Shepherd studies a gene called Arc which is active in neurons, and plays a vital role in the brain. “Arc is really key to transducing the information from those experiences into changes in the brain.”
“What is the RNA cargo? What is the signal are carrying? When Arc is released by a neuron, how far can it travel?” And perhaps more importantly, how does all of this influence the brain? If the team stops neurons from releasing Arc, how does that affect an animal’s ability to learn or to form new memories? “I can see what people are thinking: Is memory a virus?” Shepherd says, laughing.
Fruit flies have Arc genes, and Shepherd’s colleague Cedric Feschotte showed that these descend from the same group of gypsy retrotransposons that gave rise to ours. Both events gave rise to similar genes that do similar things: Another team showed that the fly versions of Arc also sends RNA between neurons in virus-like capsules. Arc has been implicated in many brain disorders, like Alzheimer’s, schizophrenia, and Fragile X syndrome.
It’s entirely possible that animals which lack Arc genes, such as fish, “Use entirely different domesticated gag proteins to achieve the same purpose.” Indeed, the human genome has more than 100 gag-derived genes.