Can a traumatic experience, or any change in our lifestyle be transmitted genetically to our children? This phenomenon, called Epigenetic inheritance has been linked in a multitude of diseases, from obesity to psychiatric problems like bipolar disorder where there is a gene that is clearly identified. But up to this date, no mechanism by which this occurs has been identified. A team of scientists from the Institute of Brain Research at the University of Zurich Switzerland, offer the key in the magazine «Nature Neuroscience».
Their work suggests that the environment leaves traces in the brain, organs and also in the gametes. And that it is through small fragments of RNA of sperm that we can pass the traces of our experience to the next generation.
Researchers have studied the molecular processes involved in non genetic inheritance of the symptoms induced by trauma in early life behavior and have identified a key component of these processes: the short RNA molecules. These RNA are synthesized from the genetic information (DNA) of enzymes that read specific sections of DNA (genes) and use them as templates to produce the corresponding RNA and, then, other enzymes fit these RNA to mature forms. Cells contain a large number of different short RNA called microRNA molecules and have regulatory functions, as they control the number of copies of a particular protein.
For a long time is has been known in psychology that traumatic experiences may induce behavioral disorders that are transmitted from one generation to the next but only recently have scientists begun to understand the physiological processes underlying hereditary trauma. There are diseases, such as bipolar disorder, that occur in families, but are not linked back to a particular gene, explains Isabelle Mansuy, director of this study.
The researchers studied the number and type of microRNA expressed by adult mice exposed to traumatic conditions in early life and compared them to non-injured rodents. Thus, they discovered that traumatic stress alters the amount of several microRNA in the blood, brain, and sperm, so while some microRNA were produced in excess, others were lower than in the tissues or cells of animal control.
These changes resulted in a poor regulation of cellular processes normally controlled by these microRNA. After traumatic experiences, the mice behaved remarkably different: they partly lost their natural aversion to bright light and open spaces and had depressive-like behavior. These behavioral symptoms were also transferred to the next generation through sperm, while the offspring was not exposed to any post-traumatic stress.
The metabolism of the descent of the stressed mice was also affected: their insulin and blood sugar levels were lower than in the offspring of parents not traumatized. «We’ve been able to demonstrate for the first time that traumatic experiences affect metabolism in the long term and that these changes are hereditary,» says Mansuy. The effects on metabolism and behavior, even persisted into the third generation.
Mansuy and her team are studying the role of short RNAS in the legacy of trauma in humans. Scientists hope that their results may be useful to develop a blood test for diagnosis.