L chain isotype regulation in horse. I. Characterization of Ig lambda genes.
Analysis of 10 cDNA encoding lambda L chains of horse Ig indicated that this species may employ a relatively small number of variable region (V lambda) genes in the splenic B cell population. The V lambda sequences of all of the cDNA analyzed were closely related (> 88% identity at the nucleotide level) and were characterized by a deletion of the amino acid residue at position 3 compared with V lambda sequences so far described in other species. The 10 V lambda sequences could be grouped into three groups, V lambda 1 to V lambda 3, on the basis of a number of linked substitutions. Sequences within the groups showed the greatest divergence in the third cdr regions and at the V-J junctions. The junctional variation included amino acid substitutions on both sides of the V-J junction as well as the insertion or deletion of two to four amino acid residues. Four C lambda genes were identified in genomic blots of horse DNA, and three of these were found expressed in splenic cDNA. The fourth C lambda gene may represent a pseudogene, inasmuch as the associated J region possessed a defective heptamer joining sequence. Six of the nine possible V lambda-C lambda combinations were found in the cDNA analyzed, suggesting that genes belonging to groups V lambda 1 through V lambda 3 may rearrange to any one of three J lambda-C lambda genes. One V lambda germline gene was characterized and found to represent a distinct V lambda group (V lambda 4), not represented in the cDNA sequences analyzed. The number of germline V lambda genes was estimated to be 20 to 30, based on analysis of restriction fragments hybridizing with V lambda probes. On the basis of these data, we propose that the V lambda repertoire in horse may consist of relatively limited number of genes, of which only a few may be used at high frequency in the splenic B cell population. The results indicate that predominance of lambda-chains in horse Ig may not simply be due to the presence of a large germline V lambda gene repertoire.
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Département de Biochimie, Université de Sherbrooke, Quebec, Canada.
Ford
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JE
Gibson
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DM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D004247:DNA / Q000032:analysis / Q000302:isolation & purification; D015723:Gene Library; D005803:Genes, Immunoglobulin; D006736:Horses / Q000235:genetics*; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007133:Immunoglobulin Joining Region / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007146:Immunoglobulin lambda-Chains / Q000235:genetics*; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D007127:Immunoglobulin Constant Regions; D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D007146:Immunoglobulin lambda-Chains; D004247:DNA