Unequal V-H gene rearrangement frequency within the large V(H)7183 gene family is not due to recombination signal sequence variation, and mapping of the genes shows a bias of rearrangement based on chromosomal location

Much of the nonrandom usage of V, D, and J genes in the Ab repertoire is du e to different frequencies with which gene segments undergo V(D)J rearrange ment. The recombination signal sequences flanking each segment are seldom i dentical with consensus sequences, and this natural variation in recombinat ion signal sequence (RSS) accounts for some differences in rearrangement fr equencies in vivo. Here, we have sequenced the RSS of 19 individual V(H)718 3 genes, revealing that the majority have one of two closely related RSS. O ne group has a consensus heptamer, and the other has a nonconsensus heptame r. In vitro recombination substrate studies show that the RSS with the nonc onsensus heptamer, which include the frequently rearranging 81X, rearrange less well than the RSS with the consensus heptamer. Although 81X differs fr om the other 7183-1 genes at three positions in the spacer, this does not s ignificantly increase its recombination potency in vitro. The rearrangement frequency of all members of the family was determined in mu MT mice, and t here was no correlation between the in vitro recombination potential and VH gene rearrangement frequency in vivo. Furthermore, genes with identical RS S rearrange at different frequencies in vivo. This demonstrates that other factors can override differences in RSS potency in vivo. We have also deter mined the gene order of all V(H)7183 genes in a bacterial artificial chromo some contig and show that most of the frequently rearranging genes are in t he 3 ' half of the region. This suggests that chromosomal location plays an important role in nonrandom rearrangement of the V(H)7183 genes.