Partial organization of bovine variable-heavy chain gene locus and influence of recombination signal sequences (RSS) on various variable region gene expression (42.6)

Abstract

Abstract An attempt has been made to determine the organization of variable-heavy chain gene locus in cattle, based on 91% assembled Hereford cow genome sequence, where both functional VH and pseudogenes are identified on chromosome 7 and 21. Of a total of 13 VH genes identified unambiguously, 6 VH genes are located on chromosome 21 and 7 VH genes are present on chromosome 7. Interestingly, the functional VH genes are distributed on both chromosome 7 and 21 raising questions about VDJ recombination occurring on two different chromosomes (Hosseini, A. et al. 2004. Int. Immunol.16:843) or via as yet unidentified mechanism that possibly permitted allelic exclusion. The presence of 10 DH-genes in the Hereford genome is confirmed as earlier reported by our laboratory (Koti, M. et al. 2010. Mol Immunol. 47:2119). Come cryptic recombination signal sequences (RSS) seem to exist within the VH encoding region requiring elucidation of their role in VDJ recombination. Nevertheless, V-gene expression in bovine B cells is influenced by the composition of RSSs. These findings, especially the presence of variable heavy chain locus on two chromosomes, raise fundamental questions about the phenomenon and mechanisms of allelic exclusion in bovine B cells.