Cloning and expression of Asian swamp eel (Monopterus albus) cxcr4 paralogues, and their modulation by pathogen infection

• This report described the gene character of cxcr4 paralogues in Asian swamp eel Monopterus albus.
• CXCR4 evolution were analysed in vertebrates, suggesting teleost cxcr4b was the origin of tetrapod CXCR4.
• Their modulation by pathogen infection was also studied.
• Our data suggested that cxcr4 paralogues might play a significant role in the immune response of Asian swamp eel.

This report described the cloning and gene expression pattern of cxcr4 paralogues, cxcr4a and cxcr4b, in Asian swamp eel Monopterus albus. The swamp eel cxcr4a cDNA contained a 1047 bp open reading frame encoding a deduced cxcr4a protein of 348 amino acids (aa) while cxcr4b had a 984 bp ORF coding for a 327 aa protein. Swamp eel cxcr4a and cxcr4b are members of G protein-coupled receptors with seven transmembrane domains. Cxcr4b from teleost is closer to tetrapod CXCR4 than to teleost cxcr4a. Like tetrapod CXCR4, all teleost cxcr4b genes have 2 exons and 1 intron. However, teleostean cxcr4a had 4–5 exons in the genomic DNA. Both cxcr4 genes had highest expression levels in the intestine and causal kidney. Stimulation with the Gram negative bacterium Aeromonas hydrophila in vivo and in vitro was able to modulate expression of cxcr4 paralogues. Poly I:C down-regulated cxcr4b expression of while it up-regulated cxcr4a expression. Acanthocephalan Pallisentis (Neosentis) celatus also increased the expression of swamp eel cxcr4 paralogues. Our data suggested that cxcr4 paralogues might play a significant role in the immune response of Asian swamp eel.Statement of relevanceThis report described cxcr4 paralogues and their modulation by pathogen infection, which is of significance in swamp eel aquaculture.