title: DNA methylation is crucial for the early development in the Oyster C. gigas.
abstract: In vertebrates, epigenetic modifications influence gene transcription, and an appropriate DNA methylation is critical in development. Indeed, a precise temporal and spatial pattern of early gene expression is mandatory for a normal embryogenesis. However, such a regulation and its underlying mechanisms remain poorly understood in more distant organisms such as Lophotrochozoa. Thus, despite DNA in the oyster genome being methylated, the role of DNA methylation in development is unknown. To clarify this point, oyster genomic DNA was examined during early embryogenesis and found differentially methylated. Reverse transcriptase quantitative polymerase chain reaction indicated stage-specific levels of transcripts encoding DNA-methyltransferase (DNMT) and methyl-binding domain proteins. In addition, as highlighted by electronic microscopy and immunohistochemistry, the DNMT inhibitor 5-aza-cytidine induced alterations in the quantity and the localisation of methylated DNA and severe dose-dependent development alterations and was lethal after zygotic genome reinitiation. Furthermore, methyl-DNA-immunoprecipitation-quantitative polymerase chain reaction revealed that the transcription level of most of the homeobox gene orthologues examined, but not of the other early genes investigated, was inversely correlated with their specific DNA methylation. Altogether, our results demonstrate that DNA methylation influences gene expression in Crassostrea gigas and is critical for oyster development, possibly by specifically controlling the transcription level of homeobox orthologues. These findings provide evidence for the importance of epigenetic regulation of development in Lophotrochozoans and bring new insights into the early life of C. gigas, one of the most important aquaculture resources worldwide.
authors.affiliation: Biologie des Organismes Marins et des Ecosystèmes Associés (BioMEA) Esplanade de la paix, Université de Caen Basse-Normandie, 14032, Caen Cedex, France, guillaume.riviere@unicaen.fr.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Riviere
authors.forename: Guan-Chung
authors.initials: GC
authors.lastname: Wu
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fellous
authors.forename: Didier
authors.initials: D
authors.lastname: Goux
authors.forename: Pascal
authors.initials: P
authors.lastname: Sourdaine
authors.forename: Pascal
authors.initials: P
authors.lastname: Favrel
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017756:Aquaculture; D001374:Azacitidine / Q000633:toxicity; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015254:DNA Modification Methylases / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D044127:Epigenesis, Genetic / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008855:Microscopy, Electron, Scanning; D010125:Ostreidae / Q000196:embryology* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018398:Homeodomain Proteins; D015254:DNA Modification Methylases; D001374:Azacitidine