The Role of Recombinant Oviduct-Specific Glycoprotein (OVGP1) During Early Events of Fertilization
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The mammalian oviductal secretory cells synthesize and secrete a major glycoprotein known as the oviduct-specific glycoprotein (OVGP1) which is in abundance around the time of fertilization. In vitro studies carried out in various mammalian species have shown that native OVGP1 interacts with gametes and early embryos; this interaction can enhance the fertilizing capacity of sperm, increase cleavage rate of early embryos, and prevent polyspermy. However, functional and mechanistic studies of OVGP1 are hampered due to the difficulty in isolating and purifying OVGP1 from oviductal fluid. In the present study, we successfully produced and purified a secretory form of recombinant hamster OVGP1 (rHamOVGP1) and recombinant human OVGP1 (rHuOVGP1) from stably transfected HEK293 cells. Results from this study showed that both rHamOVGP1 and rHuOVGP1 can bind to their homologous sperm in both the head and tail regions. Both recombinant proteins can enhance sperm capacitation through the increase of tyrosine phosphorylation of sperm proteins. In hamsters, tyrosine phosphorylated (pY) proteins were located in the equatorial segment, mid-piece, and principal piece. One of the major hamster sperm pY proteins is likely to be AKAP83. In human sperm, pY proteins were located predominantly in the fibrous sheath of the principal piece. One of the identified major pY proteins was AKAP3. AKAP proteins play a role in regulating sperm capacitation and motility. Therefore, recombinant OVGP1s are capable of further enhancing sperm capacitation likely through the increase of the signaling events that lead to increased sperm motility. In addition, the presence of recombinant OVGP1s in the capacitating medium was able to further potentiate the sperm to undergo acrosome reaction. Furthermore, the present study showed that pre-treatment of the zona pellucida and/or sperm with recombinant OVGP1s can also increase the number of sperm bound to the zona pellucida of oocytes. Cryopreserved human sperm samples were also used in this study and found to benefit from the presence of rHuOVGP1 which resulted in increasing the sperm fertilizing capacity. It is envisaged that supplementing the conditioned medium used in assisted reproductive technology with rHuOVGP1 could be beneficial for enhancing the sperm fertilizing competence.
URI for this recordhttp://hdl.handle.net/1974/26200
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