It’s a story as old as time a boy meets girl, sperm meets egg, girl has baby, and they all live happily after. If only it were that simple!
Real life, unfortunately, is far more fraught and complex than this old tale. Let’s look at the ‘sperm meets egg’ part of that story.
Although the route the sperm take is only around 6 inches, it makes the Hunger Games look like a walk in the park! Aside from the ordeal of the length of the journey itself, the 250 million sperm ‘contestants’ in the race are then eliminated by a series of challenges and barriers which include:
- Vaginal pH: not all sperm can survive the acidity of the vagina
- Female immune system: this recognises sperm cells as enemies and tries to eliminate them
- Cervical mucous: only the strongest and most persistent swimmers can get through this glue-like barrier
- Physical barriers: some sperm are caught in cavities, known as ‘vaginal crypts’, within the female reproductive tract
Of those 250 million ‘contestants’ only a few hundred will make it to the finish line, and only one will fertilise the egg.
So what is it that activates the sperm and tells the sperm to keep on swimming? According to new research undertaken by Yale School of Medicine in the US, it is a sperm protein molecule known as EFCAB9, which is found along the tails of sperm cells.
This protein is what tells the sperm to activate and go racing off, and it does this by reacting with a specific channel called CatSper, which sperm use to detect their surroundings.
Dr Jean-Ju Chung of Yale School of Medicine, the senior author of the study explained, “This molecule is a long-sought sensor for the CatSper channel, which is essential to fertilization and explains how sperm respond to physiological cues.”
To test their hypothesis, the Yale researchers created male mice that were missing EFCAB9. They found that these mice impregnated fewer females, and when they did impregnate, fewer babies were born. In the laboratory, sperm from these mice were also less active and less effective at fertilizing female eggs.
Potentially, this is a very interesting discovery because it opens the door to future treatments targeting EFCAB9 that could enhance human male fertility increasing the chances of conception.
Watch this 40 second video.
