| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1998: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
In mammals, the epididymal sperm maturation is partly supported by proteins secreted by epididymal epithelial cells. In the present study, the role of 16kDa cholesterol-binding protein(16kDa-ChBP), which was first purified from the porcine epididymal fluid, in the sperm maturation was investigated.
1. The purified 16kDa-ChBP specifically bound cholesterol with high affinity(Kd=2.3mM). The binding stoichiometry was determined that one mol cholesterol bound to one mol of the protein. The 16kDa-ChBP decreased the binding of cholesterol to sperm and reduced the amount of the bound cholesterol in sperm, suggesting that it is one of the important regulators of cholesterol content in the sperm membranes. The decrease in the cholesterol content in the porcine sperm membrane during the epididymal maturation is strongly suggested to be mediated by this protein.
2. It is also known that the cholesterol content in the sperm membranes is decreased during capacitation. It was found that in mouce the 16kDa-ChBP mRNA was expressed in ovary, oviduct and uterus as well as in epididymis. Furthermore, the level of the 16kDa-ChBP mRNA changed during sexual cycle ; it is increased in estrus and metestrus but decreased in diestrus and proestrus. This result indicates that the 16kDa-ChBP is present in the female reproductive tract, when sperm undergo capacitation. It is likely that this protein releases the cholesterol from the sperm membrane and promotes capacitation.
3. The mouse 16kDa-ChBP gene was cloned. It was found that it is devided into four exons and resides on the D-region of Chromosome 12. In order to obtain a 16kDa-ChBP-knockout mouse line, a gene targeting construct was produced.
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