Memory Gene Goes Viral
Reporter: Irina Robu, PhD
A gene crucial for learning, called Arc can send genetic material from one neuron to another by using viruses was discovered by two independent team of scientist from University of Massachusetts Medical School and University of Utah which was published in Cell. According to Dr. Edmund Talley, a program director at National Institute of Neurological Disorders and Stroke “this work is a great example of the importance of basic neuroscience research”.
Arc plays an important role in the brain’s ability to store new information, however little is known of how it works. According to the University of Utah scientists, research into the examination of the Arc gene began by introducing it into bacterial cells. When the cells made the Arc protein, it clumped together into a form that resembled a viral capsid, the shell that contains a virus’ genetic information. The Arc “capsids” appeared to mirror viral capsids in their physical structure in addition as their behavior and other properties.
At the same time, University of Massachusetts scientist led by Vivian Budnik, Ph. D and Travis Thomson, Ph.D. set out to scrutinize the contents of tiny sacks released by cells called extracellular vesicles. Their experiments in fruit flies revealed that motor neurons that control the flies’ muscles release vesicles containing a high concentration of the Arcgene’s messenger RNA (mRNA), the DNA-like intermediary molecule cells use to create the protein encoded by a DNA sequence.
Both groups similarly found evidence that Arc capsids contain Arc mRNA and that the capsids are released from neurons inside those vesicles. Also, both groups suggest that Arc capsids act like viruses by delivering mRNA to nearby cells. Furthermore, Dr. Shepherd’s team presented that the more active neurons are, the more of those vesicles they release. Dr. Shepherd’s group grew mouse neurons lacking the Arc gene in petri dishes filled with Arc-containing vesicles or Arc capsids alone. They revealed that the formerly Arc-less neurons took in the vesicles and capsids and used the Arc mRNA contained within to produce the Arc protein themselves. Finally, just like neurons that naturally manufacture the Arc protein, those cells made more of it when their electrical activity increased.
Both groups of scientists plan to examine why cells use this virus-like strategy to shuttle Arc mRNA between cells and which might allow the toxic proteins responsible for Alzheimer’s disease to spread through the brain.
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