Identification and characterization of the lamprey IRF gene

• We identified a IRF gene from Lampetra japonica.
• The expression of IRF was upregulated in intestinals upon stimulation with the rLj-HMGB1 protein.

Interferon regulatory factors (IRFs) are named for their ability to bind to and regulate interferon genes when an organism becomes infected with a virus. Numerous studies have revealed the versatile and critical functions of IRFs. In this study, an IRF gene from Lampetra japonica was identified and analyzed using bioinformatic methods. The L. japonica IRF (Lj-IRF) shares high sequence homology with other vertebrate IRFs but low sequence homology with an ascidian IRF-like protein. We also used recombinant Lj-IRF protein (rLj-IRF) to immunize New Zealand rabbits to prepare specific anti-rLj-IRF polyclonal antibodies. Enzyme-linked immunosorbent assays (ELISAs) and Western blotting assays were performed to detect the valence and specificity of the antibody. FACS analysis revealed that the Lj-IRF protein was expressed in approximately 21.14% of leukocytes and 9.60% of supraneural body cells in L. japonica, with immunofluorescence staining indicating a cytoplasmic location. The immunohistochemistry results demonstrated that IRF is distributed in the epithelial cells of the heart, supraneural body, kidneys and gills but is not detectable in intestinals or oral gland tissues. However, the expression of IRF was upregulated in lamprey intestinal tissues upon stimulation with the rLj-HMGB1 protein. Lj-IRF gene expression levels were higher in the rLj-HMGB1-stimulated group than the control group, and the expression level of Lj-IRF was significantly increased in the intestines as determined by quantitative real-time PCR. These results provide a foundation for studying the origin and evolution of the innate immune system in lampreys.