title: Sperm-Coating Beta-Defensin 126 Is a Dissociation-Resistant Dimer Produced by Epididymal Epithelium in the Bovine Reproductive Tract.
abstract: Beta-defensins are innate immune molecules, often described as antimicrobial peptides because of their bactericidal activity and are now known to have diverse additional functions, including cell signaling, chemoattraction, immunoregulation, and reproduction. In humans and primates, beta-defensin 126 has been shown to regulate the ability of sperm to swim through cervical mucus and to protect sperm from attack by the female immune system during transit toward the oviduct. Bovine beta-defensin 126 (BBD126) is the ortholog of human defensin 126, and computational analysis here revealed significant conservation between BBD126 and other mammalian orthologs at the N-terminus, although extensive sequence differences were detected at the C-terminus, implying possible species-specific roles for this beta-defensin in reproduction. We had previously demonstrated preferential expression of this and related beta-defensin genes in the bovine male reproductive tract, but no studies of bovine beta-defensin proteins have been performed to date. Here, we analyzed BBD126 protein using a monoclonal antibody (a-BBD126) generated against a 14 amino acid peptide sequence from the secreted fragment of BBD126. The specificity of a-BBD126 was validated by testing against the native form of the peptide recovered from bovine caudal epididymal fluid and recombinant BBD126 generated using a prokaryotic expression system. Western blot analysis of the native and recombinant forms showed that BBD126 exists as a dimer that was highly resistant to standard methods of dissociation. Immunohistochemical staining using a-BBD126 demonstrated BBD126 protein expression by epithelial cells of the caudal epididymis and vas deferens from both mature and immature bulls. BBD126 could also be seen (by confocal microscopy) to coat caudal sperm, with staining concentrated on the tail of the sperm cells. This study is the first to demonstrate beta-defensin 126 protein expression in the bovine reproductive tract and on bull sperm. Its dissociation-resistant dimeric structure is likely to have important functional implications for the role of BBD126 in bovine reproduction.
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin, Ireland.
authors.forename: Fernando
authors.initials: F
authors.lastname: Narciandi
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Fernandez-Fuertes
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin, Ireland.
authors.forename: Ilaina
authors.initials: I
authors.lastname: Khairulzaman
authors.affiliation: UCD School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
authors.forename: Hanne
authors.initials: H
authors.lastname: Jahns
authors.affiliation: Animal & Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Co. Meath, Ireland.
authors.forename: Deirdre
authors.initials: D
authors.lastname: King
authors.affiliation: Animal & Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Co. Meath, Ireland.
authors.forename: Emma K
authors.initials: EK
authors.lastname: Finlay
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin, Ireland.|Trinity Biomedical Sciences Institute, Trinity College, Dublin, Ireland.
authors.forename: Ken H
authors.initials: KH
authors.lastname: Mok
authors.affiliation: Department of Life Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Sean
authors.initials: S
authors.lastname: Fair
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Lonergan
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin, Ireland cliona.ofarrelly@tcd.ie.|Trinity Biomedical Sciences Institute, Trinity College, Dublin, Ireland.
authors.forename: Cliona O'
authors.initials: CO
authors.lastname: Farrelly
authors.affiliation: Animal & Bioscience Research Department, Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Co. Meath, Ireland.
authors.forename: Kieran G
authors.initials: KG
authors.lastname: Meade
mesh_terms: D000818:Animals; D002417:Cattle; D004822:Epididymis / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D008297:Male; D013094:Spermatozoa / Q000378:metabolism*; D023083:beta-Defensins / Q000378:metabolism*
chemical_list: D023083:beta-Defensins
keywords: bovine; epididymis; β-defensin 126