Toxicogenomic signatures associated with methylmercury induced developmental toxicity in the zebrafish embryos.

Methylmercury (MeHg) is a teratogen with adverse effects on embryogenesis from fish to man. The adverse developmental outcomes of MeHg are well understood, but molecular understanding of teratogenic effects is rather limited. We performed here a genome - wide transcriptional analyses of 6, 30 and 50 µg/L MeHg treated zebrafish embryos from 4 to 72 h post-fertilization (hpf) using RNA-sequencing and self-printed microarray, and conducted a systematical comparison of MeHg - induced transcriptomic responses observed in this and our previous studies. We found that genes linked to gene ontology in terms of oxidative stress, visual, photoreception and cilium, and GABAergic synapse were enriched in embryo exposed from 4 to 72 hpf. The significantly altered genes involved in MAP kinase, TGF beta signaling pathway, oxidative phosphorylation, and glutathione metabolism were enriched across different exposure scenarios. We obtain 22 genes significantly regulated by MeHg, particularly the significant changes were determined in embryos exposed to 6 µg/L MeHg, which did not cause obviously teratogenic effects. Our findings show that the genes whose expression is altered by MeHg in embryonic stages may play important roles in adverse developmental endpoints and might be served as signatures for teratogenic effects. Overall design: Identifying the marker genes which are able to assess the toxic effect of zebrafish embryos exposed to MeHg by differential genes expression analysis of RNA-seq data.Embryos were respectively exposed to 0, 6, 30, 50 µg/L MeHg at 4 to 72 hpf.