Researchers have come up with a new approach to contraception. They discovered a way to make sperms stop swimming and if they can't swim they can't cause pregnancy.
A team from the Harvard Medical School in Boston found an essential protein, dubbed CatSper, without which the sperm are literally stopped in their tracks. The finding promises to deliver safer "unisex" contraceptives, the authors write this morning in the journal Nature.
The protein is essential for sperm movement and the researchers describe it as "an ideal target for potential contraceptive drugs". It is only found in the sperm's tail and not in other tissues, and its action is not dependent on the hormones found in all birth control pills currently in use.
The researchers located CatSper when studying sperm movement in mice and then found the same protein in humans. "Targeted disruption of the gene results in male sterility in otherwise normal mice," they say. "Sperm motility is decreased markedly in CatSper mice and CatSper sperm are unable to fertilise intact eggs."
Sperm actually have a tough job once they embark on their mission to fertilise an egg. They are smaller than the head of a pin so for them the 30cm or so they have to traverse must seem like a walking tour of the entire Great Wall of China.
The discovery opens up a new form of contraception for men or women based on blocking the action of CatSper. It may also help overcome male infertility by providing extra CatSper to give sperm a kick in the tail, the authors say.
Side effects from any drug meant to act on the CatSper protein "should be low or nonexistent", the researchers say, and "normal development and behaviour, including sexual," is not affected.
