DNA methyltransferases and stress-related genes expression in zebrafish larvae after exposure to heat and copper during reprogramming of DNA methylation

Abstract

DNA methylation, a well-studied epigenetic mark, is important for gene regulation in adulthood and for development. Using genetic and epigenetic approaches, the present study aimed at evaluating the effects of heat stress and copper exposure during zebrafish early embryogenesis when patterns of DNA methylation are being established, a process called reprogramming. Embryos were exposed to 325 μg Cu/L from fertilization (<1 h post fertilization - hpf) to 4 hpf at either 26.5 °C or 34 °C, followed by incubation in clean water at 26.5 °C till 96 hpf. Significant increased mortality rates and delayed hatching were observed following exposure to combined high temperature and Cu. Secondly, both stressors, alone or in combination, significantly upregulated the expression of de novo DNA methyltransferase genes (dnmt3) along with no differences in global cytosine methylation level. Finally, Cu exposure significantly increased the expression of metallothionein (mt2) and heat shock protein (hsp70), the latter being also increased following exposure to high temperature. These results highlighted the sensitivity of early embryogenesis and more precisely of the reprogramming period to environmental challenges, in a realistic situation of combined stressors.

DNA methylation in adults and during development of the self‐fertilizing mangrove rivulus, Kryptolebias marmoratus

“…In other vertebrates, little is known about reprogramming. In fish, the only studies so far have been conducted in zebrafish, Danio rerio (Fang, Thornton, Scheffler, & Willett, 2013;Mhanni & McGowan, 2004), and it has been shown that DNA methylation reprogramming represents a highly critical window sensitive to environmental stress (Dorts et al, 2016;Martin, Laforest, Akimenko, & Ekker, 1999). Deciphering TEI, environmental cues and reprogramming are consequently important to understand the putative role of epigenetics in rapid adaptation and evolution.…”

Effects of Mine Tailings Exposure on Early Life Stages of Atlantic Cod

“…However, there was no significant elevation in total Cu concentrations in the larvae, which suggests that any slight increase in concentrations in water and chorions was not elevated enough for bioaccumulation into embryos and larvae. This is also supported by no significant elevation of metallothionein gene transcription in hatched larvae, a sensitive marker for induction of metal detoxification mechanisms (Dorts et al ). Previous studies on cod embryos and larvae found elevated mortality in larvae exposed to nominal concentrations of 11.5 μg/L Cu (Granmo et al ) and prolonged developmental time and morphological abnormalities including spinal deformations, decreased hatching rate, and reduced larval viability after exposure to nominal Cu concentrations of approximately 10 μg/L (Swedmark and Granmo ).…”

Epigenetics in aquaculture – the last frontier

“…Dorts et al . () demonstrated the combined effects of metal contamination (copper) and heat stress in zebrafish ( Danio rerio ) embryos during the DNA methylation reprogramming event. The embryos were exposed to CuCl 2 (0 and 325 μg L −1 ) from fertilization to 4 hours post‐fertilization (hpf), at either 26.5°C or 34°C, and then incubated at control conditions (26.5°C) till 96 hpf.…”

“…Temperature control is crucial in aquaculture, and its variation can have severe consequences for production, as it strongly influences growth, feeding rate and survival of the cultured organisms (Mizanur et al 2014). Dorts et al (2016) demonstrated the combined effects of metal contamination (copper) and heat stress in zebrafish (Danio rerio) embryos during the DNA methylation reprogramming event. The embryos were exposed to CuCl 2 (0 and 325 lg L À1 ) from fertilization to 4 hours post-fertilization (hpf), at either 26.5°C or 34°C, and then incubated at control conditions (26.5°C) till 96 hpf.…”