Zona pellucida
(Latin, zona pellucida = transparent zone) A specialized extracellular matrix surrounding the developing oocyte (egg, ovum) within each follicle within the ovary. This thick matrix is thought to be formed by secretions from the oocyte and the follicle granulosa cells and consists of three types of zona pellucida glycoproteins ZP1, ZP2 and ZP3 which have different roles in fertilization.
Following fertilization, the zona pellucida also surrounds the blastocyst during the first week of development, from which it "hatches".
The zona pellucida has a role in fertilization, sperm binding, preventing polyspermy, blastocyst development and preventing premature implantation (ectopic pregnancy).
ZP1
- Acronym for Zona Pellucida Binding Protein, a glycoprotein found in zona pellucida surrounding the egg.
ZP2
- Acronym for Zona Pellucida Binding Protein 2, a glycoprotein found in zona pellucida surrounding the egg. Before fertilization ZP2 binds spermatozoa. After fertilization ZP2 is proteolytically cleaved as an initial block to polyspermy.
ZP3
- Acronym for Zona Pellucida Binding Protein 3, a glycoprotein found in zona pellucida surrounding the egg required for initial zona matrix formation and during fertilization for species-specific sperm binding. Now thought to exist in 2 isoforms ZP3A and ZP3B (a second polymorphic allele).
ZPBP1
- Acronym for Zona Pellucida Binding Protein 1 A spermatozoa protein found located on the acrosome surface.
Links: Carnegie stage 1 | Carnegie stage 3
Original page links: Week 1 - Fertilization | Week 1 - Oogenesis |
