title: Bovine NK-lysin: Copy number variation and functional diversification.
abstract: NK-lysin is an antimicrobial peptide and effector protein in the host innate immune system. It is coded by a single gene in humans and most other mammalian species. In this study, we provide evidence for the existence of four NK-lysin genes in a repetitive region on cattle chromosome 11. The NK2A, NK2B, and NK2C genes are tandemly arrayed as three copies in ∼30-35-kb segments, located 41.8 kb upstream of NK1. All four genes are functional, albeit with differential tissue expression. NK1, NK2A, and NK2B exhibited the highest expression in intestine Peyer's patch, whereas NK2C was expressed almost exclusively in lung. The four peptide products were synthesized ex vivo, and their antimicrobial effects against both Gram-positive and Gram-negative bacteria were confirmed with a bacteria-killing assay. Transmission electron microcopy indicated that bovine NK-lysins exhibited their antimicrobial activities by lytic action in the cell membranes. In summary, the single NK-lysin gene in other mammals has expanded to a four-member gene family by tandem duplications in cattle; all four genes are transcribed, and the synthetic peptides corresponding to the core regions are biologically active and likely contribute to innate immunity in ruminants.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843;
authors.forename: Junfeng
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, WA 98195; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195;
authors.forename: John
authors.initials: J
authors.lastname: Huddleston
authors.affiliation: School of Biological Sciences, University of Adelaide, Adelaide 5005, Australia;
authors.forename: Reuben M
authors.initials: RM
authors.lastname: Buckley
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, WA 98195;
authors.forename: Maika
authors.initials: M
authors.lastname: Malig
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843;
authors.forename: Sara D
authors.initials: SD
authors.lastname: Lawhon
authors.affiliation: Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843;
authors.forename: Loren C
authors.initials: LC
authors.lastname: Skow
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843;
authors.forename: Mi Ok
authors.initials: MO
authors.lastname: Lee
authors.affiliation: Department of Genome Sciences, University of Washington, Seattle, WA 98195; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195;
authors.forename: Evan E
authors.initials: EE
authors.lastname: Eichler
authors.affiliation: Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843; Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, SE 75123, Sweden; Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, SE 75007, Sweden.
authors.forename: Leif
authors.initials: L
authors.lastname: Andersson
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843; jwomack@cvm.tamu.edu.
authors.forename: James E
authors.initials: JE
authors.lastname: Womack
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle / Q000235:genetics*; D033481:Chromosomes, Mammalian / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000648:ultrastructure; D018628:Gene Dosage; D020869:Gene Expression Profiling; D023061:Gene Order; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity / Q000235:genetics; D010455:Peptides / Q000494:pharmacology; D010802:Phylogeny; D011510:Proteolipids / Q000145:classification / Q000235:genetics* / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: C093238:NK-lysin; D010455:Peptides; D011510:Proteolipids
keywords: NK-lysin; antimicrobial peptides; copy number polymorphism; gene family expansion; segmental duplication