Identification of Potential Long Noncoding RNA Biomarker of Mercury Compounds in Zebrafish Embryos

Heavy metal pollution elicits severe environmental concern and health problem worldwide. Mercury is considered as a ubiquitous pollutant due to its versatile application in medicine, industry, and cosmetics. Long noncoding RNAs (lncRNAs) are transcripts greater than 200 nt without protein-encoding function. However, little is known about the mechanism of heavy metals-induced noncoding RNA changes in aquatic organisms. To reveal the epigenetic mechanism of mercury toxicity in zebrafish embryos and explore novel specific mercury-toxicological biomarkers, several well-studied lncRNAs were screened by real-time PCR, and the spatial-temporal expression of lncRNAs biomarker was evaluated by in situ hybridization. The nerve systems of zebrafish embryos were evaluated by detecting locomotor behavior and the expression of neuro-genes. We identified a mercury responsive lncRNA, metastasis-associated lung adenocarcinoma transcript 1 (malat1), among five candidate lncRNAs. HgCl₂, MeHg, PbCl₂, CdCl₂, and K₂CrO₄ exposure assay showed that malat-1 was a mercury specific induced lncRNAs. Malat1 was highly expressed in the brain region, eyes, and notochord of developing zebrafish embryos after exposure to mercury compounds. HgCl₂ showed neurobehavior disturbance and changed neuro-genes expression pattern in zebrafish larvae. This study provides a biological method to detect inorganic or organic mercury using malat1 as a novel biomarker of mercury contamination and also clues for the exploration of neurotoxicity mechanism of mercury compounds.