title: Molecular and phenotypic responses of Japanese medaka (Oryzias latipes) early life stages to environmental concentrations of cadmium in sediment.
abstract: Japanese medaka embryos were exposed to environmental concentrations of cadmium (Cd) to investigate adverse and adaptive responses in fish early life stages. Embryos were exposed during their whole development by static sediment-contact to environmental Cd concentrations (2 and 20 μg/g dry weight). Cd bioaccumulation, developmental defects, biochemical and biomolecular (qRT-PCR) responses were analyzed in embryos and hatchlings. A dose-dependent increase of Cd bioaccumulation and developmental defects was observed at hatching. Cd had clear impacts on heartbeat and cardiac morphogenesis and also induced to spinal deformities. The profile and the level of gene transcription were differentially modulated according to the Cd concentration, the duration of exposure and/or the developmental stage of fish. Pro-apoptotic bax and DNA repair rad51 transcripts were significantly repressed in embryos exposed to the highest Cd concentration. Repression of these genes was correlated to the increase of heart rate in 6-day-old embryos. NADH-dehydrogenase nd5 gene transcription was inhibited in larvae at the lowest concentration suggesting mitochondrial respiratory chain impairment, in association with Cd-induced teratogenicity. Finally, wnt1 gene was overexpressed indicating putative deregulation of Wnt signaling pathway, and suggested to be implied in the occurrence of some spinal and cardiac deformities. Results of this study permitted to propose some promising markers at the transcriptional and phenotypical level, responding to environmental concentrations of Cd. The present work also highlights the usefulness of the modified version of the medaka embryo-larval assay with sediment-contact exposure (MELAc) to investigate the toxicity and the modes of action of sediment-bound pollutants.
authors.affiliation: EPOC UMR CNRS 5805, University of Bordeaux, Avenue des Facultés, 33405, Talence Cedex, France. irisbarjhoux@hotmail.com.|UMR-I 02 INERIS-URCA-ULH SEBIO, University of Reims Champagne-Ardenne, Moulin de la Housse, BP 1039, 51687, Reims Cedex 2, France. irisbarjhoux@hotmail.com.
authors.forename: Iris
authors.initials: I
authors.lastname: Barjhoux
authors.affiliation: EPOC UMR CNRS 5805, University of Bordeaux, Avenue des Facultés, 33405, Talence Cedex, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Gonzalez
authors.affiliation: EPOC UMR CNRS 5805, University of Bordeaux, Avenue des Facultés, 33405, Talence Cedex, France.
authors.forename: Magalie
authors.initials: M
authors.lastname: Baudrimont
authors.affiliation: EPOC UMR CNRS 5805, University of Bordeaux, Avenue des Facultés, 33405, Talence Cedex, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Cachot
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D007814:Larva / Q000254:growth & development; D009990:Oryzias / Q000235:genetics*; D010641:Phenotype; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D002104:Cadmium
keywords: Cd bioaccumulation; Cd-spiked sediment; Developmental abnormalities; Fish embryos; Gene transcription; Heart rate; Metallothionein content