Liver DNA methylation and transcriptome between 1- and 3-year-old grass carp

Diseases of grass carps often occur in juveniles but not in adults that may have established disease resistance during development. We performed both DNA bisulfite and transcriptome sequencing on liver libraries of 1- and 3-year-old grass carps. Differential DNA-methylation analysis exhibited a declined methylation level through development. Functional annotation revealed that identified differentially methylated genes (DMGs) and differentially expressed genes were enriched in immune-related pathways such as PI3K-Akt signaling pathway and its related pathways. Both differentially methylated and differentially expressed genes were clustered into the growth- and immune-related function networks. Subcellular localization analysis indicated that the DMGs localized on cell membrane were significantly enriched in calcium signaling pathway and neuroactive ligand-receptor interaction pathway, implying the importance of G protein-coupled receptors to development. These findings will broaden our understanding of the key genes and pathways that affect the immune system at different development stages and the developing protective strategies in grass carp.