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Overview

Our general aim is to establish a simple mechanism which allows us to measure an estrogen concentration in a solution as precisely as possible. Therefore we want to clone the membrane progestin receptor (mPR) of the zebrafish (Danio rerio) in yeast (saccharomyces cerevisiae) and link it to a reporter gene, which allows a quantitative measurement.

Motivation

Why do we want to establish a mechanism for steroid measurement?

Steroid hormones, especially estrogens, occur in all vertebrates and play a crucial role in sexual differentiation. In recent times the pollution of waters with these hormones has become an increasing problem for the aquatic fauna. Particularly waters functionalized by humans or adjacent to human settlements, for example in areas with agricultural use, show increased estrogen-concentrations.

Scientific studies based on Danio rerio showed that the consequences are devastating. High concentrations of 17α-ethinylestradiol, a hormone in most birth-control pills, affected the sex differentiation of Danio rerio leading to development of ovotestis or complete feminization (Andersenc, 2002). Intersex-fish have been reported in UK rivers since 1978 downstream of an sewage treatment plant.

We believe that a first step in finding a solution to this environmental problem is an accurate and reliable method to quantify steroids which is easy to use and limited to an optical measurement.

Occurring Questions

On our way designing the major pathway to express a specific reporter gene to demonstrate the presence of steroid hormones, we had and still have to deal with several questions concering the choice of BioBricks, genes and vectors to construct a firm method to determine "pollution" by steroid hormones. As a conclusion, we have to meet two major requirements for our system:

• It should be as cost-efficient as possible for easy and regular application
• It should be resistant to yeast's own metabolism. (Not be disturbed by unexpected occuring expression)

At first we had to find an appropriate receptor to detect steroid hormones.

Mechanism

Receptors

Membrangebunden, 7-Transmembranrezeptor (Innen C-Terminus, außen N-Terminus), PAQR-Familie (progesterone adiponectin Q receptor), Hly-III superfamily G-Protein gekoppelt: Aktivierung von inhibitorische Gi-Einheiten: Verringerung der Aktivität der Adenylyl-Cyclase G Proteins (Protein Data Bank) Artikel zu G-Proteinen - Struktur und Funktionsweise, schöne Bilder

Sequenz mPR alpha (Zebrafisch): [http://www.ncbi.nlm.nih.gov/nuccore/AY149121.1 NCBI],

Sequenz mPR beta (Zebrafisch): [http://www.ncbi.nlm.nih.gov/nuccore/AY149120.1 NCBI]

Homologe zum mPR Alpha Danio rerio:

• Goldfisch, Carassius auratus
• Katzenwels, Ictalurus punctatus
• Hundszungen, Cynoglossus semilaevis
• Flunder, Paralichthys lethostigma
• Meerforelle, Cynoscion nebulosus
• Buntbarsch, Oreochromis niloticus
• Umberfisch, Micropogonias undulatus

Zebrafrisch (Danio rerio) In Tübingen:

• Tübingen Map of the [http://wwwmap.tuebingen.mpg.de/ Zebrafish Genome]
• [http://www.mnf.uni-tuebingen.de/fachbereiche/biologie/institute/evolutionecology/lehrbereiche/physiologische-oekologie-der-tiere/staff/volker-scheil.html Dr. Volker Scheil], The impact of potential environmental stressors on early development and cellular and biochemical biomarkers in fish, Main research: Fish embryotoxicity, histopathology and stress protein (hsp 70) responses.

Inhibitor and promotor

An appropriate inhibitor/promotor combination is a crucial step in our pathway and should be selected wisely.

Reporter gene

The last station of our signaling pathway should be a reporter gene which amplifies our initial signal to allow a quantitative measurement.

The enzyme luciferase fulfills these conditions and is possible candidate for our mechanism.

Measurement

The measurement itself should be limited to an optical one and people with lesser qualifications should be able to run it..

References

• Sumpter, Johnson (2008) Reflections on endocrine disruption in the aquatic environment
• Liew et. al. - 2012 Polygenic Sex Determination System in Zebrafish
• Hanna et al. - 2006 - Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors alpha and beta in transfected cells
• Reupke - 2011 - Detektion dopingrelevanter anaboler Steroide in Pferdeurin und Pferdeplasma mithilfe eines Reportergen-Assays in Hefezellen
• Jessica L. Smith, Brian R. Kupchak, Ibon Garitaonandia, L. Kim Hoang, Andrew S. Maina, Lisa M. Regalla, and Thomas J. Lyons - 2008 - Heterologous expression of human mPRα, mPRβ and mPRγ in yeast confirms their ability to function as membrane progesterone receptors
• “Assault on the male”, BBC 1996. Dokumentation zum Thema http://www.youtube.com/watch?v=LkxIJJI37bQ
• Dr. Volker Scheil, The impact of potential environmental stressors on early development and cellular and biochemical biomarkers in fish, Main research: Fish embryotoxicity, histopathology and stress protein (hsp 70) responses.
• Harris et al. - 2011 - The consequences of feminization in breeding groups of wild fish
• Liew et al. - 2012 - Polygenic Sex Determination System in Zebrafish
• Sumpter, Johnson - 2008 - 10th Anniversary Perspective Reflections on endocrine disruption in the aquatic environment from known knowns to unknown unknowns (and many things in between)
• Werner, Palace, Wautier - 2006 - Reproductive fitness of lake trout (Salvelinus namaycush) exposed to environmentally relevant concentrations of the potent estrogen ethynylestradiol (EE2) in a whole lake exposure experiment
• Fenske, M., Maack, G., Schäfers, C., & Segner, H. (2005). An environmentally relevant concentration of estrogen induces arrest of male gonad development in zebrafish, Danio rerio. Environmental toxicology and chemistry / SETAC, 24(5), 1088-98. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/16110986 (kein PDF)
• Schäfers, C., Teigeler, M., Wenzel, A., Maack, G., Fenske, M., & Segner, H. (2007). Concentration- and time-dependent effects of the synthetic estrogen, 17alpha-ethinylestradiol, on reproductive capabilities of the zebrafish, Danio rerio. Journal of toxicology and environmental health. Part A, 70(9), 768-79. doi:10.1080/15287390701236470
• Segner, H., Caroll, K., Fenske, M., Janssen, C. R., Maack, G., Pascoe, D., Schäfers, C., et al. (2003). Identification of endocrine-disrupting effects in aquatic vertebrates and invertebrates: report from the European IDEA project. Ecotoxicology and environmental safety, 54(3), 302-14. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/12651186 (kein PDF)
• Hanna et al. - 2006 - Cell-surface expression, progestin binding, and rapid nongenomic signaling of zebrafish membrane progestin receptors alpha and beta in transfected cells
• Thomas et al. - 2007 - Steroid and G protein binding characteristics of the seatrout and human progestin membrane receptor alpha subtypes and their evolutionary origins
• Thomas - 2008 - Characteristics of membrane progestin receptor alpha (mPR ) and progesterone membrane receptor component 1 (PGMRC1) and their roles in mediating rapid progestin actions
• Jessica L. Smith, Brian R. Kupchak, Ibon Garitaonandia, L. Kim Hoang, Andrew S. Maina, Lisa M. Regalla, and Thomas J. *Lyons - 2008 - Heterologous expression of human mPRα, mPRβ and mPRγ in yeast confirms their ability to function as membrane progesterone receptors