title: Mouse sperm begin to undergo acrosomal exocytosis in the upper isthmus of the oviduct.
abstract: Recent evidence demonstrated that most fertilizing mouse sperm undergo acrosomal exocytosis (AE) before binding to the zona pellucida of the eggs. However, the sites where fertilizing sperm could initiate AE and what stimuli trigger it remain unknown. Therefore, the aim of this study was to determine physiological sites of AE by using double transgenic mouse sperm, which carried EGFP in the acrosome and DsRed2 fluorescence in mitochondria. Using live imaging of sperm during in vitro fertilization of cumulus-oocyte complexes, it was observed that most sperm did not undergo AE. Thus, the occurrence of AE within the female reproductive tract was evaluated in the physiological context where this process occurs. Most sperm in the lower segments of the oviduct were acrosome-intact; however, a significant number of sperm that reached the upper isthmus had undergone AE. In the ampulla, only 5% of the sperm were acrosome-intact. These results support our previous observations that most of mouse sperm do not initiate AE close to or on the ZP, and further demonstrate that a significant proportion of sperm initiate AE in the upper segments of the oviductal isthmus.
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: Florenza A
authors.initials: FA
authors.lastname: La Spina
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: Lis C
authors.initials: LC
authors.lastname: Puga Molina
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: Ana
authors.initials: A
authors.lastname: Romarowski
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
authors.forename: Alejandra M
authors.initials: AM
authors.lastname: Vitale
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina; Instituto de Biología Celular y Neurociencias (IBCN), Facultad de Medicina, Universidad de Buenos Aires, (CONICET-UBA), Buenos Aires, Argentina.
authors.forename: Tomas L
authors.initials: TL
authors.lastname: Falzone
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (CONICET-UNR) and Facultad de Ciencias Biológicas y Farmacéuticas, UNR, Rosario, SF 2000, Argentina.
authors.forename: Dario
authors.initials: D
authors.lastname: Krapf
authors.affiliation: Oki Marine Biological Station, Education and Research Center for Biological Resources, Shimane University, Japan.
authors.forename: Noritaka
authors.initials: N
authors.lastname: Hirohashi
authors.affiliation: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina. Electronic address: mgbuffone@ibyme.conicet.gov.ar.
authors.forename: Mariano G
authors.initials: MG
authors.lastname: Buffone
mesh_terms: D000177:Acrosome / Q000378:metabolism; D020101:Acrosome Reaction; D000818:Animals; D054885:Cumulus Cells / Q000166:cytology*; D005089:Exocytosis; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009865:Oocytes / Q000166:cytology; D010057:Oviducts / Q000502:physiology*; D013075:Sperm Capacitation / Q000502:physiology; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*; D015044:Zona Pellucida / Q000378:metabolism
chemical_list: D049452:Green Fluorescent Proteins
keywords: Acrosomal exocytosis; Acrosome; Fertilization; Oviduct; Sperm