The human T-cell rearranging gamma (TRG) genes and the gamma T-cell receptors

Abstract

The human T-cell Rearranging Gamma genes or T-cell Receptor Gamma (TRG) chain genes, like those encoding the T-cell Receptor (TcR)α and β polypeptides, undergo rearrangements specifically in T-cells. The human TRG locus which has been mapped to chromosome 7 (7p15) is composed of 2 constant region genes (TRGC), 5 joining segments (TRGJ) and at least 14 variable gamma genes (TRGV). 8 variable genes are functional and belong to 4 different subgroups. Based on restriction fragments, the TRG rearrangements can be assigned to given V and J segments, in normal T-cells, T leukemias and lymphomas. The product of the rearranged TRG gene is the γ chain which is expressed at the surface of a subset of CD3 +4 −8 − T lymphocytes lacking the conventional receptor αβ. Structural differences exist between the different ‘gamma T-cell receptors’, the γ and δ polypeptides being disulfide or non-disulfide linked. Although the TRG + cells display a cytolytic activit, their precise function remains to be elucidated.