This microscope image provided by Osaka University and the Research Institute of Molecular Pathology in October 2024 shows the fertilization of a mouse egg marked in red and green. The DNA is marked in blue, visible in the egg cell at the top and in a sperm cell at the bottom left. Credit: Yonggang Lu/Osaka University/IMP via AP
How a sperm and an egg fuse has long been a mystery.
New research by Austrian scientists provides tantalizing clues, showing that fertilization works like a lock and key throughout the animal kingdom, from fish to humans.
“We discovered this mechanism which, to our knowledge, is really fundamental in all vertebrates,” said co-author Andrea Pauli of the Research Institute of Molecular Pathology in Vienna.
The team discovered that three proteins found in sperm join together to form a sort of key that unlocks the egg, allowing sperm to attach to it. Their findings, drawn from studies of 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 previously knew of two proteins, one on the surface of the sperm and another on the membrane of the egg. Working with international collaborators, Pauli’s lab used AlphaFold, Google DeepMind’s artificial intelligence tool, whose developers received a Nobel Prize earlier this month, to help them identify a new protein that allows the first molecular connection between sperm and egg. They also demonstrated how it works in living beings.
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This microscope image provided by the Molecular Pathology Research Institute in October 2024 shows the fertilization of a zebrafish (Danio rerio) egg by a sperm, marked in orange. Credit: IMP via AP
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This electron microscope image provided by the Research Institute of Molecular Pathology in October 2024 shows zebrafish sperm bound to the sperm entry site of a zebrafish egg. Credit: IMP via AP
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This microscope image provided by the Research Institute of Molecular Pathology in October 2024 shows human sperm. Credit: IMP via AP
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This microscope image provided by Osaka University and the Research Institute of Molecular Pathology in October 2024 shows mouse eggs, marked in red and green, and sperm, marked in blue. Credit: Yonggang Lu/Osaka University/IMP via AP
It was previously unknown how the proteins “worked together as a team to allow sperm and eggs to recognize each other,” Pauli said.
Scientists still don’t know how sperm actually enter the egg after attachment and hope to explore this further next.
Ultimately, Pauli said, such work could help other scientists better understand infertility or develop new methods of birth control.
This work provides targets for the development of male contraceptives in particular, said 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 “underscores the importance of this year’s Nobel Prize in Chemistry,” he said in an email.
More information:
Victoria E. Deneke et al, A conserved fertilization complex links sperm and eggs in vertebrates, Cell (2024). DOI: 10.1016/j.cell.2024.09.035
Journal information:
Cell
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