Selective forces shaping diversity in the class I region of the major histocompatibility complex in dairy cattle

Codner, G.F., Stear, M.J., Reeve, R. , Matthews, L. and Ellis, S.A. (2012) Selective forces shaping diversity in the class I region of the major histocompatibility complex in dairy cattle. Animal Genetics, 43(3), pp. 239-249. (doi:10.1111/j.1365-2052.2011.02239.x)

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Abstract

The major histocompatibility complex (MHC) is one of the most diverse regions of the mammalian genome. Diversity in MHC genes is integral to their function in the immune system, and while pathogens play a key role in shaping this diversity, the contribution of other selective forces remains unclear. The controlled breeding of cattle offers an excellent model for the identification and exploration of these forces. We characterized the MHC class I genes present in a sample of Canadian Holstein A.I. bulls and compared the results with those obtained in an earlier study. No evidence for a reduction in MHC diversity over 20 years was observed, but the relative frequency of some haplotypes had changed: the formerly rare A12 (w12B) haplotype had become the most common, together with A15, while A19, which dominated the earlier sample, had significantly reduced in frequency. Only 7% of bulls in the current study were MHC homozygous compared with the 14% expected under HardyWeinberg. To identify the selective forces at work, a gene substitution model was used to calculate the effects of MHC on selection traits using estimated breeding values for each bull. Significant associations between MHC and production, disease and fertility traits were identified, suggesting that MHC diversity is not merely shaped by disease in this controlled breeding system. The decrease in a common haplotype, the reduced number of homozygous bulls and the associations with disease and production traits together indicate that MHC diversity in dairy cattle is maintained by heterozygote advantage.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Reeve, Dr Richard and Stear, Professor Michael and Matthews, Professor Louise
Authors: Codner, G.F., Stear, M.J., Reeve, R., Matthews, L., and Ellis, S.A.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Animal Genetics
ISSN:0268-9146
ISSN (Online):1365-2052
Published Online:15 September 2011

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
468351The effect of selection for nematode resistance on mhc class II diversiityMichael StearBiotechnology and Biological Sciences Research Council (BBSRC)BB/F015313/1Institute of Infection Immunity and Inflammation