Scientists show how sperm and egg come together like a key in a lock

How a sperm and an egg fuse has long been a mystery.

New research by scientists in Austria provides tantalizing clues, showing that fertilization works like a key throughout the animal kingdom, from fish to humans.

“We have discovered this mechanism that, as far as we know, is fundamental to all vertebrates,” says co-author Andrea Pauli from the Research Institute of Molecular Pathology in Vienna.

The team discovered that three proteins on the sperm come together to form a kind of key that unlocks the egg, allowing the sperm to attach. Their findings, drawn from studies in zebrafish, mice and human cells, show how this process has persisted over millions of years of evolution. The results were published Thursday in the journal Cell.

Scientists were previously aware of two proteins, one on the surface of the sperm and one on the membrane of the egg. Working with international collaborators, Pauli’s lab used Google DeepMind’s artificial intelligence tool AlphaFold – whose developers received a Nobel Prize earlier this month – to help them identify a new protein that enables the first molecular connection between sperm and egg. They also showed how it functions in living things.

It was not previously known how the proteins “worked as a team to ensure that sperm and egg could recognize each other,” Pauli said.

Scientists still don’t know how the sperm actually gets into the egg after it attaches, and hope to delve deeper into that next.

Ultimately, Pauli said, such work could help other scientists better understand infertility or develop new methods of contraception.

The work provides targets for the development of male contraceptives in particular, says David Greenstein, an expert in genetics and cell biology at the University of Minnesota who was not involved in the study.

The latest study “also underlines the importance of this year’s Nobel Prize in Chemistry,” he said in an email.

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