The human T-cell receptor gamma variable pseudogene V10 is a distinctive marker of human speciation.

The V10 variable gene of the human T-cell receptor gamma locus (TCRG-V10), the only member of the subgroup III, has a structural defect which inhibits the splicing of the leader intron. We show that there is a single point mutation in the V10 leader donor splice site responsible for this situation and that this mutation is found in the different populations tested, indicating that V10 corresponds to a pseudogene in humans. We restored the splice site by mutagenesis and obtained correct splicing in vitro. Analysis of the V10 germline gene in different primates reveals functional splice sites in the closest human apes, the chimpanzee and the gorilla. The splice competence of TCRG-V10 in higher primates was addressed in peripheral blood lymphocytes from chimpanzee by specific cDNA amplification, and correct splicing of the TCRG-V10 leader intron was found as well as a majority of in frame rearrangements involving only the TCRG-J1 or J2 segments. These results suggest that V10(+)gamma /delta T cells may represent an important subset in the non-human higher primates, contrary to the situation observed in the human.