Marohn, Lasse (2007) Differentielle Genexpressionsanalyse nach PCB-Belastung beim Europäischen Aal (Anguilla anguilla). (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 76 pp.

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Abstract

The stock size of the European Eel (Anguilla anguilla) has decreased for decades, and this development has assumed alarming propotiions. Considered reasons for this decline are high fishing pressure, the loss of accessible habitats, the global climate change and, particularly, the bad health conditions of spawners. Due to the widespread infections with the swimbladder nematode Anguillicola crassus and several viruses (e .g. EVEX, Herpesvirus anguillae) and the contamination from various pollutants, many spawners seem to be unable to reproduce successfully. The dioxin-like polychlorinated Biphenyls (PCBs) are considered to be particularly harmful to the success of reproduction, because of their reproduction and embryo toxicity. The identification of unpolluted habitats, in which healthy spawners could develop, would be of great importance to restore the eel stock in Europe. Such habitats could produce spawners with big spawning capacities, which could strengthen the stock with the help of profitable reproduction. lt is necessary to gain a comprehensive knowledge of coplanar PCB levels in eels of European waters in order to identify such habitats. However, due to the difficult analysis of coplanar PCBs, this knowledge is still fragmentary. The analysis of differential gene expression could provide a relatively uncomplex alternative method and facilitates large-scale PCB monitoring. This study investigated if PCB levels of the European eel could be detected by using the inductive potencies of coplanar PCBs on the cytochrome P4501A-system (CYPlA). Therefore, the transcription activity of the cytochrome P450 lA 1-gene (CYP lA 1) was determined at different PCB levels by using a RT-PCR. Furthermore, it was tested if the coplanar PCBs had an influence on the transcription of a glyceraldehyde-3-phosphatedehydrogenase gene (GAPDH). This was carried out in order to examine if it could be used as a reference gene to standardise quantitative and semiquantitative expression analyses in PCB contaminated eels. After the intraperitoneal injection of a single <lose of different amounts of 3,3 ',4,4' -tetrachlorobyphenyl (PCB No. 77) into young eels (14 - 22 cm), the expression activities of both genes were determined in liver and gills. This study showed that the CYPlAl-expression is induced in liver and gills of the European eel by the intraperitoneal injection of PCB No. 77. The expression in gills was dose dependent, which is a basic requirement for quantitative gene expression analyses. Consequently, according to this study, the use of differential gene expression analyses for PCB-monitoring is possible. The GAPDH expression was affected by the PCB-injection, as well. High PCB concentration led to an elevated GAPDH transcription in the liver, but not in the gills. This study suggests that GAPDH shouldn't be used as a reference gene in quantitative gene expression analyses after high PCB exposures, because it is not expressed independently of high PCB concentrations.

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