Differential Expression of MicroRNAs in Embryos and Larvae of Mahi-Mahi (Coryphaena hippurus) Exposed to Deepwater Horizon Oil

Deepwater Horizon (DWH) oil causes developmental cardiotoxicity in fish species, but the molecular mechanisms are still not well understood. MicroRNAs (miRNAs) play key roles in a number of biological processes, including heart development. Therefore, the expression of miRNAs in mahi-mahi (Coryphaena hippurus) exposed to weathered slick oil and nonweathered source oil was analyzed. miRNAs were sequenced and annotated using the Fugu rubripes genome (termed the Fugu-guided approach) or aligned with known mature animal miRNAs using the Basic Local Alignment Search Tool (BLAST) method (termed the phylogenetically guided approach). Exposure of embryos to slick oil resulted in more differentially expressed miRNAs than exposure to source oil at all developmental stages. Gene ontology analysis on the target mRNAs was consistent with pathway analysis of miRNAs, predicting disruption of cardiovascular system development after oil exposure, and specific miRNA-mRNA interactions identified by ingenuity pathway analysis. Slick oil caused an overexpression of miR-133, which correlated with the decrease in the level of expression of genes related to the cardiovascular system such as potassium voltage-gated channel subfamily H member 2 (kchn2). This work is the first study linking miRNAs and mRNAs in crude oil-exposed fish, providing a new understanding of the molecular mechanism(s) of oil toxicity.