The human t cell receptor α‐δ locus: a physical map of the variable, joining and constant region genes

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Abstract
In this study a physical macro‐restriction map of the entire human a locus that spans about 1000 kilobase pairs and includes the Vα Jα and Cα genes is presented. Evidence is provided that gene duplications were involved in the increase of genomic diversity of Vα genes. In addition, we show a detailed map of a 40‐kb region located approximately 100 kg upstream of the human Cα gene. Direct evidence is provided to support that the human a chain locus, like the murine, also contains another T cell constant region gene in the a chain locus, the human σ chain gene. In addition, two J segments and one D segment have been identified. Using these genomic probes, we show that several T cell lines, including those known to express the surface γ/σ heterodimer, have rearranged this region. The design of two separate centers of rearrangement within one locus that are involved in rearrangement events at different times, and the presence of high number of J segments in this region, may render the locus highly vulnerable to chromosomal translocation during T cell developement.