Analysis of T cell receptor gamma chains from adult CD4- CD8- thymocytes

The role of T cell receptor (TcR) gamma genes in T cell development has not been determined. To extend our understanding of the repertoire of TcR gamma expression, we prepared a cDNA library from CD4-CD8- adult BALB/c thymocytes and cloned and sequenced 15 TcR gamma genes from this cDNA library. We found that two clones were transcripts of the unrearranged C gamma 2 gene and that three clones terminated in the J gamma 2 region. Nine of the remaining clones were V gamma 1.2 J gamma 2 C gamma 2 genes and five of these were in frame. Only one clone corresponded to C gamma 1 and resulted from an in-frame V gamma 2 J gamma 1 C gamma 1 join. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the gamma chain proteins from the surface of both BALB/c and C57BL/6 adult CD4-CD8- thymocytes did not detect the 32-kDa V gamma 1.2 C gamma 2 protein, but did detect the 35-kDa V gamma C gamma 1 protein. These results suggest that despite the abundance of full-length functional V gamma 1.2 C gamma 2 transcripts in the thymocyte subset, the protein product is not expressed on the cell surface as the predicted 32-kDa gamma protein. Finally, our analysis of the V-J joining of the gamma genes reveals both flexibility at the V-J junction and extensive N-region nucleotide addition that lead to diversity of the predicted protein sequence.