MOLECULAR CLONING, CHARACTERIZATION AND EXPRESSION OF MyD88 IN SQUALIOBARBUS CURRICULUS

The full cDNA sequence of Myeloid differentiation factor 88 (MyD88) in the barbel chub Squaliobarbus curriculus (designated as ScMyD88) has been cloned by using RACE-PCRs method. The complete sequence of ScMyD88 cDNA was 1779 bp that contained 855 bp open read frame encoding 284 amino acid residues with calculated molecular weight of 33.053 kD and a theoretical isoelectric point (PI) of 5.66. The ScMyD88 protein has typical structural features of the MyD88 family with a Death domains and a TIR domain. According to the comparison with known MyD88 amino acid sequences, the putative protein of ScMyD88 showed the highest identities with cyprinid fishes (90%98%) and other bony fishes (67%74%) but low identities (60%) with mammalian. MyD88 expressed in all the nine tested tissues and organs with highly expressed in the liver, head kidney and trunk kidney, and lowly expressed in the brain. The ScMyD88 was obviously up-regulated in the immune tissue at 12h and returned to the normal level after 48h challenged with GCRV. These result showed that ScMyD88 might play important roles during the immune response of barbel chub against GCRV.