1 in 500 men may carry an extra sex chromosome
In a study published in Genetics in medicine, researchers analyzed genetic data collected on more than 200,000 British men aged 40 to 70 from UK Biobank, a biomedical database and research resource containing genetic, lifestyle and health information. anonymized half a million UK participants. They found 356 men who carried either an extra X chromosome or an extra Y chromosome.
The sex chromosomes determine our biological sex. Males usually have one X chromosome and one Y chromosome, while females have two Xs. However, some males also have an extra X or Y chromosome – XXY or XYY.
Without genetic testing, this may not be immediately obvious. Males with extra X chromosomes are sometimes identified during investigations of delayed puberty and infertility; however, most are unaware that they have this condition. Males with an extra Y chromosome tend to be taller than males and adults, but otherwise have no distinguishing physical characteristics.
In today’s study, researchers identified 213 men with an extra X chromosome and 143 men with an extra Y chromosome. Given that UK Biobank participants tend to be “healthier” than the general population, this suggests that around one in 500 men may carry an extra X or Y chromosome.
Only a small minority of these men had a diagnosis of sex chromosome abnormality in their medical records or by self-report: less than one in four men (23%) with XXY and only one of the 143 men with XYY (0.7 %) had a known diagnosis.
By linking genetic data to routine health records, the team found that men with XXY had significantly higher risks of reproductive problems, including a three times higher risk of delayed puberty and a four times higher risk higher to be childless. These men also had significantly lower blood levels of testosterone, the natural male hormone. Men with XYY appeared to have normal reproductive function.
Men with XXY or XYY had higher risks of several other health problems. They were three times more likely to have type 2 diabetes, six times more likely to develop venous thrombosis, three times more likely to have a pulmonary embolism, and four times more likely to have chronic obstructive pulmonary disease ( COPD).
The researchers say it’s not clear why an extra chromosome should increase the risk or why the risks were so similar regardless of which sex chromosome was duplicated.
Yajie Zhao, a PhD student at the University of Cambridge’s Medical Research Council (MRC) Epidemiology Unit, first author of the study, said: “Even though a significant number of men carry an extra sex chromosome, very few of them are likely to be aware of this. This extra chromosome means they have significantly higher risks of a number of common metabolic, vascular and respiratory diseases – diseases that can be prevented.
Professor Ken Ong, also from the MRC’s Epidemiology Unit in Cambridge and co-lead author, added: ‘Genetic testing can detect chromosomal abnormalities quite easily, so it could be useful if XXY and XYY are more widely tested in men who come to their doctor. with a relevant health problem.
“We would need more research to assess whether there is additional value in broader screening for unusual chromosomes in the general population, but it could potentially lead to early interventions to help them avoid associated diseases.”
Professor Anna Murray, from the University of Exeter, said: ‘Our study is important because it starts from genetics and tells us about the potential health impacts of having an extra sex chromosome in an older population, without being biased by only testing men with certain characteristics as has often been done in the past.
Previous studies have shown that about one in 1,000 women have an extra X chromosome, which can lead to delayed language development and accelerated growth until puberty, as well as lower IQs than their peers.
Reference: Zhao Y, Gardner EJ, Tuke MA, et al. Detection and characterization of male sex chromosomal abnormalities in the UK Biobank study. Broom. Medium. 2022. doi: 10.1016/j.gim.2022.05.011
This article was republished from the following materials. Note: Material may have been edited for length and content. For more information, please contact the quoted source.