Model of a DNA molecule (Image: wikipedia)
Read aloud Only very few diseases are purely hereditary, but in most of the environment mixes more or less with. This happens above all by switching genes on or off. Researchers have now been able to demonstrate for the first time how the environmental factor stress activates a gene of depression and thus increases the risk of developing depression. Similarly, all the emotions experienced, such as grief, hunger, or joy, affect the gene switches and can make you sick or healthy. The genetic material is the "book of life". Everything is written in it that makes us special. "Sex, health, intelligence, even the mate choice is more or less determined by the genetic code, " says for example in a recent magazine report. But after the decoding of the human genome, the book of life has now turned out to be a highly idiosyncratic work: depending on how the environment affects it, the letters take on a different meaning. It's a book that you basically can never close and put on the shelf as read out because its statements are constantly changing. While yesterday's genes did not signal any disease, a few months later, for example, they may report oncoming depression.

"Genes have often been given a false meaning in the past. It depends not only on their sequence of letters, but also on the fact that genes are constantly switched on and off by signals from the environment, "explains Joachim Bauer, Professor of the Department of Psychosomatic Medicine at the University Hospital in Freiburg.

Each gene is controlled by such switches. They can be influenced by environmental factors such as stress, anger, joy or grief. This happens via signal substances that dock to the gene. "If it comes here to adjustments, then we get sick, " says Bauer. The position of the switch - the "on" or "off" - determines the well being of a person.

For example, in breast cancer, each tumor form has a characteristic pattern of gene switches. Apparently lifestyle and external influences have their fingers in the game tremendously, by adjusting the levers on the gene. On the other hand, the risk of breast cancer, which alone contributes to the letter sequence of the genes, is small. "In fact, only five percent of all breast cancer patients carry mutations in the known breast cancer genes BRCA 1 or BRCA 2. All other breast cancer patients - the vast majority - will suffer from cancer without hereditary factors, " emphasizes Bauer. This gives us an idea of ​​how severe the effects of the environment weigh on health and how important a point of attack, namely the switch on the gene, must be. display

"There are almost no diseases that are not determined by the environment, " affirms Klaus-Peter Lesch, professor in the Department of Psychiatry and Psychotherapy of the University of Würzburg. Only one to two percent of all diseases are purely hereditary. These include the respiratory disease cystic fibrosis or the disorder of the chorea Huntington. Although the disease with the genotype is predetermined in these cases, the severity of the lifestyle can be mitigated.

In most diseases, the hereditary predisposition is only the shell. Lesch's team is concerned with the influence of the environment on depression. There are some non-specific risk genes, but their influence is extremely low. The genes could, however, reinforce each other's effects and thereby significantly increase the risk of depression.

But before that happens, the environment has a say in it. For example, researchers recently showed how stress works. "During stress, hormones like cortisol are released. These stress hormones are used to send out signaling substances that bind to specific gene switches, which in turn determine whether a gene is active or not, "explains Lesch. At the end of the cascade, stress can turn a gene on or off. The group led by the Würzburg researchers showed that one of the many depressive genes is activated in this way.

Even in early childhood, stress hormones apparently adjust the sensitivity of the gene switch. "With balanced emotional attention, the child can handle stress even better later. The switches of the genes are apparently set robustly in the early development phase. Later, they can not be easily changed again, "says Lesch.

The brain transforms experience of interpersonal relationships into messenger substances. These signals initiate biological reaction chains in the body, which act into the cells and there on the activity of the genes. In this way joy, grief or hunger, in short all the emotions experienced, leave their mark on the gene switch. So far, only for stress the exact mechanism is known how to do that.

But researchers believe that other environmental factors trigger similar chain reactions that tip the switch. Genes are never fate, is the conclusion of the researchers. They are the framework in which our lives take place. The book of life is an adventure novel in which only the frame story is established. It stays exciting until the end of our lives.

ddp / Susanne Donner

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