The role of components of recombination signal sequences in immunoglobulin gene segment usage: a V81x model

Abstract

It has long been appreciated that some immunoglobulin (and T-cell receptor) gene segments are used much more frequently than others. The VHsegment V81x is a particularly striking case of overusage. Its usage varies with the stage of B-cell development and with the strain of mice, but it is always high in B cell progenitors. We have found that the coding sequence and the recombination signal sequences (RSS) are identical in five mouse strains, including CAST/Ei, a strain derived from the species Mus castaneus. Thus, the strain differences cannot be attributed to sequences within V81x itself. V81x RSS mediated recombination at rates significantly higher than another VHRSS. Although the V81x nonamer differs at one base pair from the consensus sequence, an RSS with this nonamer and a consensus heptamer recombines as well as the consensus RSS. When the V81x spacer is replaced by that of VA1, the frequency of recombination decreases by approximately 5-fold; thus, the contribution of variation in natural spacers to variability in VHusage in vivo is likely to be more than has been previously appreciated. Furthermore, the contribution of the heptamer and nonamer to differential VHusage in our assay is correlated inversely with their conservation throughout the VHlocus.

Unequal VH Gene Rearrangement Frequency Within the Large VH7183 Gene Family Is Not Due to Recombination Signal Sequence Variation, and Mapping of the Genes Shows a Bias of Rearrangement Based on Chromosomal Location

“…It has been shown that 81X rearranges 7-to 30-fold more frequently than the V H J558 gene in a competition substrate (22,23). However, the V H J558 genes have very poor RSS, and the nonamer is so different from the consensus that it is not clear whether they also have a shortened, less functional, 22-bp spacer (see Fig.…”

“…It has been proposed that the reason that 81X rearranges so often is due to its RSS (23). Using miniloci recombination substrates transiently transfected into pre-B cells, the relative frequency of rearrangement of 81X vs V H J558 genes was determined, and 81X rearranged ϳ15 times more often than V H J558 (22,23).…”

“…Using miniloci recombination substrates transiently transfected into pre-B cells, the relative frequency of rearrangement of 81X vs V H J558 genes was determined, and 81X rearranged ϳ15 times more often than V H J558 (22,23). However, the choice of a V H J558 gene as a competitor was likely to show a bias in favor of V H 7183, because V H J588 genes have a poor RSS.…”

Evolution of the recombination signal sequences in the Ig heavy-chain variable region locus of mammals

“…3). Several groups have emphasized that the level at which certain B cell receptor specificities occur in vivo might be dictated to some extent by family-specific RSS characteristics (24)(25)(26). RSS replacement during evolution means that under some circumstances, V genes with advantageous binding properties may evolve to have an appropriate level of representation in the immune repertoire through shuffling of RSS elements.…”

VH Gene Replacement in Thymocytes

“…Some of the elements regulating V-to-D joining are different from those regulating D-to-J joining (45)(46)(47). We can think of two possibilities as to why V H replacement occurs during thymic development in the QM strain but is not detectable in unmanipulated strains.…”