Molecular cloning and characterization of sea bass (Dicentrarchus labrax L.) CD8α

In this work, the gene and cDNA of the sea bass CD8α have been isolated and characterized. The coding sequence has an ORF of 666 bp. It retains the Ig motif that interacts with MHC and the two cysteines responsible for an intra-chain disulfide bridge. The hinge region contains the two essential cysteines involved in dimerization. The transmembrane region is well conserved in all analysed sequences. Similar to other teleosts, the cytoplasmic region lacks the consensus p56lck motif common in higher vertebrates. Analysis of the expression pattern using RT-PCR shows the highest expression in the thymus. Like in the human gene, the sea bass CD8α genomic structure is organized into six exons, which roughly correspond to separate functional domains of the protein. Southern blotting shows that CD8α exists as a single copy gene. Together, these results support the concept that the basic structure of CD8α has been maintained through evolution.