DEVELOPMENTALLY ORDERED V-J RECOMBINATION IN MOUSE T-CELL RECEPTOR-GAMMA LOCUS IS NOT PERTURBED BY TARGETED DELETION OF THE V-GAMMA-4 GENE

Mouse TCR gamma genes in the gamma 1 cluster are arranged in the order of V gamma 5, V gamma 2, V gamma 4, V gamma 3, J gamma 1, and C gamma 1 on the chromosome. During thymic ontogeny, each V gamma gene recomb ines with the J gamma 1 gene in the order of proximity to J gamma 1. T o explore the mechanism of the ordered recombination, we generated V g amma 4-deficient mice by gene targeting and the Cre/loxP system, by de leting the 4.8-kb DNA region between 3' of the V gamma 2 and 3' of the V gamma 4. In semiquantitative PCR analysis, V gamma 2-J gamma 1 reco mbination was detected frequently in adult thymus, while V gamma 3-J g amma 1 recombination preferentially occurred in fetal thymus of the mu tant mice. There was no difference in the frequency of V-J recombinati ons between control and mutant mice. Southern blot analysis also revea led that recombination of the V gamma 2 gene occurred as frequently as in control mice. In addition, there was no difference in the levels o f germline transcripts of V gamma 2 and V gamma 3 genes between contro l and mutant mice. Therefore, regulation of the V gamma-J gamma recomb ination was not affected by deletion of the V gamma 4 gene. These resu lts suggest that the ordered recombination is controlled by regulatory elements near each V gamma gene.