( Researchers have identified a key compo...)How sperm crack the whip

Researchers have identified a key component of the mechanism spermatozoa use to abruptly convert their tail motion from a steady swimming undulation to the whip-cracking snap that thrusts them into an egg. The finding opens a new research pathway that the researchers said could help scientists both recognize new forms of male infertility and design new contraceptives to thwart sperm entry into the egg.

What's more, they said, the exquisitely delicate analytical technique they used to eavesdrop on the electrical currents inside the squirming sperm cell could literally open a new window into its largely mysterious inner workings.

Howard Hughes Medical Institute investigator David E. Clapham and his colleagues published their findings in the February 9, 2006, issue of the journal Nature. Lead author on the paper was Yuriy Kirichok and the other co-author was Betsy Navarro, both in Clapham's laboratory at Harvard Medical School.

According to Clapham, it has long been known that a spermatozoa's arrival in the alkaline environment of the female reproductive tract triggers its tail's whiplike motion, called hyperactivation. In 2001, the researchers showed that a protein called CatSper1, found only in the sperm tail, was required for male fertility. Subsequently, with colleagues at the University of Washington and at the University of Texas Southwestern, CatSper was found to be required for hyperactivation. CatSper proteins are components of pores in the sperm cell membrane called ion channels. In an alkaline environment, these pores open and allow calcium to enter the cell.

In earlier experiments, the researchers had attempted to study the CatSper ion channel with a technique called patch clamp recording. In this widely used method of studying electrical activity in cells, a tiny hollow pipette is snugged tightly against the cell membrane. With gentle suction, the membrane is delicately ruptured, opening a window into the cell that
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Source:Howard Hughes Medical Institute

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