Molecular Cloning and Expression of Major Histocompatibility Complex Class Iα Gene of Swamp Eel (Monopterus albus)

Major histocompatibility complex (MHC) plays an important role in the immune response of vertebrates. In this study, we isolated MHC class Iα gene from swamp eel (Monopterus albus) by rapid amplification of cDNA ends polymerase chain reaction (RACE-PCR). In order to study the function of MHC Iα in swamp eel, tissue distribution and immune response of the MHC Iα after bacterial challenge were analyzed. All the characteristic features of MHC Iα chain structure were identified by the deduced amino acid sequence, including the leader peptide, α1, α2, and α3 domains, connecting peptide, transmembrane and cytoplasmic regions, conserved cysteines, and N-glycosylation site. The deduced amino acid sequence of the MHC Iα shares 27.3% to 69.6% similarity with those of other vertebrates. Quantitative real-time PCR (qRT-PCR) demonstrated that MHC Iα gene was ubiquitously expressed in ten tissues, comparatively higher in immune related tissues, including the liver and intestine. Challenge of M. albus with the extracellular pathogen, Aeromonas hydrophila, resulted in a significant increase in the expression of MHC Iα within 72 h after infection and these high levels were maintained for 72 h in kidneys, spleen, and skin, whereas in the intestine and liver, it was found first in the form of up-regulated and then down-regulated gene. These results demonstrated that MHC Iα gene played an important role in response to bacterial infection in M.albus