Identification and genetic mapping of bovine chemokine genes expressed in epithelial cells

RNA fingerprinting by arbitrarily primed (RAP)-PCR was used to identify two bovine genes that were differentially expressed in epithelial cells during an inflammatory response. RNA fingerprints revealed two differentially amplified transcripts when monolayers of Madin-Darby bovine kidney (MDBK) cells were stimulated with Escherichia coli O157:H7 lipopolysaccharide (LPS) in combination with cycloheximide (CX). Sequence analysis showed that both transcripts encoded members of the alpha C-X-C chemokine family; one was interleukin 8 (IL-8), and the other was a protein closely related to bovine growth-regulated protein (GRO)-gamma (89% identical). The latter putative epithelial cell inflammatory protein was designated ECIP-1. IL-8 and ECIP-1 genes were placed on the cattle genetic map with single-nucleotide polymorphism (SNP) markers amplified from genomic DNA. Multi-point linkage analysis indicated that the gene locations were indistinguishable from those of serum albumin (ALB) and vitamin D-binding protein (GC) on bovine Chromosome (BTA) 6. In humans, ALB and GC are located near IL-8, GRO-gamma, and seven other alpha chemokines on Chr 4 (HSA 4q11-4q13), suggesting that this gene cluster has been conserved on BTA6. These results provide a starting point for characterizing allelic variation in chemokine genes and their role in the pathogenesis of bacterial infections in cattle.