Molecular Characterization and Expression and DNA Methylation Analyses of a Galectin-Related Protein Gene from Cynoglossus semilaevis

Galectins, a family of β-galactoside-binding proteins, participate in both innate immunity and adaptive immunity. This study identified one novel galectin-related protein from half-smooth tongue sole Cynoglossus semilaevis, which was designated as CsGRP. The full-length cDNA of its encoding gene was 785 bp in length with a 528 bp open reading frame encoding a putative protein of 176 amino acids. The deduced CsGRP contained a putative 131-aa galactoside-binding lectin domain and 3 critical residues responsible for carbohydrate binding (R93, W109 and R114). Genomic structural analysis revealed that CsGRP consisted of five exons and four introns. CsGRP showed 68% similarity with Poecilia latipinna GRP and 67% similarity with Stegastes partitus GRP. CsGRP showed the highest expression level in liver, although its expression was detected in all tested tissues. When challenged with Vibrio harveyi, the expression of CsGRP was significantly down-regulated in liver (P < 0.05). In addition, we found that in spleen and kidney of C. semilaevis, the CpG island of CsGRP showed significantly higher (P < 0.05) methylation level in disease-resistant family of C. semilaevis (DR-Cs) than in disease-susceptible ones (DS-Cs). Our results suggested that CsGRP may play important roles in the immune response of C. semilaevis. Moreover, DNA methylation patterns provided valuable data for understanding the relationship between epigenetic regulation and immunity, which would assist the animal genetic research and improve the animal breeding in the future.