Unraveling the consecutive recombination events in the human IGK locus.
In addition to the classical Vkappa-Jkappa, Vkappa-kappa deleting element (Kde), and intron-Kde gene rearrangements, atypical recombinations involving Jkappa recombination signal sequence (RSS) or intronRSS elements can occur in the Igkappa (IGK) locus, as observed in human B cell malignancies. In-depth analysis revealed that atypical JkappaRSS-intronRSS, Vkappa-intronRSS, and JkappaRSS-Kde recombinations not only occur in B cell malignancies, but rather reflect physiological gene rearrangements present in normal human B cells as well. Excision circle analysis and recombination substrate assays can discriminate between single-step vs multistep rearrangements. Using this combined approach, we unraveled that the atypical Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints most probably result from ongoing recombination following an initial aberrant JkappaRSS-intronRSS signal joint formation. Based on our observations in normal and malignant human B cells, a model is presented to describe the sequential (classical and atypical) recombination events in the human IGK locus and their estimated relative frequencies (0.2-1.0 vs < 0.03). The initial JkappaRSS-intronRSS signal joint formation (except for Jkappa1RSS-intronRSS) might be a side event of an active V(D)J recombination mechanism, but the subsequent formation of Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints can represent an alternative pathway for IGK allele inactivation and allelic exclusion, in addition to classical Ckappa deletions. Although usage of this alternative pathway is limited, it seems essential for inactivation of those IGK alleles that have undergone initial aberrant recombinations, which might otherwise hamper selection of functional Ig L chain proteins.
Langerak
Anton W
AW
Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. a.langerak@erasmusmc.nl
Nadel
Bertrand
B
De Torbal
Anneke
A
Wolvers-Tettero
Ingrid L M
IL
van Gastel-Mol
Ellen J
EJ
Verhaaf
Brenda
B
Jäger
Ulrich
U
van Dongen
Jacques J M
JJ
D001483:Base Sequence; D045744:Cell Line, Tumor; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D005819:Genetic Markers / Q000276:immunology; D006801:Humans; D007144:Immunoglobulin J-Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis / Q000235:genetics*; D015448:Leukemia, B-Cell / Q000235:genetics / Q000276:immunology; D008213:Lymphocyte Activation / Q000235:genetics; D016393:Lymphoma, B-Cell / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000276:immunology / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000379:methods; D011995:Recombination, Genetic / Q000276:immunology*
D005819:Genetic Markers; D007144:Immunoglobulin J-Chains; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains