Sperm Meets Egg: How The Magic Really Happens

Sex Ed made it seem so simple: Join one gamete with another, and a new human is formed! We know that a man's sperm must complete a long and arduous journey to a woman's egg, and then — poof — expect an adorable baby to pop out kicking and screaming in approximately 38-42 weeks. But how, exactly, does that sperm even know that an egg is an egg?

The conception process is actually more complicated than our 7th-grade biology teacher would have us believe. Back in 2005, scientists discovered a protein — which they dubbed Izumo, after a Japanese marriage shrine — that exists on the surface of sperm cells and is essential for the sperm to recognize the egg. Still, how does this protein actually interact with the egg cell? That part remained a mystery — until now.

Yesterday, the news broke that researchers at the Wellcome Trust Sanger Institute discovered a protein called Juno (for the Greek goddess of fertility) that interacts with the Izumo protein in what they believe is the critical first step in the conception process. The proteins are attracted to one another and form a weak bond before the sperm actually fertilizes the egg and forms the zygote.

Possibly the most exciting thing about this discovery is that scientists are already exploring potential fertility treatments that will address irregularities in how the Juno and Izumo proteins function. (Because, if either protein is faulty, tough luck getting pregnant.) And, it doesn't stop there: According to the study's author, Dr. Gavin Wright, "We may be able to use this discovery to develop new contraceptives." All this from a couple of protein molecules? Well done, science. (Science Daily)