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Conception: Izumo and Juno proteins enable fusion of sperm and egg

Humans have long understood the connection between sexual intercourse and birth; and in 1876 two scientists independently described the entry of sperm into the egg and their combination into a single new nucleus. However, the scientific and medical communities have been at a loss to explain the the fundamental biology behind the initial interaction in humans and other animals until now.

Gamete insertion method
Gamete insertion method
Screenshot from https://www.youtube.com/watch?v=LJNuZQCwWaU&feature=player_embedded

On Wednesday, the journal Nature published a study by Wellcome Trust Sanger Institute researchers at Cambridge who discovered how surface proteins enable the two gametes to recognize each other, conceive, and begin life.

Japanese researchers discovered the sperm’s binding protein in 2005 and called it Izumo, after a Japanese marriage shrine. The Sanger Institute team created an artificial version of mouse Izumo, then used it to identify its single binding partner on the surface of the egg. They called the new protein Juno for the Roman Goddess of fertility and marriage equivalent to Hera in Greek mythology.

The team is now testing infertile women for defects in the Juno receptor that might cause infertility. If they find a link, health providers may be able to screen for the Juno protein easily and thus reduce the expense and uncertainty of the usual assisted fertility treatments.