biochemical markers in transplanted Perca flavescens to characterize cadmium- and copper-induced oxidative stress in the field

“…Other factors, such as epigenetic effects (induction of phenotypic variation without DNA sequence alteration) (Pierron et al, 2014;Richards, 2006), may also explain the observed differences in gene expression between the two fish groups (Pierron et al, 2014). Indeed, although the yellow perch populations used in this study were similar in body weight and length and originated from the same region with similar natural macro-environments, epigenetic mechanisms could exert a crucial influence on phenotypic plasticity and on the interactions between the fish and their environment, thereby modifying gene expression and contributing to environmentally-induced phenotypic changes (Angers et al, 2010).…”

Current Advances in Functional Genomics in Aquaculture

“…In addition, Morán et al [17] showed that salt diets used during the seawater phase triggered genome-wide methylation changes when administered in freshwater reared trout indicating that DNA methylation could play a vital role in enabling anadromous ish acclimatize to seawater after transfer from freshwater. DNA methylation and histone modiication have also been associated with adaptation changes induced by adverse environmental conditions as shown in Nile tilapia exposed to industrial pollutions [231], eels to cadmium exposure [232], sea urchin (G. crenularis) exposure to perluoroctane sulfonate (PFOS) [216] and the three-spine stickleback (G. aculeatus) hexabromocyclododecane (HBCD) exposed to 17-β oestradiol (E 2 ) and 5-aza 2′ deoxycytidine (5AdC) pollutants [233]. In summary, these studies demonstrate that DNA methylation and histone modiication contribute to nutritional, environmental and photoperiod adaptation in diferent aquatic organisms and that these factors could have an inluence on improving production in aquaculture.…”