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 were further define the polymorphism of theV gamma I subgroup genes, based on complete mapping of theEco RI andTaq I allelic restriction fragments. We describe seven haplotypes; five result from polymorphic restriction sites, the sixth corresponds to a deletion of about 10 kb encompassingV4 andV5, and the seventh results from an insertion of an additional gene,V3P, betweenV3 andV4. As a consequence of the deletion or insertion polymorphism, the number ofV gamma I subgroup genes vary from seven in haplotypeTRGVI *3 to ten in haplotypeTRGVI *4, whereas the most common haplotype,TRGVI *1, has nineV genes, five of them being functional. Frequencies of the differentTRGVI haplotypes in French, Lebanese, Tunisian, and Black African populations are given.