title: Formation and Dissociation of Sperm Bundles in Monotremes.
abstract: Because monotremes are the earliest offshoot of the mammalian lineage, the platypus and short-beaked echidna were studied as model animals to assess the origin and biological significance of adaptations considered unique to therian mammals: epididymal sperm maturation and subsequent capacitation. We show that spermatozoa from both species assemble into bundles of approximately 100 cells during passage through the epididymis and that an epididymal protein-secreted protein, acidic, cysteine-rich (osteonectin; SPARC)-is involved in bundle formation. The bundles persisted during incubation in vitro for at least 1 h under conditions that capacitate therian spermatozoa, and then underwent a time-dependent dissociation to release spermatozoa capable of fertilization. Only after this dissociation could the spermatozoa bind to the perivitelline membrane of a hen's egg, display an altered form of motility reminiscent of hyperactivation, and be induced to undergo an acrosome reaction. It is concluded that the development of sperm bundles in the monotreme epididymis mandates that they require a time-dependent process to be capable of fertilizing an ovum. However, because this functional end point was achieved without overt changes in protein tyrosine phosphorylation (a hallmark of capacitation in therians), it is concluded that the process in monotremes is distinctly different from capacitation in therian mammals.
authors.affiliation: Priority Research Centre for Reproductive Science, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, Australia Brett.Nixon@newcastle.edu.au.
authors.forename: Brett
authors.initials: B
authors.lastname: Nixon
authors.affiliation: School of Biological Sciences and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: Heath
authors.initials: H
authors.lastname: Ecroyd
authors.affiliation: Institut National de la Recherche Agronomique (INRA), Unités Mixtes de Recherches (UMR) 85 Physiologie de la Reproduction et des Comportements, Nouzilly, France Centre National de la Recherche Scientifique, UMR 7247, Nouzilly, France Université François Rabelais de Tours, Tours, France l'Institut Français du Cheval et de l'Équitation, Nouzilly, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Dacheux
authors.affiliation: INRA, Plateforme d'Analyse Intégrative des Biomolécules, Laboratoire de Spectrométrie de Masse, Nouzilly, France.
authors.forename: Francoise
authors.initials: F
authors.lastname: Dacheux
authors.affiliation: Institut National de la Recherche Agronomique (INRA), Unités Mixtes de Recherches (UMR) 85 Physiologie de la Reproduction et des Comportements, Nouzilly, France Centre National de la Recherche Scientifique, UMR 7247, Nouzilly, France Université François Rabelais de Tours, Tours, France l'Institut Français du Cheval et de l'Équitation, Nouzilly, France INRA, Plateforme d'Analyse Intégrative des Biomolécules, Laboratoire de Spectrométrie de Masse, Nouzilly, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Labas
authors.affiliation: School of Agriculture and Food Science, The University of Queensland, Gatton, Queensland, Australia.
authors.forename: Steve D
authors.initials: SD
authors.lastname: Johnston
authors.affiliation: Priority Research Centre for Reproductive Science, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: Russell C
authors.initials: RC
authors.lastname: Jones
mesh_terms: D020101:Acrosome Reaction / Q000502:physiology; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002645:Chickens; D004822:Epididymis / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D005306:Fertilization / Q000502:physiology; D008297:Male; D015676:Osteonectin / Q000502:physiology; D010987:Platypus / Q000033:anatomy & histology / Q000502:physiology*; D020543:Proteome / Q000302:isolation & purification / Q000378:metabolism; D013045:Species Specificity; D013075:Sperm Capacitation / Q000502:physiology; D013079:Sperm Maturation / Q000502:physiology; D013081:Sperm Motility / Q000502:physiology; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013094:Spermatozoa / Q000166:cytology* / Q000502:physiology*; D004442:Tachyglossidae / Q000033:anatomy & histology / Q000502:physiology*
chemical_list: D015676:Osteonectin; D020543:Proteome
keywords: SPARC; capacitation; echidna; epididymis; fertilization; monotreme; platypus; sperm; sperm competition; sperm cooperation; sperm maturation