Differential expression of metallothionein (MT) gene by trace metals and endocrine-disrupting chemicals in the hermaphroditic mangrove killifish, Kryptolebias marmoratus.

Metallothionein (MT) gene expression was studied in different tissues, development stages and gender types of the mangrove killifish (Kryptolebias marmoratus). MT expression was also studied in a time-series experiment after exposure to trace metals and endocrine-disrupting chemicals (EDCs). The brain showed the highest level of MT transcripts. Although all the development stage showed some level of MT expression, the adult hermaphrodites showed the highest expression which was significantly higher than the secondary males. In the trace metal-exposed fish, cadmium caused the strongest induction of MT. However, other trace metals such as copper and zinc also caused MT gene induction. All the EDCs suppressed the expression of MT gene, and the effect of EDCs were not gender-specific. K. marmoratus has previously shown its suitability as a model species for toxicity studies and cancer research. This study demonstrated utility of MT as biomarker in K. marmoratus. However, confounding factors such as age, gender, and tissue types appear to influence the MT expression. Response of trace and organic pollutants such as EDCs also varied greatly. These observations suggest that MT would be a specific biomarker of trace metal exposure in K. marmoratus and expression would be influenced by intrinsic factors.