Scientists have found an explanation for greater risk of autism in boys. / mizina, stock.adobe.com
Heidelberg – Autism happens 4 times more often in boys than in girls. For the first time, scientists from the Department of Molecular Human Genetics at the University Hospital of Heidelberg found an explanation: their research on human cells and brain areas of mice has shown that testosterone male sex hormones significantly activate certain genetic risks in the brain before and after delivery. The results were in Frontiers in Molecular Neuroscience published (2018; doi: 10.3389 / fnmol.2018.00337).
So far it is known that defects in these specific genes are a powerful risk factor for the development of neuronal developmental disorders. New findings suggest that these genetic defects may have a greater impact on the brain than male and female individuals.
"Now we have the first indication why – at least in relation to an important group of multiple risk genes – boys have a significantly higher risk of autism than girls," says chief author Gudrun Rappold, director of the Department of Molecular Human Genetics.
Tests of their group showed that in the young brain of male mice certain genes called SHANK 1, 2 and 3 are increasingly translate into proteins and affect it to higher levels of testosterone in the sex hormone. The Heidelberg Research Group has been researching the SHANK gene for years because defects in these parts of genetic information play an important role in the development of autism and other mental illnesses.
More testosterone – more protein bars
For tests, the team used a baby cell culture cell (neuroblastoma) as a model for the development of nerve cells. Scientists have found in these cells that the activation of the SHANK gene depends on binding testosterone to the androgen receptor. When this receptor is blocked, strong risk activation has disappeared. "We could confirm this in research in brain areas of young mice in which this androgen receptor does not form: they are activated significantly weaker than in control animals with intact receptors," explains Simone Berkel, this study together with PhD student Ahmed Eltokhij.
Researchers also studied the amount of warts in the brain of young male and female mice before and after birth. In male animals, which naturally have more testosterone in the blood and brain, significantly higher protein bar levels have been found than in women. "We believe that a larger amount of protein bars in the male brain increases the" impact "of the deficiencies in the SHANK genes and therefore leads to greater risk of autism," concludes Rappold.
In autism, a disorder is the development of nerve cells in the brain. One of the 68 children (about 1.5%) was affected. Typical symptoms are noticeable early, so the diagnosis is usually made before the age of 3 years. Autistic people have difficulties in social interaction, communication and perceptual treatment and often show intense, special interests and abilities, as well as recurring and narrow (restrictive) patterns of behavior. However, these characteristics of autistic behavior can vary widely from patient to patient – hence the autistic spectrum. © idw / energy / aerzteblatt.de