title: Duplication of chicken defensin7 gene generated by gene conversion and homologous recombination.
abstract: Defensins constitute an evolutionary conserved family of cationic antimicrobial peptides that play a key role in host innate immune responses to infection. Defensin genes generally reside in complex genomic regions that are prone to structural variation, and defensin genes exhibit extensive copy number variation in humans and in other species. Copy number variation of defensin genes was examined in inbred lines of Leghorn and Fayoumi chickens, and a duplication of defensin7 was discovered in the Fayoumi breed. Analysis of junction sequences confirmed the occurrence of a simple tandem duplication of defensin7 with sequence identity at the junction, suggesting nonallelic homologous recombination between defensin7 and defensin6 The duplication event generated two chimeric promoters that are best explained by gene conversion followed by homologous recombination. Expression of defensin7 was not elevated in animals with two genes despite both genes being transcribed in the tissues examined. Computational prediction of promoter regions revealed the presence of several putative transcription factor binding sites generated by the duplication event. These data provide insight into the evolution and possible function of large gene families and specifically, the defensins.
authors.affiliation: Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843.
authors.forename: Mi Ok
authors.initials: MO
authors.lastname: Lee
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Susanne
authors.initials: S
authors.lastname: Bornelöv
authors.affiliation: Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.|Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843.
authors.forename: Leif
authors.initials: L
authors.lastname: Andersson
authors.affiliation: Department of Animal Science, Iowa State University, Ames, IA 55001.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Lamont
authors.affiliation: Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843.|Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Veterinary Pathobiology, 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 / Q000235:genetics; D000818:Animals; D002645:Chickens / Q000235:genetics*; D019295:Computational Biology; D056915:DNA Copy Number Variations / Q000235:genetics*; D023082:Defensins / Q000235:genetics*; D019143:Evolution, Molecular; D005785:Gene Conversion / Q000235:genetics; D020440:Gene Duplication / Q000235:genetics; D005786:Gene Expression Regulation; D023281:Genomics; D059765:Homologous Recombination / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D023082:Defensins
keywords: antimicrobial peptides; chicken; copy number variation; defensin; nonallelic homologous recombination