Sperm gene hasn't changed in 600 million years

Posted by Emma Woollacott

If it ain't broke, don't fix it, they say - and there's no doubt you lot seem pretty pleased with the stuff. And now scientists have discovered that the human sperm gene has survived for 600 million years, unaltered.

Most genes specific to sex change rapidly. But there is one that's so vital that its function has barely altered throughout evolution, according to new research from Northwestern University Feinberg School of Medicine.

The gene, called Boule, is responsible for sperm production, and is found in almost all animals. It seems to be the only gene known to be exclusively required for sperm production in creatures from insects to mammals.

 
"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 Dr Eugene Xu, assistant professor of obstetrics and gynecology at Feinberg.

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

Xu found the Boule gene in sperm across different evolutionary lines: human, mammal, fish, insect, worm and marine invertebrate.

"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. It tends to change due to strong selective pressures for sperm-specific genes to evolve... 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. He originally discovered the human gene in 2001.

The discovery of the gene could have many practical uses for human health, including male contraception. When Xu’s research group knocked out the Boule gene from a mouse, the animal appeared to be healthy but did not produce sperm.