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J Immunol. 2016 May 15;196(10):4358-66. doi: 10.4049/jimmunol.1600158. Epub 2016 Apr 6.

Internal Duplications of DH, JH, and C Region Genes Create an Unusual IgH Gene Locus in Cattle.

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State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China;
Embryo Biotechnology and Reproduction Laboratory, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China;
Faculty of Health and Life Sciences, York St John University, York YO31 7EX, United Kingdom; and.
Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden.
State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China;


It has been suspected for many years that cattle possess two functional IgH gene loci, located on Bos taurus autosome (BTA) 21 and BTA11, respectively. In this study, based on fluorescence in situ hybridization and additional experiments, we showed that all functional bovine IgH genes were located on BTA21, and only a truncated ╬╝CH2 exon was present on BTA11. By sequencing of seven bacterial artificial chromosome clones screened from a Hostein cow bacterial artificial chromosome library, we generated a 678-kb continuous genomic sequence covering the bovine IGHV, IGHD, IGHJ, and IGHC genes, which are organized as IGHVn-IGHDn-IGHJn-IGHM1-(IGHDP-IGHV3-IGHDn)3-IGHJn-IGHM2-IGHD-IGHG3-IGHG1-IGHG2-IGHE-IGHA. Although both of two functional IGHM genes, IGHM1 and IGHM2, can be expressed via independent VDJ recombinations, the IGHM2 can also be expressed through class switch recombination. Likely because more IGHD segments can be involved in the expression of IGHM2, the IGHM2 gene was shown to be dominantly expressed in most tissues throughout different developmental stages. Based on the length and identity of the coding sequence, the 23 IGHD segments identified in the locus could be divided into nine subgroups (termed IGHD1 to IGHD9). Except two members of IGHD9 (14 nt in size), all other functional IGHD segments are longer than 30 nt, with the IGHD8 gene (149 bp) to be the longest. These remarkably long germline IGHD segments play a pivotal role in generating the exceptionally great H chain CDR 3 length variability in cattle.

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