Protein Profile Involved in Mammalian Oocyte Maturation, Fertilization and Early Embryogenesis (Pre-Implantation)

Abstract

Proteomic analysis of oocytes can help identify proteins that are involved in female meiotic maturation and early embryonic development. Many proteins with well-defined functions have been identified during oocyte maturation. High levels of MPF, MAPK, Mos and low levels of cAMP play an essential role in the resumption of meiosis I. Following germinal vesicle breakdown, chromosome condensation and spindle formation occurred at metaphase I by assembly of the meiotic apparatus, which includes the proteins NuMA, γ-tubulin and Polo-like kinase 1. The metaphase II arrest is a result of high levels of MPF and MAPK. Proteins involved in the stress response and redox regulation, including peroxiredoxin, GST and HSF1, are also necessary for protection against oxidative stress. During fertilization, the sperm-egg interaction requires egg surface proteins, oocyte zona pellucida, molecular chaperones, GPI-anchored proteins and CD9 to recognize sperm proteins and prevent polyspermy. Following gamete fusion, resumption and complete of meiosis II is induced by GTP and CaM kinase II activation, which inactivates MPF and activation of the anaphase promoting complex/cyclosome results in sister chromatid separation. Decondensation of the sperm head begins after zona penetration and GSH and NPM2 are necessary for male pronuclear formation. MAPK inactivation is required for pronuclear formation. At the cleavage stage, the maternal effect proteins PADI6, FLOPED and FILIA are essential for embryonic progression past the two-cell stage. After cell adhesion, cell junctions and the cytoskeleton play an important role in compaction of the morula. Par6, Par3 and protein kinase C are components of the apical polarity complex and are important for formation of the blastocoel cavity. During the blastocyst stage, TEAD4 and CDX2 are required for trophoectoderm formation. This proteomic analysis of oocytes has improved our understanding of the molecular processes that regulate oocyte maturation, fertilization and pre-implantation in mammals.

The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization

“…The first step of meiotic resumption occurs by gonadotropins activating the surrounding GCs. In mammals, the actions of LH and FSH on the meiotic resumption of the oocytes mediate an increase in cAMP production by the activation of mitogen-activated protein kinases (MAPKs) [ 31 , 36 , 37 ], which act on the GCs and promote an increase in the levels of cAMP within the granulosa cell compartment and a decrease in cAMP and cGMP in the oocyte by reducing the permeability of the gap junction between CCs and oocytes, thus inducing the resumption of meiosis as well as the cumulus expansion in preparation for ovulation and fertilization [ 32 , 38 ].…”