Organization of the murine T-cell receptor γ locus

Murine T cells carry either of two antigen receptors on their surface: αβ or γδ T-cell receptors (TCR). The function of γδ T cells is not well understood. In this population, subsets exist with tissue-specific localization, with invariant variable regions, and with specificity for self antigens. We have analyzed the murine TCR γ locus by field inversion gel electrophoresis and cosmid cloning. The structure of the complete TCR γ locus, the first complete physical map of any mouse TCR locus, is reported here. The locus spans 205 kb and consists of four clusters of genes and gene segments. Each cluster contains one or more variable elements, one joining element, and one constant element. We demonstrate that the Cγ4 gene is distinguished from the other Cγ genes in that it has an additional hinge- encoding exon. New enhancer-like elements are identified in two of the clusters, downstream from the Cγ genes. The most upstream cluster has four V elements and resembles the human TCR γ locus. The four clusters probably arose via duplications.