A new DNA study by Swiss researchers and scientists from the University of Washington School of Medicine has explained why girls are less likely than boys to have an autism spectrum disorder, Newsmax Health reports. The study, which was published in the American Journal of Human Genetics, showed that girls need more serious genetic abnormalities to develop autism, while boys are diagnosed with this disorder even if they have mild genetic mutations.
'Girls tolerate neurodevelopmental mutations more than boys do. This is really what the study shows. To push a girl over the threshold for autism or any of these neurodevelopmental disorders, it takes more of these mutations. It's about resilience to genetic insult,' said study author Sebastien Jacquemont, an assistant professor of genetic medicine at the University Hospital of Lausanne, in Switzerland.
The researchers analyzed about 16,000 DNA samples and sequencing data sets from people with neurodevelopmental disorders, including autism spectrum disorders. They also analyzed almost 800 families affected by autism. During the study, the researchers paid much attention to the copy-number variants (CNVs, individual variations in the number of copies of a particular gene) and single-nucleotide variants (SNVs, DNA sequence variations affecting a single nucleotide, which is the basic building block of DNA). It turned out that girls diagnosed with any neurodevelopmental disorder had more harmful CNVs than boys who were diagnosed with the same disorder. As for girls who suffered from autism, they turned out to have more harmful SNVs than boys with the same condition.
At first, the scientists thought that this could be somehow connected to sex chromosomes. 'The presumption has been, 'Well gee, boys have a Y chromosome and girls don't, so are there problems with the Y chromosome that explain it?'' said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven & Alexandra Cohen Children's Medical Center of New York.
But then it turned out that they were wrong, and these genetic differences are not limited to sex chromosomes.
'Women seem to be a little more resilient in terms of being able to have minor abnormalities without having a developmental problem,' Adesman said. Yet the researchers do not know why this is so.
Anyway, this research opens the door for new avenues of study.
'One study that might be helpful would be trying to understand what are the symptoms that appear a lot faster in males than females. There are a lot of alleys that could be explored,' Jacquemont said.
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