Organization of the T-cell antigen-receptor beta-chain locus in mice

We used pulsed-field gel electrophoresis to determine the organization of the beta-chain gene of the T-cell receptor for antigen in normal and mutant inbred strains of mice. In normal mice, the variable (V)- and constant (C)- region elements of this locus span 700-800 kilobases of chromosomal DNA. All but one of the V beta gene segments analyzed lie 5' of the J beta C beta locus (J beta represents the joining region), with the closest being 280-360 kilobases away. The mutant mouse strain SJL has an internal V beta-region gene deletion that compacts the V beta region by 100-200 kilobases. Taken together with other data, these results indicate that the beta-chain locus can use either a looping-out/deletion or an inversion mechanism to appose V beta to DJ beta gene segments (D is the diversity region) and can accomplish the former (at least) over very large distances.