Researchers find a gene for fear

One amazing outcome of Science is that it reveals the depths of Nature's secrets. Science offers an alternative perspective, be it a deeper perspective or a different angle of looking at things. One recent example is the identification of a fear factor- a protein the brain uses to generate one of the most powerful emotions in human beings and animals by Shumyatsky and group in Howard Hughs Medical Institute in 2005. The perspective I gained from this work is that even fear and memory are genetically controlled.

A key ingredient to a good scientific work is knowing what to look for and using the right method to search for it. With the aim of understanding the neural circuitry controling fear, the place Shumyatsky and group targeted is the amygdala, a region deep in the brain known to contribute to fear and other emotions. In fact the specific site they targeted is the lateral nucleus, the portion of the amygdala that receives stimuli about fear. Thus, the lateral nucleus played a role in processing the fearful stimuli. After dissecting the individual pyramidal cells (principle cell type) in the lateral nucleus, they found two genes, known as gastrin-releasing peptide (GRP) and stathmin.

The experiments which followed are aimed at understanding the genes. Stathmin is characterized by understanding its expression in the brain and its role in controlling fear. A powerful technology used to understand and reveal the role of the gene in controlling fear is the generation of knockout mouse.

Stathmin knockout mouse have memory deficits in conditioned fear and do not have innate fear. Evidence of deficits in conditioned fear come from observation that knockout mice showed a decreased level of freezing immediately after electric shock compared to normal mice. Evidence of lack of innate fear comes from the behavior of mice in a novel environment. Normal mice when placed in a novel open field naturally avoid the open space in the center of the arena while stathmin mutant mice runs in the aversive center of the field. The behavior of mice is quantified by measuring variables such as percentage time spent freezing and time spent in the open space. Other characterization related to the mode of function of stathmin were made. Refer to the paper in Cell, Vol 123, 697.