We all (hopefully) know where babies come from. It all starts with a single sperm miraculously making contact with an egg cell. The egg cell accepts the sperm and the two cells fuse their DNA, this is the moment of conception. Up until very recently the mechanics of this process had been unclear. How is it that only a singly sperm is able to enter the egg, and furthermore how did the sperm even attach to the egg? These questions finally have some concrete answers.
When I took Cellular and Molecular Biology I learned one very important concept: when in doubt, it’s a protein. This go to tip stands true for the secret of fertilization; it is all about the proteins. Surface proteins are one mechanism cells use to communicate with each other. Previous work had identified a protein on the surface of sperm necessary for egg recognition. This protein is called Izumo.
Izumo was discovered in 2005. It wasn’t until this year that the target of this protein was discovered. Juno is to the egg what Izumo is to the sperm. Why is it that the discovery of Juno took so long? To begin with, the interaction between Juno and Izumo is short lived. In fact, upon initial contact of the two proteins, Juno begins to disappear from the egg membrane. This mechanism is designed to ensure that only one sperm can make it into the egg. Another reason for the difficulty in finding Juno is that the interactions between Juno and Izumo are weak, another mechanism designed to limit sperm access to the egg.
Both proteins are necessary for fertilization to occur. Knockout mice for either Izumo or Juno were found to be infertile. This research could lead to potential new forms of birth control. Many women are opposed to taking the pill because of the hormones they have to ingest. Other contraceptives like IUDs can be invasive. But imagine a treatment that disrupted the Juno protein. This protein is (so far) only found in egg cells, and disruption of its synthesis shouldn’t inhibit normal ovulation and menstruation. For these reasons I think it would be great to see more options for contraception being offered.
Posted by Tim Daly