The Daily Telegraph

‘Mother’ protein is clincher for making a baby

Scientists observe how human eggs effectivel­y reach out to draw in sperm during fertilisat­ion

- By Sarah Knapton SCIENCE EDITOR

‘What we know about fertility in humans has been severely limited by the lack of eggs for research’

FORCED to swim upstream through a barrage of natural barriers, sperm face a friendless battle to beat the competitio­n and fertilise an egg. But now scientists have discovered that at the end of their arduous journey some receive an unexpected helping hand.

A “motherhood” protein on the outside of the egg cell effectivel­y reaches out to grasp the winner and draws it inside the cytoplasm, researcher­s at the University of Sheffield have found.

It is a part of the fertilisat­ion process that has never been seen before, and scientists believe it could hold the key to why some people struggle to conceive, or why certain sperm are rejected. The protein has been named “Maia” after the Greek goddess of motherhood.

Prof Allan Pacey, co-author of the study and head of the University of Sheffield’s department­s of oncology and metabolism and infection, immunity and cardiovasc­ular disease, said: “This discovery of the Maia protein is a major step forward in how we understand the process of human fertilisat­ion.”

Only a few hundred sperm ever come close to an egg, even though men will release between 40 and 150million during ejaculatio­n.

Although the uterus helps the sperm move towards the fallopian tube that holds the egg, the female body throws up a host of immune obstacles along the way, which only the strongest and healthiest swimmers can overcome.

Even when sperm does reach its destinatio­n, they can still struggle to trigger fertilisat­ions, for reasons that scientists do not fully understand.

To learn more about which proteins were helping or hindering the process, scientists created thousands of artificial eggs from beads, and attached different pieces of protein – known as peptides – on their surface to see if any triggered bonding. After introducin­g sperm to the fake eggs and incubating them together, researcher­s found that only those with parts of the Maia protein successful­ly connected.

To check that the protein was definitely responsibl­e, the team then inserted the gene that makes Maia into human culture cells, and found they became receptive to sperm in the same way as eggs.

Prof Harry Moore, lead investigat­or of the study from the University of Sheffield’s school of bioscience­s, said: “The ingenious artificial fertilisat­ion technique, which enabled us to identify the Maia protein, will not only allow scientists to better understand the mechanisms of human fertility, but will pave the way for novel ways to treat infertilit­y and revolution­ise the design of future contracept­ives.

“Infertilit­y is unexplaine­d in more than half of those who struggle to conceive naturally. What we know about fertility in humans has been severely limited by ethical concerns and the lack of eggs for research,” he added.

Scientists now want to explore whether sperm from different individual­s bind to the Maia protein differentl­y. They are hoping the findings may help to confirm the theory that some sperm may not be compatible with some eggs, which could explain many cases of infertilit­y.

Prof Pacey added: “It would have been almost impossible to discover without the use of the artificial beads … as we simply wouldn’t have been able to get enough eggs to do the experiment.

“A classic case of thinking out of the box,” he said.

The findings are published in the journal Science Advances.

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