A Northwestern University Feinberg School of Medicine led interdisciplinary research team has found that after fertilization mammalian egg releases from its surface billions of zinc atoms in 'zinc sparks,' one wave after another. Zinc fluctuations play a prime role in regulating the biochemical processes that ensure a healthy egg-to-embryo transition, and this new information should be useful in improving in vitro fertilization methods.
The researchers developed four physical methods to determine how much zinc there is in an egg and where it is located at the time of fertilization and in the two hours just after. They used it to capture images of these molecular fireworks and pinpoint the origin of the zinc sparks waves (tiny zinc-rich packages just below the egg's surface) in three dimensions.
Author Thomas V. O'Halloran said, "On cue, at the time of fertilization, we see the egg release thousands of packages, each dumping a million zinc atoms, and then it's quiet. Then there is another burst of zinc release. Each egg has four or five of these periodic sparks. We knew zinc was released by the egg in huge amounts, but we had no idea how the egg did this."
The researchers are working to see if they can correlate zinc sparks with egg quality. Author Teresa K. Woodruff said, "The amount of zinc released by an egg could be a great marker for identifying a high-quality fertilized egg, something we can't do now. If we can identify the best eggs, fewer embryos would need to be transferred during fertility treatments. Our findings will help move us toward this goal."
The study titled 'Quantitative mapping of zinc fluxes in the mammalian egg reveals the origin of fertilization-induced zinc sparks' is published in the journal 'Nature Chemistry'.