The first crucial step in the fertilization process between the sperm and egg has been discovered by researchers at the Wellcome Trust Sanger Institute. The researchers, who found the essential protein for fertilization, contend that such a discovery can help to improve fertility treatments and develop new contraceptives.

Researchers specifically found interacting proteins on the surface of the sperm and egg that are essential to the formation of new mammalian life. These proteins enable the sperm and the egg to recognize each other.

The process of fertilization takes place when an egg and sperm recognize one another and join together, forming an embryo. The Izumo protein, which is displayed on the sperm that recognizes the egg, was first identified in 2005 by Japanese researchers. They named the protein Izumo after a Japanese marriage shrine, but up until now, its mate on the egg has remained unknown.

The team of researchers found a single protein that, when paired with Izumo, is essential for fertilization. This protein is called Juno in honor of the Roman goddess of fertility and marriage.

Dr. Gavin Wright, senior author from the Sanger Institute, told EurekAlert, “We have solved a long-standing mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived.” He explained, “Without this essential interaction, fertilisation just cannot happen. We may be able to use this discovery to improve fertility treatments and develop new contraceptives.”

The scientists created an artificial version of the Izumo protein then used it to identify binding partners on the egg’s surface. When taking this approach, they found that Izumo on the sperm interacted with Juno on the egg’s surface, initiating fertilization.

Dr. Enrica Bianchi, first author from the Wellcome Trust Sanger Institute, told EurekAlert, “The binding of the two proteins is very weak, which probably explains why this has remained a mystery until now.”