Scientists Find Surprising Degree Of Genetic Variation In Human Brain

A team of researchers at the Salk Institute for Biological Studies in San Diego, Calif. has revealed in a new study that the genomic structures of individual neurons differ from each other more than previously thought. Neurons are cells that processes and transmit information through electrochemical signals in our body.

“Contrary to what we once thought, the genetic makeup of neurons in the brain aren't identical, but are made up of a patchwork of DNA,” Fred Gage, a professor at Salk and corresponding author of the study, said in a statement.

In the study, published on Nov. 1 in Science and led by Mike McConnell of the University of California, scientists isolated about 100 neurons from three people posthumously and took a high-level view of the entire genome -- looking for large deletions and duplications of DNA called copy number variations or CNVs -- and found that 41 percent of neurons had at least one unique, massive CNV that arose spontaneously. The CNVs are spread throughout the genome.

"A good bit of our study was doing control experiments to show that this is not an artifact," Gage said. "We had to do that because this was such a surprise -- finding out that individual neurons in your brain have different DNA content.”

The scientists found a similar amount of variability in CNVs within individual neurons derived from the skin cells of three healthy people, and interestingly, the skin cells were genetically different.

According to scientists, the finding, along with the fact that the neurons had unique CNVs, suggests that the genetic changes occur later in development and are not inherited from parents or passed to offspring.

While the purpose of CNVs in the healthy brain is still unclear, scientists believe that modifications might help people adapt to new surroundings encountered over a lifetime, or they might help us survive a massive viral infection.

“There's a lot more work to do to really understand to what level we think the things we've found are neuron-specific or associated with different parameters like age or genotype,” McConnell said.