title: Glycosylated chicken ZP2 accumulates in the egg coat of immature oocytes and remains localized to the germinal disc region of mature eggs.
abstract: Vertebrate eggs are surrounded by an egg coat, which is a specific extracellular egg matrix consisting of several glycoproteins with a conserved zona pellucida (ZP) domain. Two mammalian egg coat subunits, ZP2 and ZP3, have been suggested to act as sperm receptors. In bird eggs, however, ZP2 has never been identified in the egg coat of mature oocytes and ovulated eggs. Here we report that chicken ZP2 is expressed in immature small follicles and remains as an egg-coat component locally in the germinal disc region of mature eggs. RT-PCR analysis indicated marked expression of the ZP2 and ZP4 genes in the granulosa cells of immature white follicles, whereas the ZP3 and ZPD genes showed marked expression in the cells of maturing yellow follicles. ZP2 was identified in the egg coat isolated from immature follicles as a heavily N-glycosylated glycoprotein of ∼200 kDa, which was enzymatically converted to a 70-kDa deglycosylated form. Immunoblotting and immunohistological analyses showed that ZP2 was localized around the germinal disc region of mature follicles. ZP2 was accumulated in the egg coat of immature white follicles at the earlier stages of oocyte development and became a minor component in the egg coat of maturing yellow follicles, except for the germinal disc region. Localization of ZP2 in the germinal disc region of mature eggs, where sperm bind to the egg coat at high density, suggests some role for ZP2 in the preferential binding and penetration of sperm in the germinal disc region of bird eggs.
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nishio
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kohno
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Iwata
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Arai
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Meijo University, Tenpaku, Nagoya, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Okumura
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Kenzi
authors.initials: K
authors.lastname: Oshima
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Daita
authors.initials: D
authors.lastname: Nadano
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan tmatsuda@agr.nagoya-u.ac.jp.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D054239:Blastodisc / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002645:Chickens / Q000235:genetics / Q000378:metabolism; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D004528:Egg Shell / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006031:Glycosylation; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D009866:Oogenesis / Q000502:physiology; D010063:Ovum / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D013084:Sperm-Ovum Interactions / Q000235:genetics; D014018:Tissue Distribution; D000072216:Zona Pellucida Glycoproteins
chemical_list: D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins
keywords: amphibians; fertilization; fish; fowl; non-mammals; oocyte maturation; reptiles; vertebrates; vitelline membrane; zona pellucida