A biological on-off switch controlling sperm movement could be the key to effective birth control for men and women, a new study has found.
At the core of this discovery is the previously mysterious enzyme ABHD2, where experiments of researchers from UC Berkeley and Yale University showed that the protein is necessary for the biological functions to lead sperm to be more effective swimmers.
The hormone progesterone is usually put out by the ova to incite a competitive swim race among sperm, and is triggered when a calcium channel called CatSper is opened. ABHD2 appears to be between progesterone and CatSper in this process, getting the former to react with the latter and causing an active frenzy among sperm.
Sans that reaction, sperm will just normally drift along and likely run out of energy before it gets into and through cells that protect the egg. The inhibition of ABHD2 thus appears to be a contraceptive method for both sexes.
“If the receptor protein doesn’t recognize progesterone, you would be infertile. This gives us an understanding of another pathway that is involved in human sperm activity,” explains first author and postdoctoral fellow Melissa Miller.
A drug inactivating the receptor is hoped to serve as a unisex contraceptive to be taken by a male or female sexual partner. The key is to stop progesterone from inducing “a power stroke,” where sperm cells are unable to reach or enter the egg.
Doctors today still cannot figure out the culprit behind almost 80 percent of male infertility cases, partly due to little knowledge on the molecular processes in sperm production and its interaction with the egg. In 50 percent of all infertile couples, sperm may be the one to blame.
In addition, it may be wrong to think of successful fertilization as the fastest sperm winning a marathon.
“We think of it like the Tour de France, where the riders in front are blocking the wind for the actual winner,” says Miller, dubbing the process as a group sport where the initial sperm clears the way and help break through protective cells for the last guy to arrive at the egg.
The work, too, casts new light on the mystery behind how steroids like progesterone, which triggers cell reactions in a number of days or instantly, actually perform. This new research can inform scientists about steroid signaling in sperm along with many other cells.
The findings are published March 17 in the journal Science.
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