Deletion, insertion, and restriction site polymorphism of the T-cell receptor gamma variable locus in French, Lebanese, Tunisian, and black African populations.

The human T-cell receptor gamma region spans 160 kb of genomic DNA and is densely populated by coding sequences. Restriction fragment length polymorphisms have been previously documented for the constant region genes, the joining segments, and the variable genes belonging to subgroups I and IV. Here we further define the polymorphism of the V gamma I subgroup genes. based on complete mapping of the Eco RI and Taq I allelic restriction fragments. We describe seven haplotypes; five result from polymorphic restriction sites, the sixth corresponds to a deletion of about 10 kb encompassing V4 and V5, and the seventh results from an insertion of an additional gene, V3P, between V3 and V4. As a consequence of the deletion or insertion polymorphism, the number of V gamma I subgroup genes vary from seven in haplotype TRGVI*3 to ten in haplotype TRGVI*4, whereas the most common haplotype, TRGVI*1, has nine V genes, five of them being functional. Frequencies of the different TRGVI haplotypes in French, Lebanese, Tunisian, and Black African populations are given.