title: An epididymis-specific beta-defensin is important for the initiation of sperm maturation.
abstract: Although the role of the epididymis, a male accessory sex organ, in sperm maturation has been established for nearly four decades, the maturation process itself has not been linked to a specific molecule of epididymal origin. Here we show that Bin1b, a rat epididymis-specific beta-defensin with antimicrobial activity, can bind to the sperm head in different regions of the epididymis with varied binding patterns. In addition, Bin1b-expressing cells, either of epididymal origin or from a Bin1b-transfected cell line, can induce progressive sperm motility in immotile immature sperm. This induction of motility is mediated by the Bin1b-induced uptake of Ca(2+), a mechanism that has a less prominent role in maintaining motility in mature sperm. In vivo antisense experiments show that suppressed expression of Bin1b results in reduced binding of Bin1b to caput sperm and in considerable attenuation of sperm motility and progressive movement. Thus, beta-defensin is important for the acquisition of sperm motility and the initiation of sperm maturation.
authors.affiliation: Epithelial Cell Biology Research Center, Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors.forename: Chen Xi
authors.initials: CX
authors.lastname: Zhou
authors.forename: Yong-Lian
authors.initials: YL
authors.lastname: Zhang
authors.forename: Liqing
authors.initials: L
authors.lastname: Xiao
authors.forename: Min
authors.initials: M
authors.lastname: Zheng
authors.forename: Ka Man
authors.initials: KM
authors.lastname: Leung
authors.forename: Man Yee
authors.initials: MY
authors.lastname: Chan
authors.forename: Pui Shan
authors.initials: PS
authors.lastname: Lo
authors.forename: Lai Ling
authors.initials: LL
authors.lastname: Tsang
authors.forename: Hau Yan
authors.initials: HY
authors.lastname: Wong
authors.forename: Lok Sze
authors.initials: LS
authors.lastname: Ho
authors.forename: Yiu Wa
authors.initials: YW
authors.lastname: Chung
authors.forename: Hsiao Chang
authors.initials: HC
authors.lastname: Chan
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D018920:Coculture Techniques; D004822:Epididymis / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D008297:Male; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D013079:Sperm Maturation / Q000502:physiology*; D013081:Sperm Motility / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*; D023083:beta-Defensins / Q000235:genetics / Q000378:metabolism*
chemical_list: C487040:Spag11a protein, rat; D023083:beta-Defensins; D002118:Calcium