A single neuron in a normal adult brain may carry more than one thousand genetic mutations most of which may be harmless, revealed a new research by Maryland-based Howard Hughes Medical Institute (HHMI) scientists. The findings suggested that majority of these mutations appear to arise while genes are in active use.
Lead research Christopher Walsh, HHMI investigator at Boston Children's Hospital, said, "We found that the genes that the brain uses most of all are the genes that are most fragile and most likely to be mutated."
For the study, researchers isolated and sequenced the genomes of 36 neurons from healthy brains donated by three adults after their deaths. For comparison, they also sequenced DNA that they isolated from cells in each individual's heart. They found that every neuron's genome was unique, and each had more than 1,000 point mutations.
Also, the nature of the variation was not quite what the scientists had expected. Walsh said, "We expected these mutations to look like cancer mutations. Cancer mutations tend to arise when DNA is imperfectly copied in preparation for cell division, but in fact they have a unique signature all their own. The mutations that occur in the brain mostly seem to occur when the cells are expressing their genes."
Although most of the mutations the research team cataloged were harmless, they did encounter mutations that disrupted genes that, when impaired throughout the brain, can cause disease. The findings could also lead to new information about how the human brain develops.
The study is published in Science