Reducing the swimming ability of the sperm could pave way to developing a new male contraceptive pill, Australian researchers have found.

Researchers have discovered a way to cut off the fuel supply to the "motor" that drives human sperm, greatly reducing their swimming ability and opening a new avenue to develop a male contraceptive pill.

The finding throws new light on the little-understood reasons for infertility in men, the 'Sydney Morning Herald' reported.
Researchers, led by Moira O'Bryan from Monash University's school of biomedical sciences, engineered mutation in a gene called RABL2 that delivers protein fuel to the engine in a sperm's tail in mice.

The mutation resulted in sperm tails that were 17 per cent shorter than normal and a 50 per cent reduction in sperm production.

The most striking result was that all mice with the mutated gene were rendered infertile and their sperm incapable of swimming.

"They weren't wriggling or going anywhere, they were just twitching. With this mutation, we get motors that don't work properly. To be fertile, sperm need motility ... Or swimming ability," the paper quoted Professor O'Bryan as saying.

O'Bryan collaborated with scientists from the University of Newcastle, John Curtin School of Medical Research, Garvan Institute of Medical Research and the University of Cambridge for the research.

She said a future male pill might work to inhibit the RABL2 gene rather than change it permanently.

"The challenge with developing the male pill isn't rendering the sperm infertile but turning them back on again," O'Bryan said.

As RABL2 is also found in other tissues such as the brain kidneys and liver in lower concentrations, an inhibitor specific to the testes would need to be developed.