CatSper revs up sperm tails.


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 if the eggs have been stripped of their protective coat of zona pellucida.

Based on these data, says David Garbers (University of Texas Southwestern Medical Center, Dallas, TX), a CatSper inhibitor might be useful as a male contraceptive. “The problem with going after a male contraceptive is that you have millions of sperm and you have to get them all,” he says. “Amazingly enough, when this channel was gone they got no fertilization. That makes it reasonably attractive as a drug target.” ▪


Ren, D., et al.