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Principal Investigator: Dr. Susan Suarez
Contact Information: E-mail: sss7@cornell.edu - Phone: 3-3589
Sponsor: USDA - NRI Competitive Grant
Grant Number: 2004-35203-14952
Title: Mechanisms Governing Sperm Storage in the Oviduct
Annual Direct Cost: $111,640
Project Period: 9/1/04 - 8/31/07
After insemination, thousands of sperm reach the uterine tubes (oviducts, fallopian tubes). However, they are trapped just inside the entrance by binding to the epithelium lining the wall of the tubes. This forms a storage reservoir of sperm, which serves to preserve sperm until ovulation and to preventing polyspermic fertiization. Sperm bind to the epithelium via a protein produced by the seminal vesicles, PDC-109, which coats the sperm when they come into contact with seminal fluid in the male. Two closely-related seminal plasma proteins, called BSP proteins, may also be involved in sperm storage. Our specific aims are: Aim 1: To test the hypothesis that all of the BSP proteins enhance sperm binding and to determine whether they form functional complexes on the surface of sperm. Aim 2: To test the hypothesis that the BSP proteins enable sperm to bind to different receptors in the oviduct. Aim 3: To test the hypothesis that prolongation of sperm survival depends upon their binding to oviductal membranes via BSP proteins. Aim 4: To test the hypothesis that sperm binding to oviductal epithelial membranes prolongs their survival by delaying capacitation, a process that prepares sperm to fertilize eggs. Information gained will fill critical gaps in our knowledge of how the female stores sperm and regulates their movement. Furthermore, the information can be used to develop new fertility tests for semen, to improve efficiency of artificial insemination, and to develop methods of sperm storage that would not require freezing.
Although millions of bull sperm are inseminated, only thousands reach the isthmus of the oviduct. There, they are trapped in a storage reservoir by becoming stuck to oviductal epithelium. This serves to prevent polyspermic fertilization and to preserve fertility of sperm until the time of ovulation. PDC-109, a sperm-coating protein secreted by seminal vesicles, is responsible for binding sperm to the oviductal epithelium. Two closely-related seminal plasma (BSP) proteins may also be involved. Our specific objectives are (1) to test the hypothesis that all of the BSP proteins enhance sperm binding and to determine whether they form functional complexes in sperm plasma membranes; (2) to test the hypothesis that the BSP proteins bind to different ligands in the oviduct; (3) to test the hypothesis that prolongation of sperm survival depends upon their binding to oviductal membranes via BSP proteins; and (4) to test the hypothesis that sperm binding to oviductal epithelial membranes prolongs their survival by inhibiting capacitation. The evolution of 3 BSP proteins has probably enhanced sperm survival and fertility in vivo. Information ained could be used to develop new fertility tests for semen, to improve AI efficiency, and to develop methods of sperm storage that would not require freezing, thus addressing the Agricultural Issue of Genomics and Future Food and Fiber Production.
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