Differentially expressed genes in genetically divergent Nelore steers for selenium content in Longissimus dorsi muscle

Selenium (Se) is a mineral that influences the metabolism of hormones and is a co-factor of enzymes with roles in tissue protection against oxidative stress. These actions may influence feed efficiency and meat quality variation, target traits in beef cattle production. Conversely, there are few studies regarding genes that regulate or are affected by Se concentration in the muscle of beef cattle. As a strategy to find such genes, we selected, from a 120 initial population of Nelore steers, two groups with extreme estimated genomic breeding values (GEBV) for Se concentration in Longissimus dorsi in order to identify differentially expressed genes (DEGs) between contrasting groups, using an RNA-Seq approach. Our results revealed 45 DEGs, being 34 upregulated in the low Se content group. The DEGs have functions relevant to proteins in extracellular matrix, cell adhesion, skeletal system development, methylation, nucleotide and ATP bindings. Also, they were potentially associated to meat quality traits due to its role in collagen formation, ion binding, oxidation reduction, apoptosis regulation and cell fraction. The functional annotation performed using DAVID software shows a functional gene cluster associated with the epidermal growth factor (EGF), a known controller of postnatal muscle growth, where there are three upregulated genes (FBLN7, ADAM12 and COMP) and one downregulated gene (DLK1) in the low Se content group. The products of these four genes, along with growth factors, are associated with muscle and skeletal development, important features for meat production traits. Se promotes adipogenesis and lipid accumulation, common features in obesity and DLK1 is known to increase obesity in humans, perhaps explaining part of the Se effect on adipogenesis. These DEGs are also known to influence several complex diseases. For example, mutations in ADAM12 are related to brain cancer that can be diminished with Se-based treatments. Moreover, FBLN7 and COMP cause human syndromes that cause bone abnormalities. The results of this study begin to provide a more comprehensive explanation of gene expression variation associated with phenotypic expression of Se content in Nelore steers. We want to thanks FAPESP for the founding through the grant 2012/23638-8.