Normally cautious mice can be turned into daredevils by removing a gene in their brain that regulates fear, a new study has found.
Scientists say stathmin, a gene that is normally present in high levels in a part of mammals' brains called the amygdala, controls both innate and learned fear. Switching off the gene makes a fearful mouse courageous.
The discovery provides important information on how fear is experienced and processed. It could have important implications for the study of anxiety disorders in humans, and may aid in the development of gene-based therapies to treat such diseases.
"Because stathmin controls both instinctive and learned fear, it provides genetic means to study how these two types of fear work and interact to govern our emotions," said Gleb Shumyatsky, a genetics professor at Rutgers University in New Brunswick, New Jersey.
Shumyatsky is the lead author on the study, which was reported in the November 18 issue of the science journal Cell.
Among 5,000 Genes
Stathmin had been considered a fairly obscure gene, known mostly for its role in brain development and leukemia. But scientists knew the gene functions primarily in the amygdala, a key region of the brain that acts as a major responder to danger for all mammals.
Shumyatsky and his fellow researchers, including Nobel laureate Eric Kandel of Columbia University and Vadim Bolshakov of Harvard Medical School, began their work by looking at the 5,000 genes that are highly active in the amygdala.
They zeroed in on the lateral nucleus, the portion of the amygdala that receives information from the rest of the body about fearful stimuli.
The team found two genes—gastrin-releasing peptide (GRP) and stathmin—that were much more active there than in a part of the brain not thought to be involved in fear.
The scientists first studied GRP and discovered that it controls learned, but not innate, fear. Their study of stathmin revealed that it controls both types of fear.
"Both GRP and stathmin are highly concentrated in the amygdala, and this anatomic location hinted on their potentially important role in fear," Shumyatsky said.
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