When Forgetting Is Best: Tet 1, The Gene That Could Help PTSD Patients

Great films have been made in the name of memory malfunctions: Memento, Eternal Sunshine of the Spotless Mind, The Bourne Identity. (Some not so great ones, too, like 50 First Dates, but at least they tried.) But the mystery of amnesia isn't just fodder for mind-bending thrillers, though: real science is out to understand how and why we forget — and why we sometimes can't — so that those haunted by unshakable grief can find relief. Most of us want to remember things better. But for a post-traumatic stress disorder patient, being able to forget could be their only ticket to freedom. A recent breakthrough in research suggests we aren't far off from being able to do this.

It all comes down to the gene known as Tet1. It pilots memory by altering levels of DNA methylation (a biomechanical process that controls access to genes). In an MIT experiment, researchers discovered that mice with normal levels of Tet1 could eventually forget that a particular cage gave them a shock, while those with low levels of Tet1 did not forget. Theoretically, that could mean that shellshocked war victims or PTSD sufferers might have low levels of Tet1, thus making it hard for them to form to make new memories to combat their old, painful ones. But it's not just a matter of replacement. "What happens during memory extinction is not erasure of the original memory," says Li-Huei Tsai, director of MIT’s Picower Institute for Learning and Memory. "The old trace of memory is telling the mice that this place is dangerous. But the new memory informs the mice that this place is actually safe. There are two choices of memory that are competing with each other." In other words, it allows you to more appropriately choose how to weigh between good and bad memories.