Testosterone activates risk genes for autism


Boy is sitting alone in the water. / mizina, stock.adobe.com

Scientists have discovered an explanation for the increased risk of autism in boys. / mizina, stock.adobe.com

Heidelberg – Autism occurs 4 times more in boys than in girls. For the first time, scientists in the Department of Molecular Human Genetics at the University Hospital of Heidelberg have discovered an explanation: their studies in human cells and brain areas of mice have shown that the male sex hormone testosterone significantly activates certain risk genes in the brain before and after birth . The results were Borders in Molecular Neuroscience published (2018; doi: 10.3389 / fnmol.2018.00337).

Until now, it is only known that defects in these specific genes are a strong risk factor for the development of neuronal developmental disorders. The new findings suggest that these genetic defects may have a greater impact on the brains of males than females.

"We now have a first indication of why – at least in relation to an important group of the many risk genes – boys are significantly more at risk of autism than girls," says senior author of Gudrun Rappold, director of the Department of Genetics Human Molecular.

Tests from his group showed that in the young brain of male mice certain genes called SHANK 1, 2 and 3 are increasingly translated into proteins and this is influenced by higher levels of the sex hormone testosterone. The Heidelberg research group has been researching SHANK genes for years, because defects in these sections of genetic information play an important role in the development of autism and other mental illnesses.

More Testosterone – More Paw Protein

For the tests, the team used a culture of childhood brain tumor cells (neuroblastoma) as a model for the development of nerve cells. Scientists have discovered in these cells that the activation of SHANK genes is dependent on the binding of testosterone to an androgen receptor. When this receptor was blocked, the strong activation of the risk genes disappeared. "We were able to confirm this in studies in areas of the brain of young mice in which this androgen receptor is not formed: they were activated significantly weaker than in control animals with intact receptors," explains Simone Berkel, along with PhD student Ahmed Eltokhi conducted.

The researchers also studied the amount of protein in the brain of both male and female mice before and after birth. In male animals, which naturally have more testosterone in the blood and brain, significantly higher levels of Shank proteins were found than in females. "We believe that the greater amount of stem protein in the male brain increases the" impact "of defects in SHANK genes and therefore leads to an increased risk of autism," concludes Rappold.

In autism, the development of nerve cells in the brain is disturbed. One in 68 children (about 1.5%) is affected. The typical symptoms are noticeable early, so the diagnosis is usually made before the third year of life. Autistic people have difficulties in social interaction, communication and perceptual processing, and often show intense and special interests and abilities, as well as repetitive and restricted (restrictive) behavioral patterns. However, these characteristics of autistic behavior can vary widely from patient to patient – one of them, therefore, speaks of a spectrum of autism. © idw / energy / aerzteblatt.de


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