Analysis of vitelline envelope synthesis and composition during early oocyte development in gilthead seabream (Sparus aurata).
The oocyte vitelline envelope (VE) of gilthead seabream is composed of four known zona pellucida (ZP) proteins, ZPBa, ZPBb, ZPC, and ZPX. We have previously shown that the gilthead seabream ZP proteins are differentially transcribed in liver and ovary, with the expression in liver being under estrogenic control. However, although mRNA was found in both liver and ovary, only low ZPBa protein levels were detected in liver and plasma. Using isoform-specific ZP antibodies we show that ZPBa and ZPX translation products are present in the cytosol of stage I and II oocytes. In addition, the zpBa and zpX mRNAs were detected in early developing oocytes. During oocyte growth (vitellogenesis), the VE increased in thickness (>10 microm), and we show that the four ZP isoforms are present in different regions of the VE. ZPX was detected closest to the oocyte plasma membrane while the intermediate region was composed of ZPBa, ZPBb, and ZPC. At the outer layer, only ZPC was detected. When oocytes reach the fully grown stage they resume meiosis and hydration. As the oocyte expands, thinning to 4 microm, the VE acquire a striped and compact appearance at the electron microscopy level. This study provides further evidence for the oocyte origin of some ZP proteins in the gilthead seabream and suggests that the ZP proteins are differentially distributed within the VE.
Modig
Carina
C
Department of Natural Science, Orebro Life Science Center, Orebro University, Orebro, Sweden.
Raldúa
Demetrio
D
Cerdà
Joan
J
Olsson
Per-Erik
PE
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D007150:Immunohistochemistry; D008099:Liver / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009865:Oocytes / Q000254:growth & development*; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D021541:Sea Bream / Q000502:physiology*; D014817:Vitelline Membrane / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure; D014818:Vitellogenesis / Q000502:physiology*; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins