Gene structure and differential modulation of multiple rockbream (Oplegnathus fasciatus) hepcidin isoforms resulting from different biological stimulations

Hepcidin, an antimicrobial and iron-regulating peptide, is a key molecule of the innate immune system of bony fish. In this study, four isoforms of hepcidin genes were characterized from a marine Perciform fish, rockbream (Oplegnathus fasciatus), and the transcriptional modulations of these isoforms in response to different biological stimulations were also examined. All rockbream hepcidin isoform genes exhibited a tripartite structure and their promoter regions displayed typical binding motifs for the transcription factors including C/EBP, HNF, AP, NF-kβ, GATA, USF and/or STAT. Hepcidin transcripts in juvenile or fingerling tissues were dramatically induced during experimental challenges with various bacterial species, iron overload and rockbream iridovirus infection. The transcription of hepcidins was regulated in an isoform- and tissue-specific fashion. In addition, we identified for the first time that partially processed hepcidin transcripts were significantly elevated during bacterial infection and iron overload. Results from this study provide a good basis to better understand the isoform-specific role of hepcidin in the fish innate immune system.