Early rearrangements of genes encoding murine immunoglobulin kappa chains, unlike genes encoding heavy chains, use variable gene segments dispersed throughout the locus.

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Abstract
Immunoglobulin heavy-chain variable region (VH) gene segments located closest to the joining (JH) gene segments are preferentially rearranged during ontogeny, indicating that chromosomal position influences the frequency of rearrangement. In addition, certain VH gene segments are repeatedly rearranged, suggesting that the DNA sequence or structure surrounding these segments may increase the probability of rearrangement. To determine whether there is similar biased rearrangement of .kappa. variable (V.kappa.) gene segments, 25 rearrangements were sequenced from murine fetal and neonatal B-cell hybridomas and from subclones of a pre-B cell line that rearranged V.kappa. genes during in vitro culture. Four gene segments were isolated twice and one gene segment was isolated three times, suggesting that the process that targets individual variable gene segments for repeated rearrangement operates on both the VH and V.kappa. loci. Based on a current map of the V.kappa. locus, the rearranged gene segments belong to nine families that are dispersed throughout the locus. Thus, in these cell types, V.kappa. rearrangements use germ-line gene segments located across the entire locus, whereas the corresponding VH rearrangements use gene segments proximal to the JH gene segments. Heterogeneity of V.kappa. rearrangements would add diversity to the biased pool of VH rearrangements, producing a broad repertoire of antibodies early in development.