Scientists show how sperm and egg come together like a key in a lock at the beginning of life

New life begins with the meeting of sperm and egg. But how they merge with each other has long been a mystery.

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

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

The team found that three proteins on the sperm combine to form a kind of key that unlocks the egg and allows the sperm to attach. Their results come from studies of zebrafish, mice and human cells and show how this process continues over millions of years of evolution. The results were published Thursday in the journal Cell.

Scientists previously knew 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 AlphaFold artificial intelligence tool – whose developers were awarded 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 works in living things.

Until now, it was not known how the proteins “worked together as a team to enable sperm and eggs to recognize each other,” Pauli said.

Scientists still don’t know how the sperm actually gets into the egg after attachment, and they hope to study this in more detail next.

Ultimately, Pauli says, such work could help other scientists better understand infertility or develop new contraceptive methods.

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

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

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