Molecular cloning and sequence analysis of bovine T-cell receptor gamma and delta chain genes

Abstract

Nine bovine T-cell receptor (Tcr) gamma chain (Tcrg) and three Tcr delta chain (Tcrd) cDNA clones were isolated from the cDNA libraries constructed from peripheral blood lymphocytes and thymocytes. Of nine Tcrg cDNA clones, only four were rearranged and contained specific V, J, and C gene segments, but the remaining five contained specific J and C or only C gene segments without the V gene segment. Three kinds of Tcrg-C, which were highly related at the nucleotide and amino acid levels, were found and designated as Tcrg-C1, Tcrg-C2, and Tcrg-C3. Compared with human and mouse Tcrg-C, bovine Tcrg-C sequences are much longer, with about 27-55 amino acids corresponding to the hinge and connector regions, where the characteristic repetitive 5-amino acid motif (TTEPP or TTKPP) exists in sheep Tcrg-C as previously reported. From three Tcrd cDNA clones, two Tcrd-V and three Tcrd-J segments were isolated. The nucleotide and deduced amino acid sequences of bovine Tcrd-C, especially the transmembrane and cytoplasmic domains, are well conserved among species. As in bovine Tcrg-C, diversity of amino acid residues in the Tcrd-C region is concentrated in the hinge regions. Southern blot analysis showed that there are at least three Tcrg-C genes and one Tcrd-C gene in the bovine genome. The analysis also revealed the presence of Tcrg-C- and Tcrd-C-associated restriction fragment length polymorphisms among bovine breeds.