Transferrin gene expression in response to LPS challenge and heavy metal exposure in roughskin sculpin (Trachidermus fasciatus)

Transferrin plays an important role in immune response of vertebrates. In the present study, a transferrin cDNA with a partial 5′ UTR of 7 bp and a complete 3′ UTR of 345 bp was obtained from the liver of roughskin sculpin, Trachidermus fasciatus, which encodes a deduced 681 amino acid protein containing an N-terminal signal peptide and two conserved lobes. In the N-terminal lobe, the anion-binding residue Arg was substituted with Lys, which represents a common feature in fish and implies a selective preference in the transferrin evolutionary process. In contrast to mammalian transferrin, the roughskin sculpin transferrin did not contain potential N-glycosylation sites, similar to those obtained in cyprinid fish, but not in salmonid fish. Quantitative real-time polymerase chain reaction demonstrated that the transferrin transcripts were abundant in the liver, but also significant in the brain, with a lesser expression in the other nine tissues. The temporal expression profiles were detected during the LPS challenge and heavy metal exposure experiment. Transferrin mRNA expression decreased in the liver in both experiments. Nevertheless, in the main immune organs (skin, blood, and spleen), transferrin mRNA expression was up-regulated significantly. These results suggest that transferrin is involved in the innate immune response of roughskin sculpin.