Molecular cloning, characterization and expression analysis of major histocompatibility complex class I alpha gene of pufferfish (Takifugu obscurus).

The major histocompatibility complex (MHC) genes play a key role in immune response in vertebrates. In this study, an MHC I alpha homolog gene (PfMHC Ⅰα) from pufferfish (Takifugu obscurus) was identified and its subcellular localization and expression patterns of PfMHC Ⅰα after challenge in vivo and in vitro were analysed. The open reading frame of PfMHC Ⅰα was 1,089 bp in length, encoding 362 aa. The immunofluorescence result revealed that PfMHC Ⅰα was presented on the membrane of lymphocytes. qRT-PCR analysis indicated that PfMHC Ⅰα was expressed in all examined tissues, with the highest expression in skin, followed by the expression in gills and whole blood. After challenge of Aeromonas hydrophila or polyinosinic: polycytidylic acid (Poly I:C) in vitro, the expression levels of PfMHC Ⅰα on pufferfish kidney lymphocytes were significantly up-regulated, with the highest expression level at 48 hr post-challenge. After infection with A. hydrophila or Poly I:C in vivo, the expression levels of PfMHC Ⅰα in the skin, whole blood and kidneys were significantly up-regulated. Taken together, it is speculated that PfMHC Ⅰα associates with resistance to both intracellular and extracellular antigens and plays an important role in the host response against pathogen infection in pufferfish.