Memory-Erasing Gene Discovered in Mice


Finding could help people with post-traumatic stress disorder, researchers say.

PTSD, or post-traumatic stress disorder, is a psychological disorder that results from terrifying experiences. Veterans of war are at risk of this disorder because of what they have been through while engaged in combat, but others are susceptible too. PTSD can develop after one is attacked or assaulted, after abuse, after being in a car crash or from experiencing anything dangerous or scary.

Someone with PTSD often feels the fear and the “fight-or-flight” response that she originally felt when in the dangerous situation that triggered the disorder, even when in a safe environment. These recurring feelings of terror, as well as flashbacks, are often triggered by something like a sound, a smell, or anything else that reminds the person of the traumatic event.

Living with this recurrent fear can be paralyzing. In severe cases, just getting through a normal day can be close to impossible. Treatment with both medications and therapy can help, but new research has uncovered a gene that may make recovery easier and faster. Scientists have discovered a gene that may help to erase the horrible memories that plague victims of PTSD.

The Memory-Erasing Gene

Researchers from MIT worked with mice and discovered a gene called Tet 1; they published the results in the journal Neuron. The Tet 1 gene seems to play a role in memories by controlling a group of other genes that are needed for erasing old memories. To investigate what effect this gene has on memories, the researchers experimented with mice that had the gene and those that did not.

All of the mice were conditioned to fear a particular cage. This was accomplished by giving the mice a small, yet uncomfortable shock when they were in that cage. Eventually they all learned to associate the shock with the cage and showed fear when brought to that location. This is similar to what happens to people with PTSD. They associate certain things, like a sound, with a past trauma.

After creating the fear in all of the mice, the rodents were put in the cage repeatedly, but without the shock. After doing this enough times, the mice should lose the fear of the cage because the shock is no longer used. The mice with the Tet 1 gene did eventually lose their fear because the gene helped to replace the old, fearful memory with new and more pleasant ones associated with the cage. The mice without the gene were unable to forget that the cage was scary, no matter how many times they were placed in it without getting the shock.

Tet 1 and PTSD

One way of treating PTSD is called extinction learning. It involves changing how the triggers cause a fear response in the person with the disorder. For instance, for someone who has PTSD from being in a serious car crash, the sound of metal hitting metal may trigger fear and panic. By working with a professional therapist, the person can learn to replace the fear associated with that sound. It takes a lot of time and effort and success varies by individual.

Extinction learning is what the researchers used to retrain the mice to lose their fear of the cage. By introducing them to the cage without the shock, the mice were able to enjoy being in the cage. They could engage with their peers, eat, and create pleasant memories. By replacing the shock with the pleasant experiences, they were retrained to no longer fear the cage.

The researchers who found the Tet 1 gene hope that they can use it to make therapy work better for people who suffer from PTSD. The mice with the gene were able to replace their bad memories of the shock while those without the gene could not. If Tet 1 can be amplified in people with traumatic memories, they may have an easier time replacing their fearful memories with new and more pleasant ones.

Going through traumatic experiences does not always result in the development of PTSD, but for those in which it does, the experience is relived again and again. The constant fear and tension that accompany PTSD are terrible and can prevent someone from living a normal life. If new treatments can take advantage of the Tet 1 gene, those who suffer from this awful disorder may find relief sooner and more completely.

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