Swimming with sperm

A putative calcium channel specific to sperm tails may be the best target yet for a male contraceptive. The protein, dubbed CatSper, was discovered in a homology search by David Clapham and colleagues of Harvard Medical School, Boston, MA.CatSper looks like a calcium channel, although Clapham could not detect a calcium current in transfected cells, probably because another component of the channel is missing. CatSper is, however, required for a calcium influx into sperm that is triggered by cyclic nucleotides. Such signaling events may be part of the process by which sperm either gain their initial motility in the epididymis, or augment that motility (in a process called hyperactivation) when they near an unfertilized egg.

Male mice lacking CatSper are completely infertile. Their sperm move sluggishly (at approximately one third of the normal rate) and can fertilize eggs only...