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The Effects of Wastewater Effluent on Sexual Differentiation and Gene Expression in the American Bullfrog

Stephanie E. Wolff1*, Janae M. Coston1, Nik Veldhoen2, Caren C. Helbing2 and Catherine R. Propper1
  • 1 Northern Arizona University, Department of Biological Sciences, United States
  • 2 University of Victoria, Department of Biochemistry and Microbiology, Canada

Wastewater effluent (WWE) contains a broad mix of compounds, many of which impact endocrine function. This water poses a risk to wildlife health as it is often released directly into lakes, rivers and streams. Also, WWE can either indirectly or directly recharge aquifers used as sources of drinking water. The endocrine disrupting compounds (EDCs) found in WWE include bisphenol-A, alkylphenols and many steroids. Several species of fish and frogs collected downstream from WWE release have been found with gonadal abnormalities. In this study, American bullfrog (Rana catesbeiana) tadpoles were collected from a reference lake site with no WWE input and a pond that is fed strictly with WWE. Using real-time qPCR, expression of key sexual differentiation genes in gonad tissue, steroidogenic factor 1 (SF-1) and CYP19, were evaluated. These genes have been shown to be sensitive to EDCs in laboratory studies. Using these genes, we can evaluate effects of EDCs on reproductive and sexual differentiation physiology. We found that there was a female-skewed sex ratio at the wastewater site, and there was a loss of the significantly different sexually dimorphic gene expression with regards to SF-1. CYP19 expression was increased in both sexes at the WWE site and sexually dimoprhic expression was lost between the sexes. These complex mixes can have different effects on numerous parts of differentiation pathways when animals are exposed during development. In other studies, SF-1 and CYP19 gene expression is sexually dimorphic normally and expression can be changed with exposure to individual EDCs. Compared to those studies, the results seen here suggest that the WWE is acting like an estrogen, but does not show the same results seen with exposures to estradiol alone. Our results suggest that exposure to WWE, similar to results with individual compound exposure, disrupts gonadal differentiation by acting to shift expression of key genes involved in gonad formation (supported by NSF grant IOS-0723370).

Acknowledgements

I would like to thank the NSF for funding this study, the Department of Biological Sciences at Northern Arizona University, and the Department of Biochemistry and Microbiology at University of Victoria. I would also like to thank Thasanee Chantarojwong-McGuffey and Doug Margarucci for their help with tadpole collections and Emily Andrews and Priyanka Purnanada for help with histology.

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Keywords: CYP19, endocrine disruption, Gene Expression, Rana catesbeiana, sexual differentiation, SF-1, wastewater

Conference: ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology, Ann Arbor, United States, 11 Jul - 13 Jul, 2011.

Presentation Type: Poster

Topic: Endocrine disruption

Citation: Wolff SE, Coston JM, Veldhoen N, Helbing CC and Propper CR (2011). The Effects of Wastewater Effluent on Sexual Differentiation and Gene Expression in the American Bullfrog. Front. Endocrinol. Conference Abstract: ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology. doi: 10.3389/conf.fendo.2011.03.00046

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Received: 22 Jul 2011; Published Online: 09 Aug 2011.

* Correspondence: Ms. Stephanie E Wolff, Northern Arizona University, Department of Biological Sciences, Flagstaff, Arizona, 86011, United States, sw245@nau.edu