IZUMO1

Function

The sperm-specific protein Izumo, named for a Japanese shrine dedicated to marriage, is essential for sperm-egg plasma membrane binding and fusion.

Studies have shown that male Izumo knockout mice are sterile because their sperm are unable to fuse to the oocyte membrane.[1] Izumo -/- mice produced morphologically normal sperm that were able to penetrate the zona pellucida, but could not fuse with to the eggs. In-vitro human experiments have also been conducted, suggesting that Izumo is required for human gamete fusion. [1]

Through the use of Western Blot analyses, it has been shown that Izumo is only expressed in the testis and is found on mature spermatozoa. Izumo-1 located on mature spermatozoa that have undergone capacitation binds to its receptor Juno, which is located on the oolemma of eggs.