Identification and expression of the laboratory of genetics and physiology 2 gene in common carp Cyprinus carpio.

In this study, a laboratory of genetics and physiology 2 gene (lgp2) from common carp Cyprinus carpio was isolated and characterized. The full-length complementary (c)DNA of lgp2 was 3061 bp and encoded a polypeptide of 680 amino acids, with an estimated molecular mass of 77 341·2 Da and a predicted isoelectric point of 6·53. The predicted protein included four main overlapping structural domains: a conserved restriction domain of bacterial type III restriction enzyme, a DEAD-DEAH box helicase domain, a helicase super family C-terminal domain and a regulatory domain. Real-time quantitative polymerase chain reaction (PCR) showed widespread expression of lgp2, mitochondrial antiviral signalling protein (mavs) and interferon transcription factor 3 (irf3) in tissues of nine organs. lgp2, mavs and irf3 expression levels were significantly induced in all examined organs by infection with koi herpesvirus (KHV). lgp2, mavs and irf3 messenger (m)RNA levels were significantly up-regulated in vivo after KHV infection, and lgp2 transcripts were also significantly enhanced in vitro after stimulation with synthetic, double-stranded RNA polyinosinic polycytidylic [poly(I:C)]. These findings suggest that lgp2 is an inducible protein involved in the innate immune defence against KHV in C. carpio. These results provide the basis for further research into the role and mechanisms of lgp2 in fishes.