Biallelic germline transcription at the kappa immunoglobulin locus.
Rearrangement of antigen receptor genes generates a vast array of antigen receptors on lymphocytes. The establishment of allelic exclusion in immunoglobulin genes requires differential treatment of the two sequence identical alleles. In the case of the kappa immunoglobulin locus, changes in chromatin structure, methylation, and replication timing of the two alleles are all potentially involved in regulating rearrangement. Additionally, germline transcription of the kappa locus which precedes rearrangement has been proposed to reflect an opening of the chromatin structure rendering it available for rearrangement. As the initial restriction of rearrangement to one allele is critical to the establishment of allelic exclusion, a key question is whether or not germline transcription at the kappa locus is monoallelic or biallelic. We have used a sensitive reverse transcription-polymerase chain reaction (RT-PCR) assay and an RNA-fluorescence in situ hybridization (FISH) to show that germline transcription of the kappa locus is biallelic in wild-type immature B cells and in recombination activating gene (RAG)-/-, mu+ B cells. Therefore, germline transcription is unlikely to dictate which allele will be rearranged first and rather reflects a general opening on both alleles that must be accompanied by a mechanism allowing one of the two alleles to be rearranged first.
Singh
Nandita
N
Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
Bergman
Yehudit
Y
Cedar
Howard
H
Chess
Andrew
A
D000483:Alleles; D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D001854:Bone Marrow Cells / Q000378:metabolism*; D019070:Cell Lineage; D015321:Gene Rearrangement; D005803:Genes, Immunoglobulin; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D018345:Mice, Knockout; D011401:Promoter Regions, Genetic; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D001613:beta 2-Microglobulin / Q000235:genetics / Q000378:metabolism
D018398:Homeodomain Proteins; D007145:Immunoglobulin kappa-Chains; D001613:beta 2-Microglobulin; C064658:RAG-1 protein; D012313:RNA