The effects of 17-α-ethinylestradiol (EE2) on molecular signaling cascades in mummichog (Fundulus heteroclitus)

• Mummichog (Fundulus heteroclitus) were exposed to 17-α-ethinylestradiol (EE2).
• Ovarian stage and plasma estrogen were not affected by EE2 but T was depressed.
• Novel gene regulatory networks were constructed using sub-network enrichment analysis.
• Genes involved in the regulation of lipids were a major target of EE2 in the liver.
• EE2 did not affect the mRNA expression of apolipoproteins in the liver.

Exposures to ≤10 ng/L of 17-α-ethinylestradiol (EE2) will reduce or shut down egg production in freshwater fish models, while mummichog (Fundulus heteroclitus), an estuarine species, are able to produce eggs at EE2 concentrations >3000 ng/L. The objective of this study was to gain mechanistic insight into how mummichog are able to produce eggs during exposures to high EE2. Mummichog were exposed to 0, 50 or 250 ng/L of EE2 for 14 d. There were no changes in gonadosomatic index, liversomatic index, gonad development, or plasma estradiol levels after exposure to EE2. However, testosterone significantly decreased with EE2 exposures (50, 250 ng/L). Microarray analysis in the liver revealed that cell processes associated with lipids were affected by EE2 at the transcriptome level. Based on the transcriptomics data, we hypothesize that mummichog are able to maintain lipid transport and uptake into the ovary and this may be associated with apolipoproteins, facilitating normal oocyte development. Novel gene regulatory networks for protein modification targets were also constructed to learn more about the potential roles of estrogens in the teleost liver. Although post-translational modifications (PTMs) are important regulatory mechanisms, the roles of PTMs in protein regulation in fish and the susceptibility of PTMs to aquatic pollutants are largely unexplored and may offer novel insight into mechanisms of endocrine disruption.