2010-07-16 14:49

LOS ANGELES - US researchers have discovered that a sperm-producing gene in men has remained unaltered throughout evolution for 600 million years.

The so-called Boule gene appears to be the only gene exclusively required for sperm production in creatures ranging from insects to mammals, researchers at the Northwestern University Beinber School of Medicine said in a study published Thursday in PLoS Genetics.

"This is the first clear evidence that suggests our ability to produce sperm is very ancient, probably originating at the dawn of animal evolution 600 million years ago," said Eugene Xu, the study's lead author and an assistant professor of obstetrics and gynecology.

"This finding suggests that all animal sperm production likely comes from a common prototype."

The discovery of Boule's key role in perpetuating animal species offers a better understanding of male infertility, a potential target for a male contraceptive drug and a new direction for future development of pesticides or medicine against infectious parasites or carriers of germs.

"Our findings also show that humans, despite how complex we are, across the evolutionary lines all the way to flies, which are very simple, still have one fundamental element that's shared," Xu said.

"It's really surprising because sperm production gets pounded by natural selection," he said. "It tends to change due to strong selective pressures for sperm-specific genes to evolve. There is extra pressure to be a super male to improve reproductive success. This is the one sex-specific element that didn't change across species. This must be so important that it can't change."

Boule is likely the oldest human sperm-specific gene ever discovered, Xu said.

For the study, Xu searched for and discovered the presence of the Boule gene in sperm across different evolutionary lines: human, mammal, fish, insect, worm and marine invertebrate. When they removed the Boule gene from a male mouse, the animal remained healthy but did not produce sperm.

Discovery of this common gene involved in sperm production could have many practical uses for human health, including male contraception.

"A sperm-specific gene like Boule is an ideal target for a male contraceptive drug," Xu noted.

Boule also has the potential to reduce diseases caused by mosquitoes and parasites such as worms.

"We now have one strong candidate to target for controlling their breeding," Xu said. "Our work suggests that disrupting the function of Boule in animals most likely will disrupt their breeding and put the threatening parasites or germs under control. This could represent a new direction in our future development of pesticides or medicine against infectious parasites or carriers of germs."