Researchers Discover a New Method of Sperm Separation
Updated: Oct 11, 2019
While gender selection is illegal in countries such as Canada, Australia, and China, it is an accepted practice in the US. Techniques such as sperm separation and embryo genetic testing are performed to allow individuals to select the gender of their child.
There are a variety of reasons why people may opt for gender selection, including family balancing and preventing inheritance of sex-linked diseases.
In sperm separation, researchers take advantage of weight differences between X- and Y-sperm (X-chromosomes contain more genes than Y-chromosomes). Separated sperm are then used to fertilize eggs to increase the likelihood of producing an embryo with the desired gender.
Researchers at the University of Michigan set out to investigate differences in gene/receptor expression in X-sperm and Y-sperm. They also aimed to explore if these differences can be exploited to effectively separate X-sperm and Y-sperm.
The researchers found several genes encoded exclusively by X chromosomes in mouse sperm, eighteen of which were found to encode surface receptors such as TLR7 and TLR8. These receptors have a common ligand, resiquimod (R848), that the researchers used for the sperm separation procedure. When R848 was added to sperm samples, the researchers observed reduced velocity of X-sperm. This reduced the amount of X-sperm that would swim up when placed in a test tube that contained a nutrient-rich layer at the top.
Next, the researchers used either sperm collected from the top or bottom layer of the tube to fertilize mice. They found that when fast sperm were used, 83% of mice offspring were male. The use of slower swimming sperm resulted in offspring that were primarily female (81%).
R848 was found to significantly reduce the levels of ATP produced in X-sperm, which resulted in slower swimming rates. This occurred without affecting fertilization rates of the sperm.
While this innovation has several potential uses in areas such as farming-- where farmers could produce animals of a specific gender to increase profit--, scientists such as Alireza Fazeli (Tartu University) are concerned about the impact this technology may have in humans. Especially as this chemical could potentially be made widely available for consumer-use.
“I am concerned about the social impact of this. It’s so simple. You could start to do it in your bedroom. Nobody would be able to stop you from doing it.
While R848 did not seem to affect fertilization or birth rates, the long term effects of this chemical are unknown, and as such, the researchers strongly warn against its use in humans at least until further studies are performed.