A SINGLE PREDOMINANTLY EXPRESSED POLYMORPHIC IMMUNOGLOBULIN V-H GENE FAMILY, RELATED TO MAMMALIAN GROUP-I, CLAN-II, IS IDENTIFIED IN CATTLE

In order to understand the generation of antibody diversity in cattle, seven cDNAs, from heterohybridomas secreting bovine IgM and IgG1 anti bodies, were cloned and structurally analyzed for rearranged bovine VD J genes. All of the seven bovine V-H genes, together with four availab le bovine V-H gene sequences, shared a high nucleotide sequence homolo gy (84.2-93.5%). Based upon the criteria of nucleic acid homology grea ter than or equal to 80%, all of the bovine V-H gene sequences isolate d from the expressed antibody repertoire constitute a single V-H gene family, which we have designated as bovine V(H)1 (Bov V(H)1). An analy sis of 44 bovine IgM-secreting mouse x cattle heterohybridomas, origin ating from polyclonally-activated PBLs from bovine leukemia virus-infe cted cattle, revealed that all of these expressed Bov V(H)1 (100%) bas ed upon DNA sequencing and Northern dot blot. The bovine V-H genes sho wed highest DNA sequence similarity, ranging between 81.5 and 87.6%, w ith a single sheep V-H gene family (related to human V(H)4) and are, t hus, closest to the V-H genes from another ruminant species. The Bov V (H)1 gene family is most homologous to the murine V-H Q-52 (71.8-78%) and human V(H)4 (67.4-69.8%) gene families, which belong to mammalian group, I, dan, II, V-H genes. The CDR3 length of rearranged bovine VDJ genes is characteristically long (15-23 amino acids). The bovine J(H) gene segments were most homologous to human J(H)4 (82.1-87.2%) and J( H)5 (84.6-89.7%) genes, suggesting the existence of at least two J, ge ne segments. An analysis of CDRs provides evidence that somatic hyperm utations contribute significantly to the generation of antibody divers ity in cattle. Southern blot analysis of BamH I, EcoR I and Hind III d igested genomic DNA from four cattle breeds (Holstein, Jersey, Herefor d and Charolais) revealed three RFLP patterns; the genomic complexity of Bov V(H)1 ranged between 13 and 15 genes. These observations provid e evidence for polymorphism at the bovine Ig-V-H locus, similar to tha t seen in mice and humans. (C) 1997 Elsevier Science Ltd.