CHAPEL HILL -- The discovery by University of North Carolina scientists of a distinct family of proteins that bind to human sperm may offer important new clues to male fertility and possible male contraception.
A report of the new findings appears in the March issue of the journal Endocrinology.
The three proteins in the newly identified HE2 family are secreted in the epididymis, a coiled tubular network several yards long attached to the top of each testicle. As they mature, sperm pass through the epididymis and into another tube, the vas deferens, before emptying through the urethra during ejaculation.
Compared to the testes, the epididymis has been overlooked on a molecular level until very recently. Just five years ago, in 1995, it was considered by some as not essential for the development of sperm's fertilizing ability.
"Now it's known that sperm that have not passed through the epididymis fertilize an egg very poorly if at all. And after they pass through, they're more ready to fertilize an egg," said Susan Hall, PhD, research assistant professor of pediatrics at UNC-Chapel Hill School of Medicine. "In the epididymis, sperm go through certain maturational steps that are not very well understood at this point. That's why we're studying proteins that are synthesized in the epididymis and secreted into that tubule that might possibly interact with sperm in such a way to affect their maturation."
Attempting to fill in the gaps in epididymis molecular biology and to find possible protein targets for male contraception, Hall and her colleagues at UNC's Laboratories of Reproductive Biology began searching for genes expressed specifically in that organ.
Armed with grants from the privately endowed Contraceptive Research and Development Program (CONRAD), the Andrew Mellon Foundation, the NIH, and the Fogarty International Center, the UNC researchers found that three categories of HE2 epididymal proteins -- alpha, beta, and gamma -- were a
Contact: Leslie H. Lang
University of North Carolina School of Medicine