Differential expression and functional diversification of diverse immunoglobulin domain-containing protein (DICP) family in three gynogenetic clones of gibel carp

Diverse immunoglobulin (Ig) domain-containing protein (DICP) family is a novel bony fish-specific multi-gene family encoding diversified immune receptors. However, their function and the implication of binding partners remain unknown. In this study, we first identified 28 DICPs from three gibel carp gynogenetic clones and revealed their high variability and clone-specific feature. After crucian carp herpesvirus (CaHV) infection, these DICPs were significantly upregulated in head kidney, kidney and spleen. The up-regulation folds in clone A+, F and H were related to the susceptibility to CaHV, progressively increasing from resistant clone to susceptible clone. Overexpression of gibel carp DICPs inhibited interferon (IFN) and viperin promoter-driven luciferase activity. The additions of E. coli extracts and lipid A significantly enhanced the inhibition effect. In addition, gibel carp DICPs can interact with SHP-1 and SHP-2. These findings suggest that gible carp DICPs, as inhibitory receptors, might specifically recognize lipid A, and then interact with SHP-1 and SHP-2 to inhibit the induction of IFN and ISGs.