2010;19:2152C2167

2010;19:2152C2167. sympatry in Lake Thun. Many studies were initiated in search of potential causes for the unusual gonad deformations. Most of them focused on chemical contaminants, in particular on endocrine-disrupting compounds since these substances can alter gonad morphology in fish [3C6]. To day, no unequivocal evidence for chemicals as causative providers have been found out [7C9]. It appears that neither inbreeding effects nor recent hybridization between genetically unique whitefish forms are involved [10]. Inheritance of gonad deformations [11] and improper breeding of whitefish at the local hatchery [1] have also been excluded. Therefore, despite the rigorous study having been carried out to day, the causes of gonad deformations in whitefish from Lake Thun PI4KIII beta inhibitor 3 remain unknown with the exception of some rearing experiments that point to a role of the lake plankton [7,11]. In recent years, gene manifestation profiling by means of microarray analyses has become an increasingly popular tool to assess the effect of potential stressors on biological pathways at the Cish3 level of mRNA transcription, especially in fish, which are progressively used as models for studies of environmental genomics [12]. Analyses of the transcriptome provide insight into the molecular control of biological and physiological processes and specifically into response to disease, toxins, environmental challenge and other stressors [13,14]. Many of the stressor exposures for which there exists data have been accomplished in laboratories under controlled conditions. So far, only few microarray studies have been conducted with field samples because of the risk of high noise effects due to variation of sex, genotype, age and intrinsic genetic variability in gene expression in natural populations [15C18] that makes it difficult to sort out specific stressor effects. In these studies, usually a gradient approach was used where local fish populations under stress were compared to less impacted sites or to reference sites where the stressor was absent. Thus, European flounder (from several superfund sites (highly polluted) and nearby reference sites along the Atlantic coast were compared [16,20,21]. However, to our knowledge, arrays have not been used to date to compare fish from the same environment but displaying different manifestations of a phenotypic trait. Here, we applied gene expression profiling to identify new candidate PI4KIII beta inhibitor 3 genes and physiological processes associated with observed gonad deformations in whitefish from Lake Thun, and thus, to obtain insight into new potential causes. By using an synthesized rainbow trout oligonucleotide array [22], we compared expression levels of 21,492 transcripts in head kidney and liver tissue between male whitefish with normal and deformed gonads. Since we aimed at screening for gene expression patterns pointing to particular xenobiotic substances potentially contained in the lake plankton, we chose to study tissues of the main organs with respect to detoxification processes or excretion of toxic compounds. Liver is an important organ for many detoxification processes and the head kidney is a key excretory organ of toxic compounds in fish. Transcription profiles were analyzed with two complementary approaches. First, in order to identify candidate genes, we used an ANOVA-based gene-by-gene approach ([23]) to infer expression differences between groups of fish in pairwise comparisons associated with the deformation of gonads. Secondly, using the Gene Ontology (GO) database, we categorized annotated transcript probes into functionally meaningfully groupings according to molecular functions, biological processes or cellular locations in order to identify physiological pathways that are associated with deformed gonads. 2. Experimental Section 2.1. Sampling Lake Thun harbours several distinct sympatric whitefish forms [10]. A large-scale epidemiological survey revealed that gonad deformations occurred predominantly in the summer-spawning Brienzlig whitefish form and additionally in one PI4KIII beta inhibitor 3 PI4KIII beta inhibitor 3 population of the winter-spawning Albock form [2]. The two forms display.