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Switch triggering penetration of egg by sperm discovered
April 24, 2016, 3:24 pm

Researchers have pinpointed the ‘switch’ that triggers the sudden tail whip, which sperm use to penetrate and fertilize an egg. The new finding could help identify a possible cause of male infertility and could also lead to developing contraceptives that work in both women and men.

The investigators found that the surface of a sperm's tail has thousands of protein receptors that respond to the hormone progesterone released by the egg. When sperm get close to the egg, these receptors react to the progesterone and cause the tail to snap like a whip in an attempt to reach the egg.

If the receptor protein does not recognize progesterone, it could lead to infertility, said the research team at the University of California in the US. Currently, the cause of nearly 80 percent of cases of male infertility is unknown. Sperm may be the problem in half of all cases of infertile couples, the researchers said.
In addition, the study authors suggested that a drug capable of deactivating progesterone receptors on sperm might prove an effective contraceptive for both men and women.

If you can stop progesterone from inducing a power stroke, sperm are not going to be able to reach or penetrate the egg," the researchers added.

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