What Causes Male Infertility?

New research led by researchers at Brigham and Women’s Hospital (BWH) in Boston has uncovered a new gene for male infertility. In the United States, one in six couples face infertility while trying to conceive. Male infertility is a factor in around 50% of all cases, with around one in five left unexplained. The new study sheds light on the role of genetics in male infertility, with researchers identifying an abnormality in a gene called SYCP2 as a potential cause.

Researchers investigate SYCP2-driven male infertility

The findings of the study were published in the American Journal of Human Genetics, with BWH medical geneticist and corresponding author Cynthia Morton, PhD explaining how genetic variants and abnormalities in SYCP2 are linked to low sperm count and could be a key cause of male infertility.

“We hope that our evidence will contribute to this gene being in panels for diagnosis of male infertility,” says Morton. “Infertility is a big problem for young people, and 40 to 72 percent of men lack a diagnosis. This means that we have a lot of gene finding to do. My lab has a longstanding interest in studying individuals who have a balanced chromosome rearrangement where two chromosome segments swap places. In this case, it led us to an important discovery.”

The dangers of chromosomal rearrangement

The study involved a participant known as DGAP230, a male who had an alarmingly low sperm count and two-year history of infertility by the age of 28. Together with first author Samantha Schilit, PhD, Morton and the team analysed his chromosomes and observed balanced rearrangements on numbers 20 and 22. This abnormality triggered a 20-fold increase in SYCP2 activity, a gene that's linked to male infertility.

“Balanced chromosomal rearrangements in infertile men are rarely followed up beyond reporting a risk for segregation of unbalanced gametes, which can lead to recurrent miscarriage. This work shows that a chromosomal rearrangement may also disrupt or dysregulate genes important in fertility, and therefore should be considered,” explains Schilit.

While developing treatment for SYCP2 abnormalities is a future objective, Morton asserts the findings could help assist in diagnosis and minimise the stress couples experience while trying to conceive with an infertile partner.

“A diagnosis can be therapeutic in itself - even if there isn’t something that can be done to correct it. It ends the search for the underlying issue and opens the door for enrolling in clinical trials,” says Morton. “And I believe there is good reason to be optimistic; we now have better tools for discovery and can begin on the path toward therapy.”

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