The Sperminator

　　The sperm of a worm does a rather mean thing in the race towards the egg by releasing a protein to block its competitors, scientists in Beijing have found. Studies of this seemingly insignificant species may hold keys to a wide range of human problems, from birth control to a neural disease that crippled a man no less significant than Stephen Hawking, said a professor in this research.

Observing the sperm of nematode worms, a parasite found in pig intestines, researchers in Dr Miao Long's cell biology laboratory in the Institute of Biophysics in Beijing identified a protein called serine protease inhibitor (As-SRP-1). Their study, published in the January edition of the journal Proceedings of the National Academy of Sciences (PNAS), found that a sperm uses this protein to undercut other sperms in the worm equivalent of the vagina.

A research team led by Dr Dong Mengqiu at Beijing's National Institute of Biological Sciences also contributed to their study.

"Sperms undergo a process called activation to become motile [biological term for the ability to move]. In sperm activation, a protein initiator, excreted from the sperm ducts, is required to set the sperm in motion," said Miao, one of the corresponding authors of the article. Miao and his colleagues found that once activated by the initiator, a sperm releases the chemical As-SRP-1, which in return disables this initiator, so it can't go on to turn on other sperms. "Talk about burning the bridge after you have crossed it," Miao said.

"We have known that size matters when it comes to sperm competition and some accessory glands help sperm mobility. But for a sperm to kill off potential competition, that's new," he added.

Using techniques in cell biology and biochemistry, the researchers were able to see for the first time what level of selfishness a sperm is capable of to beat other sperms to the egg. "It's like putting together pieces of evidence to reconstruct a crime, only what we do is under a light microscope," Miao said.

Although their study is just one part of fundamental research, the implication of the latest sperm research could promise one day to revolutionize the industry of birth control.

"So far, all orally administered drugs are for women. Any birth control formula for men either does not work or has damaging side effects," Miao said. If there is a drug that mimics the selfish protein to block the sperm activation, there could be a new answer to male birth control. Reversely, knowledge of sperm activation may be used in fertility studies to enhance sperm activity and therefore help barren couples.

Studies on nematodes help human beings because, far apart on the evolutionary path as we are, worms and primates share some primal biological traits, said Zhao Yanmei, a cell biologist in Miao's lab and lead author of the PNAS article. "The same proteins at work in human reproduction are found working in worms or fruit flies as well," she said. This, and the fact that nematodes live a short lifespan (some live only for days, others weeks), makes the worm a perfect subject in medical studies.

For example, scientists have found a sperm protein that regulates muscle energy. According to a February article in MDA/ALS Newsmagazine, tests on nematodes suggested that reduced levels of this protein may be responsible for amyotrophic lateral sclerosis, a rare neuromuscular disease affecting about one or two in every 100,000 people worldwide, including the British theoretical physicist Stephen Hawking.

There is a long way to go from a scientific discovery to a clinical success, but transient organisms like worms and insects considerably speed up the process, said Miao.