Exposure to toxic chemicals affects cytochrome P450 transcript expression in early development in two teleost fish, killifish (Fundulus heteroclitus) and zebrafish (Danio rerio)
Janes, Zachary K.
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Synthetic chemicals with biological activity are present in the world’s oceans, many which can adversely affect the health of marine organisms. However, some organisms, such as the killifish population of New Bedford Harbor, MA, (NBH), have evolved mechanisms to deal with the high levels of chemicals such as polychlorinated biphenyls (PCBs), remaining reproductively prolific. Cytochrome P450 enzymes (CYPs) are proteins that aid in metabolizing toxic chemicals such as PCBs. Little is known about the mechanism by which these genes are passed from the mother to the egg/embryo, as well as expression and function of these genes in early development. In this study, we performed quantitative polymerase chain reaction (qPCR) to examine the expression levels of various CYP gene transcripts at selected early developmental stages to indicate which CYPs may be involved in early developmental processes or xenobiotic responses. There was variable expression of CYP transcript in both the killifish and zebrafish egg/embryo. Next, the study sought to compare CYP transcript expression in the NBH killifish population versus a population living in relatively unpolluted conditions, as well as if maternal zebrafish treatment with PCB126 would affect CYP expression levels. These are necessary stages to begin determining mechanisms of chemical effects in early development. CYP1A was highly expressed in the NBH killifish population and zebrafish, as would be expected since CYP1A is a known aryl hydrocarbon receptor (AHR) agonist. The AHR pathway is known to be activated by PCBs and induce CYP1A for metabolism of the PCBs. Future studies should determine the mechanisms by which various CYPs contribute to development, as well as function in the xenobiotic response, if any occurs, of the developing embryo.