Two tandemly organized human genes encoding the T-cell γ constant-region sequences show multiple rearrangement in different T-cell types

Abstract

The recent detailed analysis of genes that undergo rearrangement in T cells has shown that the T-cell receptor genes encoding α and β-chains are involved in specific alterations in T-cell DNA analogous to the immunoglobulin genes^1–9. A third type of gene, designated γ, has been isolated from mouse cytotoxic T lymphocytes¹⁰, and evidence suggests that the mouse displays very limited diversity in this gene system¹¹, having only three variable-region (V) genes and three constant-region (C) genes¹². The function of the so-called T-cell γ gene is unknown. We have isolated genomic genes encoding the human homologue of the mouse T-cell γ gene; as there is no evidence that this T-cell rearranging gene is anything to do with the T3 molecule, we have designated the human T-cell rearranging gene as TRG γ (ref. 13), to avoid confusion with the T3 γ-chain, and have shown that the gene locus maps to chromosome 7 in humans¹³. We now report that human DNA contains two tandemly arranged TRG γ constant-region genes about 16 kilobases apart. These two genes show multiple rearrangement patterns in a variety of T cells, including helper and cytotoxic/suppressor type, as well as in all forms of T-cell leukaemia. Our results indicate variability of this T-cell gene system in man compared with the analogous system in mouse.