title: Zona pellucida from fertilised human oocytes induces a voltage-dependent calcium influx and the acrosome reaction in spermatozoa, but cannot be penetrated by sperm.
abstract: BACKGROUND
  The functions of three zona glycoproteins, ZP1, ZP2 and ZP3 during the sperm-zona pellucida (ZP) interaction are now well established in mice. The expression of an additional zona glycoprotein, ZPB/4, in humans, led us to reconsider the classical mouse model of gamete interaction. We investigated the various functions of human ZP (hZP) during the interaction of spermatozoa with fertilised and unfertilized oocytes.
  
  
  RESULTS
  The hZP of fertilised oocytes retained their ability to bind sperm (albeit less strongly than that from unfertilized oocytes), to induce an intraspermatic calcium influx through voltage-dependent channels similar to that observed with hZP from unfertilized oocytes and to promote the acrosome reaction at a rate similar to that induced by the ZP of unfertilized oocytes (61.6 +/- 6.2% vs 60.7 +/- 9.1% respectively). Conversely, the rate of hZP penetrated by sperm was much lower for fertilised than for unfertilized oocytes (19% vs 57% respectively, p < 0.01). We investigated the status of ZP2 in the oocytes used in the functional tests, and demonstrated that sperm binding and acrosome reaction induction, but not ZP penetration, occurred whether or not ZP2 was cleaved.
  
  
  CONCLUSIONS
  The change in ZP function induced by fertilisation could be different in human and mouse species. Our results suggest a zona blocking to polyspermy based at the sperm penetration level in humans.
authors.affiliation: Biologie de la Reproduction, Hôpital Cochin, AP-HP, Université Paris Descartes, Faculté de Médecine, Paris, France. catherine.patrat@cch.aphp.fr
authors.forename: Catherine
authors.initials: C
authors.lastname: Patrat
authors.forename: Jana
authors.initials: J
authors.lastname: Auer
authors.forename: Patricia
authors.initials: P
authors.lastname: Fauque
authors.forename: Roger L
authors.initials: RL
authors.lastname: Leandri
authors.forename: Pierre
authors.initials: P
authors.lastname: Jouannet
authors.forename: Catherine
authors.initials: C
authors.lastname: Serres
mesh_terms: D020101:Acrosome Reaction / Q000502:physiology*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D009865:Oocytes / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism* / Q000502:physiology; D015044:Zona Pellucida / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D002118:Calcium