Publication Abstract

DNA Methylome reprogramming is a dynamic period of epigenetic rearrangement that occurs after fertilisation in many animal embryos. However, the existence and timing of a reprogramming period in many species of invertebrates remains unclear, including in the Pacific oyster Magallana gigas. Here, we aimed to identify whether a window of sensitivity to methylation inhibitors exists during early Pacific oyster development, with the hypothesis that this sensitivity is indicative of a period of epigenetic reprogramming within the methylome. In order to identify the precise timing of methylome reprogramming, we exposed Pacific oyster embryos to the methylation inhibitor 5-azacytidine at different intervals during early development and monitored survival and occurrence of developmental abnormalities after 44 hours of exposure. We observed a period of methylation sensitivity in Pacific oyster larvae that lasted up to approximately 11 hours post fertilisation in the current study, which is indicative of a period of methylome reprogramming. There was a substantial shift in methylation sensitivity  from approximately 8 up to 11 hours post fertilisation, which is suggestive of the window of completion of the reprogramming period. These findings provide an estimate of the precise timing for the completion of reprogramming during embryogenesis in the Pacific oyster and help to provide important information for furthering our understanding of reprogramming dynamics within Mollusca and invertebrate species. The existence of a reprogramming period could also offer an important opportunity to manipulate the epigenome in order to improve resilience to stress, including the potential to increase disease resistance via immune priming.

Sarah J Woodsford, Frederico M Batista^*, Irene Cano^*, Robert P Ellis, Ronny van Aerle*, Aaron R Jeffries*, Hannah Farley, Jennifer C Nascimento-Schulze, Mickael Teixeira Alves*, Eduarda M Santos