Izumo sperm-egg fusion protein 1 (Sperm-specific protein izumo) is encoded in humans by the IZUMO1gene.[5] In mammalian fertilisation, IZUMO1 binds to its egg receptor counterpart, Juno, to facilitate recognition and fusion of the gametes. [6]
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 fact, it is necessary to relocate the IZUMO1 to the site of oocyte fusion.[8] 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. [9] Izumo-1 located on mature spermatozoa that have undergone capacitation binds to its receptor Juno, which is located on the oolemma of eggs. [10]
^Ikawa, M., Inoue, N., Benham, A. M., & Okabe, M. (2010). Fertilization: a sperm's journey to and interaction with the oocyte. The Journal of clinical investigation, 120(4), 984-94.
^ Ellerman DA, Pei J, Gupta S, Snell WJ, Myles D, Primakoff P. Izumo is part of a multiprotein family whose members form large complexes on mammalian sperm. Molecular reproduction and development. 2009;76(12):1188-1199.
^ Bianchi E, Doe B, Goulding D, Sanger Mouse Genetics Project, Wright GJ. Juno is the egg Izumo receptor and is essential for mammalian fertilisation. Nature. 2014;508(7497):483-487.
