Effects of dietary methylmercury on Zebrafish (Danio rerio) reproductive gene transcription

Abstract

Studies have revealed that environmentally realistic concentrations of dietary methylmercury have adverse effects on reproduction in many different fish species. Recent studies have used the fathead minnow (Pimephales promelas) to determine how methylmercury is affecting reproduction on a genomic level, and researchers have seen a disregulation of three reproductive genes: zona pellucida 2 (zp2), zona pellucida 3 (zp3) and vitellogenin (vtg). Unfortunately, the fathead minnow is not an optimal species for genomic and proteomic research because of the lack of genetic information available. The zebrafish (Danio rerio) is a major developmental model species that has most of its genome sequenced, yet there are no published studies exposing zebrafish to environmentally realistic concentrations of methylmercury. I fed groups of zebrafish a low (0.89 ?g Hg g-1) or a medium concentration (3.4 ?g Hg g-1) concentration of methylmercury for a total of 60 days. The expressions of gonadal zp2, zp3 and hepatic vtg were measured with quantitative reverse transcriptase polymerase chain reaction (QRT-PRC). Both zp2 and zp3 were down-regulated in females, while there was no significant change in males. The results were not consistent with studies in other species. Further studies will be required to determine if zebrafish will make a good model for methylmercury research.