DNA reprogramming in early development and its alterations under salinity and selection programme in striped catfish (Pangasianodon hypophthalmus)

摘要: Striped catfish Pangasianodon hypophthalmus is a freshwater species intensively cultivated in Vietnam as well as in different other South-East Asian countries. Due to climate change and salinity intrusion in the lower part of the Mekong delta, a genetic selection programme is ongoing in order to select a strain of striped catfish better adapted to brackish water conditions. The first objective of this study was to determine the DNA reprogramming of this species during its early development stages under normal freshwater conditions. The second objective was to evaluate to what extent an increase of salinity would impair the DNA reprogramming in normal and selected strain of striped catfish. Under freshwater rearing conditions, global CpG methylation increased remarkably from fertilization (40.73%±8.83) to the early blastula stages (54.69%±1.87%), followed by a steady raise until the gastrula stage (64.30%±4.83). The expression of genes related to the methylation process was significantly altered during early development. In particular, dnmt1 mRNA showed a dramatic decrease in the early stages, from fertilization to early gastrulation, and the level remained stable in the later stages. Similarly, mecp2 accumulation decreased significantly from fertilization to early gastrulation. Conversely, dnmt3ba4 was significantly upregulated during the same period and then gradually decreased until 1 day after hatching (dph). A remarkable increase from early gastrula stage to somite development was observed in dnmt3aa transcript accumulations while dnmt3ab3 and dnmt3ab expression showed similar patterns with the gradual increase in late gastrulation at …