Study, traumas are inherited. From parents to children and grandchildren up to the third generation

Researchers at the Brain Research Institute at the University of Zurich have managed to identify small fractions of genetic material called microRNA. These are short sequences, vehicles with which instructions to build proteins are transmitted but also preserve the memory of traumatic events.

They leave indelible scars, marks that have been handed down for generations. Traumas can be hereditary, fears pass from father to son. And mark lives. These genetic transmissions have been studied in mice but probably also affect humans.

The process by which traumas can be passed down to the third generation. The secret of this inheritance lies in microRNAs, genetic molecules that regulate the functioning of cells, organs and tissues. Trauma alters these ‘molecular directors’, and the defect is passed on to the offspring through gametes. To unveil a mechanism so far mysterious is a study by the University of Zurich, published in ‘Nature Neuroscience’.

Coordinated by Isabelle Mansuy, researchers at the Brain Research Institute have managed to identify some key components of this process, small fractions of genetic material called microRNA. These are short sequences, the vehicles with which the instructions to build proteins are transmitted but also retain the memory of traumatic events. “There are diseases such as bipolar disorder that are passed down in the family despite not being traceable to a particular gene,” recalls Mansuy, a professor at the Swiss Federal Institute of Technology (ETH) and the University of Zurich.

To identify the mechanism, they compared adult mice that had been exposed to traumatic conditions early in life with other, non-traumatized mice. Researchers studied the number and type of microRNAs in traumatized rodents and found that traumatic stress alters the amount of numerous microRNAs in the blood, brain, and sperm fluid by excess or by default. Modifications that affect the functioning of cells regulated by these mini-molecules.

The researchers observed that the traumatized mice modified their behavior. For example, they lost their natural aversion to open spaces and light, and showed signs of depression. Characteristics that through the sperm were transferred to the offspring, even if the specimens of the progeny did not suffer stress or trauma. The metabolism of stressed mouse puppies also changed: insulin and blood sugar levels, for example, were lower than those of mice born to non-traumatized parents.

“We were able to show for the first time – summarizes Mansuy – that traumatic experiences influence the long-term metabolism, that induced changes are hereditary” and that the effects of inherited trauma on metabolism and psychological behaviors persist until the third generation. “The imbalance of microRNAs in sperm has proven to be a key factor in passing the effects oftrauma from parent to child”.

Although many questions remain open and will have to be clarified in subsequent studies, the authors point out, the conclusion is that “environmental conditioning leaves traces in the brain, organs and gametes, and through gametes these traces are transmitted to the next generation”. The Zurich team is now trying to verify whether microRNAs are also the ‘culprits’ in humans.

Taken from: La Repubblica Scienze of 13.4.2014

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