popular science

baby, you’re a firework – a story of when a sperm meets an egg

Sparks literally fly when a sperm and an egg hit it off.

Light is very often used as a pure metaphor for life — but life and light aren’t just linked poetically. Once fertilized, the human egg releases billions of zinc sparks from its surface.

So, babies, every single one of you is a literal, molecular firework.

So, scientifically and poetically speaking, life and light are the same, in a way.

Researchers at Northwestern University first discovered in 2011 when they found zinc sparks flashing at the very moment of conception in mice.

In 2014, they figured out a way to capture images of this zinc-sparking event. Using cutting-edge technology they developed, the team is the first to capture images of these molecular fireworks and pinpoint the origin of the zinc sparks: tiny zinc-rich packages just below the egg’s surface.

They achieved the holy grail of biological research in 2016: The team observed the same thing occurring in human egg cells.

How does this happen in the first place?

Egg cells rely on zinc for their most vital functions, from maturing into a healthy egg to developing into an embryo. The 2014 research published in Nature Chemistry showed that each human egg cell has around 8,000 zinc compartments, each of which contains a million zinc atoms.

When sperm meets an egg — although, as the human experiments demonstrated, all you need is a sperm enzyme — the egg releases a flurry of zinc atoms all at once.

And then — the show.

Under the researcher’s fluorescent sensor, it looks like microscopic fireworks all over the place, aka around the embryo.

Tiny explosion after tiny explosion.

And the whole spectacle lasts for up to two hours after conception.

So, every time the egg is fertilized and a human is conceived, your body celebrates with a firework.

But hold on — this isn’t just a fun spectacle, it happens to be incredibly useful.

The size of these explosions tells scientists a lot about the viability of the embryo produced.

Zinc fluctuations play a central role in regulating the biochemical processes that ensure a healthy egg-to-embryo transition, and this new unprecedented quantitative information should be useful in improving in vitro fertilization methods.

Often, we don’t have the info on whether the egg or embryo is truly viable until we see if a pregnancy happens.

That’s the reason this is so so so transformative.

If we have the ability up front to know if an egg is viable or not, it will help scientists know which embryo to transfer, avoid a lot of heartaches and achieve pregnancy much more quickly.

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