Bovine P-selectin mediates leukocyte adhesion and is highly polymorphic in dairy breeds.

Bovine P-selectin (SELP) mediates leukocyte rolling and primes leukocyte adhesion to endothelium, both essential for leukocyte recruitment to an infection site. We investigated SELP-mediated adhesion between bovine peripheral blood leukocytes (PBLs) and cultured bovine aortic endothelial cells pre-activated with lipopolysaccharide (LPS). We examined gene polymorphism for bovine selectins SELP, l-selectin (SELL) and E-selectin (SELE) and compared their SNP frequency between five dairy breeds (Holstein, Friesian, Jersey, Ayrshire and Brown Swiss). LPS treatment caused a rapid (10min) and slower (4h) enhancement of PBL adhesion (P<0.01). Antibody blocking of SELP inhibited LPS induced cell adhesion. SELP was highly polymorphic, with 9 of the 13 SNPs in its exons, whereas only three synonymous SNPs in SELL and one in SELE. The resulting amino acid changes for the three missense SELP SNP were located in the lectin domain and in two consensus repeat (CR) regions, CR2 and CR5. The Val475Met variant locus in the CR4 and CR5 linking region was very close to a predicted N-acetyl-d-glucosamine glycosylation site, which is likely to influence SELP function. The AA genotype was under-represented, only being found in 1% of 373 heifers genotyped from the 5 breeds (P=0.056), suggesting that AA homozygous animals carrying the Val475Met substitution for SELP may have compromised development. Our study thus confirmed that SELP mediates the attachment of PBL to endothelium and provides novel evidence that its high polymorphism is likely to affect biological function. This may potentially influence leukocyte migration and fertility, both key to successful performance in dairy cows.