Only a few hundred sperm come close to an egg, although men will release 40 to 150 million during ejaculation.
While the uterus helps sperm move toward the fallopian tube that contains the egg, the female body throws up a series of immune obstacles along the way that only the strongest and healthiest swimmers can overcome.
Even when the sperm reach their destination, they can still struggle to trigger fertilizations, for reasons scientists don’t fully understand.
The sperm attaches to the egg with the protein Maia
To learn more about which proteins were helping or hindering the process, the scientists created thousands of artificial eggs from beads and attached different pieces of proteins, known as peptides, to their surface to see if any link
After introducing sperm into the fake eggs and incubating them together, the researchers found that only those with parts of the Maia protein successfully attached.
To check that the protein was definitely responsible, the team inserted the gene that makes Maia into human cultured cells and found that they became receptive to sperm in the same way as eggs.
Professor Harry Moore, lead researcher on the study from the University of Sheffield’s School of Biosciences, said: “The ingenious artificial fertilization technique that allowed us to identify the Maia protein will not only allow scientists to better understand the mechanisms of human fertility, but also pave the way for new ways to treat infertility and revolutionize the design of future contraceptives.