Immune genes, IL1β and Casp9, show sexual dimorphic methylation patterns in the zebrafish gonads

There is a crosstalk between the immune and the reproductive systems in which sexual dimorphism is a common pattern in vertebrates. In the last years, epigenetics has emerged as a way to study the molecular mechanisms involved during gonadal development, which are responsible to integrate environmental information that contributes to assign a specific sexual phenotype (either an ovary or a testis). In the fish gonads, it is known of the existence of the reproduction-immune system interactions although the epigenetic mechanisms involved are far to be elucidated. Here, we used the zebrafish (Danio rerio) as a model to study the DNA methylation patterns of two well-known innate immune genes: IL1{beta} and Casp9. DNA methylation levels were studied by a candidate gene approach at single nucleotide resolution and further, gene expression analysis were carried out. Results showed that there was clear sexual dimorphism in the DNA methylation levels of the two immune studied genes, being significantly higher in the testes when compared to the ovaries. In summary, and although much research is needed, here we present two potential candidates as epimarkers with forthcoming applications in the livestock and fish farming production, for example, in immune fish diseases or sexual control programs.