Résumé
Epigenetics has been widely studied on various model species. However, its implications within the Mollusca phylum, the second most diverse in animal kingdom, remain largely unexplored. This lack of knowledge is particularly pronounced for the Pacific oyster Magallana gigas whose adaptative potential has made it the most widespread mollusk worldwide in aquaculture. Most research on M. gigas focused on DNA methylation, revealing that methylation patterns are mainly intragenic and mosaic. These studies demonstrated that DNA methylation encodes information from environmental fluctuations to which oysters are exposed. But variations in DNA methylation pattern resulting from environmental fluctuations could not be clearly associated with geneexpression profiles. This caveat led to the conclusion that a more comprehensive understanding of environmental effects requires examining the organism's entire chromatin structure rather than limiting the analysis to DNA methylation. Therefore, we performed a multiOmic analysis combined with the use of epigenetic modulators. This approach aims to provide a better description of M. gigas chromatin structure. It includesChromatin Immunoprecipitation sequencing (ChIP-seq) to map histone post-translation modifications, Enzyme-Methyl sequencing (EM-seq) to analyze DNA methylation, Transposase-Accessible Chromatin sequencing (ATAC-seq) to assess chromatin accessibility and RNA sequencing (RNA-seq) to establish a link with transcription. The combination of these four methods by MultiOmics Factor Analysis aims to uncover composition and mutual interactions of the elements of the M. gigas epigenome and their relation to transcription. On a broader scale, this work contributes to enhance our comprehension of mollusk epigenetic mechanisms but also underscores the importance of epigenetics in environmental adaptation and resilience.