An essential component of how sperm move has been discovered, opening up new avenues for the understanding and treatment of male infertility.
Scientists at the University of Toledo, Ohio, have made a new discovery about the function of a part of the sperm that was previously thought to only act as a 'shock absorber'. What was believed to be a rigid structure in the neck of the sperm, the atypical centriole, has now been discovered to be essential for sperm movement.
Corresponding author Professor Tomer Avidor-Reiss now believes that the atypical centriole 'is an evolutionary innovation whose function is to make your sperm move better'.
For a sperm to successfully fertilise an egg in the reproductive tract, it needs powerful motility. It was previously thought that this motility was driven by another set of centrioles sliding together in the sperm's tail. This new finding, published in Nature Communications, instead showed that the atypical centriole in the sperm's neck acts as a transmission centre, coordinating the response from the tail with a 'kinking' action in the sperm's head, powering the sperm's movement. This finding challenged the belief that the head is passive as the sperm moved.
Professor Avidor-Reiss hopes that this research will open up new avenues to understanding why some men are infertile. 'If the centriole is defective, this coupling between the sperm tail and head is going to be defective... This knowledge allows us to identify a subgroup of infertile men that was not revealed before.'
The researchers involved in the study, led by PhD candidate Sushil Khanal, used a state-of-the-art technique called STORM microscopy to look at the structure of the sperm in high definition. By identifying what the function of these components is within the sperm cells, they can also understand what to expect in healthy sperm. They suggested that the kinking action of the sperm head could be responsible for sensing the reproductive tract environment whilst the swimming motion may enhance the ability of the sperm to get through the protective outer layers of the egg for fertilisation.
Professor Avidor-Reiss added that 'these studies call for a revision in our understanding of sperm centrioles both in sperm movement and in the early embryo'.
With this new understanding, the movement of the sperm and function of the centriole could be used as a test for diagnosing the cause of male infertility. Furthermore, therapies could be developed for patients that have sperm with dysfunctional centrioles.