In addition, the scientists have discovered a potent inhibitor, called undecanal, that blocks the effects of bourgeonal on sperm.
"It appears that undecanal binds to the same receptor protein as bourgeonal, but without performing its function," Zimmer said. "When bourgeonal then tries to bind, it can't; undecanal out-competes bourgeonal, and completely inhibits the response of sperm to follicular fluid.
"We are rapidly making strides in identifying the functional role in fertilization of remote chemical communication between sperm and eggs," Zimmer added. "We are learning how chemical communication occurs. Knowing the molecular structure, we are now defining the physiological function."
The German cell physiologists had isolated human genes that code for olfactory-like receptor proteins, and found that the expression of these receptor proteins in humans was localized to sperm. They did not know the function of the genes, but saw Zimmer's research on abalone, and agreed to work together to learn how the receptors are organized and how they respond.
"This research may help us answer the question of whether sperm can be caused to behave in a way that increases the likelihood of successful fertilization," Zimmer said. "We have developed techniques to track sperm cells -- their speed and direction -- with respect to the egg. We can follow what sperm do in the presence of an egg, and study how fast they are swimming, and the angle at which they are swimming.
"This has been the best collaboration I have ever worked on," Zimmer said. "This is a perfect example of the importance of basic research. We were working with a marine animal; a group in Germany isolated a human gene and identified a receptor protein on human sperm that responds to bourgeonal, but did not know its function. They got a hold of us, and within a month, we had shown
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Contact: Stuart Wolpert
stuartw@college.ucla.edu
310-206-0511
University of California - Los Angeles
1-Apr-2003