title: Identification of candidate genes and physiological pathways involved in gonad deformation in whitefish (Coregonus spp.) from Lake Thun, Switzerland.
abstract: In 2000, fishermen reported the appearance of deformed reproductive organs in whitefish (Coregonus spp.) from Lake Thun, Switzerland. Despite intensive investigations, the causes of these abnormalities remain unknown. Using gene expression profiling, we sought to identify candidate genes and physiological processes possibly associated with the observed gonadal deformations, in order to gain insights into potential causes. Using in situ-synthesized oligonucleotide arrays, we compared the expression levels at 21,492 unique transcript probes in liver and head kidney tissue of male whitefish with deformed and normally developed gonads, respectively. The fish had been collected on spawning sites of two genetically distinct whitefish forms of Lake Thun. We contrasted the gene expression profiles of 56 individuals, i.e., 14 individuals of each phenotype and of each population. Gene-by-gene analysis revealed weak expression differences between normal and deformed fish, and only one gene, ictacalcin, was found to be up-regulated in head kidney tissue of deformed fish from both whitefish forms, However, this difference could not be confirmed with quantitative real-time qPCR. Enrichment analysis on the level of physiological processes revealed (i) the involvement of immune response genes in both tissues, particularly those linked to complement activation in the liver, (ii) proteolysis in the liver and (iii) GTPase activity and Ras protein signal transduction in the head kidney. In comparison with current literature, this gene expression pattern signals a chronic autoimmune disease in the testes. Based on the recent observations that gonad deformations are induced through feeding of zooplankton from Lake Thun we hypothesize that a xenobiotic accumulated in whitefish via the plankton triggering autoimmunity as the likely cause of gonad deformations. We propose several experimental strategies to verify or reject this hypothesis.
authors.affiliation: Computational and Molecular Populations Genetics Lab, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland. David.Bittner@eawag.ch
authors.forename: David
authors.initials: D
authors.lastname: Bittner
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Cossins
authors.forename: Helmut
authors.initials: H
authors.lastname: Segner
authors.forename: Laurent
authors.initials: L
authors.lastname: Excoffier
authors.forename: Carlo R
authors.initials: CR
authors.lastname: Largiadèr
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D004032:Diet / Q000009:adverse effects / Q000662:veterinary; D012734:Disorders of Sex Development / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology; D020558:GTP Phosphohydrolases / Q000276:immunology / Q000378:metabolism; D020869:Gene Expression Profiling; D005802:Genes, MHC Class II; D056726:Genetic Association Studies / Q000379:methods* / Q000662:veterinary; D060226:Head Kidney / Q000276:immunology / Q000503:physiopathology; D060106:Lakes; D008099:Liver / Q000276:immunology / Q000503:physiopathology; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods* / Q000662:veterinary; D059748:Proteolysis; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D012487:Salmonidae; D015398:Signal Transduction; D013557:Switzerland; D013737:Testis / Q000187:drug effects / Q000276:immunology / Q000503:physiopathology; D018631:ras Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D020558:GTP Phosphohydrolases; D018631:ras Proteins