title: Gene expression changes related to endocrine function and decline in reproduction in fathead minnow (Pimephales promelas) after dietary methylmercury exposure.
abstract: BACKGROUND
  Methylmercury (MeHg) is a known neurotoxic agent, but the mechanisms by which MeHg may act on reproductive pathways are relatively unknown. Several studies have indicated potential changes in hormone levels as well as declines in vertebrates with increasing dietary MeHg exposure.
  
  
  OBJECTIVE
  The purpose of this study was to identify alterations in gene expression associated with MeHg exposure, specifically those associated with previously observed changes in reproduction and reproductive biomarkers. Fathead minnows, Pimephales promelas, were fed one of three diets that were similar to documented concentrations of MeHg in the diets of wild invertivorous and piscivorous fish. We used a commercial macroarray in conjunction with quantitative polymerase chain reaction to examine gene expression in fish in relation to exposure to these environmentally relevant doses of MeHg.
  
  
  RESULTS
  Expression of genes commonly associated with endocrine disruption was altered with Hg exposure. Specifically, we observed a marked up-regulation in vitellogenin mRNA in individual Hg-exposed males and a significant decline in vitellogenin gene expression in female fish with increasing Hg concentrations. Other genes identified by the macroarray experiment included those associated with egg fertilization and development, sugar metabolism, apoptosis, and electron transport. We also observed differences in expression patterns between male and female fish not related to genes specifically associated with reproduction, indicating a potential physiological difference in the reaction of males and females to MeHg.
  
  
  CONCLUSIONS
  Gene expression data may provide insight into the mechanisms by which MeHg affects reproduction in fish and indicate how MeHg differs in its effect from other heavy metals and endocrine-disrupting compounds.
authors.affiliation: Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA. rklaper@uwm.edu
authors.forename: Rebecca
authors.initials: R
authors.lastname: Klaper
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Rees
authors.forename: Paul
authors.initials: P
authors.lastname: Drevnick
authors.forename: Daniel
authors.initials: D
authors.lastname: Weber
authors.forename: Mark
authors.initials: M
authors.lastname: Sandheinrich
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Carvan
mesh_terms: D000821:Animal Feed; D000818:Animals; D003530:Cyprinidae / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D052244:Endocrine Disruptors / Q000633:toxicity*; D004781:Environmental Exposure; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008767:Methylmercury Compounds / Q000633:toxicity*; D046228:Microarray Analysis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects*; D014819:Vitellogenins / Q000097:blood; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D052244:Endocrine Disruptors; D008767:Methylmercury Compounds; D012333:RNA, Messenger; D014819:Vitellogenins; D014874:Water Pollutants, Chemical