Gamete recognition in mice depends on the cleavage status of an egg's zona pellucida protein.
At fertilization, mouse sperm bind to the zona pellucida (which consists of glycoproteins ZP1, ZP2, and ZP3) that surrounds eggs. A ZP2 cleavage model of gamete recognition requires intact ZP2, and a glycan release model postulates that zona glycans are ligands for sperm. These two models were tested by replacing endogenous protein with ZP2 that cannot be cleaved (Zp2(Mut)) or with ZP3 lacking implicated O glycans (Zp3(Mut)). Sperm bound to two-cell Zp2(Mut) embryos despite fertilization and cortical granule exocytosis. Contrary to prediction, sperm fertilized Zp3(Mut) eggs. Sperm at the surface of the zona pellucida remained acrosome-intact for more than 2 hours and were displaced by additional sperm. These data indicate that sperm-egg recognition depends on the cleavage status of ZP2 and that binding at the surface of the zona is not sufficient to induce sperm acrosome exocytosis.
Gahlay
Gagandeep
G
Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Gauthier
Lyn
L
Baibakov
Boris
B
Epifano
Olga
O
Dean
Jurrien
J
D000177:Acrosome / Q000502:physiology; D020101:Acrosome Reaction; D000818:Animals; D002448:Cell Adhesion; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism; D005089:Exocytosis; D005260:Female; D005298:Fertility; D005306:Fertilization; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D013075:Sperm Capacitation; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism*; D000072216:Zona Pellucida Glycoproteins; D015053:Zygote / Q000378:metabolism
D004527:Egg Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D050505:Mutant Proteins; D011134:Polysaccharides; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; C000606519:Zp1 protein, mouse; C000606520:Zp2 protein, mouse; C000606521:Zp3 protein, mouse