It has long been regarded as the chromosome that “does not mean much” other than as a symbol of masculinity. However, despite the long-known association between the Y chromosome and gender determination, there is in fact more about the significance and roles of the Y chromosome to the human genome than what most people know. Recent studies have demonstrated the contribution of the gene content in the Y chromosome to the differences between men and women, particularly in terms of health and susceptibility towards diseases.

The risk of Alzheimer’s and cancer

To shed light on the significance of Y chromosomes to human health, Jan Dumanski, Lars Forsberg and colleagues examined the loss of this chromosome in batches of blood cells of over 3,000 male participants ranging from 37 to 96 years of age, whose data were obtained from three long-term studies. They found that participants with the highest portion of blood cells with no Y chromosome present were more prone to be diagnosed with Alzheimer’s Disease (AD).

In the study (which was published in the American Journal of Human Genetics), researchers also tested the possible effects of smoking on the loss of Y chromosomes – taking into account the fact that smoking is not only a popular risk factor for the development of Alzheimer’s, but also cancer development and tumours outside the respiratory tract, which occur more common in men than women. The results implied that smoking could considerably influence the loss of Y chromosomes, consequently increasing the risks for Alzheimer’s Disease as well as cancer.

“You have probably heard before that the Y chromosome is small, insignificant and contains very little genetic information. This is not true. Our results indicate that the Y chromosome has a role in tumour suppression and they might explain why men get cancer more often than women,” highlighted Dumanski, professor at the Department of Immunology, Genetics and Pathology, Uppsala University. He added, “We believe that analyses of the Y chromosome could in the future become a useful general marker to predict the risk for men to develop cancer.”

In a more recent study, Dumanski’s colleague Lars Forsberg also examined the negative effects of cells without the Y chromosome on normal immune cell functions. His findings revealed that defective immune functions of the affected blood cells could possibly lead to affected men to have an increased risk for mortality as well as various other disorders.

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What's the future for men?

An increased risk for pathology and mortality associated with the loss of the Y chromosome in blood cells could help to explain men’s shorter life expectancy compared to women.
An increased risk for pathology and mortality associated with the loss of the Y chromosome in blood cells could help to explain men’s shorter life expectancy compared to women.

But if the Y chromosomes disappear – does that mean the world has to prepare for a future without men?

The discovery made by a group of experts led by Professor Sun Yingli at the Beijing Institute of Genomics, who analysed the X and Y chromosomes of 72 male donors suggests that the prediction about the extinction of men due to the loss of Y chromosomes seems to be exaggerated and, perhaps, too far-fetched.

Men can breathe a sigh of relief as the study findings, published in PLoS One, reveal that the function and phenotypes of human males have been protected by a stable DNA methylation pattern for tens of thousands of years.

Another study conducted by researchers at the Whitehead Institute in Cambridge, Massachusetts led by Daniel Bellot and David Page also helps to explain why the Y chromosome should be given more credit than it deserves. In the study which was published in the journal Nature, scientists reconstructed the evolution of the Y chromosome across eight mammals.

They discovered that the human Y chromosome has lost merely one ancestral gene over the past 25 million years. Their findings point to a small set of genes preserved in the human Y chromosome which make it an essential component for male viability. “This is not just a random sampling of the Y’s ancestral repertoire. This is an elite bunch of genes,” said Page.

That having said, men should not be extremely worried that the disappearance of Y chromosomes would mean that their state of health is doomed, either. “Having loss of Y is not 100% predictive that you will have either cancer or Alzheimer’s,” says Lars Forsberg. According to Forsberg, there were men in the study who had the mutation and lived without any symptoms well into their 90s. “But in the future, loss of Y in blood cells can become a new biomarker for disease risk and perhaps evaluation can make a difference in detecting and treating problems early.” MIMS

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