Scientists Discover "Fireworks" in the Bedroom: Zinc Sparks in Fertilization

When a sperm cell fuses with an egg, it triggers the sudden release of zinc atoms from the egg’s surface. That’s been known since 2011. Now, for the first time ever, scientists have observed these “sparks” in action and figured out where they come from.

The Discovery of Zinc Sparks

“The egg first has to stockpile zinc and then must release some of the zinc to successfully navigate maturation, fertilization, and the start of embryogenesis,” said Dr. Thomas V. O’Halloran, a professor of chemistry and molecular biosciences at Northwestern University in Chicago and one of the scientists involved in the research.

“For the study, the researchers used a set of new imaging techniques to count and map the positions of individual zinc atoms in mouse eggs. They discovered that every egg has about 8,000 tiny compartments called vesicles, each containing about one million zinc atoms. The compartments release their contents simultaneously when the egg is fertilized.”

How Zinc Sparks Work in Egg Fertilization

Each egg has four or five of these periodic sparks, which O’Halloran described as “beautiful to see, orchestrated much like a symphony.” This discovery shows that while scientists knew that zinc was released in huge amounts, they did not know exactly how the egg was able to do this.

Implications for Fertility Treatments

The findings also have practical applications in fertility treatments. According to the researchers, the new imaging techniques may help fertility doctors identify eggs that are most likely to yield healthy embryos.

“If we can identify the best eggs, fewer embryos would need to be transferred during fertility treatments,” said Dr. Teresa K. Woodruff, an expert in ovarian biology at the university.

A paper describing the research was published in the journal Nature Chemistry.