Searching for non-V kappa transcripts from the human immunoglobulin kappa locus

The 76 V kappa (variable) gene segments of the human immunoglobulin kappa locus (Ig kappa) were cloned in two contigs. Within each contig the distances between the genes range from a few hundred bp to 31 kb. We have now studied the question of whether transcripts are produced from intergenic regions, from regions near the kappa locus or from V kappa orphon regions. RNAs from several cell lines were converted to cDNAs which were then hybridized to the cosmid and phage lambda clones of the locus and of the orphon regions; the conditions were chosen such that the hybridization of transcripts with repetitive elements was minimized. The expression of a rearranged V kappa gene in a lymphoid cell line was readily detected. Also, a region 46 kb downstream from C kappa (constant) and a cDNA clone from a non-lymphoid cell line hybridizing to this region were studied in some detail. No transcripts were found, however, to be derived from the intergenic regions of the germ-line kappa locus which is in keeping with current ideas on the evolution of the V kappa multigene family.