Unlocking the Origin of Fear

Mice Lacking the Stathmin Gene Don't Show Normal Fear Responses

Nov. 17, 2005 -- Scientists have a new clue about the roots of fear.

This fear factor doesn't go bump in the night. Instead, it's a gene -- the stathmin gene, to be precise.

Mice without that gene behave differently from normal mice. They act, well, less mousy in situations that scare normal mice, Gleb Shumyatsky, PhD, and colleagues report in Cell.

Shumyatsky is an assistant professor of genetics at Rutgers, the State University of New Jersey.

Another expert who worked on the study was Eric Kandel, MD, of Columbia University. Kandel shared the 2000 Nobel Prize in physiology or medicine with two other brain researchers.

May Prompt New Treatments

"This is a major advance in the field of learning and memory that will allow for a better understanding of posttraumatic stress disorder, phobias, borderline personality disorder, and other human anxiety diseases," Shumyatski says in a news release.

"It will provide important information on how learned and innate fear is experienced and processed and may point the way to apply new therapies," he continues.

Learned, Innate Fear

People are born with some fears. Those are called innate fears. Other fears are learned.

For instance, a child who's bullied at school may become fearful about school. That's a learned fear, the baggage of bad experiences. Fearing predators is innate, the researchers note.

They tested the stathmin gene's effects on both types of fear. The tests were only done on mice, not people.

Fear Test

The study focused on healthy mice with or without the stathmin gene.

Mice lacking the gene were slower to leave a wide open space. Normal mice scurried for cover. Mice naturally avoid being out in the open, the researchers note.

The mice without the stathmin gene also were less scared by a sound that they'd learned to associate with a mild foot shock.

The stathmin gene was required for the mice's learned and innate fear, the researchers report.

Focused on Fear

To see if the stathmin gene had other tricks up its sleeve, the scientists did another test that didn't involve fear.

They put mice in a water maze. The mice had to get to a platform and remember how to do so when the platform was hidden.

Both groups of mice performed similarly. The stathmin gene didn't affect the mice's spatial skills or memory, write the researchers. That's because this task depends on another area of the brain that is not highly concentrated with the stathmin gene.

Inside the Brain

The stathmin gene may work on a brain area called the amygdala, which processes emotions including fear.

In mice lacking the stathmin gene, the amygdala had more microtubules, which are like scaffolds, Shumyatsky says in a news release.

"For memory, the brain needs to quickly disassemble and rebuild microtubules to form connections where they are needed,' he explains.

"It appears that loss of stathmin might interfere with this ability in the amygdala, leading to the overproduction of microtubules in certain areas," Shumyatsky continues. "In essence, the cells lose their flexibility."

Fear may not boil down to one gene. In September, other researchers reported that the neuroD2 gene plays a role in mice's fear.