Male infertility affects one out of 20 adult men worldwide, and headless sperm are often seen in the semen of male infertility patients. In some infertile males, all their sperm are headless, a condition called "acephalic sperm."

Despite its high incidence among infertile men, the mechanism behind acephalic sperm remains elusive. Until now.

A research team led by University of Nevada School of Medicine researcher Wei Yan, M.D., Ph.D., professor of physiology and cell biology, has discovered that the acephalic sperm condition is caused by either a lack of, or a partial formation of the sperm neck, and that proper sperm neck formation requires an evolutionarily conserved gene called Spata6, which encodes a protein participating in the transportation of "building blocks" essential for sperm neck assembly inside the testis. When Spata6 gene is mutated, the sperm neck either lacks or becomes fragile, leading to separation of the head from the tail.    

This study solved the long-standing mystery of headless sperm in both humans and agricultural animal species with fertility problems. A paper reporting this discovery appeared online in the Proceeding of the National Academy of Sciences on Jan. 19.

"Now that the cause of the acephalic sperm condition is known, we hope that novel diagnostics and even therapeutics can be developed in the near future," said Yan. "We are also seriously considering the possibility of using this gene as a drug target for developing non-hormonal male contraceptive pills." Research in the Yan lab at the School of Medicine is supported by grants from the National Institutes of Health.