A. Six et al., CHARACTERIZATION OF AVIAN T-CELL RECEPTOR-GAMMA GENES, Proceedings of the National Academy of Sciences of the United Statesof America, 93(26), 1996, pp. 15329-15334
In birds and mammals T cells develop along two discrete pathways chara
cterized by expression of either the alpha beta or the gamma delta T-c
ell antigen receptors (TCRs). To gain further insight into the evoluti
onary significance of the gamma delta T-cell lineage, the present stud
ies sought to define the chicken TCR gamma locus. A splenic cDNA libra
ry was screened with two polymerase chain reaction products obtained f
rom genomic DNA using primers for highly conserved regions of TCR and
immunoglobulin genes. This strategy yielded cDNA clones with character
istics of mammalian TCR gamma chains, including canonical residues con
sidered important for proper folding and stability. Northern blot anal
ysis with the TCR gamma cDNA probe revealed 1.9-kb transcripts in the
thymus, spleen, and a gamma delta T-cell line, but not in B or alpha b
eta T-cell lines. Three multimember V gamma subfamilies, three J gamma
gene segments, and a single constant region C gamma gene were identif
ied in the avian TCR gamma locus. Members of each of the three V gamma
subfamilies were found to undergo rearrangement in parallel during th
e first wave of thymocyte development. TCR gamma repertoire diversific
ation was initiated on embryonic day 10 by an apparently random patter
n of V-J gamma recombination, nuclease activity, and P- and N-nucleoti
de additions to generate a diverse repertoire of avian TCR gamma genes
early in ontogeny.