Identification and analysis of the chicken CD3ɛ gene

The chicken T cell receptor CD3 epsilon gene was isolated using a degenerate polymerase chain reaction. The 1883 bp long cDNA encoded a transmembrane protein of 16.9 kDa lacking N-linked glycosylation sites. Comparison of the chicken and mammalian CD3 epsilon proteins revealed low homology in the extracellular domain with clusters of similarities located around the N-terminal cysteine residue and proximal to the transmembrane region. The high conservation of the cytoplasmic domain included motifs important for signal transduction. The alignment of all CD3 gamma, CD3 delta and CD3 epsilon proteins allowed the identification of highly conserved residues and motifs. Southern blot analysis indicated the presence of a single copy CD3 epsilon gene. The expression of the CD3 epsilon transcript was limited to T cells and natural killer cells. A recessive mutation of the CD3 epsilon gene in the CB chicken strain enabled the mapping of the epitope recognized by the CT3 monoclonal antibody. This analysis of the first non-mammalian CD3 epsilon gene provides novel information about evolutionary conserved structural features and its expression in natural killer cells.