Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/3/2009
Publication Date: 1/6/2010
Citation: Mousel, M.R., White, S.N., Hoesing, L.M. 2010. Association analysis of a CCR5 variant with ewe lifetime production. Plant and Animal Genome Conference Proceedings. P571.
Interpretive Summary: In sheep, modification in a gene, called CCR5, is associated with reduced concentration of ovine progressive pneumonia virus (OPPV) DNA. Increased OPPV DNA concentration was associated with increased signs of ovine progressive pneumonia (OPP). Thus, sheep with the genetic modification may be less likely to develop clinical signs of OPP, and a genetic test for the modification may enable producers to reduce the incidence of OPP. However, before a genetic test can be used, we must determine whether the genetic modification affects ewe lifetime production. A total of 370 Rambouillet, Polypay and Columbia ewes were tested for the CCR5 modification. Their lifetime production records for total number of lambs born, total number of lambs raised to weaning, total kilograms of lamb weaned and age, in years, at last lambing were evaluated to determine if CCR5 had an effect on these production traits. No statistically significant association was found between the production traits and the CCR5 modification. Thus, using the CCR5 modification in a genetic test to reduce concentrations of OPPV DNA should not result in reduced production in the traits we evaluated.
Technical Abstract: A deletion in the promoter region of CCR5 associates with a 50% reduction in proviral concentration (log10 env copies/microgram DNA) of ovine progressive pneumonia virus (OPPV) in sheep blood. Because OPP provirus blood concentrations correlate with the degree of histological lesions in affected tissues, use of the CCR5 promoter variant in marker-assisted selection might reduce pathology. We determined whether the three CCR5 promoter genotypes and four ewe lifetime production traits were associated. DNA and lifetime records from 370 Rambouillet, Polypay, and Columbia ewes were used. Production traits, per ewe, included: total adjusted 120-d weaning weight of all lambs born (120d kg), total lifetime number of lambs born (TB), total count of lambs raised to weaning (TR), and age of ewe, in years, at last lambing. A Taqman assay was used to genotype the CCR5 promoter insertion/deletion. For association analysis, mixed procedure of SAS 9.1 was used. The model included breed, CCR5 promoter insertion/deletion genotype, year ewe was born, and age at last lambing as fixed effects, sire as a random effect, and OPP provirus concentration as a covariate. Breed and age at last lambing were significantly associated with TB (P<0.01), TR (P<0.01), and 120d kg (P<0.01). None of the three CCR5 promoter insertion/deletion genotypes had significant positive or negative associations with any of the ewe lifetime production traits (all P>0.59). Thus, using the CCR5 promoter deletion in marker-assisted selection to reduce concentrations of OPPV should not result in deleterious correlated responses with the economically important production traits we evaluated.