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

Area of Science:

• Immunogenetics
• Molecular Biology
• Human Genetics

Background:

• The human immunoglobulin kappa (Ig kappa) locus contains 76 V kappa (variable) gene segments organized into two contigs.
• Intergenic regions within the Ig kappa locus and associated orphon regions were previously uncharacterized regarding transcriptional activity.

Purpose of the Study:

• To determine if transcripts are produced from the intergenic regions of the germ-line human Ig kappa locus.
• To investigate potential transcription from regions near the kappa locus and from V kappa orphon regions.

Main Methods:

• RNA from various cell lines was converted to complementary DNA (cDNA).
• cDNA was hybridized to cosmid and phage lambda clones of the Ig kappa locus and orphon regions.
• Hybridization conditions were optimized to minimize detection of repetitive elements.

Main Results:

• Expression of a rearranged V kappa gene in a lymphoid cell line was confirmed.
• A region 46 kb downstream from C kappa (constant) and its corresponding cDNA were analyzed.
• No transcripts were detected originating from the intergenic regions of the germ-line Ig kappa locus.

Conclusions:

• The germ-line Ig kappa locus intergenic regions do not appear to produce transcripts.
• These findings align with current evolutionary models of the V kappa multigene family.