How Sperm Home In On Eggs

Researchers have identified a calcium transporter on the cell membranes of sperm that plays a role in sperm mobility.

AsianScientist (Nov. 27, 2018) – A protein in the cell membranes of sperm that enables them to move towards egg cells has been identified by Japanese researchers. The scientists published their findings in Scientific Reports.

Sperm, bacteria and other microscopic organisms sense varying concentrations of chemicals in their environment—concentration gradients—to approach or avoid something. This is a process known as chemotaxis.

In this study, a team of scientists led by Professor Manabu Yoshida from the Misaki Marine Biological Station at the University of Tokyo, Japan, studied chemotaxis in sperm from sea squirts—brainless tubular creatures that are only mobile as larvae.

The researchers used a technique known as affinity column chromatography to isolate the attractant released by the sea squirt egg. Subsequently, laser-based mass spectrometry helped identify what chemicals were present in sperm and egg samples. A high-speed camera was also used to view sperm behavior in slow motion.

“We identified that a calcium transport protein—plasma membrane Ca2+ ATPase (PMCA)—has a key role in sperm chemotaxis,” said Yoshida. “PMCA is abundant in the tails or flagella membranes of the [sea squirt’s] sperm. It binds to the species-specific attractant and alters how the flagella waves, thus directing movement of the sperm cell.”

“With these methods we also found PMCA responsible for regulating cellular calcium, which makes it a promising target for drug research,” Yoshida added.

The article can be found at: Yoshida, et al. (2018) Ca2+ Efflux via Plasma Membrane Ca2+- ATPase Mediates Chemotaxis in Ascidian Sperm.


Source: University of Tokyo; Photo: Shutterstock.
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