Full-length sequence and expression analysis of a myeloid differentiation factor 88 (MyD88) in half-smooth tongue sole Cynoglossus semilaevis.

Myeloid differentiation factor 88 (MyD88) is a universal and crucial adaptor protein, which plays an essential role in the intracellular signalling elicited by IL-1R/TLR superfamily. In the present study, we report the full-length sequence of MyD88 gene in half-smooth tongue sole (Cynoglossus semilaevis). In the 2855 bp genomic sequence, five exons and four introns were identified. The cloned cDNA exhibited 110 bp of 5' UTR, 576 bp of 3' UTR and 858 bp of the entire open-reading frame encoding a polypeptide of 285 amino acids. The protein sequence included a typical conserved cytosolic Toll/interleukin-1 receptor (TIR) domain, an intermediate domain (ID) and a death domain (DD), and shared greater than 70% identity with Japanese flounder Paralichthys olivaceu ortholog. Real-time polymerase chain reaction (RT-PCR) analysis indicated a broad expression of csMyD88, especially in ovary and spleen. Quantitative RT-PCR analysis indicated that the csMyD88 mRNA levels were significantly increased in the spleen and head kidney after inactive Vibrio anguillarum challenge and the expression of csMyD88 appeared to be developmentally regulated during C. semilaevis ontogeny. Although, species-specific differences were present, the similarity between mammalian and piscine MyD88s suggested that the main function of MyD88 might be conserved across vertebrates.