Scientists Surprised to Find No Two Neurons Are Genetically Alike

Accepted dogma holds that—although every cell in the body contains its own DNA—the genetic instructions in each cell nucleus are identical. But new research has now proved this assumption wrong. There are actually several sources of spontaneous mutation in somatic (nonsex) cells, resulting in every individual containing a multitude of genomes—a situation researchers term somatic mosaicism. “The idea is something that 10 years ago would have been science fiction,” says biochemist James Eberwine of the University of Pennsylvania. “We were taught that every cell has the same DNA, but that's not true.” There are reasons to think somatic mosaicism may be particularly important in the brain, not least because neural genes are very active.

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Mature neurons stop dividing and are among the longest-living cells in the body, so mutations will stick around in the brain. “In the skin or gut, cells turn over in a month or week so somatic mutations aren’t likely to hang around unless they form cancer,” McConnell says. “These mutations are going to be in your brain forever.” This could alter neural circuits, thereby contributing to the risk of developing neuropsychiatric disorders. “In psychiatric disease we don't know that much yet, and that’s largely the goal [to find an answer],” McConnell says. “It’s a good hypothesis but it’s going to require this big, multi-team effort to really address it.”To investigate, the consortium will sequence brain DNA from control and patient samples. “Before you can get to your destination you have to have a map, and this is going to help build that map of somatic mutations that have potential for influencing neural functioning and disease,” says Eberwine, who was not involved in the new research. “So this consortium is critically important for neuroscience.”

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